Download - Plant Pathology Workshop Manual
Plant Pathology Workshop
Healthy Plants = Healthy World
or
Don’t Get Caught With Your Plants Down!
Introduction
• Introductory video from APS
• Introduction to plant pathology – historical plant disease plagues and current ones
Plant Pathogen Groups
• Abiotic plant problems vs. biotic plant problems; disease triangle concept
• Viroids, Viruses, Bacteria, Fungi and Nematodes
• First Activity: Which Plant Pathogen Are You? Florida centric version
General Concepts of Plant Pathology
• Introduce concepts of signs, symptoms, pathogenicity, virulence, etiology, epidemiology
• Vectors move plant pathogens too!
• Second Activity: How Do Spores Move from Plant to Plant?
o Demonstration on spore dispersal without using spores or water.
Plant Disease Management
• Introduce the concepts of disease management including exclusion, plant resistance,
cultural controls, chemical controls, biological controls
Make Your Own Microscope
• Third Activity: $10, $4 and $1 smartphone microscopes
Plant Genetic Engineering
• Agrobacterium-mediated transformation, gene gun, protoplast fusion, genome editing
• Fourth Activity: Agrobacterium tumefaciens
o Inoculate plants with this bacterium to take home and watch the disease develop.
The Importance of Biological and Genetic Diversity
• Where is the genetic origin of the food we eat?
• Fifth Activity: Purple Potato Eaters - What kid doesn’t eat potato chips?
Plant Pathology Workshop
University of Florida/IFAS
Department of Plant Pathology
All materials presented in this workshop can be found at this site:
http://flrec.ifas.ufl.edu/featured-3-menus/extension/plant-pathology/plant-pathology-workshop/
At the above web page, you will find all the PowerPoints, any text files that
accompany the PowerPoints, and instructions for various activities.
Much of the information presented in the workshop has been obtained from
either The American Phytopathological Society (APS) or from the University of
Florida/IFAS Electronic Data Information Source (EDIS). Publications available on
EDIS are written by University of Florida/IFAS faculty and reviewed every 3 years
to insure the material is valid and as up-to-date as possible.
The American Phytopathological Society (www.apsnet.org)
• APS Education Center: most material is found under the “Introductory” section
http://www.apsnet.org/edcenter/Pages/default.aspx
o Introduction to the Pathogen Groups
o Plant Disease Lessons on 100 different diseases: pathogen, host, symptoms and signs,
disease cycle, management, significance, references, photos. Some of the lessons have
been translated into Chinese, Portuguese and Spanish.
o Special Topics in Plant Pathology
o Laboratory Exercises
o Feature Articles on Plant Pathology Topics
o Illustrated Glossary
• Office of Public Relations and Outreach
http://www.apsnet.org/members/outreach/opro/Pages/OutreachResources.aspx
o Which Plant Pathogen Are You? activity
o Plant Pathology Career Poster and Brochures and Video
https://www.youtube.com/user/PlantDisease
o Plant Pathology Storybook (English, Spanish and Chinese)
o Plants Get Sick Too! Poster
o Plant Detectives Poster
o Short, Funny Videos on the importance of diseases and plant doctors
http://www.apsnet.org/members/outreach/opro/Pages/OutreachVideos.aspx
• APS Bookstore
http://www.apsnet.org/apsstore/shopapspress/pages/newreleases.aspx
If you are interested in obtaining a cool T-shirt, APS Store sells one with the slogan
“Don’t Get Caught with Your Plants Down” plus other cool Plant Pathology T-shirts, see:
http://www.apsnet.org/apsstore/shopapspress/Pages/Tshirts.aspx
University of Florida/IFAS Extension
• Electronic Data Information Source (EDIS): http://edis.ifas.ufl.edu (any topic – use the
“Search” box)
• Solutions for Your Life: http://solutionsforyourlife.ufl.edu/ (any topic!!)
University of Florida, Institute of Food and Agricultural Sciences (IFAS)
http://ifas.ufl.edu/
• Research: http://research.ifas.ufl.edu/
• Extension: http://sfyl.ifas.ufl.edu/
• Teaching (College of Agricultural and Life Sciences: http://cals.ufl.edu/
• Department of Plant Pathology: http://plantpath.ifas.ufl.edu/
• Location of UF/IFAS centers and extension offices: http://ifas.ufl.edu/maps/
•
Florida Department of Agriculture and Consumer Services (FDACS)
• Division of Plant Industry (DPI)
http://www.freshfromflorida.com/Divisions-Offices/Plant-Industry
As with any project, there will be errors, both factual and typographical. As you use the
materials, please report such errors to Dr. Monica Elliott at [email protected].
1
WELCOME
Institute of Food and Agricultural SciencesBUT we are so much more!
“The Mission of UF/IFAS is to develop
knowledge in agricultural, human and
natural resources and to make that
knowledge accessible to sustain and
enhance the quality of human life.”
On July 2, 1862, President Abraham Lincoln signed into law what is generally referred to as the Land-Grant Act. The new piece of legislation, which was introduced by U.S. Representative Justin Smith Morrill of Vermont, granted each state 30,000 acres of public land for each senator and representative under apportionment based on the 1860 census.
Proceeds from the sale of these lands were to be invested in a perpetual endowment fund that would provide support for colleges of agriculture and mechanical arts in each of the states.
The establishment of Florida Agricultural College at Lake City in 1884 under the Morrill Act marked the beginning of what became the College of Agriculture of the University of Florida in 1906.
While the University traces its roots to 1853 and the establishment of the state-funded East Florida Seminary, UF/IFAS traces its roots to the Morrill Act of 1862, which established the land-grant university system.
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UF/IFAS was created in 1964 to consolidate the agricultural, natural resources, and life sciences teaching, research and extension programs at the University of Florida. UF/IFAS is a federal-state-county partnership throughout Florida.
Teaching• The College of Agricultural and Life Sciences• The School of Natural Resources and Environment• Portions of the College of Veterinary Medicine
Research• The Florida Agricultural Experiment Station supports research
programs at 12 regional Research and Education Centers.• Providing research support at 4 Research and Demonstration sites
(farms), 1 research forest, and 1 biological field station
Extension• The UF/IFAS Extension has at least one office in every county.• Funded by state, federal and local county dollars
This center is just 1 of 12 across Florida!
Every county has a UF/IFAS Extension office.
1Introduction to Plant Pathology History
Plants Get Sick Too!
Healthy Plants Healthy World
1
Course Objectives1) Introduce the basics of plant pathology, providing a historical
background and relevance to current plant issues.
2) Illustrate the difference between abiotic and biotic plant
problems and the different organisms that cause plant diseases.
3) Introduce plant pathology concepts, such as etiology,
epidemiology, pathogen spread and disease management, including the importance of plant diversity.
4) Reinforce concepts with hands-on demonstrations.
5) Provide lecture, laboratory and demonstration materials that
meet Florida educational standards.
6) Provide the opportunity to earn Continuing Education Units.
Plants Get Sick Too!
Healthy Plants = Healthy World
2
Plant Pathology (Phytopathology)
•Is the study of plant diseases.
•Combines knowledge of plants and microbiology.
•Examines infectious plant pathogens, which include fungi, bacteria, nematodes, viruses and viroids.
3
2Introduction to Plant Pathology History
Plant Pathologists (Plant Doctors)
•Study plant diseases to determine cause, spread and management - very similar to medical (humans and animals) researchers.
•Diagnose plant problems.
•But, our “patients” don’t talk back, don’t complain when we examine them, and don’t require an ethical panel to approve our research.
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Plant Pathologists (Plant Doctors)
If a student likes microbiology but doesn’t like the thought of working with humans or animals, then perhaps they should consider becoming a plant doctor!
https://www.youtube.com/user/PlantDisease
Click on above link. When YouTube video page appears, click on box in lower right corner of video to obtain full screen view. When finished, hit “escape”.
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https://www.youtube.com/playlist?list=PLBv5AZR5ofbjzSGw30Tf1pbirwxUZjKuG
Plant Pathologists (Plant Doctors)
For a lighter view of the importance of plant diseases and plant doctors, see one or all of these 10 short videos (30 seconds each).
Don’t Get Caught WithYour Plants Down!
6
3Introduction to Plant Pathology History
7
Plant Pathology: Past to Present Illustrated Storybook
Plant Pathology: Past to Present is an illustrated storybook describing the origin, relevance, and science of plant pathology. The story unfolds as if told by Anton deBary, father of plant pathology, and is suitable for elementary and secondary students to adults.
The book may be downloaded and freely reproduced and distributed.Available in Chinese and Spanish.
ACKNOWLEDGEMENTSThe title Plant Pathology - Past to Present was provided in 1998 by Mame Maloney. Mame's title was the winner of 38 titles submitted by students in Katie Jerolamon's 1998 6th grade class at Edward's Middle School, Central, SC.The illustrated storybook was prepared by the Youth Programs Committee of the American Phytopathological Society.
http://www.apsnet.org/members/outreach/opro/
Pages/IllustratedStorybook.aspx
Plant Pathology: Past to Present
Smut of wheat (and other grains) was recorded as early as 1900 BCE in ancient Babylon (southwest of current Baghdad, Iraq).
http://www.apsnet.org/edcenter/intropp/l
essons/fungi/Basidiomycetes/Pages/StinkingSmut.aspx
Stinking Smut(Common Bunt)
of Wheat
R. Johnston
J. Riesselman
R. Johnston, University of Montana, Copyright free
J. Riesselman, University of Montana, Copyright free
8
Plant Pathology: Past to Present
In 715 BCE, the Romans created the gods “Robigo” and “Robigus” to protect wheat
from the wheat leaf rust fungus, which has reddish-colored spores.
The Robigalia festival was held in April to protect the fields from this disease.
USDA Cereal Lab
http://www.ars.usda.gov/Main/
docs.htm?docid=11269
9
4Introduction to Plant Pathology History
Plant Pathology: Past to Present
Today, another type of rust on wheat is threatening the world: wheat stem rust, specifically strain Ug99, which was first
detected in Uganda, Africa.
http://www.apsnet.org/edcenter/intropp/lessons/fungi/
Basidiomycetes/Pages/StemRust.aspx
USDA Cereal Lab
http://rusttracker.cimmyt.org/?page_id=2210
Plant Pathology: Past to Present
White vs. Dark Bread
In ancient times, poor people ate bread made from rye, which
produced a dark bread.
11
Plant Pathology: Past to Present
But, during cool, wet weather, the developing rye grain often became infected with a fungus and produced purplish-black grain-like structures called “ergots”.
These were ground with the grain and used to make bread.
http://www.apsnet.org/edcenter/intropp/
lessons/fungi/ascomycetes/Pages/Ergot.aspx
By Burgkirsch at german wikipedia, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=3665162
By Rasbak - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=295119
12
5Introduction to Plant Pathology History
Plant Pathology: Past to Present
•Ergot contains the chemical ergotamine.
•Consuming ergotamine in the bread caused gangrene. “St. Anthony’s Fire” was the name of a condition in the Dark Ages. Many victims hallucinated and died in horrible pain.
13
Plant Pathology: Past to Present
•Ergotamine causes severe constrictions in blood vessels (vasoconstrictor).
•Today, ergotamine is safely used as a vasoconstrictor for migraines (usually with caffeine) or post-partum bleeding.
•Majority of ergot alkaloids derived via fermentation
•But, some are obtained by growing of triticale (hybrid of wheat and rye)
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1637017/
14
Plant Pathology: Past to Present• Potato (from Peru) was introduced into Europe about 1750. It eventually became a food staple in Europe among the poor.
• In Ireland, tenant farmers paid the landlord in wheat but survived on potatoes.
•But, in the 1840s, a series of wet, coolsummers led to an epidemic of a potato disease called “late blight”.
By Howard F. Schwartz, Colorado State University, United States, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=793329815
6Introduction to Plant Pathology History
•Thousands of Irish starved to death, and 1.5 million emigrated to escape starvation.
• If you are of Irish descent, your family may have moved from Ireland due to this potato disease.
Plant Pathology: Past to Present
http://www.apsnet.org/edcenter/intropp/lessons/fungi/
Oomycetes/Pages/LateBlight.aspx
Public Domain, https://commons.wikimedia.org/w/index.php?curid=232492
By User AlanMc on en.wikipedia - taken by me (AlanMc) in 2006, Public Domain, https://commons.wikimedia.org/w/index.php?curid=1342329
16
Plant Pathology: Past to Present
Late blight is still a serious disease worldwide on potato and tomato.
D. Inglis, Washington State University, Copyright free
D. Inglis, Washington State University, Copyright free
D. Inglis, Washington State University, Copyright free
17
Plant Pathology: Past to Present
Why do the British drink tea?
•Coffee has been a popular beverage in Europe since 1600s.
•But, in the 1800s, the fungal disease “coffee rust” devastated the British coffee plantations in Ceylon (now Sri Lanka).
http://www.apsnet.org/edcenter/intropp/lessons/fungi/
Basidiomycetes/Pages/CoffeeRust.aspx
•British switched to growing and drinking tea.
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7Introduction to Plant Pathology History
Plant Pathology: Past to Present
Tulip Mania
• Plant diseases affect ornamental plants too!
• In the 1630s in the Netherlands (current name), tulips with a particular multi-color trait became highly prized – lots of speculative buying, future contracts, short selling, buying on margin, market bubble, etc.
•Most highly prized were tulips with streaks on solid color background.
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Plant Pathology: Past to Present
Tulip Mania
•Now know the streaking was due to the tulip-breaking virus, actually two viruses.
•Viruses are spread by an insect called an aphid.
•Viruses are still present today, especially in southern Europe.
•Today, tulips with streaks are due to breeding.
20
Plant Pathology: Past to Present
Chestnut Blight and Dutch Elm Disease
•Has anyone seen a chestnut tree or an American elm tree?
•Both native trees were essentially wiped out by fungal pathogens which were accidently introduced into the U.S.
http://www.apsnet.or
g/publications/apsnetfeatures/Pages/Chestn
utBlightDisease.aspx
http://www.apsn
et.org/edcenter/intropp/lessons/f
ungi/ascomycete
s/Pages/DutchElm.aspx
http://www.washington.edu/news/2010/08/05/campus-losing-another-tree-to-dutch-elm-disease/21
8Introduction to Plant Pathology History
Plant Pathology: Past to Present
Laurel Wilt
The latest invader is a fungus that is killing trees in the Lauraceae (laurel) family, which includes redbay, sassafrass and avocado.
https://www.youtube.com/watch?v=2x7vgFWLHkY#t=90
http://www.freshfromflorida.
com/Divisions-Offices/Plant-Industry/Save-the-Guac
Save the Guac!
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Plant Pathology: Past to PresentLaurel Wilt
•Fungus initially spread by an exotic ambrosia beetle that was introduced into Georgia in 2002 by infested packing materials, such as wooden crates and pallets.
•Still unclear if the fungus was introduced or was already present (and just needed the right vector!)
•Based on greenhouse studies, native ambrosia beetles appear capable of transmitting the fungus.
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Plant Pathology: Past to Present
Laurel Wilt
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9Introduction to Plant Pathology History
Plant Pathology: Past to Present
Citrus Greening or Huanglongbing
https://edis.ifas.ufl.edu/ch198
http://www.crec.ifas.ufl.edu/extension/greening/index.shtml
http://solutionsforyourlife.ufl.edu/hot_topics/agriculture/citrus_greening.shtml
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Plant Pathology: Past to Present
Citrus Greening or Huanglongbing
•The pathogen is a fastidious bacterium that is vectored by the Asian citrus psyllid.•Both the pathogen and the insect were introduced into Florida.
http://entomology.ifas.ufl.edu/creatures/citrus/acpsyllid.htm26
Plant Pathology: Past to Present
http://www.dontpackapest.com
Don’t Pack a Pest
https://www.youtube.com/watch?feature=player_embedded&v=x0S99cwnDqM
Important to think about impact of moving plants inside Florida, the U.S. and worldwide.
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10Introduction to Plant Pathology History
Plant Pathology: Past to Present
Imagine a world without bananas, chocolate, tomatoes, . . . and hamburgers!
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Plant Pathology: Past to Present
Some plant pathogens are useful:
•Free-branching poinsettia is due to a phytoplasma (special type of bacterium).
http://www.apsnet.org/publications/apsnetfeatures/
Pages/Poinsettia.aspx
Mike Klopmeyer of Ball FloraPlantMike Klopmeyer of Ball FloraPlant Mike Klopmeyer of Ball FloraPlant
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Plant Pathology: Past to Present
Some plant pathogens are edible:
•Corn smut is a delicacy in Mexico, where it is called huitlacoche. To get more people to eat it in the U.S., they renamed it the “Mexican truffle”.
http://www.apsnet.org/edcenter/intropp/lessons/fungi/
Basidiomycetes/Pages/CornSmut.aspx
By Russ Bowling from Greenwood, SC, USA - Huitlacoche, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=42024636
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11Introduction to Plant Pathology History
Plant Pathology: Past to Present
Some plant pathogens are medicinal:
•Ganoderma lucidum complex (lingzhimushroom or reishi mushroom) contains compounds used for medicinal purposes in Asia for thousands of years.
By Eric Steinert - photo taken by Eric Steinert at Paussac, France, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=452328
31
Plant Pathology: Past to Present
Botrytis is a fungus you often see on fresh strawberries. It also causes a disease of wine grapes, but under certain conditions it is called Noble Rot, as it will result in a grape that is used to make sweet dessert wines, such as Sauternes.
Some plant pathogens are useful:
http://edis.ifas.ufl.edu/fe95732
Plant Pathology: Past to Present
Some plant pathogens are useful:
•Sometimes we deliberately use plant pathogens to control exotic, invasive weeds.
http://www.apsnet.org/publications/apsnetfeatures/Pages/
WeedBiocontrolPart2.aspx
•Tobacco Mild Green Mosaic Virus controlling Tropical Soda Apple in Florida
• Patented by Drs. R. Charudattan and E. Hiebert, formerly UF/IFAS Pathology Department; now BioProdex, Inc.
https://plants.ifas.ufl.edu/plant-directory/solanum-viarum/#VII-F
http://www.apsnet.org/publications/apsnetfeatures/Pages/
WeedBiocontrolPart1.aspx
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12Introduction to Plant Pathology History
Plant Pathology: Past to Present
Some plant pathogens are useful:
•The most useful plant pathogen is Agrobacterium tumefaciens, a bacterium that causes crown gall of many stone fruit crops.
•The “original” genetic engineer!!
But, we will save this one for a later discussion and activity!
34
Plant Pathology: Past to Present
Sources of Information on Plant Diseases
�APS Education Center and Outreach• http://www.apsnet.org/edcenter/Pages/default.aspx• http://www.apsnet.org/members/outreach/opro/Pages/OutreachResources.aspx
�University of Florida/IFAS Extension• http://edis.ifas.ufl.edu/• http://solutionsforyourlife.ufl.edu/
�Florida Department of Agriculture and Consumer Services (FDACS), Division of Plant Industry (DPI)• http://www.freshfromflorida.com/Divisions-Offices/Plant-Industry
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Plant Pathology: Past to Present
Don’t Get Caught with
Your Plants Downhttps://www.youtube.com/playlist?list=PLBv5AZR5ofbjzSGw30Tf1pbirwxUZjKuG
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Text for Plant Pathology PowerPoint “Introduction_History”, Page 1
Text for UF/IFAS/Plant Pathology “Introduction_History” PowerPoint
Slide Text: The text below is supplementary to what is presented on the slide itself
1 The American Phytopathological Society (APS) is a non-profit professional
organization. Their mission is “Discover and disseminate new knowledge of plant
systems worldwide to meet humanity’s need for safe and nutritious food, affordable
fiber, sustainable forests, and verdant landscapes; and promote the development and
adoption of economically and environmentally sustainable practices to ensure plant
health.” Website: http://www.apsnet.org
One department within the University of Florida/IFAS is the Department of Plant
Pathology. Members of this department are located in Gainesville (main campus) and
at 9 centers across the entire state. We are known for our research on diseases of
diverse crops including citrus; vegetables such as tomato, pepper and cucurbits;
ornamentals including foliage plants and flowering and woody ornamentals; field crops
including soybean, peanut and sugarcane; and tropical fruits.
Website: http://plantpath.ifas.ufl.edu
2 There are 6 objectives for this course.
3 Phytopathology is a hard word to remember, so we use “plant pathology” to describe
this scientific discipline.
4 Most people know what it meant when you state someone is a “doctor”. One of the
best ways to describe a plant pathologist is to state we are “plant doctors”. We strive
to keep plants healthy, just like the medical doctor strives to keep humans healthy!
5 This is a 4-minute video that we hope would encourage students to consider a career
in plant pathology. It was produced by the American Phytopathological Society.
https://www.youtube.com/user/PlantDisease
6 Plant doctors like to have fun too! These short videos (30 seconds each) are a lighter
view to illustrate the importance of our discipline. Think about it – what would the
world do without certain plants? No grapes for grape jelly on your PB&J or for wine.
No cotton for your blue jeans. No fresh vegetables and fruits. No trees in the
landscape. We need plants, and someone has to keep the plants healthy!
http://www.apsnet.org/members/outreach/opro/Pages/OutreachVideos.aspx
7 Portions of the rest of this PowerPoint follow the story line from a coloring book that
APS developed entitled: Plant Pathology: Past to Present. It is now available in
English, Chinese and Spanish – free to download. High school and middle school
Text for Plant Pathology PowerPoint “Introduction_History”, Page 2
students use the storybook for mentoring grade school students. A few plant
pathologists have been known to get out their crayons too!
http://www.apsnet.org/members/outreach/opro/Pages/IllustratedStorybook.aspx
8 Plant diseases are not new. A disease of grain crops called “smut” was recorded
thousands of years ago in ancient Babylon. Stinking smut or common bunt disease of
wheat can still be found in wheat fields across the world. It is caused by a fungus, and
it really does stink. Obviously, you do not want infested grain being used to make flour
for bread or tortillas or any other wheat-based product.
http://www.apsnet.org/edcenter/intropp/lessons/fungi/Basidiomycetes/Pages/Stinkin
gSmut.aspx
Note the web link in this slide. One resource that APS has on their website is the “APS
Education Center” - http://www.apsnet.org/EDCENTER/Pages/default.aspx. There are
lessons about various diseases, articles on plant pathogen groups, lab exercises, an
illustrated dictionary . . . and more.
9 This is another disease documented very early in human history.
http://www.ars.usda.gov/Main/docs.htm?docid=11269
10 Rust diseases are still problematic in this world. Wheat stem rust has been a
devastating disease in parts of Africa. Just like human diseases, new plant pathogens
emerge or move to new parts of the world, and old pathogens find new ways to attack
the plant – there will always be a need for plant pathologists and other scientists who
work with plants! We have to eat, feed our animals, clothe ourselves and build
shelters for our families.
http://www.apsnet.org/edcenter/intropp/lessons/fungi/Basidiomycetes/Pages/StemR
ust.aspx
http://rusttracker.cimmyt.org/?page_id=22
11 Today, we are encouraged to eat whole grain breads. But, at one time, white bread
was the bread of the rich and dark bread was the bread of the poor. If you had white
bread on your table, it meant that you had the money to “refine” the wheat grain and
didn’t need rye grain to make your bread.
12 One disease of rye grain (and other grain crops and grasses) is called “ergot”. The
pathogen infects the plant ovary and replaces the grain kernel with a pathogen
structure called a sclerotium (sclerotia is plural). A sclerotium is called "ergot".
“Ergot” is the French word for "spur." The French noted some resemblance between
the sclerotia and the spurs on rooster legs, hence “ergot”. These ergots were ground
up with the healthy rye grains to make bread, and that led to vary serious
consequences, including death. But, we eat fungi all the time. What would it matter if
we ate the sclerotia/ergots?
Text for Plant Pathology PowerPoint “Introduction_History”, Page 3
http://www.apsnet.org/edcenter/intropp/lessons/fungi/ascomycetes/Pages/Ergot.aspx
13 Ergot contains the chemical ergotamine, which causes gangrene. Wheat is graded
as “ergoty” when it contains more than 0.05% (a very small amount!) by weight of the
ergot/sclerotia. In February 2016, the Egyptian government rejected a cargo shipload
of wheat because it contained “ergoty” grain. They were rejecting it not only because
the grain could be harmful, but just as important, Egypt is considered free of this
disease and did not want the fungus introduced into Egypt.
http://www.reuters.com/article/egypt-wheat-idUSL8N15V5A5
14 But, as with most things, there is a “good” side to ergot. In other words, scientists did
determine that the ergotamines could be useful. Most are now produced by
fermentation using the fungus, but some are obtained from grain deliberately grown
to be infected with the plant pathogen and produce sclerotia/ergots.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1637017/
15 The lowly potato and its importance in history: Did you know that potatoes are native
to Peru, and not Idaho? The explorers introduced it to Europeans, and it quickly
became a food staple, especially among the poor. But, as with most monocultures
(large amount of land producing the same plant species), disaster eventually struck in
the form of a plant disease called “late blight”.
16 The website shown here tells the story of this disease and its effect on the world.
http://www.apsnet.org/edcenter/intropp/lessons/fungi/Oomycetes/Pages/LateBlight.aspx
17 As with most of our plant diseases, late blight, which also affects tomatoes, is still a
serious disease world-wide. And, as we will learn later, the pathogen is no longer
considered a fungus.
18 Why do the British drink tea? Once again, a plant pathogen affects the social and
economic norms of the world!
http://www.apsnet.org/edcenter/intropp/lessons/fungi/Basidiomycetes/Pages/Coffee
Rust.aspx
19 It is not just plant diseases of food crops that have affected world history! One of the
first “economic bubbles” was “Tulip Mania”. Yes, the lowly tulip that we see in the
florist shops each spring (too hot to grow tulips in Florida) also has its place in history.
20 The tulip streaking in the 1600s that was so highly sought after was due to a virus;
actually, we now know it was two (2) viruses. As we will learn in another PowerPoint
presentation, viruses are usually spread from plant to plant by insects. The viruses
affecting tulips is spread by aphids. The viruses are still present in southern Europe.
Text for Plant Pathology PowerPoint “Introduction_History”, Page 4
But, in the U.S., when you see a streaked tulip, you are seeing the result of crop
breeding.
21 Tree diseases are important also! Most of you have never seen a chestnut tree or
American elm tree because of plant pathogens introduced into the U.S. The original
Dutch elm disease pathogen was introduced into the U.S. in the 1920s by furniture
makers who used imported European elm logs to make veneer for cabinets and tables.
The beetle that spreads the fungal pathogen had been introduced earlier into the U.S.
Unfortunately, American elm trees had been planted extensively as a landscape tree,
especially along streets, in the U.S. – essentially a monoculture. The disease
eliminated American elm trees from the east coast and eventually made it all the way
to the west coast of the U.S. by the mid-1970s. The photo shown here is from the
University of Washington campus in Seattle in 2010. Great efforts have been made
using chemical and biological controls to try to save these trees on the west coast and
elsewhere, but treatments are not always effective.
http://www.apsnet.org/publications/apsnetfeatures/Pages/ChestnutBlightDisease.aspx
http://www.apsnet.org/edcenter/intropp/lessons/fungi/ascomycetes/Pages/DutchElm.aspx
22 In Florida, we are facing a similar situation today. Laurel wilt disease affects trees in
the Lauraceae family, which includes the native redbay and sassafras. And, it also
includes avocado. The Florida Department of Agricultural and Consumer Services
(FDACS) established a consumer awareness campaign called “Save the Guac!” – if you
want to eat guacamole, we need to save the avocado industry and the avocado tree in
your backyard (if you live in central and south Florida).
http://www.freshfromflorida.com/Divisions-Offices/Plant-Industry/Save-the-Guac
The link to a 10-minute video about this problem is shown on the screen and below:
https://www.youtube.com/watch?v=2x7vgFWLHkY#t=90
23 Laurel wilt disease has turned into a very complicated story. But, we do know that
introduction of an exotic beetle via infested crate packing materials started the deadly
process. In most parts of Florida, it was not truly appreciated how many native
redbay, sassafras and other trees in the Lauraceae family composed our native forests.
This is the classic story of not appreciating something until it is gone!
24 One way the beetle and perhaps the pathogen was moved throughout the state was
via firewood. People would cut down the forest (and landscape) trees that died from
Laurel Wilt and use it for firewood at campsites. Everyone plays a role in limiting the
spread of plant pests!
25 Citrus greening or Huanglongbing (try saying that 3 times really fast!!) is another
disease that requires an insect to move the pathogen (a bacterium) from plant to
plant.
https://edis.ifas.ufl.edu/ch198
Text for Plant Pathology PowerPoint “Introduction_History”, Page 5
http://www.crec.ifas.ufl.edu/extension/greening/index.shtml
http://solutionsforyourlife.ufl.edu/hot_topics/agriculture/citrus_greening.shtml
26 Both the pathogen and the insect vector were introduced into Florida. This disease
has had a dramatic economic impact on the citrus industry in Florida!
http://entomology.ifas.ufl.edu/creatures/citrus/acpsyllid.htm
27 Laurel wilt and Citrus greening (Huanglongbing) are just two diseases that illustrate the
importance of plant security at our borders and ports of entry. While you may want to
share the exotic fruit or plant you observed outside of Florida and the U.S., it may be
infected with a pathogen or carrying an insect pest – Don’t Pack a Pest! The APHIS
beagle brigade is an important part of U.S. plant and food security . . . and they are so
adorable!
http://www.dontpackapest.com
https://www.youtube.com/watch?feature=player_embedded&v=x0S99cwnDqM
28 We have just touched on a few plant pathogens that have influenced history and/or
influence us today. There are many more!
29 As with ergotamine derived from the plant disease “ergot”, there are other plant
pathogens that have purposefully or accidently been determined to be useful to
humans. One of them is a phytoplasma (special type of bacterium) that we learned
will result in a more beautiful poinsettia. It makes the plant branch more to obtain a
more dense, compact plant.
http://www.apsnet.org/publications/apsnetfeatures/Pages/Poinsettia.aspx
30 And depending on your heritage, you may already be familiar with huitlacoche or corn
smut. This is a Mexican delicacy. One person’s plant disease is another person’s
favorite food!
http://www.apsnet.org/edcenter/intropp/lessons/fungi/Basidiomycetes/Pages/CornS
mut.aspx
31 How many of you have seen Ganoderma coffee or tea advertised? This woody, shelf-
like mushroom is the basidiocarp (sexual spore producing structure) of the Ganoderma
lucidum complex. Compounds that this fungal complex produces have been used in
Asian folk medicine for 2000 years, and we now know much more scientifically about
these compounds and why they are effective.
32 Do you like sweet dessert wines, especially Sauternes? But, did you know they were
the result of a plant pathogen? So, a fungus that can easily destroy the Florida
strawberry crop is highly desired in certain grape-producing areas of the world!
http://edis.ifas.ufl.edu/fe957
Text for Plant Pathology PowerPoint “Introduction_History”, Page 6
33 We also use plant pathogens to control weeds. This is just one example: a virus
discovered by UF/IFAS plant pathologists is patented for use to control the invasive
(introduced) tropical soda apple, which is a major weed problem in pastures in the
southern half of Florida.
http://www.apsnet.org/publications/apsnetfeatures/Pages/WeedBiocontrolPart1.aspx
http://www.apsnet.org/publications/apsnetfeatures/Pages/WeedBiocontrolPart2.aspx
34 Probably the most useful plant pathogen is Agrobacterium tumefaciens, a bacterium
that causes crown gall of many stone fruit crops. However, once plant pathologists
learned how it infected plants and exactly how it caused the galls (tumors), it quickly
became the basis of early genetic engineering research. Think of this pathogen as the
“original genetic engineer”! But, we will save the mysteries of this pathogen for later.
35 This is a list of sources of information on plant diseases and the pathogens which cause
them.
36 This is the link to the short (30-second) fun videos about the loss of plants due to plant
pathogens, and why the world will always need plant pathologists!
Plant Pathogen Groups 1
•Abiotic Plant Problems
•Biotic Plant Problems (Plant Diseases)
•Disease Triangle
•Plant Pathogens: Bacteria, Fungi,
Oomycota, Viruses, Viroids,
Nematodes
Abiotic vs. Biotic Plant Problems
Discuss:
Photos used from various UF/IFAS Extension Publications or provided by UF/IFAS faculty and staff, unless otherwise stated1
Abiotic Plant Problems
Abiotic plant problems are caused by
environmental factors, either natural or man-made
non-infectious, non-living (abiotic = without life)
• Unfavorable soil properties or structure
• Nutrient imbalances
• Moisture extremes
• Temperature extremes
• Light extremes
• Physical injuries
• Chemical toxicity
• And in Florida, lightning strikes!
2
Abiotic Human Problems
• Vitamin deficiencies
• Cholesterol imbalances
• Mercury or lead poisoning
• Broken bones
• Burns
• Allergic Reaction
• Others?
3
Plant Pathogen Groups 2
Abiotic Plant Problems
• Can kill plants
• Can predispose plants to infection by plant
pathogens
• Can be natural, such as temperature extremes
• Can be due to human activity, such as improper
use of fertilizers or pesticides
• It is common to have both biotic and abiotic
problems affecting plant at same time,
independently!
4
• Lightning strikes
• Car or lawn equipment exhaust
• Animals - moles, armadillos, urine
Abiotic: Physical Injuries
5
Abiotic: Cold Temperatures
6
Plant Pathogen Groups 3
Abiotic: Plants can be sunburned
too – not just tourists!
7
Abiotic: Excess Water
Oedema: little pimples form
on leaf; roots taking up water
faster than plant can use or
transpire
T. Broschat, UF/IFAS/FLREC
8
Abiotic: Low Soil Moisture
9
Plant Pathogen Groups 4
Abiotic: Nutrient Deficiency
Tomato: Calcium
Sunflower: Iron
Palm: Potassium
Celosia: Manganese
Citrus: Zinc
Palm: Manganese
Photos from various UF/IFAS Extension Publications10
Abiotic: Chemical Damage
Herbicide damage
Excessive iron chelete applied to soil
Herbicide damage
11
Biotic Plant Problems
Biotic plant problems or diseases
require a second organism that will
infect the plant and disrupt its
normal appearance and growth –
infectious, living
12
Plant Pathogen Groups 5
Plant Disease Triangle
Susceptible Host• Immunity or resistance is the rule for plants
• Some plant pathogens are very host
specific; others have a wide host range
Pathogen• Pathogens are not found “everywhere”
Favorable Environment• All the environmental factors surrounding
the host and pathogen may help the
pathogen infect the host and determine the
severity of disease development.13
Plant Disease Triangle
Susceptible
Host
DISEASE
PathogenFavorable
Environment
14
Plant Disease Triangle
Pathogen
Susceptible
Host
Favorable
Environment
X
Pathogen
Favorable
Environment
X
Pathogen
Favorable
Environment
XNO
Disease
NO
Disease
NO
Disease
15
Plant Pathogen Groups 6
Plant Pathogens
•Fungi
•Oomycetes
•Bacteria (including fastidious
bacteria)
•Viruses and Viroids
•Nematodes
16
Fungi and Oomycetes
• Oomycetes used to be considered a family
within the Kingdom Fungi
• Fungi now considered more closely related
to animals than Oomycetes
• Oomycetes now considered more closely
related to plants and algae
• Both fungi and Oomycetes are eukaryotes
that digest food externally and absorb
nutrients directly through their cell walls
17
• Heterotroph: obtain carbon and energy from
other organisms
• Biotroph: obtain nutrients from living host
• Saprotroph (saprophyte, saprobe): obtain
nutrients from dead host
• Nectrotroph: infect a living host, then kill host
cells to obtain nutrients
• Obligate: can only grown in association with
its host plant (can’t grow on artificial media)
Fungi and Oomycetes
Life styles:
18
Plant Pathogen Groups 7
Character Oomycota True Fungi
Sexual reproduction
Heterogametangia;
Fertilization of oospheres
by nuclei from antheridia
forming oospores.
Oospores not produced;
Sexual reproduction
results in zygospores,
ascospores or
basidiospores
Nuclear state of
vegetative myceliumDiploid Haploid or dikaryotic
Cell wall composition Beta glucans, celluloseChitin; cellulose rarely
present
Type of flagella on
zoospores, if produced
Two types; one whiplash,
directed posteriorly; the
other fibrous, ciliated,
directed anteriorly
If flagellum produced,
usually of only one type:
posterior, whiplash
Mitochondria With tubular cristae With flattened cristae
Fungi and Oomycota
From: Why are Phytophthora and other Oomycota not true Fungi? By Amy Y. Rossman and Mary E. Palm
http://www.apsnet.org/edcenter/intropp/PathogenGroups/Pages/Oomycetes.aspx
Also see: http://www.apsnet.org/edcenter/intropp/PathogenGroups/Pages/IntroOomycetes.aspx19
https://www.youtube.com/watch?v=lB4QYN7dlgc
https://www.youtube.com/watch?v=PxF8OwDtJh0&ebc=ANyPxKr-
XPjQG4MBmaGz5uf5WqgjD3b5370YlqKjvvIxp1IOGGJso3YgDPyd2RI8niluJ1hxA-ALaRk9ZdlDQk2P3tGWEQXIkw
Phytophthora:
• Zoospores emerging from sporangium
• Zoospores attracted to root exudates
and infecting the root
Oomycota
20
Oomycota
Diseases caused by Oomycetes:• Root rots of numerous plants
Pythium spp.
• Late blight of potato and tomatoPhytophthora infestans
• Downy mildew of grape and impatiensPlasmopara viticola – grapes
Plasmopara obducens – impatiens
• Sudden oak death (Ramorum blight)
killing oak species in CAPhytopthora ramorum
21
Plant Pathogen Groups 8
True Fungi
Fun Fungal Factoids:
• About 99,000 known fungal species, and we
add about 1,200 each year
• Most plant diseases (70%) are caused by fungi
• But, fewer than 10% of the known fungi cause
plant diseases
22
True Fungi
Fun Fungal Factoids:• Plant pathogenic fungi are parasites, but not all
plant parasitic fungi are pathogens!!
• Parasite obtains nutrients from a living host plant
� If causes disease with symptoms (disrupts
normal growth and appearance of plant),
parasite is a pathogen
� If simply depends on plant host for
nutrition, parasite is either a beneficial
symbiont or an endophyte
23
True Fungi
Fun Fungal Factoids:• Endophyte example:
• Neotyphodium (Ascomycota) – beneficial
for landscape grasses (heat and water
stress) but not beneficial for pasture grasses
as fungus produces alkaloids that are bad
for animals
• Beneficial symbiont examples:
• Mycorrhizae – root/fungal association
• Lichen – algal/fungal association
24
Plant Pathogen Groups 9
True Fungi
http://www.apsnet.org/edcenter/intropp/PathogenGroups/Pages
/IntroFungi.aspx
Main fungal groups (phyla):
• Ascomycota
• Basidiomycota
• Chytridiomycota
• Zygomycota
• Glomeromycota (arbuscular
mycorrhizae)
• Sixth one may be added
25
True Fungi
Four phyla with plant pathogens:
• Ascomycota – most plant pathogens
• Basidiomycota – Rusts, Smuts and Rotters
• Chytridiomycota – pathogens and vectors of
plant viruses
• Zygomycota – Mucor, Rhizopus – post-harvest
diseases of fleshy fruits and vegetables
26
Ascomycota
Fungi and Sex and Names • If a fungus is reproducing without sex, spores produced
are asexual spores = conidia, which come in all different
sizes, shapes and colors
• If fungus is reproducing with sex, spores produced are
sexual spores = ascospores
• Ascospores are produced in a saclike structure called an
ascus
• Fungi often have two Latin names – one for the asexual
stage and one for the sexual stage
• Some fungi only produce conidia; some fungi only
produce ascopsores; some fungi produce both27
Plant Pathogen Groups 10
Ascomycota: Sexual Spores
By CarmelitaLevin - Own work, CC BY-SA 4.0,
https://commons.wikimedia.org/w/index.php?curid=41198837
By CarmelitaLevin - Own work, CC BY-SA 4.0,
https://commons.wikimedia.org/w/index.php?curid=41198109
Sordaria asci and ascospores Serenomyces asci and ascospores28
By Beth Des Jardin, UF/IFAS, FLREC
By Beth Des Jardin, UF/IFAS, FLREC
Ascomycota: Asexual Spores
Lasiodiplodia
Fusarium
Exserohilum
Cylindrocladium
Pestalotiopsis
Phomopsis
29 All photos by Beth Des Jardin, UF/IFAS, FLREC
Basidiomycota(Rusts, Smuts and Wood Rotters)
• can produce up to 5 different spore types
• can complete life cycle on one host, or some
complete their life cycle on two hosts
• devastating diseases that humans have dealt with
since they started cultivating crops (wheat, etc.)
• we are still trying to manage these diseases,
primarily by breeding for resistance
https://www.youtube.com/watch?v=AeuP5IYP5HA
Life cycle of wheat stem rust
Rusts
30
Plant Pathogen Groups 11
By Boom10ful (Own work) [CC BY-SA 4.0 (http://creativecommons.org/licenses/
by-sa/4.0)], via Wikimedia Commons
By Rasbak (Own work) [GFDL (http://www.gnu.org/copyleft/fdl.html)
or CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via
Wikimedia Commons
Jim Plaskowitz, USDA/ARS, Public Domain
Tilletia indica
Karnal Bunt
basidiospore
Ustilago maydis
Corn Smut
Huitlacoche
Ustilago nuda
Loose Smut
Basidiomycota(Rusts, Smuts and Wood Rotters)
Smuts
31
Basidiomycota(Rusts, Smuts and Wood Rotters)
Wood Rotters
Ganoderma zonatum
Ganoderma Butt Rot
Armillaria tabescens
Armillaria Root Rot
32
Chytridiomycota
By USDA-APHIS-PPQ - USDA-APHIS-PPQ Agence canadienne d'inspection des aliments,
Public Domain, https://commons.wikimedia.org/w/index.php?curid=5603175
Synchytrium endobioticum
Black Wart Disease of Potato
Olpidium brassicae transmits a
virus that causes Lettuce Big Vein
• include pathogens and a vector of a plant virus
• obligate fungi
Gerald Holmes, California Polytechnic State University at San Luis Obispo, Bugwood.org
33
Plant Pathogen Groups 12
Bacteria
� Bacteria• do not cause nearly as many diseases as fungi
or viruses
• plant pathogens include both gram-positive and
gram-negative bacteria
• easily grow on artificial media
• many species are subdivided into pathovars,
indicating distinctive pathogenicity to one or
more plant hosts
http://www.apsnet.org/edcenter/intropp/PathogenGroups/Pages/Bacteria.aspx
34
Bacteria
� Fastidious Bacteria• all are vascular colonizers vectored by insects
• very difficult to grow artificially, if at all
• group without cell walls:� phytoplasma – phloem-limited; Candidatus
Phytoplasma palmae
� spiroplasma – phloem-limited; Spiroplasma
kunkelii
• group with cell walls:� phloem-limited bacteria - Candidatus Liberobacter
asiaticum (=Huanglongbing pathogen)
� xylem-limited bacteria - Xylella fastidiosa
http://www.apsnet.org/edcenter/intropp/PathogenGroups/Pages/Fastidious.aspx35
Bacteria
•Fastidious bacteria are very small
Spiroplasma
XylellaPhytoplasma
36
Plant Pathogen Groups 13
Viruses
http://www.apsnet.org/edcenter/intropp/PathogenGroups/Pages/PlantViruses.aspx
• are non-cellular; assemble themselves
• mature virus particles are dormant
• they come “alive” and reproduce only inside
infected cells – obligate parasites
• virus particles (virions) composed of:
� genome (nucleic acid) – ss+RNA,
ss-RNA, dsDNA
� protein protective shell (capsid)
� some enveloped within lipoprotein
membrane
37
Viruses
• range from 30 nm diameter (spherical viruses)
to 2 µm (filamentous viruses)
38
McGraw-Hill Concise Encyclopedia of Bioscience. S.v. "Plant viruses and viroids." Retrieved May 21 2016 from http://encyclopedia2.thefreedictionary.com/Plant+viruses+and+viroids
Viruses
• immobile – rely on other organisms to be moved
around from plant to plant
• passive transmission – mechanically, vegetative
propagation (cuttings) or seed
• active transmission requires vector
� plant-feeding arthropods, especially aphids
and whiteflies
� nematodes
� plant-parasitic fungi
39
Plant Pathogen Groups 14
Viroids• naked, infectious RNA – no protein coat
• genomes between 246-375 nucleotides
• do not produce any proteins when they
infect a plant cell
• use the host cell RNA polymerase to
reproduce their RNA and move into other
plant cells
• spread through vegetative propagation,
mechanical contamination, pollen and
seed; vectors not necessary
http://www.apsnet.org/publications/apsnetfeatures/Pages/Viroids.aspx40
Viroids• They may be small, but the diseases can still
be devastating!
• Cadang-Cadang is a viroid disease of coconut
palms that has destroyed over 30 million
palms in the Philippines
• Potato spindle tuber viroid is model pathogen
http://www.apsnet.org/edcenter/intropp/lessons/viruses/Pages/PotatoSpindleTuber.aspx41
Nematodes
http://www.apsnet.org/edcenter/intropp/PathogenGroups/Pages/IntroNematodes.aspx
• are roundworms (multicellular animals)
• most are free-living (40%) – feed on
bacteria, fungi, protozoans and other
nematodes
• but, many are parasites of animals (44%)
and plants (15%)
• need water (even if minimal)
• Caenorhabditis elegans – bacterial-
feeding nematode (not plant parasitic)
http://www.apsnet.org/EDCENTER/K-12/NEWSVIEWS/Pages/Nematodes.aspx42
Plant Pathogen Groups 15
Nematodes
• Plant Parasitic Nematodes:� have a hollow mouth spear called a stylet
� stylet connected to pharynx, which is
connected to the intestine
� stylet used to puncture plant cells, withdraw
food, and secrete protein and metabolites that
aid the nematode in parasitizing the plant
Endoparasitic
Ectoparasitic
Nematode
Human Hair
43
Which Plant
Pathogen
Are YOU?
Bacteria, Fungi, Oomycota,
Viruses, Viroids, Nematodes
4444
45
This is based on the American Society for Microbiology's
educational activity, What Microbe Are You? A full lesson
plan for the ASM activity can be found online:
www.asm.org/index.php/educators/k-12-classroom-
activities/23-education/k-12-teachers/8214-what-microbe-
are-you
Which Plant Pathogen Are You?
is a "personality quiz" aimed at
engaging audiences and creating
awareness about plant pathology.
It can also be used as an ice-
breaker or classroom activity.
Plant Pathogen Groups 16
Which Plant Pathogen Are YOU?
46
#16 I am . . .
Phytophthora capsici
Spots, rots and blights
I am a fungus-like pathogen
(oomycete) that loves my
fruits and veggies - except
lima beans.
Wet, humid conditions help
me thrive. I can cause seed
rots, seedling blights, leaf
spots, fruit rots – look at this
zucchini:
Photo: UF/IFAS, PP176
Oomycota
Electronic Data Information System (EDIS)
http://edis.ifas.ufl.edu46
Which Plant Pathogen Are YOU?
47
#16 I am . . .
Phytophthora capsici
Spots, rots and blights
I am a fungus-like pathogen
(oomycete) that loves my
fruits and veggies - except
lima beans.
Wet, humid conditions help
me thrive. I can cause seed
rots, seedling blights, leaf
spots, fruit rots – look at this
zucchini:
Photo: UF/IFAS, PP176
Oomycota
47
• 30 cards, each with a
different pathogen
• Many, but not all, have
an EDIS document that
a you can refer to for
more information
• EDIS publications are
reviewed at least every
3 years to keep the
information up to date
• Photos can be used from EDIS documents, but please
acknowledge the source.
48
Text for Plant Pathology PowerPoint “Plant Pathogen Groups”, Page 1
Text for UF/IFAS/Plant Pathology “Plant Pathogen Groups” PowerPoint
Slide Text: The text below is supplementary to what is presented on the slide itself
1 Topics that will be discussed in this powerpoint.
2 Abiotic plant problems are not caused by plant pathogens, but rather are caused by
environmental factors, either natural or man-made.
3 This is no different than with human problems. Many times what we refer to as
human diseases have no pathogen causing the “disease”. These are a few examples
of human problems that would be considered “abiotic”.
4 It is extremely important to know, especially when trying to diagnose the plant
problem, that both biotic and abiotic problems can affect the plant at the same time.
Sometimes they are interacting with each other, but at other times, they are
completely independent of each other.
5 The photos of the palm trees are examples of lightning strikes directly to the trees.
Palms are often the tallest element in the landscape, and they contain more water
than hardwood trees. This is why we believe they are often hit by lightning. Our
beloved pet dog often damages Turfgrass when they urinate. But, we still love them!
6 We love our tropical plants, like bananas, but they are not always well-adapted to our
southern temperate or sub-tropical climates in Florida. In some situations, it is not
the actual temperature that is so damaging, but the sudden, quick drop in
temperature.
7 Sunburned palm leaflets and a sunburned red pepper fruit.
8 A common problem of orchids and other fleshy-leaves plants is oedema. “Water,
water everywhere” is not usually conducive for plant growth.
9 Just as too much water can be problematic, so can too little water. Wilting plants is a
common symptom of drought, but leaf necrosis (dead tissue) is an even better
indicator of drought stress.
10 Six examples of nutrient deficiency symptoms. Some plants, such as palm trees, are
more likely to die from nutrient deficiencies than from diseases, and often the
nutrient deficiency is due to improper fertilization.
11 It is not only herbicides than can damage plants, improper use of fertilizers can cause
problems also.
Text for Plant Pathology PowerPoint “Plant Pathogen Groups”, Page 2
12 Diseases are biotic plant problems, as there is a second organism (and sometimes 2 or
3) that are infecting the plant and disrupting its normal appearance and growth.
13 A major concept in plant pathology is referred to as the Plant Disease Triangle. It has
been expanded upon, but it still helps to explain why diseases occur. The idea is that
a specific disease will not occur unless the susceptible host and the pathogen are
interacting within a favorable environment.
14 A crude drawing to illustrate the Plant Disease Triangle. The point is that only when
all 3 components of a disease overlap does disease develop.
15 This slide illustrates that if all 3 components of a disease do NOT overlap, disease does
NOT occur. We will bring in the vector component of some plant pathogens later in
the workshop. For now, we will keep it simple.
16 This is the list of plant pathogens – a wide variety of sizes and lifestyles!
17 First, we will discuss fungi and Oomycetes. As scientists learn more about an
organisms, we reclassify what kingdom it belongs to and expand the number of
kingdoms representing life.
18 Fungi and oomycetes represent many lifestyles. These are the major ones pertinent
to plant pathology.
19 This chart illustrates the differences between oomycote and the “true” fungi. If you
want to learn more about these differences, links are provided in the slide.
http://www.apsnet.org/edcenter/intropp/PathogenGroups/Pages/Oomycetes.aspx
http://www.apsnet.org/edcenter/intropp/PathogenGroups/Pages/IntroOomycetes.aspx
20 These are cool videos of zoospores, which are unique to Oomycota. The top one is 55
seconds. The bottom one is 90 seconds (cool music with this one, so have sound on if
possible).
https://www.youtube.com/watch?v=lB4QYN7dlgc (55 sec)
https://www.youtube.com/watch?v=PxF8OwDtJh0&ebc=ANyPxKr-
XPjQG4MBmaGz5uf5WqgjD3b5370YlqKjvvIxp1IOGGJso3YgDPyd2RI8niluJ1hxA-
ALaRk9ZdlDQk2P3tGWEQXIkw (90 sec)
21 These are the diseases caused by some Oomycetes.
22 Fun fungal factoids. While fungi are highly abundant on earth and are the major
cause of plant diseases, there are only a few fungi that are known to cause plant
diseases.
Text for Plant Pathology PowerPoint “Plant Pathogen Groups”, Page 3
23 More fun fungal factoids. Again, not all fungi associated with plants are pathogens.
24 Endophyte example, which like many relationships, can be good for one organism, but
bad for another. Two examples of beneficial fungal symbiosis.
25 These are the main fungal groups – not all contain plant pathogens. For example, the
arbuscular mycorrhizae of the Glomeromycota are not pathogens.
http://www.apsnet.org/edcenter/intropp/PathogenGroups/Pages/IntroFungi.aspx
26 These are the four fungal phyla that contain plant pathogens.
27 Most plant pathogens are in the Ascomycota phyla. Sex and the Fungi! It can become
very confusing when we start talking about fungal names in the Ascomycota. In the
past, we often used one name for the asexual state and an entirely different one for
the sexual state.
28 Sordaria is not a plant pathogen, but these photos are good illustrations of 8
ascospores in the ascus (bottom photo), with the asci (plural for ascus) emerging from
the ascocarp. The photos on the right illustrate ascospores within asci (top photo)
and individual ascospores of the palm fungus Serenomyces.
29 These are examples of conidia (asexual spores) of different fungal species. All
different shapes and sizes, with and without appendages. Pestalotiopsis conidia have
3 appendages at one end and a short, single one at the opposite end. Lasiodiplodia
conidia start as hyaline (colorless), single-cell structures, but as they age, they darken
and become 2-celled structures. Exserohilum produces large, cigar-shaped conidia.
Some Phomopsis species produce these boomerang-like conidia. Most Fusarium
oxysporum pathogens produce two different types of conidia – macroconidia (the
larger one) and microconidia (the smaller ones). Cylindrocladium produces a very
uniform 2-celled, hyaline spore with nice rounded ends.
30 The Basidiomycota phyla of true fungi primarily contains rust fungi, smut fungi and
fungi that rot wood. The rust fungi are very interesting. They have a multi-spore life
cycle and can have a multi-host life cycle. These are some of the most devastating
diseases worldwide and control has normally relied on breeding for resistance.
https://www.youtube.com/watch?v=AeuP5IYP5HA
31 We have already been introduced to the smuts.
32 Most, but not all, wood decay fungi that are plant pathogens are in the Basidiomycota
phylum. These are two examples of wood decay pathogens that commonly occur in
Florida.
Text for Plant Pathology PowerPoint “Plant Pathogen Groups”, Page 4
33 There are not very many Chytridiomycota fungi that are associated with plant
diseases, but all are obligate fungi (they need the plant host for survival). This is an
example of two chytrids – one which causes a disease of potato and one which
transmits (vectors) a virus that causes a disease of lettuce.
34 Bacteria cause diseases of plants, but not nearly as many diseases as fungi and
viruses.
http://www.apsnet.org/edcenter/intropp/PathogenGroups/Pages/Bacteria.aspx
35 There are a special group of bacteria, fastidious bacteria, that are especially important
in Florida. One group are called phytoplasmas, which do not have cell walls. Lethal
yellowing and Texas Phoenix Decline of palms are caused by phytoplasmas. Citrus
greening (Huanglongbing) is caused by a fastidious bacterium. All of these fastidious
bacteria are moved from plant to plant by an insect vector.
http://www.apsnet.org/edcenter/intropp/PathogenGroups/Pages/Fastidious.aspx
36 These are photos of a phytoplasma, spiroplasma and Xylella.
37 Viruses are unique and one discussion that you can have with students starts with the
question: Are viruses living organisms? What do you think?
http://www.apsnet.org/edcenter/intropp/PathogenGroups/Pages/PlantViruses.aspx
http://plantpath.ifas.ufl.edu/plant-virus-profiles/#
38 Illustration of the size difference of virus particles. The one on the left has a size bar
of 75 nm. The size bar for the photo on the right is 500 nm.
39 All viruses are spread by movement – either passive or active. Most are moved by
arthropods. Since mites are one vector, we technically can’t state “insects”.
40 An even smaller “organism” that causes plant diseases is a viroid.
http://www.apsnet.org/publications/apsnetfeatures/Pages/Viroids.aspx
41 Size is not important when causing a disease. Even viroids cause devastating diseases.
42 Nematodes are multicellular animals, but we do include them as plant pathogens.
http://www.apsnet.org/edcenter/intropp/PathogenGroups/Pages/IntroNematodes.aspx
http://www.apsnet.org/EDCENTER/K-12/NEWSVIEWS/Pages/Nematodes.aspx
43 Characteristics of plant parasitic nematodes. An endoparasitic nematode does live
within the plant cell for part of its life, whereas an ectoparasitic lives on the outside of
the plant and simply attacks from the outside. Nematodes not only attack roots, but
Text for Plant Pathology PowerPoint “Plant Pathogen Groups”, Page 5
they can occur on above ground plant parts too. Florida is ideal for nematodes as
they need water to survive.
44 Which Plant Pathogen Are YOU?
45 Now, it is time to answer that question. This personality test was developed by APS,
but adapted from the ASM personality test. There are a series of questions to answer
that will lead you to a number which corresponds to a pathogen and the disease(s)
that it causes.
www.asm.org/index.php/educators/k-12-classroom-activities/23-education/k-12-
teachers/8214-what-microbe-are-you
46 There is a “card” for each pathogen/disease. For most, but not all pathogens and
diseases, next to the credit for the photo (bottom left corner), there is a letter +
number listed. This corresponds to a publication about the pathogen/disease in the
UF/IFAS Electronic Data Information System (EDIS). When you go to the EDIS home
page (http://edis.ifas.ufl.edu , type in the letter/number in the search box.
47 There are 30 cards representing 30 pathogens/diseases. Again, most, but not all, will
have an EDIS document, which means that the disease does occur in Florida or has
the strong possibility of occurring in Florida. Others are very common or very
important diseases elsewhere in the world, but not in Florida. For example, coffee
rust is included, as some of us in our coffee every day!
EDIS publications are reviewed at least every 3 years to keep the information as
current as possible. They are written by the experts in their field of science. You are
very welcome to use the information and the photos in EDIS documents, but please
acknowledge where the information and photos are obtained.
48 Now, which plant pathogen are YOU!
The American Phytopathological Society
Which Plant Pathogen Are You?
Which Plant Pathogen Are You? is a "personality quiz" aimed at engaging audiences
and creating awareness about plant pathology. It can also be used as an ice-breaker or
classroom activity.
The activity can also be used on a deeper level to discuss the concepts of pathogen
and the environment, methods of dispersal or dissemination, and host range. It can
easily be adapted or modified for specific pathogen groups or plants - create your own
game!
This is based on the American Society for Microbiology's educational activity, What
Microbe Are You? A full lesson plan for the ASM activity can be found online:
www.asm.org/index.php/educators/k-12-classroom-activities/23-education/k-12-
teachers/8214-what-microbe-are-you
This version of the quiz is a more Florida centric version of the original APS version,
meaning many Florida plant diseases and pathogens are featured. There are a series of
questions to answer that will lead you to a number which corresponds to a pathogen
and the disease(s) that it causes.
You can provide participants with "trading cards" with the name of their particular plant
pathogen. There are 30 cards representing 30 pathogens/diseases. There is a “card”
for each pathogen or disease. For most, but not all pathogens and diseases, next to the
credit for the photo (bottom left corner), there is a letter plus number listed. This
corresponds to a publication about the pathogen/disease in the UF/IFAS Electronic
Data Information Source (EDIS). When you go to the EDIS home page
(http://edis.ifas.ufl.edu), type in the letter/number in the search box.
Again, most, but not all, will have an EDIS document, which means that the disease
does occur in Florida or has the strong possibility of occurring in Florida. Others are
very common or very important diseases elsewhere in the world, but not in Florida. For
example, coffee rust is included, as some of us in our coffee every day!
EDIS publications are reviewed at least every 3 years to keep the information as current
as possible. They are written by the experts in their field of science. You are very
welcome to use the information and the photos in EDIS documents, but please
acknowledge where the information and photos are obtained.
I would rather be . . .
I prefer to work . . .
SOLO
Which PLANT PATHOGEN
Are You?
Swimming in
the ocean
Flying a
kite
Walking
in the rain
Digging
in the dirt
My favorite activity is . . .
I’m
kinda
picky!
I am(see #7)
I’m
NOT
picky!
I am(see #8)
I am(see #9)
I am(see #10)
I am(see #11)
I am(see #12)
I’m
kinda
picky!
I’m
NOT
picky!
I’m
kinda
picky!
I’m
NOT
picky!
Flying a
kite
Walking
in the rain
Digging
in the dirt
My favorite activity is . . .
I’m
kinda
picky!
I am(see #13)
I’m
NOT
picky!
I am(see #14)
I am(see #15)
I am(see #16)
I am(see #17)
I am(see #18)
I’m
kinda
picky!
I’m
NOT
picky!
I’m
kinda
picky!
I’m
NOT
picky!
Sitting in my
favorite restaurant
Hiking in the
woods
Flying a
kite
Walking
in the rain
Digging
in the dirt
My favorite activity is . . .
I’m
kinda
picky!
I am(see #1)
I’m
NOT
picky!
I am(see #2)
I am(see #3)
I am(see #4)
I am(see #5)
I am(see #6)
I’m
kinda
picky!
I’m
NOT
picky!
I’m
kinda
picky!
I’m
NOT
picky!
I would rather be . . .
At home in
my garden
Fresh
air
The
scent of rain
Rich
soil
My favorite scent is . . .
I’m
kinda
picky!
I am(see #19)
I’m
NOT
picky!
I am(see #20)
I am(see #21)
I am(see #22)
I am(see #23)
I am(see #24)
I’m
kinda
picky!
I’m
NOT
picky!
I’m
kinda
picky!
I’m
NOT
picky!
Traveling around
the world
Fresh
air
The
scent of rain
Rich
soil
My favorite scent is . . .
I’m
kinda
picky!
I am(see #25)
I’m
NOT
picky!
I am(see #26)
I am(see #27)
I am(see #28)
I am(see #29)
I am(see #30)
I’m
kinda
picky!
I’m
NOT
picky!
I’m
kinda
picky!
I’m
NOT
picky!
I prefer to work . . .
AS PART OF A TEAM
When it comesto food . . .
When it comesto food . . .
When it comesto food . . .
When it comesto food . . .
When it comesto food . . .
When it comesto food . . .
When it comesto food . . .
When it comesto food . . .
When it comesto food . . .
When it comesto food . . .
When it comesto food . . .
When it comesto food . . .
When it comesto food . . .
When it comesto food . . .
When it comesto food . . .
START by selecting
“I prefer to work . . . ”
• Solo
• As Part of a Team
Department of Plant Pathology
EDIS = Electronic Data Information Source: http://edis.ifas.ufl.edu/
University of Florida/IFAS Extension
Below are EDIS documents referenced in the “Which Plant Pathogen Are You?” personality quiz.
• http://edis.ifas.ufl.edu/fr386: Bot Canker of Oak in Florida Caused by Diplodia corticola and
D. quercivora
• http://edis.ifas.ufl.edu/pp54: Ganoderma Butt Rot of Palms
• http://edis.ifas.ufl.edu/pp194: Citrus Canker
• http://edis.ifas.ufl.edu/pp308: Ornamental Ficus Diseases: Identification and Control in
Commercial Greenhouse Operations
• http://edis.ifas.ufl.edu/for236: Pitch Canker Disease of Pines
• http://edis.ifas.ufl.edu/enh217: Armillaria Root Rot (Also known as Mushroom Root Rot,
Shoestring Root Rot, Honey Mushroom Rot)
• http://edis.ifas.ufl.edu/: Southern Wilt of Geranium
• http://edis.ifas.ufl.edu/eny061: Susceptibility of Flowers and Bedding Plants to Root-Knot
Nematodes
• http://edis.ifas.ufl.edu/pp281: Citrus Black Spot: No Longer an Exotic Disease
• http://edis.ifas.ufl.edu/pp152: Alternaria Brown Spot (Citrus)
• http://edis.ifas.ufl.edu/pp176: Vegetable Diseases Caused by Phytophthora capsici in
Florida
• http://edis.ifas.ufl.edu/pp309: Impatiens Downy Mildew
• http://edis.ifas.ufl.edu/pp146: Lethal Yellowing of Palms
• http://edis.ifas.ufl.edu/pp121: A Series on Diseases in the Florida Vegetable Garden:
TOMATO
• http://edis.ifas.ufl.edu/hs371: Citrus Canker and Greening Handling Protocols for Master
Gardener Plant Clinics
• http://edis.ifas.ufl.edu/pp212: Tospoviruses (Family Bunyaviridae, Genus Tospovirus)
• http://edis.ifas.ufl.edu/lh079: Take-all Root Rot
• http://edis.ifas.ufl.edu/in1097: Dagger Nematode Xiphinema spp. (Cobb, 1913) Inglis, 1983
(Nematoda: Enoplea: Dorylaimia: Dorylaimina: Xiphinematinae)
• http://edis.ifas.ufl.edu/hs1136: Redbay Ambrosia Beetle-Laurel Wilt Pathogen: A Potential
Major Problem for the Florida Avocado Industry
• http://edis.ifas.ufl.edu/pp317: Rose Rosette Disease: A New Disease of Roses in Florida
• http://edis.ifas.ufl.edu/in174: Xylella Fastidiosa Diseases and Their Leafhopper Vectors
#4 I am . . .
Phytophthora
cinnamomi
Phytophthora root rot
I like hiking in the woods. I’ll
infect over 100 hosts,
including azalea,
rhododendron, eucalyptus,
avocado, pine, juniper,
hemlock, spruce, fir, cedar,
and cypress (not picky).
I like the rain – it creates the
wet soils
that I love.
#2 I am . . .
Ganoderma zonatum
Butt Rot of Palms
I’m a really bad dude and
not picky - I can kill all palm
trees in Florida!
My spores are produced in a
conk that emerges from the
trunk. The spores blow with
the wind to spread through-
out the landscape. You can’t
escape me!
Photo: Monica Elliott, UF/IFAS, PP54
#3 I am . . .
Xanthomonas citri
subsp. citri
Citrus Canker
I’m a bacterial pathogen
that causes a serious
disease of citrus. I love
warm, moist conditions!
To help prevent the spread
of me around Florida,
homeowners are required
to purchase citrus trees
from a
certified
nursery.
#5 I am . . .
Fusarium circinatum
#6 I am . . .
Armillaria mellea
Pitch canker
I am a fungus that loves to
hike in the woods. I am
kind of picky – I only infect
pine trees and Douglas-firs.
After infection, I can cause
the pine to exude a large
amount of resin – yuck!
No part of the tree is safe
from me. I will
kill seedlings
too!
Armillaria root disease,
shoestring root rot
I am a soil-borne fungus that
infects a wide host range of
trees, vines and woody
species. I cause a white rot
of wood and I produce
“honey mushrooms” at the
base of trees.
Photo: Jason Smith, UF/IFAS, ENH1217
Photo: David Norman,
UF/IFAS, PP308
#1 I am . . .
Diplodia corticola
Bot Canker of Oak
I’m kinda picky! I only like
live oaks in Florida. My
nickname is “Bot” because I
belong to the fungal family
Botryosphaeriaceae.
Windy kite-flying weather
helps me spread my
spores, but stressed trees
are more susceptible.
Photo: Jason Smith,
UF/IFAS, FOR318
Ascomycota
Ascomycota BasidiomycotaOomycota
Basidiomycota
Photo:
UF/IFAS, PP194
Photo: Jason Smith,
UF/IFAS, FOR236
#7 I am . . .
Mycosphaerella
fijiensis
#10 I am . . .
Ralstonia
solanacearum
#8 I am . . .
Lasiodiplodia
theobromae
#9 I am . . .
Hemileia vastatrix
#11 I am . . .
Heterodera spp.
#12 I am . . .
Meloidogyne spp.
Rot and Dieback
I love the tropics, but I'm not
a picky eater - I cause
rotting and dieback in
grapes, citrus, and about
500 host plants. I’ve even
been known to infect a
human toenail or two!
Black sigatoka of banana,
black leaf streak
I’m a fungus, and I’m partial to
the tropics. A nice wet, windy
day will help me spread my
spores. I’m pretty picky –
banana is my fav food -
especially
Cavendish,
the world’s
major
commercial
variety.
Coffee rust
I’m found in the tropics, or
wherever coffee is grown.
You could say I'm a picky
eater - I literally live on
coffee. I bet you do too!
Bacterial wilt of
solanaceous plants & some
ornamentals, potato brown
rot of potato and more . . .
I am a bacterial pathogen and I
can infect hundreds of plant
species (I’m not picky)! I can
be found in tropical,
sub-tropical &
some temperate
regions. Look
what I did to this
geranium!
Cyst nematode
I am a plant parasitic
nematode. Each of my
relatives (species) tend to
feed on and infect the roots
of specific plants (digging in
the dirt) – e.g., soybean cyst
nematode and soybean,
potato cyst nematode and
potato.
Root knot nematode
I am a plant parasitic
nematode, and I must admit
I cause a lot of damage to
agricultural crops world-
wide. I like digging in the
dirt . . . I've been known to
feed on the roots of nearly
2000 different plants (not
picky!)
Photo: Monica Elliott, UF/IFAS
NG005
Photo: Soybean cyst nematode and egg (USDA ARS)
Photo: Tim Momol,
UF/IFAS, PP206
Meloidogyne
incognita
Photo: USDA ARS
NG005, ENY061
Photo: Scot Nelson,
University of Hawaii
Ascomycota Ascomycota Basidiomycota
Photo: Smartse via Wikimedia Commons
#13 I am . . .
Guignardia citricarpa
#16 I am . . .
Phytophthora capsici
#14 I am . . .
Alternaria alternata
#15 I am . . .
Magnaporthe oryzae
#17 I am . . .
Plasmopara obducens
#18 I am . . .
Agrobacterium
tumefaciens
Spots, rots and blightsCitrus black spot
My disease name describes
me well. I’m an important
fungal disease of citrus, and
there’s nothing like a wet,
windy day to help me
spread my spores!
Photo: UF/IFAS, PP152
Spots, rots and blights
I am a fungus-like pathogen
(oomycete) that loves my
fruits and veggies - except
lima beans.
Wet, humid conditions help
me thrive. I can cause seed
rots, seedling blights, leaf
spots, fruit rots – look at this
zucchini:
Crown gall
I am a bacterial pathogen,
commonly found in the soil
(digging in the dirt), where I
infect the roots of many fruit
and nut trees and dozens of
other plant species (not a picky
eater!). I am nature’s genetic
engineer and can be useful in
the lab!
Impatiens Downy Mildew
I am a fungus-like pathogen
that adores pretty impatiens,
especially the young ones
you plant in your flower
beds. I cover them with my
mycelia (and then kill them)!
Photo: UF/IFAS, PP281
I’m a fungus that can infect
hundreds of plants,
including citrus and papaya.
I’m also associated with
lung infections and mold
allergies (I’m not picky!) I
can be found in the air and
my spores are spread in
kite-flying weather.
Rice blast
I’m one of the most
important and devastating
diseases worldwide. I am a
fungus that infects rice
(pretty picky eater). I thrive
under warm, wet and humid
conditions.
Photo: USDA ARS
AscomycotaAscomycota
Oomycota
Photo: UF/IFAS, PP176 Photo: Ian Maguire, UF/IFAS, PP309
Photo: Wikipedia
Ascomycota
Oomycota
Photo: David Norman, UF/IFAS, PP308
#19 I am . . .
Candidatus
Phytoplasma palmae
#22 I am . . .
Tomato spotted wilt
virus (TSWV)
#20 I am . . .
Tomato yellow leaf
curl virus (TYLCV)
#21 I am . . .
Candidatus
Liberibacter asiaticus
#23 I am . . .
Gaeumannomyces
graminis var. graminis
#24 I am . . .
Xiphinema americanum
Lethal yellowing (LY)
I like to work as part of a team:
I am a phytoplasma vectored
by a plant-hopper (insect).
I infect mainly coconut palms
(kind of picky) but have been
documented in over 35 other
palm species.
I am only found
in the Caribbean
Basin and
Florida.
Citrus Greening or
Huanglongbing
Dagger nematode
I am one of the most important
plant parasitic nematodes in
agriculture. I’m found in the
soil and I’ll eat corn and
soybean, virtually all fruits,
conifers, grasses, ornamentals
and more (not a picky eater).
I like to work as
part of a team:
I’m a vector of
Tomato ringspot
virus and other
viruses.
Take-all Root Rot
I am a soil-borne disease of
many Florida turfgrasses,
such as St. Augustinegrass
and bermudagrass. Put me
together with nematodes, and
we will party all night!
I am a bacterial pathogen
vectored by a psyllid (insect). I
only infect citrus trees. But, I
am another bad dude of the
plant pathology world – citrus
be afraid, be very afraid!
I infect over 1000 species,
including many vegetables,
peanut and tobacco (I’m not
a picky eater). I am
vectored by thrips (we work
as a team). This is what I do
to tomatoes!
Photo: Hank Dankers, UF/IFAS, PP212 Photo: UF/IFAS, LH079
Photo: UF/IFAS, PP121 Photo: UF/IFAS, HS371
Photo: Nigel Harrison,
UF/IFAS, PP146
I mostly infect tomatoes, but
have been known to infect
other veggie plants. I am
transmitted by a whitefly
species. Young, diseased
plants are severely stunted..
Often, fruit set is poor or
non-existent. No ketchup
for your French fries!
Photo: Tesfamarian Mengistu, UF/IFAS,
IN1097
#25 I am . . .
Puccinia graminis
#28 I am . . .
Xylella fastidiosa
#26 I am . . .
Raffaelea lauricola
#27 I am . . .
Rose rosette virus
#29 I am . . .
Fusarium oxysporum#30 I am . . .
Rhizoctonia solani
Laurel wilt
Laurel wilt is a fungus disease
of the laurel family – redbay,
sassafras etc., but avocados
may be my most well-known
host. I am spread by the
redbay ambrosia beetle (we
work as a team).
Rhizoctonia damping-off,
blight and rot
I am a soil-borne fungus found
around the world. I’m not a
picky eater (I have a broad
host range – turfgrass,
potatoes, cereals, sugarbeet,
cucumber, rice). I like to work
as part of a team (R. solani is
common in root rot complexes
and seedling blights).
Fusarium wilt
I am found in soils worldwide,
often part of a root rot complex
and/or assoc. with nematodes
(team player). Although I’m
diverse, formae speciales
(based on host plant) generally
have a limited host range, e.g.-
F. oxysporum f. sp. lycopersici
causes vascular wilt in tomato.
Rose Rosette Disease
I’m picky – I only like roses,
both wild and cultivated. I like
to work as part of a team – I
am spread by an eriophyid
mite Phyllocoptes fructiphilus.
I cause a wide range of
symptoms on roses. The
severity of the disease
depends on the rose species
and cultivar.
Stem rust
I am a fungal disease of wheat
and barley. Throughout
history, I have been a threat to
the world supply of wheat,
although farmers now grow
disease-resistant varieties.
Wheat and an alternate host,
barberry, help me complete my
complex life cycle (but I can
survive on wheat alone). My
windborne spores like to travel
the world.
Photo: UF/IFAS, PP200
Photo: Binoy Babu, UF/IFAS, PP317
I am thought to
be native to
Asia, now I’m
also in the
southeast US
(world traveler)
Photo: Albert Mayfield,
FDACS, HS1136
I am a bacterial pathogen and
I’m creating news headlines
around the world: Olive Quick
Decline Syndrome in Italy,
Pierce’s disease in grapes,
Citrus variegated chlorisis in
Brazil, and bacterial leaf
scorches in many trees. I am
spread by leafhoppers (we
work as a team).
Photo: UF/IFAS, IN174
Photo: USDA ARS
Basidiomycota Ascomycota Ascomycota
Ascomycota Basidiomycota
Photo: UF/IFAS,
MG442
Plant Disease General Concepts 1
University of Florida - IFAS
Plant Disease
General Concepts�Signs
�Symptoms�Etiology�Epidemiology
�Pathogenicity�Virulence
Photos used from various UF/IFAS Extension Publications or provided by UF/IFAS faculty and staff, unless otherwise stated.
1
University of Florida - IFAS
Signs vs. Symptoms
�Sign of Disease
• observation of the organism causing
the disease (objective observation)
�Symptom of Disease
• observation of how the host is
manifesting infection by pathogen
and disease development due to a
pathogen
2
University of Florida - IFAS
Signs vs. Symptoms
Ganoderma zonatum - fungus
Symptoms of Ganoderma Butt Rot
Photos from The Carter Center
Dracunculus medinensis - nematode
Symptoms of Guinea worm disease or dracunculiasis
3
Plant Disease General Concepts 2
Signs of Disease
University of Florida - IFAS 4
Bacteria oozing from leaf
Mycelia (cottony growth)
Rust spores on leaf
Rust spores on leaf
Signs of Disease
University of Florida - IFAS 5
Fungal sclerotia inside stem
Powdery mildew mycelia
Fungal mycelia and sclerotia
Fungal mycelia
Signs of Disease
University of Florida - IFAS 6
Pycnidia (fungal structures with spores) on branch
Pythium oospores on roots (microscopic view)Fungal mycelia on roots (microscopic view)
Pycnidia (fungal structures with spores) on orange skin
Plant Disease General Concepts 3
Disease
Symptoms
Plant
Organs
And
Functions
University of Florida - IFAS 7
Types of Symptoms
• spot – small, distinct lesion on leaf, fruit . . .
• blight – spots that have coalesced or merged together; more tissue being affected
University of Florida - IFAS 8
Types of Symptoms
• rot – tissue is breaking down (fruit, roots);
usually mushy, but can be dry• wilt – plant droops due to water stress; can be
systemic (xylem) or due to root rot
University of Florida - IFAS 9
Plant Disease General Concepts 4
Types of Symptoms
•canker – sunken lesions; usually on stems or
woody tissue; but can occur on fruit
University of Florida - IFAS 10
Types of Symptoms
• gall – masses of undifferentiated growth; usually
on stems or woody tissue (branches) but can be on roots
University of Florida - IFAS 11
1
S. Browning, University of Nebraska, Lincolnhttp://hortupdate.unl.edu/peach-leaf-curl
• patches, decline – terms often used in
association with grasses (turf, grain crops)
Types of Symptoms
University of Florida - IFAS 12
Plant Disease General Concepts 5
Symptoms Caused by Bacteria
• leaf spots and blights – water soaked, greasy
• soft rots of fruits
• wilts (systemic – xylem)
• cankers
• gall (overgrowths/cell proliferation)
University of Florida - IFAS 13
Symptoms Caused by Fungi/Oomycota
• leaf spots and blights (including rust and powdery mildew)
• soft or dry rots of fruits, bulbs . . .
• root rots
• wilts (systemic – xylem)
• overgrowths/cell proliferation –clubroot, galls, warts, witches’-broom
• scabs, cankers, patches and decline
University of Florida - IFAS 14
Symptoms Caused by Viruses
• dwarfing or stunting to some degree
• mosaics – light green, yellow or white
areas intermingled with green – leaves or fruits
• ring spots – chlorotic or necrotic rings –
leaves, fruits or stems
University of Florida - IFAS 15
Plant Disease General Concepts 6
Symptoms Caused by Viruses
University of Florida - IFAS
Mosaic
Ringspot
Dwarfing
16
• Pathogenicity: the pathogen either does
or does not cause a disease; a question with yes or no answer
• Virulence: relative capacity of pathogen to cause disease; range from minimal damage
to dead plant
• Etiolgy: determining the cause of disease
Plant Pathology Terms
17
Etiology and Pathogenicity Testing
1) Consistent isolation of a pathogen from
symptomatic host tissue
2) Pathogen is grown in pure culture and its
characteristics documented
3) Inoculation of a healthy plant with the pure culture of the pathogen, and inoculated plant
must then develop symptoms similar to those observed initially
4) Recovery of the same pathogen used for inoculation purposes
18University of Florida - IFAS
This is general scheme; non-culturable plant pathogens have special rules.
Plant Disease General Concepts 7
University of Florida - IFAS 19
Etiology and Pathogenicity Testing
Example: Fusarium Wilt of Queen Palm
The “potential” pathogen isolated consistently
from symptomatic tissue was Fusarium.
Isolated Three Fusarium Species
(sometimes from the same tissue piece)
1) F. incarnatum-equiseti species complex (6 isolates)
isolated from Fusarium wilt symptomatic palms in Australia
2) F. oxysporum (43 isolates)
known Fusarium wilt pathogen of palms worldwide
3) F. proliferatum (9 isolates)
known pathogen of palms; can cause wilt symptoms
Etiology and Pathogenicity Testing
Example: Fusarium Wilt of Queen Palm
20
Control F. oxysporum
F. incarnatum-equiseti F. proliferatum
21University of Florida - IFAS
Plant Disease General Concepts 8
• Epidemiology: study of the factors
influencing the initiation, development and spread of infectious disease
Plant Pathology Terms
22
But, how do pathogens enter
the plant?
•Viruses and Viroids and Fastidious Bacteria
most require vectors; a few mechanical entry
•Bacteria – most enter through natural
openings or wounds
•Fungi & Oomycetes – enter through natural
openings, wounds; by mechanical pressure
or enzymes they produce; a few by vectors
•Nematodes – stylets used to gain entry
How do pathogens enter plant?
University of Florida - IFAS 23
Stoma
(plural=stomata)Plant Epidermis
How do pathogens enter plant?
24
Plant Epidermis
Stoma
(plural=stomata)
Plants have natural openings:
stoma or stomata (plural)
Plant Disease General Concepts 9
Leafhopper
(insect vector)Use mouth parts to
penetrate
How do pathogens enter plant?
25
Bacteria
on water film,
enter
through stoma
How do pathogens enter plant?
26
Leafhopper
(insect vector)Use mouth parts to
penetrate
Fungal Spore
entering through stoma
How do pathogens enter plant?
27
Leafhopper
(insect vector)Use mouth parts to
penetrate
Bacteria
on water film,
enter
through stoma
Plant Disease General Concepts 10
Appressorium
fungal structure from spore for direct
penetration
Fungal Spore
entering through stoma
How do pathogens enter plant?
28
Leafhopper
(insect vector)Use mouth parts to
penetrate
Bacteria
on water film,
enter
through stoma
Appressorium
fungal structure from spore for direct
penetration
Fungal Hyphae
can grow between cells or penetrate cells
How do pathogens enter plant?
Fungal Spore
entering directly through stoma
29
Leafhopper
(insect vector)Use mouth parts to
penetrate
Bacteria
on water film,
enter
through stoma
Disease Development
• pathogen comes in contact with plant
• pathogen infects plant – penetration, can be
direct or indirect; with or without vector
• incubation period – time between penetration
and first appearance of symptoms
• pathogen increases within plant, uses host to
grow and reproduce
• symptoms observed continue to increase
30
Plant Disease General Concepts 11
Susceptible
Host
DISEASE
Pathogen
Favorable
Environment
31
Disease DevelopmentEnvironmental conditions influence each and
every step in disease development process!!
Susceptible
Host
DISEASE
PathogenFavorable
Environment
Vector required for
some pathogens!
University of Florida - IFAS
Nematode FungusW. Deacon, Univ. of Edinburgh
Insect
32
MiteUSDA/ARS
Disease Development
How do plant pathogens move
from plant to plant if they are not moved by a vector?
University of Florida - IFAS
• Wind dispersal of spores
• Splash dispersal of spores – rain, irrigation• Physical movement of soil-borne pathogens
that don’t produce spores – ex: soil tillage
• Nematodes swim or move with soil• Seed associated – internal or external• Plant associated – cuttings, grafting
33
Plant Disease General Concepts 12
How do plant pathogens move
from plant to plant if they are not moved by a vector?
University of Florida - IFAS
Time to have some fun!
Cheap, easy way to demonstratespore dispersal without
water or spores!
34
Splash Dispersal of Spores
University of Florida - IFAS 35
Text for Plant Pathology PowerPoint “Plant Disease General Concepts”, Page 1
Text for UF/IFAS/Plant Pathology “Plant Disease General Concepts” PowerPoint
Slide Text: The text below is supplementary to what is presented on the slide itself
1 These are topics we will briefly discuss and illustrate.
2 This explains the difference between sign of a disease and symptom of a disease.
3 There are not very many good examples of signs vs. symptoms of human diseases, but
this is one: Guinea worm disease or dracunculiasis. The Guinea worm is a nematode.
People with Guinea worm disease have no symptoms for about 1 year. Then, the
person begins to feel ill, with slight fever, itchy rash, nausea, vomiting, diarrhea,
dizziness (symptoms). Eventually, a blister (symptom) develops as shown in the top
photo. This blister gets bigger over several days and causes a burning pain. When the
person puts this affected body part in cool water to ease the symptoms, it is thought
that the nematode (sign of the disease) detects the temperature change and bursts
from the blister to release hundreds of thousands of larvae into the water. Once the
nematode bursts from the blister, health workers try to very carefully remove the
nematode (bottom photo).
Ganoderma butt rot disease of palms is a plant disease example of symptoms vs.
signs. This fungal pathogen infects the trunk tissue of the palm below ground level,
and slowly decays certain tissues within the trunk. As the wood decay increases
internally, symptoms of the disease are expressed by the plant: lower leaves die
prematurely and remaining leaves start to wilt. After the palm is near death, the
fungus begins to emerge from the trunk to eventually form a hard, shelf-like structure
called a basidiocarp. This structure produces fungal spores that are released into the
environment.
4 Examples of signs of a disease – i.e., the observable physical presence of the
pathogen.
5 More examples of signs of a disease.
6 More examples of signs of a disease. The top two photos can be viewed without a
microscope, although a hand lens would be useful. The bottom two photos are
viewed under the microscope.
7 Cartoon of plant organs on left with disease symptom names on right. Common
disease names are usually a combination of plant organ affected plus the most
obvious symptom.
8 Examples of symptom types. This is explanation of spot vs. blight.
Text for Plant Pathology PowerPoint “Plant Disease General Concepts”, Page 2
9 While we often think of “rot” as being mushy and smelly, that is not always the case.
Xylem is the water conducting tissue within the plant. When a pathogen affects the
xylem, usually by blocking or destroying the tissue, the plant is deprived of water,
which results in a wilt. However, any time the roots are affected (usually a decay or
rot), a wilt will also be the symptom expressed as the roots are the plant organs that
take up water from the soil or potting medium.
10 Canker is another symptom type: citrus canker on the left
11 Galls can be caused by insects, but galls can also be caused by fungi (peach leaf curl –
Taphrina on the left) and one particular bacterial pathogen, Agrobacterium
tumefaciens (right).
12 With turfgrass and grain crops, the terms “patch” and “decline” are used to indicate
that large areas in the landscape or field are being affected by the same pathogen.
13 This is a list of symptoms associated with bacterial diseases of plants. The photo
illustrates the “water soaked” or “greasy” symptom.
14 List of symptoms associated with fungal diseases of plants.
15 Plants infected with viruses exhibit symptoms that are not usually expressed when
the plants are infected with other plant pathogens. Dwarfing and stunting can be
caused by most pathogens, but are often associated with viruses. The next slide
illustrates these symptoms.
16 Example of dwarfing (compared to control), ringspot and mosaic symptoms.
17 Pathogenicity vs. virulence; etiology definition
18 Etiology and pathogenicity testing usually go together. These are the four steps
required to prove a culturable organism (nematode, bacterium or fungus) is causing
the disease symptoms observed. This looks easier than it actually is, because we
don’t always know the environmental factors associated with disease development.
19 This is an example of how we determined what fungus was causing queen palms to
die throughout most of Florida. This was a new disease. The typical symptom is
shown in the photo second from the left. When we cut through the rachis (leaf stem),
we can observe the discolored tissue. After surface disinfecting the tissue very well,
this discolored tissue was placed on agar plates to determine what would grow out of
Text for Plant Pathology PowerPoint “Plant Disease General Concepts”, Page 3
the tissue. We consistently isolated species of Fusarium. This is still the “potential”
pathogen as we need to complete the pathogenicity studies.
20 In this example, the predominant fungus isolated (43 isolates) was Fusarium
oxysporum. But, two other Fusarium species could also be isolated, sometime from
the same tissue. Because we knew that these two other Fusarium species could also
cause disease of palms, we had to test all three Fusarium species for pathogenicity.
21 This slide illustrates that only Fusarium oxysporum could kill queen palms. Therefore,
we could now state that Fusarium oxysporum was the pathogen, and the other two
Fusarium species were not.
22 Definition of epidemiology – this is no different from human or animal epidemiology
of infectious diseases. But, perhaps the first question you probably want to know is
how do pathogens enter the plant in the first place? Obviously, plants are different
from humans and animals.
23 Examples of plant entry for the four major groups of pathogens.
24 This is a cartoon of a leaf surface and cross-section. It is important to note that plants
have a structure called a stoma (plural-stomata). The stoma (sometimes called a
stomate) is a tiny opening or pore that is used for gas exchange. Air enters the plant
through these openings. The carbon dioxide from the air is used in photosynthesis.
25 Insect vectors such as a leafhopper uses its mouthparts to penetrate into the leaf
epidermis. If this was a root, we would observed a nematode stylet penetrating into a
root.
26 Bacteria need either natural openings, such as stomata, or wounds to enter into the
plant tissue. Here the bacterial cells are in a film of water and will enter via a stoma.
27 Fungi have multiple ways of entering plant tissue. An easy way is to enter via a stoma.
Unlike bacteria, a fungal spore is usually too large to enter directly. Usually, the
fungal spore will germinate to produce a fungal thread (hyphae), which will then
enter the tissue via the stoma.
28 Other fungi produce enzymes that degrade the tissue and allow for the fungus to
enter the tissue. Others, as shown here, produce a special structure called an
appressorium, and then penetrates directly into the tissue using turgor pressure.
Think of it as a mini-jackhammer!
29 Once the fungus has penetrated into the tissue, the hyphae can grow between plant
cells or penetrate into plant cells.
Text for Plant Pathology PowerPoint “Plant Disease General Concepts”, Page 4
30 Disease development steps are stated on this slide.
31 Remember the disease triangle. It takes more than just a susceptible host and
virulent pathogen – environment is critical also. Environment influences every step in
the disease development process.
32 If the pathogen requires a vector for pathogen entry into the plant, vectors are
influenced by the environment also.
33 How do plant pathogens move from plant to plant if they are not moved by a vector?
This slide states the more common methods.
34 We will now demonstrate a cheap, easy way to demonstrate spore dispersal without
water or spores!
35 Photos of the demonstration.
Spore Movement Demonstration, Page 1
Demonstration of Plant Pathogen Dispersal Without Using Live Plants or Pathogens
APS Office of Public Relations and Outreach
Just like humans, plants are susceptible to diseases caused by microorganisms, including (from
smallest to largest in size) viroids, viruses, phytoplasmas, bacteria and fungi. Students are
repeatedly told to cough into their arm or tissue to prevent spread of human diseases such as flu
and colds, but they are seldom told how plant diseases are spread. This demonstration illustrates
one method of plant disease spread, water splashing of fungal spores or bacterial cells. Living
plants and pathogens are not required, and neither is water. Instead, coffee grounds are
substituted for spores or cells and polymer balls are used for water drops. Pathogen spread is the
result of velocity (magnitude and direction) of each polymer ball at the point of impact and the
amount of coffee grounds (spores or cells) it hits.
It is suggested that prior to the demonstration, a color illustration of a leaf spot or fruit spot
disease cycle is shown, along with fungal spore photographs. To enhance the demonstration, it is
useful to have a plant, plant part (e.g., large leaf) or fruit exhibiting leaf or fruit spot symptoms,
along with a healthy counterpart. If that is not possible, silk plants and artificial fruits can be
used. “Spots” are added to these substitutes using glitter glue.
For the demonstration, the following items are needed:
• Clear plastic storage container (~66 qt.; 13 in. high x 24 in. long x 16 in. wide)
• Round container, without lid (~6 in. high, 6 in. diam.; e.g., empty 34 oz. coffee container)
• Color leaf prints
• Embroidery hoop or very large rubber band
• Coffee grounds
• Orbeez (http://orbeezone.com)
• Colander
• Plastic bowl (>2 cup size)
• Measuring spoons
• Paper towels
• Laminated illustration of leaf spot or fruit spot disease cycle
Orbeez are superabsorbent polymer balls that are initially the size of a pin head, but expand with
addition of water (maximum 14-mm diam.) and will be used to simulate rain drops in this
exercise. Final size depends on how long the Orbeez are left soaking in water. According to the
Orbeez™ website, 3/4 cup of Orbeez are obtained from one package (150 per package), after the
addition of 1 1/2 cups water and allowing expansion for at least 3 hr. After soaking to plump the
Orbeez, drain in colander and place in bowl.
Spore Movement Demonstration, Page 2
The color leaf print is placed on top of the empty round container (without lid) and held in place
with an embroidery hoop or rubber band (Fig. 1). The paper needs to be relatively tightly fitted
on the round container to allow the Orbeez to bounce and successfully simulate rain splash. The
container with leaf print is then placed inside the clear plastic storage container (Fig. 1A). This
larger container serves as containment for the bouncing Orbeez and can be the storage and
transport container for demonstration supplies. About 1 tsp. of coffee grounds is placed on the
color print, while explaining that the coffee illustrates a “leaf spot” that is producing spores (Fig.
1B). About 1 tbsp. of Orbeez (rain drops) are then dropped onto the coffee (spores), from at
least 6 in. above the coffee. The coffee (spores) spreads from the initial “leaf spot” to other
portions of the paper leaf (Fig. 1C).
Clean-up and care:
The paper leaf print will eventually become soggy and need to be replaced. We suggest having
multiple copies on hand. Also, the Orbeez will become coated in coffee after several
simulations, but they are reusable. They can be washed, dried and then stored in a container for
future use. They can also be thrown in the trash, or incorporated into soil. Do not wash them
down the drain.
Suggested question to enhance active learning:
“How can you prevent plant diseases that are spread by water splashing?” Answers include:
• No overhead irrigation (use drip lines)
• Place plants indoors or in greenhouses to prevent spread by natural rainfall
• Buy healthy plants, so the disease is not introduced (exclusion)
• Remove diseased plants or plant parts as soon as spot symptoms are observed
• Use plant cultivars/varieties that have been bred for disease resistance
Other questions that can be posed include:
• What are other methods of disease spread? Examples: wind, humans, insects. Blowing
glitter onto felt or a sticky surface is useful for demonstrating wind-blown spores.
• What is a fungus and fungal spore? Giant Microbes (http://giantmicrobes.com) sells plush
dolls (two sizes) of Penicillium chrysogenum and a plush toy that is a petri dish with
spores of this fungus.
• What is a bacterium and bacterial cell?
• What is a plant disease? And, how is it different from a disorder, such a nutrient
deficiency?
Spore Movement Demonstration, Page 3
Plant Disease Management 1
University of Florida - IFAS
Plant Disease Management
Uses an Integrated Approach•Exclusion
•Plant resistance
•Cultural controls•Chemicals
•Microbiologicals
1
University of Florida - IFAS
Integrated Plant Disease Management
Exclusion• Regulation of plant material at ports, city,
county, state or country boundaries – federal and state rules
• Pathogen-free seed or plants
• Seed certification• Meristem culture
• Cuttings from clean “mother” plant
under sterile conditions
2
http://www.dontpackapest.com
Don’t Pack a Pest
https://www.youtube.com/watch?feature=player_embedded&v=x0S99cwnDqM
University of Florida - IFAS
Integrated Plant Disease Management
Exclusion
3
Plant Disease Management 2
University of Florida - IFAS
Integrated Plant Disease Management
ExclusionWhere did all the impatiens go?
https://edis.ifas.ufl.edu/pp309
Downy Mildew caused by Plasmopara obducens on Impatiens walleriana
4
University of Florida - IFAS
Integrated Plant Disease Management
Plant Resistance �Genetic• Immunity is the rule in the plant kingdom• If immunity does not exist, plant breeders develop
cultivars with resistance to specific pathogens• Constitutive and inducible defenses
�Chemically or Biologically Induced• Application of chemicals or biologicals to induce
production of defense compounds
�Adaptation• Plant adaptation to site
5
University of Florida - IFAS
Integrated Plant Disease Management
Plant Resistance
• Graft susceptible top onto resistant root stock •http://content.ces.ncsu.edu/grafting-for-disease-resistance-in-heirloom-tomatoes
•http://edis.ifas.ufl.edu/ep339: For Florida, roses grafted on 'Fortuniana' rootstock thrive
Genetic
6
Plant Disease Management 3
University of Florida - IFAS
Integrated Plant Disease Management
Plant Resistance
http://www.apsnet.org/edcenter/intropp/topics/Pages/OverviewOfPlantDiseases.aspx
• Constitutive: continuous defenses; includes
cell walls, waxy epidermal cuticles, bark, leaf hairs – physical and chemical barriers
• Inducible: defenses (chemicals or proteins)
produced in response to invading pathogens;
includes toxic chemicals, pathogen-degrading enzymes, deliberate plant cell suicide
Genetic
7
University of Florida - IFAS
Integrated Plant Disease Management
Plant Resistance
� Systemic Acquired Resistance (SAR)
• Activated when pathogen infects tissue
• Long-lasting systemic immunity, even in
tissues not infected
• Relatively broad spectrum
• Usually associated with increase in
phytohormone salicylic acid (SA)
Genetic
8
University of Florida - IFAS
Integrated Plant Disease Management
Plant Resistance Chemically Induced
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4306307/pdf/fpls-05-00804.pdf
Systemic Acquired Resistance (SAR)
• Use of SA or SA analogs can induce SAR-like responses
• Provides resistance in plant tissues
beyond application site (systemic)• Often referred to as “plant activators”• Benzothiadiazoles (ex: Actigard) used
for plant protection
9
Plant Disease Management 4
University of Florida - IFAS
Integrated Plant Disease Management
Plant Resistance
Biologically Induced� Systemic Acquired Resistance SAR)
• Weak viruses � Induced Systemic Resistance (ISR)• Triggered by non-pathogenic plant growth
promoting rhizobacteria• Involves jasmonic acid and ethylene, rather
than salicylic acid
doi: 10.1128/AEM.71.9.4951-4959. Appl. Environ. Microbiol. Sept. 2005 vol. 71, no. 9, pp. 4951-4959
doi: 10.1105/tpc.113.111658. Plant Cell May 2013 vol. 25, no. 5, pp. 1489–1505
10
University of Florida - IFAS
Integrated Plant Disease Management
Plant Resistance
Adaptation
“Right Plant for the Right Site”
• temperate vs. tropical; cold induction
• dry vs. rainy• soil type: sand vs. clay
• day length
• others?• Genetic resistance can be overcome if
site is not right for the plant species11
University of Florida - IFAS
Integrated Plant Disease Management
Cultural Controls• Crop rotation
• Alternate host eradication – for pathogens and vectors
• Sanitation of tools, equipment, potting
containers, shoes, etc.• Improved plant environment, especially water
management, air circulation
• Nutrient management• Soil treatment, such as solarization, tillage• Mulches or other barriers
12
Plant Disease Management 5
University of Florida - IFAS
Integrated Plant Disease Management
Chemical ControlsFungicides Bactericides Nematicides
Insecticides Fumigants
• Seed treatments
• Soil treatments• Root drenches
• Disinfecting tools
• Foliar sprays
• Trunk injections• Trunk sprays
• Post-harvest use
�For fungicides and bactericides, the “cides” is not
accurate. Most suppress rather than kill.�There are no chemicals to use against plant viruses.
13
University of Florida - IFAS
Integrated Plant Disease Management
Chemical Controls
From: http://www.apsnet.org/publications/apsnetfeatures/Pages/Fungicides.aspx
Also see: http://www.apsnet.org/edcenter/intropp/topics/Pages/Fungicides.aspx
Figure 1. U.S. Crop Protection Fungicide Use
14
University of Florida - IFAS
Year Fungicide Primary Use
1637 Brine (Salt) Cereal seed treatment
1755 Arsenic Cereal seed treatment
1760 Copper sulfate Cereal seed treatment
1824 Sulfur (dust) Powdery mildew and other pathogens
1833 Lime sulfur Broad spectrum foliar pathogens
1885 Bordeaux mixture Broad spectrum foliar pathogens
1891 Mercury chloride Turf fungicide
1900 CuOCl2 Especially Phytophthora infestans
1914 Phenylmercury chloride Cereal seed treatment
1932 Cu2O Seed and broad spectrum foliar diseases
1934 Dithiocarbamates patented Broad spectrum protectants
1940 Chloranil, Dichlone Broad spectrum seed treatment
Integrated Plant Disease Management
Chemical Controls
(IN)Organic Fungicides: https://www.extension.purdue.edu/extmedia/bp/bp-69-w.pdf
15
From: http://www.apsnet.org/publications/apsnetfeatures/Pages/Fungicides.aspx
Organic Materials Review Institute: http://www.omri.org/
Plant Disease Management 6
University of Florida - IFAS
Integrated Plant Disease Management
Chemical Controls
FRAC Code Chemical Class Mode of action / inhibition
Resistance risk
1 Benzimidazoles Beta-tubulin assembly in mitosis (cytoskeleton and motor proteins) high
2 Dicarboximides MAP/Histidine-kinase in osmotic signal transduction medium-high
3 Azoles, Pyrimidines C-14 demethylation in sterol biosynthesis in membranes medium
4 Phenylamides RNA polymerase I (nucleic acid synthesis) high
5 Morpholines ^8 and ^7 isomerase and ^14 reductase in sterol biosynthesis low-medium
7 Carboxamides Succinic acid oxidation (respiration) medium
9 Anilinopyrimidine Methionine biosynthesis (amino acid and protein synthesis) medium
11 Strobilurins Mitochondrial synthesis in cytochrome bc1 (respiration) high
16 Various chemistry Melanin biosynthesis (two sites) in cell wall medium
40 Carboxylic acid amides Cellulose synthase (cell wall formation in Oomycetes) low-medium
M1 Inorganics Multisite contact low
M3 Dithiocarbamates Multisite contact low
M5 Phthalimides Multisite contact low
Mode of action of some major fungicides classes, their FRAC code and resistance risk
Fungicide Resistance Action Committee: http://www.frac.info; http://edis.ifas.ufl.edu/pi131
16
University of Florida - IFAS
Integrated Plant Disease Management
Chemical Controls
From:
17
University of Florida - IFAS
Integrated Plant Disease Management
Microbiological Controls
� Fungi: Trichoderma, Candida, Muscodor, Pythium, Ulocladium,
Verticillium
� Bacteria: Bacillus group, Streptomyces, Xanthomonas,
Pseudomonas, Pantoea, Pasteuria, Agrobacterium, Paecilomyces, Burkholdaria
https://www.epa.gov/pesticides/biopesticides
http://www.apsnet.org/edcenter/advanced/topics/Pages/BiologicalControl.aspx
18
Plant Disease Management 7
University of Florida - IFAS
Integrated Plant Disease Management
Microbiological Controls
� Effective because they produce:• Antibiotics• Lytic enzymes• Biocidal volatiles
� Effective because they outcompete the
pathogens
• Detoxification enzymes• Iron-chelating siderophores
19
University of Florida - IFAS
Integrated Plant Disease Management
Microbiological Controls
Bacillus subtilis strains:•QST 713•MBI 600•GB03•FZB24
Registered by EPA as biopesticide
20
University of Florida - IFAS
Plant Disease Management
Uses an Integrated Approach•Exclusion
•Plant resistance
•Cultural controls•Chemicals
•Microbiologicals
21
Plant Disease Management 8
University of Florida - IFAS 22
Is there a place for
GMOs in our integrated
plant disease
management tool box?
Integrated Plant Disease Management
GMOs
University of Florida - IFAS
Some diseases cannot be
controlled with any currently
available methods!
23
Integrated Plant Disease Management
GMOs
Florida Example:
Bacterial Spot Disease of TomatoesThe Good, the Bad, and the Ugly: What the Future Could Hold for Bs2 Tomatoes
http://edis.ifas.ufl.edu/hs1259
Text for Plant Pathology PowerPoint “Plant Disease Management”, Page 1
Text for UF/IFAS/Plant Pathology “Plant Disease Management” PowerPoint
Slide Text: The text below is supplementary to what is presented on the slide itself
1 Plant disease management uses an integrated approach.
2 One tool we use is to exclude the pathogen from the site where the susceptible plants
might be grown. This requires establishing regulations at county, state and federal
level. This is also accomplished by producing pathogen-free seed or plants, which is
also regulated, either by rules or by self-regulation within a company or nursery.
3 Here is our cute little beagle again! He is cute, but he has a very serious job to do.
4 If you recall, we have already spoken about a number of tree diseases that now occur
because either the pathogen or the vector or both were brought from other countries
into the U.S. Sometimes diseases re-emerge. One example is Downy mildew of
impatiens used as bedding plants. While the fungus Plasmopara obducens had been
documented in the U.S. since the late 1800s, it had not been a problem of impatiens.
Then there was an outbreak of this disease in the United Kingdom in 2003, followed
by outbreaks in the U.S. the following year. South Florida landscapes with impatiens
were virtually wiped out in 2012. One way being used by nurseries to manage this
disease is to start their material from seed, rather than buying seedlings, which could
already be infected.
https://edis.ifas.ufl.edu/pp309
5 Plant resistance is another way to manage diseases. Most plants are tolerant of plant
pathogens, so we consider immunity to be the rule in the plant kingdom. There are
three ways to develop plant resistance to specific plant pathogens: genetic
resistance, chemically or biologically induced resistance and adaptation to the
growing site.
6 Traditional breeding has been the backbone of genetic resistance, but we also have
learned that for certain diseases, we can graft susceptible tops onto resistant root
stock. This is being done for heirloom tomatoes and, in Florida, for roses. One of the
main reason heirloom tomatoes fell out of favor is because they were so susceptible
to certain plant pathogens. Grafting provides a compromise.
http://content.ces.ncsu.edu/grafting-for-disease-resistance-in-heirloom-tomatoes
http://edis.ifas.ufl.edu/ep339
7 Genetic resistance can be viewed as defenses provided by the plant, either physical or
chemical defenses. Constitutive defenses are usually physical in nature. Inducible
defenses are usually chemical in nature (specific chemicals or proteins) produced by
plant in response to the plant being invaded by the plant pathogen.
Text for Plant Pathology PowerPoint “Plant Disease Management”, Page 2
http://www.apsnet.org/edcenter/intropp/topics/Pages/OverviewOfPlantDiseases.aspx
8 Systemic Acquired Resistance (SAR) is a relatively broad spectrum defense that is
activated when the pathogen infects the tissue and creates a long-lasting systemic
immunity. The phytohormone salicylic acid (SA) is viewed as the primary plant
defense chemical.
9 SAR-like response can be induced artificially (exogenous chemicals) using salicylic acid
or salicylic acid analogs. These are often referred to as “plant activators”. Actigard is
an example of a product in the trade.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4306307/pdf/fpls-05-00804.pdf
10 Plant resistance can also be induced biologically. SAR can be induced by weak viruses.
Plants are inoculated with a viral strain that is minimally virulent, but which is
recognized by the plant as an “invasion”. SAR is induced. When the plant is attacked
by a virulent strain, SAR is already induced and the plant is “prepared” to defend itself
against this new invader. Induced systemic resistance is triggered by a special group
of bacteria that induce jasmonic acid and ethylene for protection against pathogens,
rather than salicylic acid.
11 Adaptation of a plant is resistance but from a very different viewpoint. If the plant is
grown in a location/environment that is ideal for its growth, it is less likely to be
affected by plant pathogens because it is being grown under optimum conditions.
12 Cultural controls are actions that we (humans) can do to reduce the possibility of
plant infection by a pathogen, reduce development of disease (both on an individual
plant or entire nursery or field) or reduce spread of the pathogen. These are just a
few examples.
13 We also use chemical controls to prevent or reduce disease development and spread
of the pathogen or vector. These are examples of how these chemicals might be used
for plant protection. Note that there are no chemicals to use for plant viruses – i.e.,
there are no plant viricides. Chemical management of viral diseases usually relies on
managing the vector, for example, using an insecticide if the vector is an insect.
14 Since fungi cause the majority of diseases, fungicides are one of the primary chemicals
used in disease control. This figure illustrates that amount (pounds) of fungicides
actually used in the U.S. has decreased over time.
http://www.apsnet.org/publications/apsnetfeatures/Pages/Fungicides.aspx
http://www.apsnet.org/edcenter/intropp/topics/Pages/Fungicides.aspx
15 Chemical control of diseases is not new! The chemicals shown in orange are still used
today. These are inorganic chemicals (contain no carbon), but they are considered
Text for Plant Pathology PowerPoint “Plant Disease Management”, Page 3
“organic” fungicides because they are not synthetic chemicals per se. Organic
fungicides may or may not be permissible to use in certified organic food production
and processing. Organic Materials Review Institute is a non-profit organization “that
provides an independent review of products, such as fertilizers, pest controls,
livestock health care products, and numerous other inputs that are intended for use
in certified organic production and processing.”
https://www.extension.purdue.edu/extmedia/bp/bp-69-w.pdf
http://www.omri.org/
16 Fungicides have shifted over the years from products that are have multiple sites of
action to those with more targeted sites of action. This makes them safer to use
around humans. However, this also makes it easier, in some cases, for pathogens to
develop resistance to these fungicides. The Fungicide Resistance Action Committee
(FRAC) is an international group that monitors fungicide use and resistance
development.
http://www.frac.info
http://edis.ifas.ufl.edu/pi131
17 This figure illustrates which fungicides were being used the most in 2008 on 21
selected crops. Note that copper fungicides are still major products for plant
protection.
18 Plant pathologists have learned how to use microbes, primarily bacteria and fungi, to
help manage plant diseases. Many of these microbes have been developed into
biopesticides that are commercially available.
http://www.apsnet.org/edcenter/advanced/topics/Pages/BiologicalControl.aspx
https://www.epa.gov/pesticides/biopesticides
19 These are the reasons for the effectiveness of these biopesticides. Some produce
chemicals that inhibit the plant pathogen, but some simply are able to outcompete
the pathogen in a particular niche.
20 This is an example of a commercially available product.
21 Integrated disease management – using all the tools in our tool box to prevent and
manage diseases.
22 Is there a place for genetically modified organisms (GMOs) in plant disease
management?
23 It must be acknowledged that some diseases cannot be controlled with any available
methods, or cannot be controlled quickly enough when they strike for a producer to
save the crop economically. This is where GMOs may be most useful. One example is
Text for Plant Pathology PowerPoint “Plant Disease Management”, Page 4
bacterial spot of tomatoes caused by Xanthomonas species, which is currently
managed using copper fungicides and other chemicals.
Bacterial spot is a disease that affects both peppers and tomatoes. Genes (Bs2 is one
example) have been identified in pepper for resistance to this pathogen, and have
been successfully used by developing resistant pepper varieties via conventional
breeding. Unfortunately, finding similar resistance in tomatoes has not been
successful. But, if the Bs2 gene from pepper is introduced into tomatoes, the
transgenic tomatoes are resistant to bacterial spot. These tomatoes are NOT being
grown commercially! Two hurdles before they will be grown commercially – the
transgenic tomato must be de-regulated, and the public must accept transgenic
tomatoes before a tomato grower will produce them.
http://edis.ifas.ufl.edu/hs1259
$10 Smartphone to digital microscope
conversion! by Yoshinok
• Build a rudimentary stand for about $10 that
will transform your smartphone into a digital
microscope.
• Video (5 minute) to explain the process:
• Detailed instructions at “instructables.com”http://www.instructables.com/id/10-Smartphone-to-digital-microscope-conversion/
https://www.youtube.com/watch?v=KpMTkr_aiYU
1
Finished Product with Smartphone
2
� Materials required:
• 3x 4 ½” x 5/16” carriage bolts
• 9x 5/16” nuts
• 3x 5/16” wing nuts
• 5x 5/16” washers
• ¾” x 7” x 7” plywood -- for the base
• ⅛” x 7” x 7” plexiglass -- for the camera stage
• ⅛” x 3” x 7” plexiglass -- for the specimen stage
• Scrap plexiglass (~ 2"x 4") for specimen slide (optional but useful)
• Laser pointer focus lens (use two for increased magnification)
• LED click light (necessary only for viewing backlit specimens)
� Tools: Drill, Assorted drill bits, Ruler, Sharpie, Fine-nosed pliers
Materials and Tools
3
4
5
• Laser pointers:
http://www.dollartree.com/household/electronics/2-in-1-
Laser-Pointer-Key-
Chains/500c548c548p338654/index.pro?method=search
• Lights: http://www.dollartree.com/Xtreme-Values-New-
Arrivals/new-arrivals/Plastic-Flower-Shaped-LED-Push-
lights/1155c653c653p360749/index.pro?method=search
• Lenses: If you don't have a laser, these lenses have produced
comparable
results: http://www.aixiz.com/store/product_info.php/cPath/
46/products_id/374/osCsid/37cabc139b4f03b0e0a522178def
ae7e
Where to find some of the components
6
Disassembling the Laser Pointer
to Obtain the Lens
1 2
3 4
7
Disassembling the Laser Pointer
6
5
7
8
Laser Pointer Disassembled
Lens – don’t lose it!
9
LENS
10
11
One and Four Dollar Microscopes 1
+
Smartphone Microscope
By: Eric Zunica
NEM 3002 – Principles of Nematology
Entomology and Nematology Department
+Introduction –
� How to build a $1 dollar laser microscope
� How to build a $4 dollar smartphone microscope
� Comparison of 3 slide images with 3 different smart phones
� Discussion concerning why this simple technology would be
useful in the classroom.
� Microscope conclusion
+Building a $1 dollar microscope
� Open the paper clip.
� Use pliers to make a circle at
the end of the paper clip.
� Use rubber band to hold the
paper clip in place.
� Position the paper clip so that
the red laser shines through
the hole at the end of the
paper clip.
� Use a white wall to project
images.
A B
C D
E F
One and Four Dollar Microscopes 2
+Building a $4 dollar microscope
� Remove the batteries from the
laser pointer.
� Remove “warning sticker”
from laser shaft.
� Use pliers to gently remove
the top part of the laser.
� Remove the green
motherboard from the shaft of
the laser.
A B
C
+Building a $4 dollar microscope
� Use a flat-head screwdriver to
unscrew the black plastic screw.
� Remove the magnifying lenses.
� Locate the flat side of the lenses.
� Gently separate the plastic box
provided in the kit.
� Insert the magnifying lenses, flat
side up, into the hole that
corresponds with your phones
camera position.
B A
C D
E
+Building a $4 dollar microscope
� Remove push light from the
box and insert 3 AAA
batteries.
� Break apart two close pins and
discard metal spring.
� Cover push light with
parchment paper.
� Cover push light and
parchment paper with the
plastic box without drilled
holes.
A
B
One and Four Dollar Microscopes 3
+Building a $4 dollar microscope
� Stack the other part of the plastic box with holes and the magnifying lenses on top of the solid plastic box.
� Insert close pin halves into each corner between the plastic box halves.
� Open your smart phones camera app and put your smart phone in the plastic box.
� Insert a specimen slide between the plastic box halves and enjoy your $4 dollar microscope.
A
B
Plant Genetic Engineering 1
Genetic Engineering and Biotechnology
1
�What is Biotechnology?
�How Genetic Engineering Is Accomplished
�Success Stories in Plants
�Issues
What is Biotechnology?
"Biotechnology" means any technological
application that uses biological systems,
living organisms, or derivatives thereof, to
make or modify products or processes for
specific use.
Definition from Convention on Biological Diversity
https://www.cbd.int/
Biotechnology Over Time
�Traditional Biotechnology
• Growing plants
• Raising animals
• Plant and animal breeding
• Fermentation (bread, beer, wine, fish sauce)
�Genetic Engineering - Recombinant DNA and tissue-
culture-based biotechnology
• Genome Editing – Precision breeding
Plant Genetic Engineering 2
Current Uses of Biotechnology
�Agriculture• Transgenic Plants [disease resistance, drought
tolerance, nutrient use efficiency, plant-based
products such as vaccines]
• Transgenic Animals
• Transgenic Microbes
�Pharmaceutical• Insulin
• Antibiotics
• Cancer therapy
�Others• Mining
• Petroleum spill clean-up with microbes
Food Quiz: Pick the GMO
Japanese Pear
Plant Genetic Engineering HistoryAgrobacterium tumefaciens has been naturally
genetically engineering plants for centuries!
A: Agrobacterium tumefaciens
B: Agrobacterium genome
C: Ti Plasmid :
a: T-DNA
b: Vir genes
c: Replication origin
d: Opines catabolism genes
D: Plant cell
E: Mitochondria
F: Chloroplast
G: NucleusFrom Wikimedia Commons
By Chandres, 2008
Plant Genetic Engineering 3
Plant Genetic Engineering HistoryAgrobacterium tumefaciens infects plant cell
Steps 1 & 2: Bacterial cell weakly
attaches itself to the plant cell. It
then produces cellulose fibrils to
anchor it to the plant cell
(infection).
Step 3: When the bacterium
detects certain compounds
produced by the plant in
response to bacterial infection, vir
(virulence) genes [located on b of
the Ti plasmid (C)] start producing
various compounds.
Step 4: One vir gene complex
cuts the T-DNA (a) from the Ti
plasmid (C).
From Wikimedia Commons
By Chandres, 2008
Ti plasmid
Plant Genetic Engineering HistoryAgrobacterium tumefaciens infects plant cell
Step 5: In the meantime, other vir
genes produce compounds that
coat the T-DNA to help export it
into the recipient plant cell
Step 6: Other vir genes make the
nucleus of the plant cell receiving
the T-DNA more receptive.
Step 7: T-DNA is integrated into
the host genome.
T-DNA contains genes that will
force the plant to produce special
amino acids called opines, which
the bacteria can metabolize as its
food source!From Wikimedia Commons
By Chandres, 2008
T-DNA
T-DNA
T-DNA
Plant Genetic Engineering HistoryAgrobacterium tumefaciens
To cause gall formation, the T-DNA encodes genes for the
production of auxin or indole-3-acetic acid via a pathway not
normal for plants, so the plant can’t regulate its production . . . only
the pathogen! Other T-DNA genes code for production of
cytokinins. Together, cell proliferation and gall formation occur.
D. Norman, UF/IFAS, MFREC
Plant Genetic Engineering 4
Plant Genetic Engineering
�Agrobacterium-mediated transformation
�Gene Gun
�Protoplast transformation and fusion
�Genome editing
Plant Genetic Engineering HistoryAgrobacterium tumefaciens infects plant cell
From Wikimedia Commons
By Chandres, 2008
•To transform plant cells,
the desired gene
sequence is cloned into
the T-DNA (a).
•The T-DNA is the
delivery vehicle of the
desired gene sequence
into the plant cell.
T-DNA
T-DNA
T-DNA
Plant Genetic EngineeringUsing Agrobacterium tumefaciens
“Transient and stable
expression of the firefly
luciferase gene in plant cells
and transgenic plants”
Ow et al. Science (Nov. 1986)
When tobacco plant was
sprayed with the chemical
substrate luciferin, the plant
glowed temporarily.
Science/AAAS
Plant Genetic Engineering 5
Gene Gun - Biolistic
https://www.youtube.com/watch?v=2G-yUuiqIZ0
( 5 ½ minutes)
Hawaiian Rainbow PapayaInserted papaya ring spot virus coat
protein using high speed particle
bombardment method (relies on
pressure)
http://www.apsnet.org/publications/apsnetfeatures/Pages/papayaringspot.aspx
Gene Silencing
RNA interference, or RNAi, a molecular mechanism that defends plants, fungi,
and animals against viruses made of RNA, a chemical relative of DNA. When a
RNA virus takes over a host cell, it needs to copy itself and the copying
process creates double strands of RNA. The RNAi defense mechanism
recognizes these double-stranded RNAs as foreign and degrades them plus
any single-stranded RNAs that it “recognizes”.
Proteins are made on single-stranded RNA templates, so a gene targeted by
RNAi can’t produce the protein that it usually makes. The gene has not been
changed, but it no longer can be used to make proteins or duplicate the viral
RNAs. We speak of a RNAi-targeted gene as being “knocked down” or
“silenced.” This natural gene silencing mechanism is why genetically modified
(GM) papaya that contains a coat protein gene from Papaya Ringspot Virus is
able to resist the virus
Biotech in Focus, April 2016, University of Hawaii Cooperative Extension Service
http://www.ctahr.hawaii.edu/biotechinfocus/backissues.html
Protoplast FusionSomatic Fusion
From Wikimedia Commons, Mnolf, 2009
Protoplasts of two
distinct species of plants
are fused together to
form a new hybrid plant
with the characteristics
of both
Example for plant disease resistance: Plant Cell Reports, August 2013, Volume 32, pp. 1231-1241
Development of somatic hybrids Solanum × michoacanum Bitter. (Rydb.) (+) S. tuberosum L. and
autofused 4x S. × michoacanum plants as potential sources of late blight resistance for potato
breeding by P. Smyda et al.
Plant Genetic Engineering 6
Genome Editing Using CRISPRClustered Regularly Interspaced Short Palindromic Repeats
How CRISPR/Cas9 technology works:• The “guide RNA” is attached to Cas9, a
bacterial enzyme that will cut the DNA
sequence at the desired site in the
genome.
• Once the genome is broken, the guide
RNA/Cas9 disappear, and the cell will try
to repair the cut, which can disable or
knock out a particular gene.
• Or, scientists can insert a new segment of
DNA into the cut, essentially pasting a
gene into the desired location and
changing the genome.
Genome Editing Using CRISPRClustered Regularly Interspaced Short Palindromic Repeats
• The CRISPR system was first discovered in
bacteria and functions as a defense against
foreign DNA, either viral or plasmid.
• Used for gene knock-out, repression or activation
• CRISPR does have limits! But, because of its
precision and simplicity, it is “the” genetic tool of
the moment.[addgene (non-profit): https://www.addgene.org]
GMOAnswers.com
GMO Answers is funded by the members of The Council for Biotechnology Information,
which includes BASF, Bayer, Dow AgroSciences, DuPont, Monsanto Company and
Syngenta.
The independent experts who answer consumer questions are not paid by GMO
Answers to answer questions. Experts donate their time to answer questions in their
area of expertise for the website. They do so because they are passionate about helping
the public better understand GMOs and how our food is grown.
Supporting partners are organizations, companies and others who are committed to the five
core principles of GMO Answers and have added their support to this initiative. To date
those partners include The American Council on Science and Health, The American Farm
Bureau Federation, American Seed Trade Association, American Soybean Association, The
American Sugarbeet Growers Association, Minnesota Crop Production Retailers, National
Association of Wheat Growers, National Corn Growers Association, National Cotton Council,
Ohio AgriBusiness Association, South Dakota Agri-Business Association, The U.S. Beet Sugar
Association, Western Sugar
Plant Genetic Engineering 7
Plant Genetic Engineering 8
National Academy of Science Report on GE Crops - May 2016
http://nas-sites.org/ge-crops/ FREE: full report; short report; slides from news release
While recognizing the inherent difficulty of
detecting subtle or long-term effects in
health or the environment, the study
committee found no substantiated evidence
of a difference in risks to human health
between currently commercialized
genetically engi-neered (GE) crops and
conventionally bred crops, nor did it find
conclusive cause-and-effect evidence of
environmental problems from the GE crops.
Plant Genetic Engineering 9
National Academy of Science Report on GE Crops - May 2016
In 2015, almost 180 million hectares of GE crops were planted
globally, which was about 12% of the world’s planted cropland
that year. There were herbicide-resistant varieties of maize
(corn), soybean, cotton, canola, sugar beet, and alfalfa, and
insect-resistant varieties of maize, cotton, poplar and egglplant.
Figure 1.
Commercially Grown
Genetically Engineered
Crops Worldwide.
http://nas-sites.org/ge-crops/ full report; short report; slides from news release
National Academy of Science Report on GE Crops - May 2016
H
Genetically Modified Cropscurrently planted in the U.S.CROP TRAITS
Maize (corn) Herbicide tolerance, insect resistance
Soybean Herbicide tolerance, insect resistance,
high oleic acid content
Cotton Herbicide tolerance, insect resistance
Canola Herbicide tolerance, high oleic acid content
Sugar beet Herbicide tolerance
Alfalfa Herbicide tolerance
Papaya Disease (virus) resistance
Squash Disease (virus) resistance
Potato Resists bruising; reduced asparagine content
Apple Delayed browning
Plant Genetic Engineering 10
Genetically Modified Crops
� Intelligence Squared U.S., December 3, 2014 Debatehttp://intelligencesquaredus.org/debates/past-debates/item/1161-genetically-
modify-food (about 20 minutes)
• This page is good for obtaining information for both sides of the debate.
Spoiler alert: GM Foods win!
https://www.geneticliteracyproject.org/�Genetic Literacy Project
�GMOanswers https://gmoanswers.com
• can ask any question; PowerPoint; posters, brochures, etc. - all free and free to
use
�Florida Tomatoes – GM tomatoes have been developed to resist
a devastating bacterial disease, but . . .• The Good, the Bad, and the Ugly: What the Future Could Hold for Bs2 Tomatoes
http://edis.ifas.ufl.edu/hs1259
Food Quiz: Pick the GMO
Japanese Pear
Food Quiz: Pick the GMO
No, derived
by
mutagenesis
No
No
No, derived
by
mutagenesis
YES
MAYBE
YES
No
interspecies crossgrapefruit x tangerine
No
interspecies crossapricot x plum
REPORT IN BRIEF
Genetically Engineered Crops: Experiences and Prospects
May 2016Board on Agriculture and Natural Resources
DIVISION ON EARTH AND LIFE STUDIES
Claims and research that extol both the benefits of and risks posed by GE crops and food have created a confusing landscape for the public and policy-makers. Using evidence accumulated over the last two decades, this report assesses purported negative effects and purported benefits of currently commercialized GE crops. The report also assesses emerging genetic-engineering technologies, how they might contribute to future crop improvement, and what technical and regulatory challenges they may present. To carry out its task, the report’s authoring committee delved into the relevant literature (more than 900 research and other publications), heard from 80 diverse speakers at three public meetings and 15 webinars, and read more than 700 comments from members of the public to broaden its understanding of issues surrounding GE crops.
EXPERIENCES WITH GENETICALLY ENGINEERED CROPS Since the 1980s, biologists have used genetic engineering in crop plants to alter characteristics, such as longer shelf life for fruit, higher vitamin content, and resistance to
diseases. However, the only characteristics that have been introduced through genetic engineering into widespread commercial use are those that provide insect resistance and herbicide resistance. In 2015, GE herbicide resistance, insect resistance, or both were available in fewer than 10 crop species and grown on about 12 percent of the world’s planted cropland (see Figure 1). In its evaluation of experiences with GE crops, the committee examined the long-term data available on the use of insect and herbicide resistance in the most commonly grown GE crops to date: soybean, cotton, and maize. A few other GE characteris-tics—such as for resistance to specific viruses in papaya and squash and reduction of browning in the flesh of apples and potatoes—have been incorporated into some crops in commercial production as of 2015, but were produced on a relatively small number of hectares worldwide.
Agronomic and Environmental Effects Insect-resistant GE crops contain genes from Bacillus thuringiensis (Bt), a soil bacterium that gives crops a built-in insecticide. Plants with this characteristic can kill targeted
New technologies in genetic engineering and conventional breeding are blurring the once clear distinctions between these two crop-improvement approaches. While recognizing the inherent difficulty
of detecting subtle or long-term effects in health or the environment, the study committee found no substantiated evidence of a difference in risks to human health between currently commercialized genetically engi-neered (GE) crops and conventionally bred crops, nor did it find conclusive cause-and-effect evidence of environmental problems from the GE crops. GE crops have generally had favorable economic outcomes for producers in early years of adoption, but enduring and widespread gains will depend on institutional support and access to profitable local and global markets, especially for resource-poor farmers.
insects that ingest them. Following are conclusions about various effects of Bt crops based on available data:
• Bt Crop Yield. Bt in maize and cotton from 1996 to 2015 contributed to a reduction in crop losses (closing the gap between actual yield and potential yield) under circumstances where targeted insect pests caused substantial damage to non-Bt varieties and synthetic chemicals could not provide practical control.
• Abundance and diversity of insects. In areas of the United States and China where adoption of either Bt maize or Bt cotton is high, some insect-pest populations are reduced regionally, benefiting both adopters and nonadopters of Bt crops. Some secondary (non targeted) insect pests have increased in abundance, but there are only a few cases where the increase has posed an agro-nomic problem. Planting Bt crops tended to result in higher insect biodiversity than planting similar varieties without the Bt trait and using synthetic insecticides.
• Insecticide use. Application of synthetic insecticides to maize and cotton has decreased following the switch from non-Bt varieties to Bt varieties, and in some cases, the use of Bt crops has been associated with lower use of insecticides in non-Bt varieties of the crop and other crops in the same area.
• Insect resistance. Target insects have been slow to evolve resistance to Bt proteins when crops produced a high enough dose of Bt protein to kill insects with partial genetic resistance to the toxin and there were refuges where susceptible insects survived. Where resistance-management strategies were not followed, damaging levels of resistance evolved in some target insects.
Herbicide resistance allows a crop to survive the application of a herbicide which would otherwise kill it. Most herbi-cide-resistant GE crops are engineered to be resistant to glyphosate, commonly known as RoundUp®. Conclusions based on the available evidence include the following:
• Herbicide-resistant crop yield. Studies indicate that herbicide-resistant crops contribute to greater yield where weed control is improved because of the specific herbicides that can be used in conjunction with the herbicide-resistant crop.
• Herbicide use. Total kilograms of all types of herbicide applied per hectare of crop per year declined when herbicide-resistant crops were first adopted, but the decreases have not generally been sustained. However, total kilograms of herbicide applied per hectare is an uninformative metric for assessing changes in risks to the environment or to human health due to GE crops; because the environmental and health hazards of different herbicides vary, the relationship of kilograms of herbicide applied per hectare and risk is poor.
• Weed-species distribution. In locations where glyphosate is used extensively, weed species that are naturally less susceptible to that herbicide may populate a field. The committee found little evidence that agro-nomic harm had resulted from such shifts in weed species.
• Weed resistance. In many locations, some weeds have evolved resistance to glyphosate. Integrated weed-management approaches can be used to delay resistance, especially in cropping systems not yet exposed to continuous glyphosate applications. Further
FIGURE 1. Commercially Grown GE Crops Worldwide. In 2015, almost 180 million hectares of GE crops were planted globally, which was about 12 percent of the world’s planted cropland that year. There were herbicide-resistant varieties of maize, soybean, cotton, canola, sugar beet, and alfalfa, and insect-resistant varieties of maize, cotton, poplar, and eggplant.
research is needed to improve strategies for manage-ment of resistance in weeds.
Overall, the committee found no conclusive evidence of cause-and-effect relationships between GE crops and environmental problems. However, the complex nature of assessing long-term environmental changes often made it difficult to reach definitive conclusions.
Comparisons with conventional breeding The committee assessed detailed surveys and experiments comparing GE to non-GE crop yields and also examined changes over time in overall yield per hectare of maize, soybean, and cotton reported by the U.S. Department of Agriculture (USDA) before, during, and after the switch from conventionally bred to GE varieties of these crops. Although the sum of experimental evidence indicates that GE herbicide resistance and insect resistance are contrib-uting to actual yield increases, there is no evidence from USDA data that the average historical rate of increase in U.S. yields of cotton, maize, and soybean has changed.
Human Health EffectsGE crops and foods derived from them are tested in three ways: animal testing, compositional analysis, and aller-genicity testing and prediction. Although the design and analysis of many animal-feeding studies were not optimal, the many available animal experimental studies taken together provided reasonable evidence that animals were not harmed by eating foods derived from GE crops. Data on the nutrient and chemical composition of a GE plant compared to a similar non-GE variety of the crop some-times show statistically significant differences in nutrient and chemical composition, but the differences have been considered to fall within the range of naturally occurring variation found in currently available non-GE crops.
Many people are concerned that GE food consumption may lead to higher incidence of specific health problems including cancer, obesity, gastrointestinal tract illnesses, kidney disease, and disorders such as autism spectrum and allergies. In the absence of long-term, case-controlled studies to examine some hypotheses, the committee examined epidemiological datasets over time from the United States and Canada, where GE food has been consumed since the late 1990s, and similar datasets from the United Kingdom and western Europe, where GE food is not widely consumed. No pattern of differences was found among countries in specific health problems after the introduction of GE foods in the 1990s.
Social and Economic EffectsAt the farm level, soybean, cotton, and maize with GE herbicide-resistant or insect-resistant traits (or both) have generally had favorable economic outcomes for producers who have adopted these crops, but there is high heteroge-neity in outcomes. The utility of a GE variety to a specific farm system depends on the fit of the GE characteristic and the genetics of the variety to the farm environment and the quality and cost of the GE seeds. In some situations in which farmers have adopted GE crops without identifiable economic benefits, increases in management flexibility and
other considerations may be driving adoption of GE crops, especially those with herbicide resistance.
The cost of GE seed may limit the adoption of GE crops by resource-poor smallholders. In most situations, the differ-ential cost between GE and non-GE seed is a small fraction of total costs of production, although it may constitute a financial constraint because of limited access to credit. In addition, small-scale farmers may face a financial risk when purchasing a GE seed upfront if the crop fails.
The committee heard diverse opinions on the ability of GE crops to affect food security in the future. GE crops, like other technological advances in agriculture, are not able by themselves to address fully the wide variety of complex challenges that face smallholders. Such issues as soil fertility, integrated pest management, market development, storage, and extension services all need to be addressed to improve crop productivity, decrease post-harvest losses, and increase food security. Even if a GE crop may improve productivity or nutritional quality, its ability to benefit intended stake-holders will depend on the social and economic contexts in which the technology is developed and diffused.
PROSPECTS FOR GENETIC ENGINEERING OF CROPSEmerging genetic-engineering technologies such as CRISPR/Cas9 promise to increase the precision with which changes can be made to plant genomes and expand the array of characteristics that can be changed or introduced, such as: improved tolerance to drought and thermal extremes; increased efficiency in photosynthesis and nitrogen use; and improved nutrient content. Insect and disease resistance are likely to be introduced into more crop species and the number of pests targeted will also likely increase. If deployed appropriately, such characteristics will almost certainly increase harvestable yields and decrease the probability of crop losses to major insect or disease outbreaks. However, it is too early to know whether complex genetic changes that substantially improve photosynthesis, increase nutrient-use efficiency, and increase maximum yield will be successfully deployed. Therefore, the committee recommends balanced public investment in emerging genetic-engineering tech-nologies and other approaches to address food security.
REGULATION SHOULD FOCUS ON NOVEL CHARACTERISTICS AND HAZARDSAll technologies for improving plant genetics—whether GE or conventional—can change foods in ways that could raise safety issues. Therefore, it is the product that should be regulated, the report finds, not the process (i.e., genetic-engineering or conventional-breeding techniques). New plant varieties should undergo safety testing if they have intended or unintended novel characteristics with potential hazards.
The United States’ current policy on new plant varieties is in theory a product-based policy, but USDA and the Environmental Protection Agency (EPA) determine which plants to regulate at least partially on the process by which they are developed. This approach is becoming less technically defensible as emerging technologies blur
the distinctions between genetic engineering and conventional plant breeding. For example, CRISPR/Cas9 could make a directed change in the DNA of a crop plant that leads to increased resistance to an herbicide; the same change could be made using chemical- or radiation-induced mutagen-esis in thousands of individual plants followed by genome screening to isolate plants with the desired mutation—an approach considered conventional breeding by most national regulatory systems
The report recommends the development of a tiered approach to safety testing using as criteria novelty (intended and unintended), potential hazard, and exposure. New -omics technologies—such as proteomics and transcriptomics—that can compare the DNA sequence, RNA expression, and molecular composition of a new variety with coun-terparts already in widespread use will allow such testing for novel characteristics, better enabling the tiered approach (see Figure 2). The committee is aware that -omics technologies are new and that not all developers of crop varieties will have access to them; therefore, public investment will be needed.
Regulating authorities should be proactive in communicating information to the public about how emerging genetic-engineering technologies or their products might be regulated and how new regulatory methods may be used. They should also proactively seek input from the public on these issues. Policy regarding GE crops has scientific, legal, and social dimensions, and not all issues can be answered by science alone, the report finds.
Committee on Genetically Engineered Crops: Past Experience and Future Prospects—Fred Gould (Chair), North Carolina State University; Richard M. Amasino, University of Wisconsin-Madison; Dominique Brossard, University of Wisconsin-Madison; C. Robin Buell, Michigan State University; Richard A. Dixon, University of North Texas; José B. Falck-Zepeda, International Food Policy Research Institute (IFPRI), Washington, DC; Michael A. Gallo, Rutgers-Robert Wood Johnson Medical School (retired); Ken Giller, Wageningen University, The Netherlands; Leland Glenna, Pennsylvania State University; Timothy S. Griffin, Tufts University; Bruce R. Hamaker, Purdue University; Peter M. Kareiva, University of California, Los Angeles; Daniel Magraw, Johns Hopkins University School of Advanced International Studies, Washington, DC; Carol Mallory-Smith, Oregon State University; Kevin Pixley, International Maize and Wheat Improvement Center (CIMMYT), Mexico; Elizabeth P. Ransom, University of Richmond, VA; Michael Rodemeyer, University of Virginia, Charlottesville (formerly); David M. Stelly, Texas A&M University and Texas A&M AgriLife Research; C. Neal Stewart, University of Tennessee, Knoxville; Robert J. Whitaker, Produce Marketing Association, Newark, DE; Kara N. Laney (Study Director), Maria Oria (Senior Program Officer), Janet M. Mulligan (Senior Program Associate for Research, until January 2016), Jenna Briscoe (Senior Program Assistant), Samuel Crowell (Mirzayan Science & Technology Policy Fellow, until August 2015), Robin A. Schoen (Director, Board on Agriculture and Natural Resources), Norman Grossblatt (Senior Editor), National Academies of Sciences, Engineering, and Medicine
The National Academies of Sciences, Engineering, and Medicine appointed the above committee of experts to address the specific task requested by the Burroughs Wellcome Fund, Gordon and Betty Moore Foundation, New Venture Fund, U.S. Department of Agriculture, and National Academy of Sciences. The members volunteered their time for this activity; their report is peer-reviewed and the final product signed off by both the committee members and the Academies. This report brief was prepared by the Academies based on the committee’s report.
For more information, contact the Board on Agriculture and Natural Resources at (202) 334-3062 or visit at http://nas-sites.org/ge-crops. Copies of Genetically Engineered Crops: Experiences and Prospects are available from the National Academies Press, 500 Fifth Street, NW, Washington, DC 20001; (800) 624-6242; or as free PDFs at www.nap.edu.
Permission granted to reproduce this brief in its entirety with no additions or alterations. Permission for images/figures must be obtained from their original source.
© 2016 The National Academy of Sciences
Locate information on related reports at http://dels.nas.edu/banrDownload (free) or purchase this report at www.nap.edu
FIGURE 2. Proposed Strategy for Evaluating Crops Using -Omics Technologies. New -omics technologies could be used to determine the extent to which the novel characteristics of the plant variety are likely to pose a risk to human health or the environment, regardless of whether the plant was developed using genetic-engi-neering or conventional-breeding processes.
HS1259
The Good, the Bad, and the Ugly: What the Future Could Hold for Bs2 Tomatoes1
S. F. Hutton, J. W. Scott, J. B. Jones, R. E. Stall, G. E. Vallad, B. J. Staskawicz, and D. M. Horvath2
1. This document is HS1259, one of a series of the Horticultural Sciences Department, UF/IFAS Extension. Original publication date April 2015. Visit the EDIS website at http://edis.ifas.ufl.edu.
2. S. F. Hutton, assistant professor, Horticultural Sciences Department, UF/IFAS Gulf Coast Research and Education Center, Wimauma, FL; J.W. Scott, professor, Horticultural Sciences Department, Gulf Coast Research and Education Center, UF/IFAS Extension, Wimauma, FL; G. E. Vallad, associate professor, Horticultural Sciences Department, Gulf Coast Research and Education Center, UF/IFAS Extension, Wimauma, FL; J.B. Jones, professor, Plant Pathology Department, UF/IFAS Extension, Gainesville, FL; R. E. Stall, emeritus professor, Plant Pathology Department, UF/IFAS Extension, Gainesville, FL; B. J. Staskawicz, professor, Department of Plant and Microbial Biology, University of California, Berkeley, CA; and D. M. Horvath, Two Blades Foundation, Evanston, IL
The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other UF/IFAS Extension publications, contact your county’s UF/IFAS Extension office. U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.
Over the past several years there has been considerable discussion within the Florida tomato industry about Bs2 tomatoes. Previous and ongoing trials conducted by University of Florida researchers have consistently and repeatedly demonstrated the benefits of these cultivars for bacterial spot disease management, while growers and industry members who have visited these trials likewise recognize the potential for Bs2 tomatoes to make Florida tomato production a much more sustainable operation. But what does the future really hold for this technology? What benefits might be realized by the adoption of Bs2 tomato varieties, and what challenges stand in the way of their commercial production?
What Are Bs2 Tomatoes?Bs2 tomatoes are transgenic tomatoes that have been engineered to contain the Bs2 gene from pepper. As such, they are considered a genetically modified (GM) food, or a genetically modified organism (GMO). (For more informa-tion about GMOs see Schneider, Schneider, and Richardson 2002). Bs2 transgenic tomatoes were developed by the Two Blades Foundation, a charitable scientific organization, which holds an exclusive license to the Bs2 gene, in col-laboration with scientists at the University of California and the University of Florida.
Bacterial spot is a major disease of both pepper and tomato, especially in Florida and other warm, humid production regions of the world. Plant resistance is desired because chemical control is costly and sometimes ineffective when conditions are favorable for development of the disease. In pepper, conventional (non-GMO) breeding efforts have been very successful due to the discovery and use of several individual resistance genes. Seven of these resistance genes have been reported (Potnis et al. 2012; Stall, Jones, and Minsavage 2009), four of which have been exploited in commercial varieties (Bs1, Bs2, Bs3, and bs5). The majority of these genes behave in a manner consistent with the gene-for-gene hypothesis devised by Henry Flor (1955). By this model, a resistance gene in the plant must recognize a corresponding gene, commonly referred to as an avirulence gene, in the bacterium in order for the plant to be resistant; thus both genes are necessary for resistance to bacterial spot. In most cases where single resistance genes are deployed, crops remain disease-free for a period of time (usually a few years), until a mutation occurs in the pathogen’s avirulence gene, rendering the corresponding resistance gene ineffective. This was the case with pepper varieties containing Bs2 alone, which became available in 1984 (Cook 1984) and were widely grown in the 1990s. But after only several years, bacteria containing mutations in the Bs2 avirulence gene became prevalent in the field
2The Good, the Bad, and the Ugly: What the Future Could Hold for Bs2 Tomatoes
(Pernezny and Collins 1999), and when deployed alone, Bs2 resistance was no longer effective against such strains. Fortunately, not all pathogen strains carry a mutant Bs2 avirulence gene (Wichmann 2005), and pepper breeders have enjoyed some success against bacterial spot by pyra-miding Bs2 with other resistance genes (for example, Bs2 combined with Bs3). This strategy also helps prolong the “life” of the resistance genes, since the pathogen can only survive/spread if mutations occur in all avirulence genes at the same time.
In contrast to pepper, tomato breeders have been unsuc-cessful in developing bacterial spot resistant varieties by conventional approaches. Although the UF/IFAS tomato breeding program has maintained an active breeding project for resistance since the early 1980s, no resistant varieties have been developed. There are several reasons for this, including limited sources of resistance, resistance that is conferred by multiple genes rather than a single gene (which makes the breeding process much more compli-cated), mutations in pathogen avirulence genes resulting in ineffective resistance genes, and introduction of exotic pathogen strains which overcome the resistance (Hutton et al. 2010). In short, tremendous efforts on the breeding front have been unable to combine horticultural acceptability with high levels of resistance in tomato.
The Bs2 gene from pepper was cloned in the late 1990s when the gene conferring resistance was identified (Tai et al. 1999).The researchers also determined that transgenic tomatoes containing the pepper Bs2 gene were resistant to bacterial spot. Because of the difficulty in developing resistant tomato varieties by conventional means, many have considered Bs2 tomatoes an important tool to manage this devastating disease.
The GoodThere are several reasons why Bs2 tomatoes are an attractive strategy for management of bacterial spot:
• The Bs2 gene occurs naturally in plants. What is more, it occurs naturally in a major food crop, pepper. The protein product of the Bs2 gene is safe for consumption, attested to by more than two decades of the public’s consumption of bell peppers containing Bs2.
• The Bs2 gene provides excellent disease control in tomatoes (Figure 1). This was demonstrated in a multi-year experi-ment where Bs2 tomatoes maintained extremely low levels of disease compared to susceptible controls, while inbred lines with conventionally-bred resistance had intermediate levels of infection (Horvath et al. 2012).
• Bs2 is effective against all field strains of the tomato bacterial spot pathogen. This was determined by surveying bacteria samples from the production regions of Florida and parts of Georgia; all strains contained a recognizable Bs2 avirulence gene, meaning that Bs2 would provide effective resistance throughout the southeast production region (Horvath et al. 2012). Additionally, many of the mutations which have occurred in the Bs2 avirulence gene and which provide the pathogen a means to escape detection by the resistance gene also result in a loss of fitness of the bacterium (Kearny and Staskawicz 1990), meaning that the mutant strains are often weaker and less likely to survive and/or cause severe infections.
• Higher yields are obtained with Bs2 tomatoes. In repeated trials, Bs2 inbreds and hybrids maintain a 1.5-fold or greater yield increase over the non-transgenic versions of these inbreds and hybrids; when conditions were favorable for disease, these increases were often 2-fold or greater (Horvath et al., 2012, 2014).
• Bs2 tomatoes are a green technology. Because these toma-toes have a significant yield advantage over traditional varieties, increased production can be realized without increasing fertilizer, pesticide, plastic, or other inputs. Thus the carbon footprint per unit of production can be reduced. In addition, because Bs2 tomatoes provide good control for bacterial spot, copper and other chemical sprays for management of this disease can be reduced or eliminated, which can further reduce environmental impact.
• The Bs2 gene is a simple, highly effective tool for tomato breeders to utilize. As described above, most of the conventionally bred resistance is controlled by multiple
Figure 1. Bacterial spot resistance in tomato conferred by the pepper Bs2 gene. On the left are symptomless Bs2 transgenic plants of the hybrid, Fla. 8314; on the right are severely infected non-transgenic plants of the cultivar VF36. The picture was taken from a trial conducted in Florida in spring 2012, for which all plants in the trial were inoculated with the bacterial spot pathogen.
3The Good, the Bad, and the Ugly: What the Future Could Hold for Bs2 Tomatoes
genes, meaning that breeders have to sift through many more plants to identify those that are most resistant. Fur-thermore, unlike the resistance provided by the Bs2 gene, current conventionally bred resistance genes only provide tolerance or partial resistance; thus breeders spend a great deal more time and effort trying to distinguish between “shades of gray,” vs. presence or absence of disease.
The BadAlthough years of repeated trials have demonstrated the ability of the Bs2 gene to effectively eliminate bacterial spot in tomatoes, the success of this gene in tomatoes hinges on its ability to recognize the pathogen’s Bs2 avirulence gene. So if mutations occur in the Bs2 avirulence gene (which they will) that prevent recognition, Bs2 could be rendered ineffective at controlling bacterial spot of tomato. As was discussed earlier, this is what occurred in non-transgenic Bs2 pepper varieties in only a matter of years. In fact, such mutations already have been observed on a limited scale in Bs2 tomato trials (Horvath et al. 2014).
In order to prolong the “life” of Bs2 resistant tomatoes, care will need to be taken to limit the emergence and spread of resistance-breaking strains. Several strategies are available, any number of which might be employed.
• Deployment of Bs2 exclusively in varieties that contain conventionally bred tolerance or partial resistance to bacterial spot. This is a good strategy because a pathogen must simultaneously overcome multiple mechanisms of resistance. But this is easier said than done because of the challenges of conventional breeding for tolerance or partial resistance conferred by multiple genes, as already discussed.
• Employment of cultural practices to minimize the emergence and spread of mutant strains of the pathogen. Further research is needed to identify helpful strategies that are not already practiced. Ultimately, those cultural practices that are based on good sanitation all the way from seed production to the growers’ fields will go a long way to minimize bacterial spot outbreaks and the introduction of resistance-breaking strains.
• Deployment of Bs2 in combination with other novel resis-tance genes. As scientists expand their understanding of plant disease resistance, there will no doubt be additional resistance genes discovered—whether in relatives of to-mato, in other Solanaceous species, or in entirely differ-ent plant families—and some of these genes may provide useful levels and alternative mechanisms of resistance. As long as these genes do not rely on recognition of the same avirulence gene in the pathogen, the pyramiding of Bs2
with one or more of these likely would prove extremely long-lasting. This strategy of pyramiding resistance genes to promote their durability is not novel; examples include combining multiple conventionally bred resistance genes to Striga in sorghum (Ejeta 2007), as well as pyramiding multiple transgenic insect resistance genes in cotton (Li et al. 2014).
The UglyThere currently are no Bs2 tomatoes being produced for sale or consumption, and this will not change until two hurdles are passed. The first is the de-regulation process. It takes years for a transgenic crop to be de-regulated, and the process is costly. The Two Blades Foundation has invested significant resources toward the development and testing of this GMO. However, additional funds are needed in order to complete the de-regulation process, and many potential investors are wary due to concerns about public acceptance—which is the second hurdle.
Even though this gene has the potential to increase yields while decreasing pesticide applications, and even though it is naturally present in peppers, which are very closely related to tomatoes, the Bs2 resistance gene does not naturally occur in tomatoes. Since peppers and tomatoes cannot be intercrossed, the only way to utilize this gene in tomatoes is through the use of transgenic technology. Ultimately, because growers will only produce what they can sell, the future of Bs2 tomatoes relies on whether or not the public will accept and buy their product.
Going ForwardIf deployed carefully, Bs2 tomatoes have the potential to significantly advance the sustainability of tomato produc-tion in bacterial spot-prone environments by increasing yields while reducing pesticide inputs. The Bs2 protein product is known to be safe based on decades of its con-sumption in pepper. But before Bs2 tomatoes can be grown, the de-regulation process must be completed; and before Bs2 tomatoes will be grown, producers must be satisfied that they can sell their product. Thus public controversy over GMO technology has everything to do with the future of Bs2 tomatoes.
Although there is considerable opposition to and great skepticism over GM technology, it is evident that much of this is based on the public’s perception of the science. A recent Intelligence Squared U.S. debate illustrated this: after hearing concerns over GMOs addressed by both GMO-skeptics and by supporters of GMO technology, an audience changed from 32% supportive of GM technology
4The Good, the Bad, and the Ugly: What the Future Could Hold for Bs2 Tomatoes
before the debate, to 60% afterward (Fraley et al. 2014). The opinion shift after that debate suggests that increasing acceptance of Bs2 tomatoes (and other GMOs) will depend on transparency and open discussion between scientists and the general public to show these crops’ benefits to consumers, growers, and the environment.
Literature CitedCook, A. A. 1984. “Florida XVR 3-25 Bell Pepper.” Hort-Science 19:735.
Ejeta, G. 2007. “Breeding for Resistance in Sorghum: Exploitation of an Intricate Host-Parasite Biology.” Crop Sci. 47:S216–S227.
Flor, H. H. 1955. “Host-Parasite Interactions in Flax Rust—Its Genetics and Other Implications.” Phytopathology 45:680–685.
Fraley, R., A. V. Eenennaam, C. Benbrook, and M. Mellon. “Genetically Modified Food.” Intelligence Squared U.S. Debate. Kaufman Center, New York. 3 Dec. 2014. Debate. http://intelligencesquaredus.org/debates/past-debates/item/1161-genetically-modify-food.
Horvath, D. M., S. F. Hutton, G. E. Vallad, J. B. Jones, R. E. Stall, D. Dahlbeck, B. J. Staskawicz, D. Tricoli, A. V. Deynze, M. H. Pauly, and J. W. Scott. 2014. “The Pepper Bs2 Gene Confers Effective Field Resistance to Bacterial Leaf Spot and Yield Enhancement in Florida Tomatoes.” Acta Hort. (in press).
Horvath, D. M., R. E. Stall, J. B. Jones, M. H. Pauly, G. E. Vallad, D. Dahlbeck, B. J. Staskawicz, and J. W. Scott. 2012. “Transgenic Resistance Confers Effective Field Level Control of Bacterial Spot Disease in Tomato.” PLoS ONE 7(8):e42036.
Hutton, S. F., J. W. Scott, W. Yang, S. C. Sim, D. M. Francis, and J. B. Jones. 2010. “Identification of QTL Associated with Resistance to Bacterial Spot Race T4 in Tomato.” Theoretical and Applied Genetics 121(7):1275–1287.
Kearney, B. and B. J. Staskawicz. 1990. “Widespread Distribution and Fitness Contribution of Xanthomonas campestris pv. Vesicatoria Avirulence Gene avrBs2.” Nature 346:385–386.
Li, L., Y. Zhu, S. Jin, and X. Zhang. 2014. “Pyramiding Bt Genes for Increasing Resistance of Cotton to Two Major Lepidopteran Pests: Spodoptera litura and Heliothis armig-era.” Acta Physiol. Plant 36:2717–2727.
Pernezny, K. and J. Collins. 1999. “A Serious Outbreak of Race 6 of Xanthomonas campestris pv. Vesicatoria on Pepper in Southern Florida.” Plant Dis. 83:79.
Potnis, N., G. Minsavage, J. K. Smith, J. C. Hurlbert, D. Norman, R. Rodrigues, R. E. Stall, and J .B. Jones. 2012. “Avirulence Proteins AvrBs7 from Xanthomonas gardneri and AvrBs1.1 from Xanthomonas euvesicatoria Contribute to a Novel Gene-for-Gene Interaction in Pepper.” Mol. Plant Microbe Interact. 25:307–320.
Schneider, K. R., R. G. Schneider, and S. Richardson. 2002. “Genetically Modified Food.” FSHN02-2. Gainesville, FL: University Florida Institute of Food and Agricultural Sciences. http://edis.ifas.ufl.edu/fs084.
Stall, R. E., J. B. Jones, and G. V. Minsavage. 2009. “Durability of Resistance in Tomato and Pepper to Xantho-monads Causing Bacterial Spot.” Annu. Rev. Phytopathol. 47:265–284.
Tai, T. H., D. Dahlbeck, E. T. Clark, P. Gajiwala, R. Pasion, M. C. Whalen, R. E. Stall, and B. J. Staskawicz. 1999. “Expression of the Bs2 Pepper Gene Confers Resistance to Bacterial Spot Disease in Tomato.” Proc. Natl. Acad. Sci. USA 96:14153–14158.
Wichmann, G., D. Ritchie, C. S. Kousik, and J. Bergelson. 2005. “Reduced Genetic Variation Occurs among Genes of the Highly Clonal Plant Pathogen Xanthomonas axonopodis pv. Vesicatoria, Including the Effector Gene avrBs2.” Appl. Envir. Microb. 71:2418–2432.
THE
JOURNAL • RESEARCH • www.fasebj.org
What consumers don’t know about geneticallymodified food, and how that affects beliefsBrandon R. McFadden,*,1 and Jayson L. Lusk†
*Department of Food and Resource Economics, University of Florida, Gainesville, Florida, USA; and †Department of Agricultural Economics,
Oklahoma State University, Stillwater, Oklahoma, USA
ABSTRACT: In the debates surrounding biotechnology and genetically modified (GM) food, data from consumerpolls are often presented as evidence for precaution and labeling. But how much do consumers actually knowabout the issue?Newdata collected fromanationwideU.S. survey reveal low levels ofknowledge andnumerousmisperceptions about GM food. Nearly equal numbers of consumers prefer mandatory labeling of foods con-taining DNA as do those preferring mandatory labeling of GM foods. When given the option, the majority ofconsumers prefer that decisions about GM food be taken out of their hands and be made by experts. Afteranswering a list of questions testing objective knowledge of GM food, subjective, self-reported knowledgedeclines somewhat and beliefs about GM food safety increase slightly. Results suggest that consumers thinkthey knowmore than they actually do aboutGM food, and queries aboutGM facts cause respondents to reassesshow much they know. The findings question the usefulness of results from opinion polls as a motivation forcreating public policy surrounding GM food.—McFadden, B. R., Lusk, J. L. What consumers don’t know aboutgenetically modified food, and how that affects beliefs. FASEB J. 30, 000–000 (2016). www.fasebj.org
KEY WORDS: GM food • labeling • public acceptance • public knowledge
Debate about biotechnology in plant research andabout genetically modified (GM) food in the UnitedStates has intensified in recent years, with mandatorylabeling ballot initiatives appearing in California, Col-orado, Connecticut, Maine, Oregon, and Washington.The Vermont legislature passed the first U.S. manda-tory labeling law for GM food (1), an action that hasprompted competing legislation in the U.S. Congress(2). At the heart of the debate is stated public oppositionto GM food, and public opinion may be a proximatecause of policy (3). Indeed, public opinion polls are of-ten used to characterize consumer sentiment and mo-tivatemoreprecautionarypolicies forGMfood.Apparentconsumer concern could lead to a climate that impedesparticular research methods and lowers the potentialreturn to investments in biotechnology applications.
The seemingly high level of public opposition is puz-zling given the views of most scientists on the issue. Itcould be argued that gaps between science and the publichave always existed (4) and are increasing (5). However,the gap is extraordinarily large regarding the safety ofGM
foods.Only 37%ofU.S. consumers believe thatGMfood issafe to eat; in contrast, 88% of scientist members of theAmerican Association for the Advancement of Sciencebelieve GM food is safe to eat (6). The gap between publicand scientific assessmentofGMfoodsafetywas the largestamong all issues studied, including vaccines, climatechange, and fracking, by a recent Pew Research Centerstudy (6). The divide may indicate a need for better sci-ence communication.However, previous research on thetopic has shown that simply providing statements fromthe scientific community does not substantively changebeliefs about the safety ofGMfood, and in fact results in abacklash among a segment of the population (7, 8).
There are several psychologic and behavioral-economicfactors thatmaycause thepublic to formbeliefs inconsistentwith those of scientists. Theworld is full of uncertainty, andconsumers form beliefs subject to constrained time, in-formation, and computational capabilities. These con-straints often require consumers to use heuristics, orrules of thumb, which can lead to biases when decisionsconcern uncertain risks, benefits, and consequences (9).Biases are perhaps more pronounced when consumershave little knowledge about an issue that is contempo-raneously covered by the media, as has been the casewith GM food (10, 11). In addition to media, other socialinfluences likely shape beliefs. For example, consumersare more likely form a belief about an issue that is re-flective of others who share similar values, as suggestedby cultural cognition theory (12). Moreover, consistent
ABBREVIATIONS: GM, genetically modified
1 Correspondence: Department of Food and Resource Economics, 1195McCarty Hall A, University of Florida, Gainesville, FL 32611, USA.E-mail: [email protected]
doi: 10.1096/fj.201600598This article includes supplemental data. Please visit http://www.fasebj.org toobtain this information.
0892-6638/16/0030-0001 © FASEB 1
The FASEB Journal article fj.201600598. Published online May 19, 2016.
signaling from others within a group may cause someconsumers to hold a belief that is perceived to be con-sistent with most scientists when it is not (7, 13).
Here we contribute to the understanding of publicconcern about GM food safety by examining consumerknowledge about genetics and agricultural production.While a large number of studies have asked questionsabout consumer knowledge (14–16), this survey delvesinto the issuemore exhaustively and offers insight into thelevel of knowledge of U.S. consumers about genetics andagricultural production. Furthermore, although framingeffects of GM food labels has been assessed (17), this studyrelates consumer knowledge to the emerging policy issueof mandatory labeling. Moreover, unlike prior research,we here show how consumers’ expressed knowledge andsafety beliefs are affected by such questioning. The resultsdescribedwithin are from a nationwide survey conductedin September 2015 of over 1000 U.S. respondents.
MATERIALS AND METHODS
Data Collection
This studywas approved by the institutional reviewboard at theUniversity of Florida. The surveywas conducted online andwascompleted by a sample of 1004 participants enrolled onto anonline panel maintained by Survey Sampling International andtheir associated partners. Opt-in online panels produce estimatesthat are as accurate as other data collection methods, like tele-phone surveys (18). The survey was fielded from September16, 2015, through September 28, 2015. Survey Sampling In-ternational prescreened participants by gender, education, andincome to ensure the sample was representative of the U.S.population. According to the 2012 U.S. Census Bureau, womenrepresented 50.8% of the population, 28.2% of persons aged 25and older held a bachelor’s degree, and the median householdincome was $52,762. Our sample closely matched these pop-ulation statistics. Fifty-three percent of the survey sample com-prised women, 35% held a bachelor’s degree, and the medianincome category was $40,000 to $59,999. Given the sample size,the margin of error is63.2% for dichotomous questions.
Survey Overview
For the sake of brevity, a brief overview of the questions askedare described below. The specific questions asked by thesurvey and summary statistics for responses may be found inthe Supplemental Data. After consenting to take the survey,participants were asked 10 blocks of questions. Blocks 2through 8 were randomized across participants to minimizeorder effects. Questions associated with each block were asfollows: 1) a question to determine subjective knowledgeableabout GM food, with responses varying on a 5-point scale from“very unknowledgeable” to “very knowledgeable,” a questionthat determinedrespondent level of agreementwitha statement,“Food that has genetically modified ingredients is safe to eat,”with responses varying on a 5-point scale from “strongly dis-agree” to “strongly agree,” and a question that measured con-fidence in the response to the previous agreement question; 2) aquestion that determined if respondents knew howmany genesare altered by different plant breeding techniques (i.e., selection,hybridization, genetic marker assisted breeding, genetic modi-fication, mutagenesis) with response categories “none,” “1 to 9genes,” “10 ormoregenes,” “Impossible to know,” and “I donot
know,” and questions that determined knowledge about theproportion of corn and wheat acres planted with GM seed; 3)questions that testedknowledge aboutwhat crops on themarketwere GM, the purposes or outcomes associated with modifica-tion, and whether GM animals were currently being sold; 4)questions that tested knowledge about when GM crops werefirst grown, and theaverage time it takes for aGMcroporanimalto be approved for human consumption; 5) questions that testedawareness of GM and non-GM herbicide-tolerant crops; 6)questions that tested awareness of the time it takes to create anew variety of GM and non-GM corn; 7) questions that de-termined support or opposition for mandatory labeling of foodand how the issue of mandatory labeling should be decided; 8)questions that tested general knowledge of food DNA; 9) ques-tions in block 1 were repeated; and 10) demographic questions.
Thus, we have within-subject measures of how self-reportedsubjective knowledge, beliefs about GM food safety, and confi-dence in those beliefs changed after answering the questionsasked in blocks 2 through 8. Participants were not informed ofthe correct responses to the questions asked, and therefore anychanges in the within-subject measures were completely a resultof self-reflection. Carewas taken toword questions in an easy-to-read and understandable manner. Nevertheless, the issues areinherently technical in nature and may be difficult to answercorrectly for many people. Nevertheless, it is important to un-derstand the level of public knowledge about genetics and agri-cultural production, particularlywhen assertions are beingmadeabout consumer knowledge and preferences. Furthermore, re-sponses to some of the questions askedmay provide insight intowhy some of the public is not accepting of GM foods. For in-stance, there is a sentiment thatGM isnot natural because it altersgenes in a lab; however, it is unclearwhether people are averse tothe altering of genes in general or averse to genes being altered ina lab setting that could not occur in nature.
RESULTS
Before asking questions that tested knowledge about ge-netics and agriculture production, respondents were firstqueried about self-reported, subjective knowledge of GMfood and beliefs about the safety of GM food. On a 5-pointscale, 8%rated themselves as“veryknowledgeable”aboutGM food, and the highest proportion, 32%, rated them-selves as “somewhat knowledgeable,”with the remaining60% being undecided or not knowledgeable. Results re-garding the safety of eating GM food aligned with pre-vious studies (6, 8). Thirty-four percent believed GM foodwas not safe to eat, 34%believed itwas safe, and32%werein the middle. Respondents in the middle were less con-fident in their beliefs about GM food safety (P , 0.01,Satterthwaite test).
Low levels of knowledge about genetics may invokeconcerns about GM interfering with nature relative toother breeding techniques. Respondents were asked howmanygenes are typically alteredbyvariousplantbreedingtechniques. The various breeding techniques queriedweregenetic marker–assisted breeding, genetic modification,hybridization, mutagenesis, and selection. The results areillustrated by Fig. 1. Approximately half of the sampleindicated theydidnotknowhowmanygeneswerealteredfor the various breeding techniques. Nevertheless, beliefsabout the number of genes altered were significantly de-pendent on breeding technique (P , 0.01, Pearson’s x
2
test). Moreover, compared to the other listed breeding
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techniques, a significant proportion of respondentsthought selection did not alter any genes (Tukey’s post hoctest). Conversely, compared to genetic marker–assistedbreeding, mutagenesis, and selection, a significant pro-portion of respondents thought GM altered 10 or moregenes (Tukey’s test). Thus, respondents associate GMwithmore genetic alteration, which is not consistent withactual practice because selection alters thousands of geneswhile GM typically alters a select few.
Consumers had the option to choose “I don’t know” forthe pervious question. However, when forced to answer aquestion that asked if corn always contained the samegenesbeforeGMwaspossible, 49%of respondents thoughtcorn had always contained the same genes. Further vali-dating that some consumers have little knowledge of basicgenetics were the responses to 2 other questions. Thirty-three percent of respondents thought non-GM tomatoesdid not contain genes, and 32% thought vegetables did nothave DNA. Taken together, these results indicate that atleast of a third of consumers have little to no knowledgeabout genetics.
The most widely adopted GM crops, relative to totalproduction for a given commodity, are corn, cotton, pa-paya, soybeans, and sugar beets. Respondentswere askedwhat crops on the market were GM. Fifty-five percent ofthe sample thought corn was GM, and corn was the onlycommodity to receive more than 50%. A much smallerproportion thought that cotton, papaya, and sugar beetswere GM, at 19, 14, and 18%, respectively. About a third,34%, thought soybeans were GM. Approximately 15% ofconsumers thought all the crops present as response op-tions were GM, including carrots and onions, which 28and 21% of respondents, respectively, thought were GM.Thirty-two percent responded “I don’t know.”
Although respondents were more aware of GM cornthan any other GM commodity, many respondents werenot aware of the extent of GM corn adoption. In 2015,approximately 92%of all corn plantedwasGE (19). Yet onaverage respondents thought 56%(SD24%)of cornplanted
wasGM; they also thought 52% (SD 23%) ofwheat plantedwas GM. Currently there are no acres of GM wheat; nev-ertheless, consumers thought GM corn and wheat wereadopted at similar levels. In addition to crops, 46% of thesample thought there were GM animal food products onthe market.
The commodities previously listed (i.e., corn, cotton,papaya, soybeans, and sugar beets) were modified to beresistant to insects, herbicide, or disease. The reason formodification of GM commodities may not be obvious toconsumers. Respondents were asked why GM commod-ities on themarketmayhave beenmodified. Amajority ofconsumers thought GM commodities currently on themarket were modified to be resistant to insects and dis-ease, at 53 and 52%, respectively. However, only 35% ofconsumers thought GM commodities on the market weremodified to be resistant to herbicides. The result is curiousin light of the recent heightened public discussion anddebate about the safety of glyphosate relative to that ofpesticides.
After answering numerous questions that tested ob-jective knowledge, the questions at the beginning of thesurvey on expressed knowledge and safety beliefs wererepeated. Figure 2 illustrates the change in subjective self-reported knowledge for the sample. It is obvious that themass shifts from the right (i.e., the knowledgeable cate-gories) to the left (i.e., the neither and unknowledgeablecategories) and there was a significant decrease in thenumber of respondents in the “somewhat knowledge-able” category.What is not obvious from the figure is howindividual consumers flowed across these categories afteranswering questions. Paired t tests indicated that afteranswering questions, there were significant increases tothe “very unknowledgeable” (t = 2.68) and “neither un-knowledgeable/knowledgeable” (t = 3.54) categories andsignificant decreases to the “somewhat knowledgeable”(t = 24.69) and “very knowledgeable” (t = 23.86) cate-gories. Together, these results suggest consumers thinkthey knowmore than they actually do, and queries about
Figure 1. Consumer beliefs about number ofgenes altered by various breeding techniques.Significant differences were determined usingTukey’s post hoc text. **P = 0.05, ***P = 0.01.
CONSUMERS AND GM FOOD 3
objective knowledge cause some respondents to reassesshow much they know.
Unexpectedly, simply asking objective-knowledgequestions slightly changed beliefs about GM food safety.Changes in beliefs are illustrated in Fig. 3. Consumerswere significantly more likely to believe GM food wassafe to eat after a series of questions that tested objectiveknowledge about genetics and GM food (P , 0.01, Stu-dent’s t test and Wilcoxon signed rank test). At the indi-vidual level, there was a significant decrease to the“disagree” category (t=22.77, paired Student’s t test) anda significant increase to the “strongly agree” category (t =2.49, paired Student’s t test). While there was a modestchange in beliefs, confidence in beliefs, on average, did notchangeafter answeringquestions (P=0.84, Student’s t test;P = 0.95, Wilcoxon signed rank test). This was also trueeven when the sample was restricted to only those whohad a change in belief (P = 0.73, Student’s t test; P = 0.67,
Wilcoxon signed rank test). However, consumers whochanged safety beliefswere less confident both before (P=0.04, Satterthwaite test) and after (P = 0.02, Satterthwaitetest) answering knowledge questions than consumerswho did not have a belief change.
Public concern about the safety of GM food is oftenexpressed by demands for mandatory labeling; however,the public may prefer to default to experts for decisionsrelated to biotechnology if they are uncertain or believethemselves to be unknowledgeable. Respondents wereasked several questions to determine preferences forlabeling (Fig. 4). While 84% of respondents supportedmandatory labeling for food containing GM ingredients(Fig. 4A), there was also overwhelming support for man-datory labeling of food containing DNA (Fig. 4B). Eighty-percent of consumers supporteda label for food indicatingthe presence or absence of DNA—an absurd policy thatwould apply to the majority of foods in a grocery store.
Figure 2. Subjective knowledge before and afteranswering questions about GM crops.
Figure 3. Beliefs about safety of consumingGM food before and after answering questionsabout GM.
4 Vol. 30 September 2016 MCFADDEN AND LUSKThe FASEB Journal x www.fasebj.org
Rather than asking whether consumers want manda-tory labeling, a more instructive question might be howthey believe such an issue should be decided. A questionsimilar to that posed by Gaskell et al. (20) was applied tothe case of labeling, and results indicated that only 35%thought decisions about mandatory labeling shouldmainly be basedon the views of averageAmericans,withthe remainder believing that the issue should be decidedby experts (Fig. 4C). Furthermore, only 8% thought theissue ofmandatory labeling should bedecidedby aballotinitiative, and themajority, 58%, thought the issue shouldbe decided by the U.S. Food and Drug Administration(Fig. 4D). Therefore, althoughmost consumers support amandatory label for GM food, most consumers alsothought the decision should be made experts with moreknowledge. Indeed, as previous results suggest, con-sumers had little knowledge of basic genetics.
DISCUSSION
Althoughmany consumers claimed to be opposed to GMfood, there was an overall lack of knowledge about
GM food. Previous research determined that providingconsumers with information from the scientific commu-nity about the safety of GM food did not affect opposition(8). However, simply asking knowledge questions aboutGM food appears to have informed consumers that op-position was formed without adequate knowledge, andsubjective knowledge and beliefs did change.
Whether mandatory labels should be required for GMfood is a highly contentious topic. In the debates sur-roundingmandatory labels, data from consumer polls areoften presented as evidence for precaution and labeling.Our results here indicate that consumer polls are not anadequate proxy for the decision of whether a mandatorylabel should be required. Consumers also express supportfor absurd policies like DNA labeling. Such statements ofsupport indicate a low level of knowledge about basicgenetics, or they may indicate how consumers psycho-logically handle difficult questions. It has been argued thatindividuals attempt to economize on scarce cognitive re-sources by unconsciously substituting an easier questionfor a hard one (21). Rather than seriously weighing thepros and cons of mandatory labeling, the similarity in
Figure 4. Views about mandatory labeling.
CONSUMERS AND GM FOOD 5
responses to the DNA labeling question suggests thatpeople may instead be substituting these questions with asimperquestion like,“Doyouwant free informationabouta topic about which you know very little?” This psycho-logic processwould lead to similar levels of support to twovery different policy questions.
In addition to asking whether people wanted manda-tory GM labeling, respondents were also queried abouttheir“meta”preferences forhowsuchadecision shouldbemade. When given the option, the majority of consumersprefer that decisions about mandatory labeling of GMfood be taken out of their hands and be made by experts.This finding is consistent with the notion that consumers’self-assessed knowledge of the topic is low. Consumersroutinely defer to experts on complex decisions (e.g.,obtaining retirement advice, filing taxes, or selling ahouse). Indeed, the choice to defer to an expert is itself anadmission of knowledge inadequacy.
After a bit of reflection, and with the benefit of hind-sight, it seems obvious that consumer polls may not be aproximate cause for policy. It is unlikely that someonewould give a negative answer to a question that involveszero cost and may provide future benefit. Possibly con-firming this idea was the result that nearly equal numbersof consumers prefer mandatory labeling of foods con-tainingDNAasdo those preferringmandatory labeling ofGM foods.
ACKNOWLEDGMENTS
The authors acknowledge the Willard Sparks EndowedChair (Oklahoma State University) and the Hatch Research,Education, and Extension project online reporting tool(REEport; FLA-FRE-005422) (U.S. Department of Agriculture;https://nifa.usda.gov/tool/reeport). Author contributions: B. R.McFadden and J. L. Lusk were involved in all parts of theresearch and writing of this article.
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Received for publication April 29, 2016.Accepted for publication May 12, 2016.
6 Vol. 30 September 2016 MCFADDEN AND LUSKThe FASEB Journal x www.fasebj.org
Genetic Diversity 1
Biological Diversity
1
"Biological diversity" means the variability
among living organisms from all sources
including, inter alia, terrestrial, marine and
other aquatic ecosystems and the ecological
complexes of which they are part; this
includes diversity within species, between
species and of ecosystems.
Definition from Convention on Biological Diversity
https://www.cbd.int/
Biological Diversity
2
“Country of origin of genetic resources"
means the country which possesses those
genetic resources in in-situ conditions.
"Domesticated or cultivated species" means
species in which the evolutionary process has
been influenced by humans to meet their
needs.
Definition from Convention on Biological Diversity
https://www.cbd.int/
Genetic Diversity 2
Corn (Maize) originated in Mexico
4
Centro Internacional de Mejoramiento de Maíz y Trigo
International Maize and Wheat Improvement Center
Domestication of Zea mays ssp. parviglumis, native to the Balsas
River valley in south-eastern Mexico
Banana/Plantain (Musa)
5
Center of origin of the
wild banana stretches
from India to Papua
New Guinea including
Malaysia and IndonesiaInternational Institute
of Tropical Agriculture
Nigeria
http://www.apsnet.org/publications/apsnetfea
tures/Pages/PanamaDiseasePart1.aspx
http://www.apsnet.org/publications/apsnetfea
tures/Pages/PanamaDiseasePart2.aspx
History of banana production in
Latin America and why bananas
are under threat:
Rice originated between Himalayas and Indochina
6
https://www.youtube.com/watch?v=RdwcIF_cm5Y
International Rice
Research Institute
Philippines
• Oryza sativa or Asian rice is the
most commonly grown and eaten
rice. It contains two groups of rice:
indica and japonica
• Oryza glaberrima or African rice
originated in West Africa, but is not
widely cultivated. It has been used
as gene source.
• Twenty-three wild species of rice
that are found in Asia, Africa,
Australia and the Americas.
Genetic Diversity 3
7
Watermelon originated in southern Africa
Spanish settlers were growing watermelons in Florida in 1576. Minimal breeding until 1954
by USDA in SC. Dr. Crall, UF/IFAS, developed “Jubilee” variety in 1963. Seedless watermelons
are sterile hybrids that develop fruits, but no seeds. The seeds for growing them are
produced by crossing a normal watermelon with one that has been changed genetically by
treatment with a chemical called colchicine. The seeds from this cross will produce plants
that, when pollinated with pollen from normal plants, produce seedless melons.
Potatoes originated in Peru
8
Blue Potato Chips Really Do Come From Blue Potaoes!
9
Use Food to Teach about Biological Diversity