Researchers have been trying to breed fungus-resistant chestnut trees for 100 years

AILSA CHANG, HOST:

And now a checkup of sorts on the American chestnut, a tree that was a big part of forests in the eastern United States until 1904, when a fungus from Asia started killing them. Since the 1920s, researchers have been trying to breed fungus-resistant chestnut trees. Roxy Todd of member station Radio IQ in Virginia reports that a hundred years later, they're still at it.

ROXY TODD, BYLINE: At the Meadowview chestnut orchard in southwest Virginia, tens of thousands of chestnut trees grow on hilly pastures. Sitting in his truck, Vasiliy Lakoba looks over the vast orchard that he manages.

VASILIY LAKOBA: With each successive generation, you're trying to retain as much resistance as possible.

TODD: Resistance to the fungus called chestnut blight that nearly wiped out American chestnuts.

(SOUNDBITE OF TRUCK ENGINE STARTING)

TODD: He restarts his truck to drive to a tree where chestnut blight surrounds the trunk. It looks like the tree has bulging sores on it.

LAKOBA: And really, it sort of cinches in and effectively girdles the tree. And it's game over from there.

TODD: Many of the trees in this orchard have various degrees of this parasite, which will eventually kill most of them. To get a tree that could fight off the fungus or live longer with it, scientists have been crossbreeding American chestnuts with Chinese chestnuts, creating a hybrid.

LAKOBA: Well, when we say hybrids, we mean that the genetics of the two species become mixed.

TODD: This isn't genetic modification done in a lab. This is slowly nudging the trees along from generation to generation over decades. There are some trees at the Meadowview orchard that are showing promise, says Lakoba. He points to one tall and straight tree that appears to be fighting off the fungus.

LAKOBA: Certainly this is much, much, much improved over what the wild-type American ancestors of this tree looked like under similar disease conditions.

TODD: Ideally, chestnut should be able to survive hundreds of years in the wild and grow to a hundred feet tall. The oldest trees here are 33 years old. Lakoba says it may take another hundred years of breeding to get a chestnut tree that can again take root in wild forests.

For NPR News, I'm Roxy Todd in Meadowview, Va.

(SOUNDBITE OF KACEY MUSGRAVES SONG, "SLOW BURN") Transcript provided by NPR, Copyright NPR.