Our forests are facing many challenges

Chestnut Blight

How a single gene may help save the American Chestnut

2

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

Keystone forest species

(environmental benefits)

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

Forest History Society

American chestnut tree had diverse forms

photo in MI, 1980s by Alan D. Hart

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

Spring 1912

1912 photo of blight in NY

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)

How do we get the gene in?

How do we test for blight resistance?

Coexistence of C. parasitica and chestnut trees

Therefore, the tree tolerates the fungus

The fungus survives on American chestnut

similar to Chinese chestnut

Inheritance of blight tolerance Pollination with transgenic pollen

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

26

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

Questions?

"We humans are more than consumers,

we have gifts of our own to give to the

earth." Dr. Kimmerer at the U.N.