our forests are facing many challenges chestnut...
TRANSCRIPT
How a single gene may help save the American Chestnut
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Many undergrads, high school
students, collaborators, and
many volunteers…
Current research team:
Bill Powell (Director)
Chuck Maynard (Co-Director Emeritus)
Linda McGuigan (TC lab Manager)
Allison Oakes (Post doctoral fellow)
Kaitlin Breda (Admin assistant)
Andrew Teller (Research Analyst)
Andy Newhouse (PhD grad student)
Tyler Desmarais (MS grad student)
Dakota Matthews (MS grad student)
Vern Coffey (MS grad student)
Yoks Bathula (MS grad student)
Xueqing Xiong (MS grad student)
Erik Carlson (MS grad student)
Hannah Pilkey (MS grad student)
The work of well over 100 people over the years
Agricultural
Wood products
Chestnuts roasting on an
open fire, The Christmas
Song
(by Torme and Wells in 1946)
Social/historical
Restoration of the American chestnut may benefit many endangered species
Carolina northern flying squirrel
(Glaucomys sabrinus)
Small Whorled Pogonia,
Isotria medeoloides,
Habitat promoted by American chestnut
American chestnut was predominant
before these species were endangered
American burying beetle More mast, more rodents, supports
Chestnut blight in the U.S.
In 1904, discovery
of chestnut
blight in the Bronx
Zoo (Merkel)
~50 years spread through natural range
killing ~4 billion American chestnut trees Allegheny Chinkapin, C. pumila var. pumila
Ozark Chinquapin, C. pumila var. ozarkensis
Chestnut blight on related species:
Chestnut blight also survives on oaks
After over a century of unsuccessful attempts at combating the blight,
what are the choices for restoration?
Chestnut f1 hybrids are OK for ornamentals or crops,
Not for restoration
American chestnut
C. dentata
European chestnut
C. sativa
Chinese chestnut
C. mollissima
Japanese chestnut
C. crenata
Are hybrids suitable for restoration?
Lion: Panthera leo Tiger: Panthera tigris
Liger: Panthera hybrid
American chestnut
Castanea dentata
(canopy tree)
Chinese chestnut
Castanea mollissima
(orchard tree)
Unlikely to replace the
American chestnut
Better ways:
TACF Meadowview
Farm, VA
Dr. Fred Hebard
(started 1983)
Dr. Jared Westbrook
(current)
Goal is for 1/16
Chinese chestnut
genome to contain
the required 3 to 6
more blight
resistance loci
(#genes?)
~38,000 CC genes + ~38,000 AC genes
Unwanted traits
Unwanted traits
Unwanted traits
What if you
didn’t have to
select out any
unwanted
traits?
1/16 Chinese chestnut genes:
10 pages or 2,375 words It was very exciting at
that season to roam the
then boundless chestnut
woods of Lincoln, … Henry David Thoreau, “Walden: or
Life in the Woods,” 1899
Making very small
changes, adding
only 2 words
CC AC
Breeding & Transgenics: (Both viable options & both have advantages & disadvantages)
Chestnut has ~ 38,000 gene pairs
blight resistant
100% American chestnut + blight resistance
What genes do we test? Forest Health Initiative grant: Asian species
Quantitative resistance, therefore requires multiple genes:
Possibilities so far out of 28 being tested:
1. Acid phosphatase (C. mollissima)
2. Laccase-like protein (C. mollissima)
3. Lipid transfer protein (C. mollissima)
4. Cystatin (C. mollissima)
5. Glutathione s-transferase (C. mollissima)
6. Deoxy-arabino-heptulosonate phosphate synthase (C. mollissima)
7. Subtilisin-like protease (C. seguinii)
Or other plants? stilbene synthase (grape) – phytoalexins like resveratrol (Dr. Joe Nairn, UGA)
oxalate oxidase (wheat and many other plants) (Dr. Randy Allen, Texas Tech)
Remember, it is not the source of the gene that is important,
it is the function of the gene that is key.
Oxalate oxidase (OxO) from wheat ubiquitous enzyme in many plants & fungi
(non-gluten enzyme)
Wheat
Rice
Barley
Sorghum
Banana
Oil palm
Date palm
Barrel clover
Strawberry
Beet
Cacao
Peanut
Peach & Apricot
Goatgrass
Stiff brome
Wild einkorn
Perennial
ryegrass
Castor bean
Insulin plant
Spiny amaranth
Azalea
Mosses (6 spp.)
Fungi
Not a pesticide (more like an antitoxin)
Does not kill the fungus, no ‘cidal’ activity.
Detoxifies oxalate (oxalic acid)
Since the fungus survives, less selective
pressure to overcome the oxalate oxidase.
Oxalate oxidase (OxO) from wheat ubiquitous enzyme in many plants & fungi
(non-gluten enzyme)
On transgenic American chestnut, changes
the fungal lifestyle from a pathogen
to a saprophyte (coexist).
(like on Chinese chestnut & some oaks)
Coexistence of C. parasitica and chestnut trees
Therefore, the tree tolerates the fungus
The fungus survives on American chestnut
similar to Chinese chestnut
Darling 311 T1 Seedling
OxO Transgenic American
Chestnut
Full Sibling Control
Non-Transgenic American
Chestnut
Photographed 13 weeks after inoculation with C. parasitica strain EP155
Federal regulatory review:
Non-regulated status Voluntary -
No further questions Registration?
New paradigm
for regulators
Many typical comparative studies, plus additional experiments
for restoration trees
(slide by Andy Newhouse)
A unique opportunity with the Darling
lines of blight resistant
American chestnut:
Rescuing the surviving
genetic diversity.
18 in. DBH American chestnut
Manlius, NY
Unique feature of the ‘Darling’ American chestnut trees:
Rescuing genotypes surviving trees
Transgenic
American
chestnut
TACF conservation orchards
Or surviving wild population
Or backcross trees
pollen
Regionally
adapted
Continue to
maximize
out-crossing
Allows:
Allelic rescue,
local adaptation,
and increases
genetic diversity
T1 Genotypes
½ mother & ½ father
Parental
allelic
composition
Offspring
50% OxO & fully blight resistance
seed
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Supplier of pollen
Pest or Pathogen destroys the trees
Applications to forest health
Need to take a holistic approach
Early development of pest & pathogen resistant trees for restoration
Containment procedures buying time
Rescue
genetic
diversity Genetic engineering
& breeding