ORNL plant-microbe, biochemistry expertise tapped to restore the American chestnut

Scientists at the Department of Energy's Oak Ridge National Laboratory were part of a multi-institutional team that explored how modern scientific approaches such as genomics and biochemical profiling can be combined to understand and improve disease resistance in the iconic American chestnut tree.

The American chestnut, Castanea dentata, once dominated eastern forests with numbers in the billions. The trees grew 100 feet tall on average, and were prized as sources of sturdy, long-lasting lumber for cabins and barns and for abundant chestnut yields that supported livestock and humans. But the tree was decimated by the spread of two fungal pathogen species in the 1900s, with today's American chestnut sprouts typically surviving only a few years before succumbing to what is commonly called the chestnut blight.

The American Chestnut Foundation (TACF), based in Asheville, North Carolina, is sponsoring research that brings together genomics, biological assays and predictive models to identify which genes and strategies are most likely to result in a successful hybrid that has increased blight resistance, but retains the desired height and crown form of the American chestnut. Restoration of the American chestnut to its native range in eastern hardwood forests would be a triumph of U.S. science and innovation.

In a study published in Science, the TACF collaborated with researchers from ORNL, the HudsonAlpha Institute for Biotechnology, Virginia Tech, the U.S. Forest Service, Purdue University, the DOE Joint Genome Institute, and numerous other academic institutions to take on the challenge. They discerned how a complex array of resistance strategies can be combined to accelerate the development of tree populations with blight resistance.

At ORNL, a team of scientists with unique expertise in plant-microbe interactions and biochemistry developed a detailed inventory of the different chemicals present in susceptible, resistant and hybrid chestnut trees for the project. After creating the tree chemical profiles, ORNL researchers tested the compounds against the blight fungus. They discovered that disease-resistant chestnuts contained a high level of a certain class of chemical compounds such as triterpene sterols that reduced or stopped the fungus's growth.

The presence of these chemicals in trees before they are exposed to the fungal pathogens comprises what is known as constitutive or active defense. The thousands of progeny generated from previous and future breeding trials can be screened for these defense compounds to identify the best candidate trees for further research and cross-breeding.

"Understanding and harnessing these natural defenses is a major step toward restoring a species that once defined eastern North American forests," said Tim Tschaplinski, who led the ORNL team and is section head for Biodesign and Systems Biology. "The project drew on ORNL's deep expertise in plant-microbe interactions and biochemical analysis, which are critical for understanding disease resistance and overall plant health. We're excited that these capabilities can benefit the broader plant science community."

The ORNL research team also included Jack Orebaugh, Madhavi Martin, Joanna Tannous, Tomás Rush and Nancy Engle. The work drew on capabilities developed at ORNL as part of the DOE Office of Science Biological and Environmental Research program, including the Plant-Microbes Interfaces Science Focus Area, the Secure Ecosystem Engineering and Design Science Focus Area, as well as the Center for Bioenergy Innovation, the latter focused on developing biomass feedstock crops for new chemicals, fuels and materials.

Read more about the project in TACF's announcement.

UT-Battelle manages ORNL for the Department of Energy's Office of Science, the single largest supporter of basic research in the physical sciences in the United States. The Office of Science is working to address some of the most pressing challenges of our time. For more information, please visit energy.gov/science. - Stephanie Seay