On a morning in early spring, Craddock steers a clanking maroon van south of Chattanooga toward Bendabout Farm, where he oversees three of his five experimental chestnut orchards. The chestnuts will soon be coming into bloom, giving him just a few weeks to do the matchmaking for a new generation. He seems slightly frazzled. "Chestnut breeding time," he admits, "is a time of great anxiety."
Craddock follows breeding procedures championed by corn geneticist Charles Burnham, who helped found the American Chestnut Foundation (TACF) in the early 1980s. Since that time, TACF has led the effort to breed blight-resistant hybrids at its experimental farm in Virginia. In the technique, known as backcrossing, successive generations of Asian-American hybrids are crossed with pure American trees. The idea, Craddock says, is first to transfer blight-resistance characteristics to the American species, then phase out all other Asian traits (the Asian trees, shorter and less hardy, are not well adapted to U.S. forests) by subsequent crosses with American chestnuts.
Scientists predict it will take at least five generations of crosses to produce a highly resistant tree. Even so, the odds are daunting: for every hundred trees produced, only a handful acquire resistance. "If you were a professional gambler," says Craddock, "you'd never bet on the American chestnut tree." Still, TACF's efforts appear to be paying off: the program expects to have its first blight-resistant nuts ready to test in forests by 2007 or 2008. But TACF's trees can't restock the entire Eastern United States, nor should they. A resistant hybrid that flourishes in Virginia could falter in Maine or Georgia, which is why TACF wants to develop local chapters that can draw on an area's native stock to breed blight-resistant trees. Craddock and his helpers, for instance, scoured Tennessee for remaining American chestnuts with which to create his first locally adapted hybrid generation.
He gestures proudly to a row of 15-foot-high saplings, their saw-tooth-edged leaves fluttering in the breeze. They are the first Tennessee hybrids that he bred, planted seven years ago. Each will soon be challenged with a shot of blight fungus, and those few that show some resistance will be selected for breeding the next generation. "Unfortunately, you've got to kill some of them," he explains, wagging the slim branch of one tree. "That's sad because they're my babies. But if we don't do it, we won't be able to make progress in the breeding program."
Craddock, like other chestnut researchers, is exploring another anti-blight strategy—using a virus to cripple the fungus. The virus, whose effects were first described by a French researcher in 1965, blunts the fungus' virulence, thereby giving the infected trees a fighting chance. U.S. researchers have been testing the virus since the early 1970s and have found that while the virus may save individual trees, the method isn't potent enough to protect a whole forest. Craddock and others suspect that the trees most likely to benefit from this method already have some ability to fight the blight. If so, chestnut restorationists may be able to use partially resistant trees coupled with virus control to outwit it.
It's one thing, of course, for chestnuts to thrive in an orchard and quite another for them to flourish in a forest. "From the plant's point of view, the forest is an extremely harsh environment," says Craddock. "Trees are competing for nutrients and light. And you've got the constant pressure of predation. There are insects and mollusks, mammals and fungi—and they're all trying to eat you. I don't think we can expect to plant seeds all over the mountains and come back in 50 years and find a chestnut forest." Still, Craddock is confident that chestnut forests will return. Not in his lifetime, but maybe in his grandchildren's. "If you really like chestnuts," he says, "you've got to be an optimist."