Native trees adapt to the climate and environmental conditions of their area to survive. Researchers from the College of Natural Resources and Environment in collaboration with the American Chestnut Foundation confirmed this by examining the genomes of American chestnut trees sampled throughout the Appalachian Mountains and grouping the samples according to their specific environmental region.
The research, recently published in the Proceedings of the National Academy of Sciences journal, has the potential to help the foundation restore the American chestnut population and adapt breeding to the changing climate.
“To understand historical local adaptation to climate, we sequenced the genomes of many wild chestnut stump sprouts and identified relationships between the genomes at these different places and the environment of those places,” said Jason Holliday, professor at the Department of Forest Resources and Environment. Conservation.
What the team discovered, according to Holliday, was a high degree of genetic adaptation to different environments in chestnut trees. Team members then divided the Appalachians into three areas based on similar adaptations of the native trees: one group in the north, one in the center and a third in the south.
Fungal disease decimated the American chestnut tree in the early 20th century, killing billions of trees and altering the life cycle of the species native to the Appalachian Mountains. Due to chronic fungal infections, the species cannot reproduce, migrate or evolve in response to climate change. The American Chestnut Foundation has been working for the past four decades to create a genetically modified, disease-resistant strain, but adaptive diversity has not been a focus until now.
“The American Chestnut Foundation breeding program used pollen from various places throughout its range, so one question is: have they captured the adaptive diversity present in the wild American chestnut range in a way that would allow them to develop families that are very suitable for specific planting locations,” says Holliday.
Using deep learning software, researchers were able to predict the geographic origin of a given genome sequence by training this model using trees with known origins. The results showed that the foundation did a good job of producing trees with adaptive diversity, although attention must be paid to not losing this diversity through further breeding for resistance to the disease.
In the future, in addition to providing guidance for collecting and preserving more of this diversity from the three regions identified by the study, this information may help the foundation recover specific blight-resistant American chestnut families based on regions in which their genome best fits together.
Alex Sandercock, lead author of this paper, was a doctoral student in the genetics, bioinformatics and computational biology program and a graduate fellow of the Institute for Critical Technology and Applied Sciences at the time of the study.
Jared Westbrook, co-author of the paper and scientific director of the American Chestnut Foundation, said Sandercock’s work has developed achievable goals for how many American chestnut trees should be retained in each of the three regional populations.
“We learned that the American Chestnut Foundation still has more work to do to preserve trees of the southernmost U.S. population, which are especially important to conserve because these are the most genetically diverse and likely best adapted to the warmer climates of the future,” said Westbrook.
Funding for this research was provided in part by the Institute for Critical Technology and Applied Sciences at Virginia Tech and the National Institute of Food and Agriculture.
