Goss’s Wilt Disease and Its Effect on the Corn Belt

Carolina Mlynarczyk

Special Guest:Tom Vilsack Secretary of Agriculture

USDA Secretary of Agriculture Tom Vilsack • Nation's 30th Secretary

of Agriculture.• As leader of the U.S.

Department of Agriculture (USDA), Vilsack is working hard to strengthen the American agricultural economy, build vibrant rural communities and create new markets for the tremendous innovation of rural America.

• In Vilsacks four years at the Department, USDA has supported America's farmers, ranchers and growers who are driving the rural economy forward, provided food assistance to millions of Americans, carried out record conservation efforts, made record investments in our rural communities and helped provide a safe, sufficient and nutritious food supply for the American people.

• Promoting American agriculture by conducting cutting-edge research and improving markets at home and abroad.

• 2009-2012 represent the strongest four years in history for agricultural trade, and new trade agreements President Obama signed with Colombia, South Korea and Panama will create even more export opportunities for American farmers and ranchers.

• Here at home, USDA has helped increase the number of farmers markets by 67 percent since 2008, and today there are more than 200 new regional food hubs to help connect farmers with broader regional markets.

• Prior to his appointment, Vilsack served two terms as the Governor of Iowa, in the Iowa State Senate and as the mayor of Mt. Pleasant, Iowa.

• He led a comprehensive effort to improve the safety of the American food supply, implementing changes to food safety standards to prevent illnesses by reducing the prevalence of E. coli, salmonella and campylobacter in our meat and poultry.

Overview

• About Corn• What is Goss’s Wilt Disease• Problem/Paradigm• Models of Success/Research/Studies• Solutions• Budget• Call to Action

Where Else is Corn Besides the

Obvious?

• Many of our foods are produced from corn and corn extract:

• Cereals• Peanut Butter• Snack foods • Soft drinks• Vitamins• Fuel alcohol – helps

gasoline burn cleaner, reducing air pollution in addition to not polluting water

Understanding Corn• An ear of corn averages 800 kernels in 16

rows• A pound of corn consists of approximately

1,300 kernels. • 100 bushels of corn produces approximately

7, 280, 000 kernels. • Each year a single U.S farmer provides food

and fiber for 129 people- 97 in the U.S. and 32 overseas.

• In the U.S corn production measures more than two times that of any other crop.

Importance of Corn• “The economic value of the U.S. corn

crop was $76 billion last year, with U.S. growers producing an estimated

12 billion bushels, more than a third of the world’s supply. It is

the largest production crop worldwide, providing food for billions of people and livestock and critical

feedstock for production of biofuels” (O’Brien, 2012).

What is Goss’s Wilt Disease?• Goss’s wilt (Clavibacter michiganensis subsp.

Nebraskensis) is a bacterial disease that may cause systemic infection and wilting of corn plants.

• Causes severe leaf blighting - more prevalent and more damaging to the corn crop.

• Higher levels of corn residue from corn-after-corn production and reduced tillage are likely contributing factors in the spread of this disease.

• Prevalence of summer storms (hail, wind and rainstorms) that damage corn leaves has a large impact on the severity of infection and yield loss in a given growing season.

• Once on the plant, bacteria invade plant tissue through wounds caused by hail, heavy rain, wind or mechanical damage

• Plants may be infected at any stage of development. • Wet weather and high relative humidity favor

development of Goss’s wilt. This is because leaf wetness is required for infection to occur, and the bacteria spread most readily in humid weather.

• The disease did spread under generally hot, dry conditions has also been documented but not at all as often as the spread of the bacteria in warm climates.

Symptoms

• Infection of corn: Plant injury often due to hail or rain storm.

• Long irregular lesions • Leaf freckle symptoms • Varnish-like exudate • Vascular discoloration: Orange

Recap:

• The disease is a buildup of bacteria in the vascular bundles that inhibit the plants ability to transfer water which then results in stunted growth and wilting as if the plant was drought stressed.

Biggest prevention/detection issue:

Bacteria OVERWINTERS. To overwinter is to pass through or wait out the

winter season, or to pass through that period of the year when "winter" conditions (cold or sub-zero

temperatures, ice, snow, limited food supplies) make normal activity or even survival difficult or near

impossible. In some cases “winter” is characterized not necessarily

by cold but by dry conditions; passing through such periods could likewise be called overwintering.

Because of overwintering:

• Goss’s Wilt can be most severe the year following a Goss’s Wilt infection because of the increased amount of bacteria in the residue.

• So, a field with light infections one year will have the potential to turn into a moderate or high infection the following year with high yield loss expected if a Goss’s Wilt susceptible hybrid is planted back on the same field that same year.

• Since the infected residue can be carried by wind (as well as other weather conditions and sometimes water irrigation systems), the bacteria can be carried over to other fields.

• As a result new strains of bacteria can be formed because it resides in different hybrids.

Lesions that eventually encompass entire corn leaf:

Leaf blight phase of Goss’s Wilt

• These plants have discolored vascular tissue (right), with a slimy bacterial exudate in the stalk.

Midwestern Corn Belt

Disease Cycle of Goss’s Wilt in Corn

Where is Goss’s Wilt NOW?• Until recently, significant Goss’s wilt damage was largely

confined to corn fields in Nebraska (where disease was first seen in 1969 in Lexington) and parts of Colorado, Kansas and South Dakota.

• Second spotting of the disease was reported by 1975, in Iowa, Kansas, South Dakota and Colorado.

• In the last two years, however, significant damage has been reported in Iowa, Illinois, Indiana, Minnesota, and Wisconsin.

• The sudden spread of Goss’s wilt across primary corn growing states places it among the major corn diseases capable of causing leaf loss, lower stalk quality and reduced yields in corn. (Detrimental to economy).

Focusing on Iowa

• Over 55% of Iowa’s corn goes to foreign markets.

• The rest is used in other parts of the U.S.

• Disease incidents in affected fields ranged from 20 to 60%.

• Heavily affected fields have corn yield losses approaching 50%.

“Until 2008, Goss’s Wilt has been confined to western Nebraska and a handful of counties in eastern Colorado. But that year it was found in

Iowa, Illinois, Indiana and Wisconsin. In 2011, a particularly virulent year, farms in much of Illinois lost as many as 60 bushels of corn per acre to the

disease (the usual yield is 200 bushels per acre). So did many counties in Indiana” (Strom, 2013).

Inheritance of Resistance to Goss’s Wilt in Sweet Corn

(Model of Success)

• It was reported that reaction to Goss’s bacterial wilt and blight of corn was probably controlled by more than one major gene.

• Inheritance of susceptibility and resistance appeared to be quantitative with partial dominance for susceptibility.

• Experiment tests uses of diallel (crossing of two or more strains at once to make hybrids in all possible combinations) mating.

“About 90 % of the corn grown in the U.S. comes from seeds that have been

engineered in a laboratory, their DNA modified with genetic material not naturally found in corn species. Almost all American

corn, for instance, is now engineered to resist the powerful herbicide glyphosate (often sold

as Roundup), so farmers can kill weeds without killing their corn” (Strom, 2013).

Corn is now grown based on genes selected by hybrid vigor.

Through Research Scientists have found…

• That corn continues to diversify as it adapts to changing climates and habitats.

• So, not only does bacteria adapt but corn as well.

• Significant variations in the physical size of genomes of different varieties (genome = entirety of an organisms hereditary information) which could be of extreme importance when creating hybrids.

“…Ware and another international team in 2009 provided a genetic blueprint of the corn genome and identified roughly 1 million genetic markers. Using a sophisticated, population-genetics scoring model, Chia and his colleagues were able to identify 55 million markers. The achievement is expected to vastly enhance the ability of scientists and breeders to track and select for valuable regions of the genome to enhance targeted traits” (O’Brien, 2012).

First Report of Goss's Bacterial Wilt and Leaf Blight on Corn Caused by Clavibacter michiganensis subsp.

nebraskensis in Indiana

• Eighteen plants were mechanically inoculated at growth stage V1 to V2 with a bacterial suspension of approximately 1 × 108 CFU/ml prepared from cultures grown on CNS for 10 days at 28°C (2).

• Inoculum was rubbed onto leaves dusted with Carborundum and 0.1 ml of the bacterial suspension was injected into stems with a hypodermic needle.

• Nine control plants were inoculated with sterile water. • Plants were kept at greenhouse conditions (24°C) with

supplemental 400W high-pressure sodium light.

• Within 5 to 8 days, leaves and stems of all 18 inoculated plants developed water-soaked, necrotic lesions.

• No symptoms were observed in control plants.• Bacteria were re-isolated from symptomatic plants on

CNS medium as described above, and gram-positive colonies were obtained.

• Re-isolated strains were identical to C. michiganensis subsp. nebraskensis by D16S2 DNA sequence analysis, confirming the causal agent of the disease.

Simple Complex Solutions

1. Corn growers can burn and bury corn crop residue to decrease their chances of having a widespread outbreak of the disease next year

Tilling Soil

2. Since the bacteria survives in infested residue, any type of tillage operation that buries residue to encourage decomposition may be effective in reducing the rate of new infections.

Rotate Crops

3. Rotating out of corn into other crops such as soybeans or small grains will help reduce primary sources that make it easy for the bacteria to infest corn. ***corn-on-corn acres are one of the reasons why Goss’sWilt is so prevalent because it leads to overwintering the same pathogens that caused it in the first place.

Weed Control!!!

4. Weed control is a must since other hosts for the pathogen include green foxtail, shatter cane and barnyard grass. These weeds grow around corn so to prevent the spread of the pathogen, weeds must/should be taken care of.

Clean! Clean! Clean!

5. Avoid spreading the pathogen by simply harvesting and tilling soil last and then cleaning tools to avoid the spread of the pathogen to other uninfected fields.

Producing plant hybrids

• Each research study conducted, shows that plant hybrids are the best way to prevent Goss’s Wilt.

• Although, more than 100 new strains of the bacterium have been discovered, recurrent selection of seeds should be effective enough in increasing resistance in corn as new forms of corn seeds are chosen by hybrid vigor.

• In addition to producing resistant seeds, it is important to keep in mind that tilling, crop rotation, etc. are very important as well.

Budget• Agronomists annual salary = $ 58,450 x 2 = $116,900 • Plant pathologist salaries ranging from $32,435 to

$73,415 per year- 55,500 x 2 = $111,000• Soil and Plant Scientists earned a median annual

salary of $58,740 x 2 = $117,480• Bag of Hybrid seeds (ex. Hybrid A & B):80,000 kernels/seeds (100 ears of corn) per bag = 150 x 2 (hybrid A & B)= $300 x 4 = $ 1,200Total: $346, 580 per year (all other labor is done by farmers themselves).

Call to Action

• As a result of healthier corn, market will increase.

• Farmers income will increase• Need for production of hybrids = production

of jobs = better economy.• Provide healthy food to the

populations/government buying the corn.

Thank you Secretary Tom Vilsack for attending!

Thank you everybody for listening &

feel free to ask me any questions!