Grain Gene Fights Fungus

The American chestnut may be on the verge of a comeback. More than 125 years after Asian chestnuts arrived in the United States carrying a fungus that caused the near eradication of one of the most common Eastern forest trees, scientists at the SUNY College of Environmental Science and Forestry are growing healthy American chestnuts again.

According to researchers William Powell and Chuck Maynard, spores from the fungus that causes chestnut blight infect a wound in chestnut trees; the fungus forms oxalic acid, which eventually kills the vascular tissue of the tree. Between three and four billion American chestnuts were killed by blight by 1950. Just a few million are believed to have survived. Since the late 1980s, Powell and Maynard have been working to develop an American chestnut that is blight-resistant, as the Asian variety is.

With funding from the American Chestnut Foundation and numerous other agencies, including campfire clubs and the Wild Turkey Federation, Powell identified a gene in wheat that combats the oxalic acid produced by the fungus. “The wheat gene encodes an enzyme that breaks down oxalic acid into hydrogen peroxide and carbon dioxide, both of which trees need to grow,” explained Powell, a molecular plant biologist. “It detoxifies the acid, taking the fungus’ weapons away. It doesn’t kill the fungus, so the fungus doesn’t evolve a way to overcome it.”

By inserting this one gene into the embryos of American chestnuts, the scientists are producing trees that are 99.9993 percent identical to the native species. “No one has done this for a forest tree before,” said Maynard, a tree improvement specialist. “We hope this resistance gene will get passed on to surviving trees and their offspring will carry it on.”

To ensure that the blight-resistant trees do not have a negative effect on the environment, Powell and Maynard are conducting a series of field tests to assess such factors as leaf litter decomposition, the feeding habits of insects, the growth of ecologically important fungi, and the composition of the nuts. They say that all of the results so far are normal. They achieved an important milestone last year when the trees with the wheat gene were inoculated with the blight and remained as healthy as a group of control trees that were inoculated with only water. The next step is to seek approval from the U.S. Department of Agriculture, the Environmental Protection Agency, and the Federal Drug Administration for the public to grow and plant the trees, a process the researchers expect will take about five years. By then, their field testing will be complete and they will have produced about 10,000 American chestnut trees for distribution, after which they hope the nursery industry will take over production.

American chestnuts were once prominent enough to earn a place in American culture – think of how many Chestnut Streets remain long after the trees disappeared. Its wood is rot-resistant, making it suitable for use in construction, and its abundant nuts were once a dietary staple for wildlife. A crowdfunding campaign raised more than $100,000 to grow the first batch of blight-resistant chestnuts. “People just love this tree,” Powell said.


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