New Tools to Bring Back the American Chestnut

American chestnut bur.Photo courtesy of the American Chestnut Foundation.

It’s been a long time now since American chestnut trees dominated the forest canopies of the East, so long that there are few people alive who remember stands with trees nearly the size of redwoods or the pungent smell of chestnuts in bloom that filled the forests before the blight came.

It’s taken almost 30 years of crossbreeding remaining American chestnut trees with blight-resistant Chinese chestnuts to produce seedlings that are almost pure American chestnut with genes for blight-resistance. The Forest Service and others are planting seedlings produced by The American Chestnut Foundation (TACF) in numerous locations, but it will still take another generation to find out if they will live and reproduce. In the South, survival is complicated by Phytophthora, an organism that causes root rot that can quickly bring an end to seedlings.

Earlier this fall, the Southern Research Station (SRS) and other partners involved in the Forest Health Initiative (FHI) announced success in using genetics and biotechnology to develop American chestnut seedlings ready for blight-resistance testing in the field.

FHI, launched in 2009 as a new approach for addressing emerging forest disease and pests using new biological sciences resources, took on the restoration of the American chestnut as one of its first projects. In addition to the biological sciences research, the approach includes a social science component designed to engage the public in conversations about the issues involved in genetically engineering forest trees for restoration purposes. 

American chestnut tree in the Southern Appalachians. Photo courtesy of the American Chestnut Foundation.

Scientists at the Southern Institute for Forest Genetics (SIFG) are working with collaborators to provide candidate genes for resistance to chestnut blight and Phytophthora root rot—the two most deadly diseases of American chestnut. So far, researchers have identified 27 genes from Chinese chestnut, which is resistant to chestnut blight, and transferred them each into the American chestnut genome, developing 27 separate “lines” to test. These lines are now being grown as plants that will be tested in the field for resistance to blight and root rot.

“FHI developed genomic resources to map the major genes for resistance to chestnut blight and root rot and to compare portions of American and Chinese chestnut genomes,” says Dana Nelson, SIFG project leader who serves as leader of FHI’s Science Team as well as principal investigator on the American chestnut project. “By successfully reaching its goal of producing plantable American chestnut seedlings for testing within three years, this project demonstrates the power of genomics and biotechnology to address forest health and ecosystem restoration issues in the future.”

Collaborators on the American chestnut project include other U.S. Forest Service regions and research stations, universities, and TACF.

FHI intends to use this approach as a template for other forest health challenges such as emerald ash borer, hemlock woolly adelgid, and many others as they arise. The FHI is a multi-stakeholder collaborative effort jointly funded by the Forest Service, U.S. Endowment for Forests and Communities, and Duke Energy.

For more information:  Dana Nelson at dananelson@fs.fed.us

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