William Powell is using genetic engineering to revive an American tree that was wiped out nearly a century ago.

Powell, a professor at the State University of New York College of Environmental Science and Forestry, has worked for the last three decades to reintroduce the American chestnut to the wild.

American chestnut trees nearly went extinct after a fungal blight came to the United States from Asia, according to the American Chestnut Foundation. Approximately 90 percent of the nearly four billion trees were killed by blight, Powell said.

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Powell has been working on revitalizing the American chestnut for 35 years. He began researching chestnuts when he was a graduate student at Utah State University, far from the areas that chestnuts are indigenous to.

“I grew up, like most people, not even knowing about the chestnut because we had lost them many decades earlier to chestnut blight,” Powell said.

The species was left functionally extinct, meaning that it can no longer function in the ecosystem normally, Powell said. It is rare that a surviving American chestnut can grow large enough to produce nuts before being hit by blight and chopped to a stump, he added.

The blight fungus cannot compete with the microorganisms in the soil, so the roots of the chestnut trees are protected. The trees can sprout at the root collar and send up new shoots, he said, but those shoots rarely grow large enough to flower or cross pollinate to make nuts.

The ecosystem is already prepared to accept the American chestnut back to the wild, Powell said. Tests that fed leaf litter of both natural and genetically engineered trees to wood frogs found that there was no difference between the trees to animals in the ecosystem.

“One-hundred years is a long time to us, but 100 years is not a long time for the ecosystem,” he said.

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Nutritional testing also showed no difference between wild American chestnuts and the genetically engineered nuts his team produced, he said.

The trees were so valuable because they were a vital and stable food source for wildlife in forests looking to fatten up for winter, Powell said. The nuts were also one of the most valuable and profitable crops for farmers, who would harvest the nuts from wild trees, he added.

In his 35 years of research, Powell hasn’t eaten a single chestnut his team engineered, but he’s sure he will be the first person to eat one.

“They’re very precious, so we don’t eat them,” Powell said. “We go out and plant them.”

The American Chestnut Foundation experimented with both backcross breeding as well as genetic engineering. Powell’s team at SUNY-ESF worked on genetically engineering the chestnut to be blight-resistant like Asian species of chestnut.

Backcross breeding involves creating hybridizations of Asian chestnut tree species and American chestnuts to make blight-resistant trees, but those experiments did not result in trees that had tall growth height or were a good substitute in the American chestnut’s ecosystem, he said.

“There are no different risks of introducing a genetically-engineered American chestnut than a non-genetically-engineered American chestnut because we’re making a very small change, only adding a couple genes to the tree to confer the resistance,” Powell said.

The newly-engineered chestnut detoxifies an acid the fungus uses to hurt the tree. The new genes don’t even hurt the fungus, but instead make them resistant to the fungus, he said.

Planting will occur at sites where American chestnut is indigenous. The restoration program will focus on places that lost American chestnuts and deforested areas that won’t disturb the ecosystem, Powell said.

American chestnut trees are native to the East Coast, from Maine to Georgia, and also existed as far west as Tennessee, Powell said. The greatest devastation to the American chestnut population happened along the Appalachian Mountains, where 25 percent of standing timber of American chestnut was lost, he said.

It could take several years to make American chestnut available to the public, Powell said.

The team has to work with multiple regulatory agencies to bring the trees to the public sphere. They must go through the Food and Drug Administration because chestnuts are a food product, Powell said, as well as the Environmental Protection Agency to determine whether the blight-resistant gene editing conducted constitutes a pesticide.

Research is funded by the American Chestnut Foundation, New York state, the Templeton Foundation and several crowdfunding campaigns, Powell said. Funding has also come from USDA grants, National Science Foundation grants and ArborGen, a tree biotechnology company.

“Whether it’s genetically engineered or not genetically engineered, putting it back is going to be beneficial to wildlife,” Powell said.

Published on January 15, 2019 at 11:50 pm

Contact Kennedy: krose100@syr.edu | @KennedyRose001