Scientists Work to Restore Chestnuts
to the East
June 2004
Stately giants once ruled the eastern forests of the United States. Towering up to 100 feet in virgin stands, mature American chestnuts (Castanea dentate) averaged up to five feet in diameter. A productive, late-flowering tree, its abundant nuts were the most important food source for a range of wildlife including birds, squirrels, bears, and deer.
Rural eastern U.S. economies were as dependent on chestnuts as the wildlife. Nuts were fed to livestock and gathered by many Appalachian families for sale in the big cities. The relatively lightweight, highly rot-resistant wood was also used to make a wide variety of supplies including railroad ties, fence posts, fine furniture, and musical instruments.
At the beginning of the 20th century, one-quarter of the hardwood tree population from southern Maine as far west as Mississippi was a chestnut, according to the American Chestnut Foundation. And many of the dry ridge tops of the central Appalachians were so crowded with trees that the mountains appeared snow-capped in early summer when the chestnut canopies filled with creamy white flowers.
But, by 1950, a deadly fungus known as chestnut blight (Cryphonectria parasitica), likely imported into the United States on Asian chestnut trees, obliterated American chestnut populations. Spores carried by wind, rain, and animals entered trees through fresh injuries in the bark, eventually cutting off the flow of nutrients, destroying about 3.5 billion trees.
Now, 100 years after the blight was first identified in New York City's Bronx Zoo, researchers are honing in on the science necessary for a viable chestnut revival. Repopulating the chestnut's native range presents a significant challenge, but using traditional methods of genetic engineering and plant breeding, scientists have been working to create a variety of blight-resistant trees.
Strategies include crossing the blight-resistant Chinese chestnut with resilient American specimens, interbreeding American chestnuts that survived the blight in an effort to create robust trees, and inserting genes conferring fungal resistance from other plants into chestnut trees. Scientists have also attempted to battle the fungus directly with a virus known to limit infestation in European trees. However, due to differences in how the fungus spreads on the two continents, this approach has met with the least success.
For a true revitalization, researchers agree that one technique alone is unlikely to do the trick. A combination of scientific strategies will be necessary to bring the American chestnut back.
Sources: Associated Press, American Chestnut Foundation
