SYRACUSE — American chestnuts used to be unique and beautiful trees, providing sustenance and shelter for wildlife and a healthy and profitable nut crop for humans. These trees were huge, majestic and very long-lived compared to other species in America’s eastern forests. But tragically, American chestnuts were almost entirely wiped out when an invasive blight fungus was accidentally introduced to the United States in the late 1800s. Without human intervention, populations of pure American chestnut will likely continue to decline until they are all but gone.
However, there are relatives of the American chestnut that evolved with the blight fungus in Asia; they usually tolerate blight infections without much damage. There have been multiple efforts to breed American with Chinese chestnuts to get desirable characteristics from both species, but traditional breeding is a slow and unpredictable process that is limited by undesirable traits from Chinese chestnut that make them less suited to competing in eastern U.S. forests.
The American Chestnut Foundation’s backcross breeding program shows promise in producing trees with American chestnut growth traits, but since blight resistance in Chinese chestnuts is controlled by several genes, inheritance by future generations of chestnuts is inconsistent (think hair color in humans: a child’s hair isn’t always the same color as either parent, but there are general trends that are somewhat predictable). Recent technological advances in genomic screening are improving this process, but it will still probably require multiple generations of breeding, and blight resistance in backcrossed offspring will likely never equal that of the Chinese chestnut ancestor.
At the College of Environmental Science and Forestry (ESF) here in Syracuse, our research team is trying a different approach. We’re using the tools of biotechnology to produce fully American chestnut trees that successfully tolerate blight infections, protecting the tree without even harming the blight fungus itself. What we did was copy a single gene from wheat — though the same gene is found in many other plants like corn and bananas, and there are no similarities to gluten or other allergens — and transferred it into American chestnuts. This enzyme breaks down a toxin called oxalic acid, which is produced by the fungus and kills American chestnut tissues. [Read more…]