Our forests are facing many challenges Chestnut Blight
How a single gene may help save the American Chestnut 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) Many undergrads, high school students, collaborators, and many volunteers 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 2
Wood products Agricultural Social/historical Chestnuts roasting on an open fire, The Christmas Song (by Torme and Wells in 1946)
Keystone forest species (environmental benefits)
Restoration of the American chestnut may benefit many endangered species Carolina northern flying squirrel (Glaucomys sabrinus) More mast, more rodents, supports American burying beetle Small Whorled Pogonia, Isotria medeoloides, Habitat promoted by American chestnut American chestnut was predominant before these species were endangered
Forest History Society American chestnut tree had diverse forms photo in MI, 1980s by Alan D. Hart
Chestnut blight in the U.S. ~50 years spread through natural range killing ~4 billion American chestnut trees Chestnut blight on related species: Allegheny Chinkapin, C. pumila var. pumila Ozark Chinquapin, C. pumila var. ozarkensis In 1904, discovery of chestnut blight in the Bronx Zoo (Merkel) 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 Japanese chestnut C. crenata American chestnut C. dentata Chinese chestnut C. mollissima European chestnut C. sativa
Are hybrids suitable for restoration? Unlikely to replace the American chestnut Lion: Panthera leo Tiger: Panthera tigris American chestnut Castanea dentata (canopy tree) Chinese chestnut Castanea mollissima (orchard tree) Better ways: Liger: Panthera hybrid
~38,000 CC genes + ~38,000 AC genes TACF Meadowview Farm, VA Dr. Fred Hebard (started 1983) Dr. Jared Westbrook (current) Unwanted traits Unwanted traits Unwanted traits Goal is for 1/16 Chinese chestnut genome to contain the required 3 to 6 more blight resistance loci (#genes?) What if you didn t have to select out any unwanted traits?
Breeding & Transgenics: (Both viable options & both have advantages & disadvantages) Chestnut has ~ 38,000 gene pairs 1/16 Chinese chestnut genes: CC AC 10 pages or 2,375 words Making very small changes, adding only 2 words It was very exciting at that season to roam the blight resistant then boundless chestnut woods of Lincoln, Henry David Thoreau, Walden: or Life in the Woods, 1899 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) Remember, it is not the source of the gene that is important, it is the function of the gene that is key. 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)
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
Oxalate oxidase (OxO) from wheat ubiquitous enzyme in many plants & fungi (non-gluten enzyme) Detoxifies oxalate (oxalic acid) Not a pesticide (more like an antitoxin) Does not kill the fungus, no cidal activity. Since the fungus survives, less selective pressure to overcome the oxalate oxidase. 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 Supplier of pollen Regionally adapted T1 Genotypes ½ mother & ½ father pollen seed Parental allelic composition Continue to maximize out-crossing Transgenic American chestnut TACF conservation orchards Or surviving wild population Or backcross trees Offspring 50% OxO & fully blight resistance Allows: Allelic rescue, local adaptation, and increases genetic diversity 26
Applications to forest health Need to take a holistic approach Pest or Pathogen destroys the trees Containment procedures buying time Genetic engineering & breeding Rescue genetic diversity Early development of pest & pathogen resistant trees for restoration
"We humans are more than consumers, we have gifts of our own to give to the earth." Dr. Kimmerer at the U.N. Questions?