Tests on American, Chinese chestnut hybrid seedlings planted at secret locations demonstrate improved resistance to blight

Wendy Lisney

KNOXVILLE, Tennessee , August 14, 2011 (The Associated Press) – Optimism is sprouting from blight-resistant chestnut seedlings in the Cherokee National Forest and other remote outdoor labs.

The seedlings are hybrids of American chestnuts and Chinese chestnuts.

The U.S. Forest Service, the University of Tennessee and the American Chestnut Foundation are working with the seedlings. They are also being tested in North Carolina, Virginia and other remote forest settings.

The American chestnut valued for its lumber and mast characteristics was decimated by a fungus during the 1990s.

U.S. Forest Service researcher Stacy Clark told The Knoxville News Sentinel long-term conclusions but the hybrids appear to be more resistant than their pure American counterparts.

Researchers are keeping the seedling locations secret to protect them from theft or vandalism.

The seedlings have been planted each year since 2009. Each site has 400 chestnut trees representing four combinations: pure American chestnuts, pure Chinese chestnuts, the latest generation of hybrid blight-resistant chestnuts and hybrids from intermediate backcross generations.

American chestnuts are still sprouting from remnant root stock, but the trees eventually succumb to the blight, typically by the time they're 10 to 15 years old.

For more than 30 years the American Chestnut Foundation has been back crossing American chestnuts with blight-resistant Chinese chestnuts. The most blight-resistant chestnuts bred by the American Chestnut Foundation are predominantly American trees.

The chestnut seedling plots are checked at least three times a year.

Clark said this year "the trees have put on more growth than the last two years. Basically, we're finding out what these trees need to survive."

The chestnuts were raised from seeds in state nurseries before being transplanted in the national forests. Researchers so far have been pleased to discover that damage from browsing from mammals, especially whitetailed deer, has not been a major detriment. The crossbred chestnuts also break their buds late enough in the spring to generally avoid frost.

Researchers know chestnuts seedlings grow best when exposed to plenty of sunlight.

"We're hoping to continue monitoring these trees for at least the next 10 years," Clark said. "Our goal is to determine the best prescription for planting chestnuts in the woods on a forest-wide scale."

Scott Schlarbaum, director of UT's tree improvement program, said success of the chestnut breeding project shows that the battle against exotic pests and diseases attacking native forests can be won.

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