For the past 30 years, the American Chestnut Foundation has diligently practiced selective breeding in an effort to revive the American chestnut.
TACF technicians cross the American species with a chestnut variety from China that resists the Cryphonectria parasitica fungus. Offspring that are most resistant to the fungus are selected, especially those that are most similar to the American chestnut. These selections bear, for example, thinner and narrower leaves. Then those offspring are re-crossed with the American chestnut. Six generations of crossing have yielded a hybrid with 94 percent of its genes coming from the American variety.
Last year, the American Chestnut Foundation planted 150,000 such hybrid seeds, according to Ruth Goodridge, communications director of the organization. The ultimate goal is to generate seeds for the hybrid that can be sown to grow into blight-resistant trees.
However, the genetics of the hybrids can be unpredictable, Scott Merkle, a forest biologist at UGA who is involved in genetic engineering efforts to revive the American chestnut, told scienceline.org.
“No matter how much traditional breeding is done, you still end up with a lot of genes from the Chinese chestnut, and you don’t know what these genes are,” Merkle said.
Successes with the chestnut tree are important because they could provide lessons that help conservationists save other trees.
