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The American chestnut, once one of the most common trees in eastern forests, all but disappeared a century ago, when a blight took down about four billion of these giants. Researchers have developed a blight resistant chestnut using genetic engineering that they hope can be used to bring back this iconic tree. But some groups worry about the long term consequences of releasing a GMO tree into the wild.

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Retired environmental scientist Mike Aucott has become a chestnut enthusiast in recent years. At the Allegheny National Forest this fall, he walked over a rocky ridge, covered in low bush blueberry shrubs. “This is the kind of place you tend to find remnant surviving Americans,” he said.

historical photo of American Chestnuts

This photo, taken in the mid- to late 19th century, shows how large and abundant the American chestnut was in the forests of the eastern United States. Photo: Forest History Society, Durham, NC

American chestnuts were some of the largest, fastest growing, and useful trees in eastern forests. They stood more than 100 feet tall and as much as ten feet in diameter. The wood was rot resistant, with a straight grain, used in everything from cradles to coffins. The nuts not only inspired holiday songs, they were a source of food for people and wildlife. When American chestnuts succumbed to the blight, an estimated five species of insect went extinct.

American chestnuts still grow in forests. Aucott found one that produced nuts two years ago, but the top of the tree now looks dead. “That shows that the blight is getting into it,” he said.

American chestnut with a canker

An American chestnut shown here with the canker from the blight. It will eventually kill the tree. Photo courtesy of SUNY College of Environmental Science and Forestry

What people call the blight is a fungus that was brought to the U.S. when chestnut trees were first imported from China and Japan a century ago.

These Asian varieties are adapted to the fungus, which produces an acid that creates a lethal canker on American chestnuts.

Decades of Disappointment

People who want to see it tower in the eastern forests again have faced decades of disappointment. The roots continue to sprout and start to grow.And as it grows, it will get the blight again, get killed down again. It’s stuck in this cycle,” explained researcher William Powell. “Eventually the roots run out of energy and the whole tree dies.” 

Powell has been working 35 years to restore the American Chestnut, most of that at the State University of New York in Syracuse, where he is director of the American Chestnut Research & Restoration Project.

People have been trying for much longer to make a hybrid Chestnut that is resistant to the blight. 

“I’ve seen papers all the way back to the 1920s, hybridizing it with the Japanese chestnut, the Chinese chestnut, all kinds of different things, trying to make blight resistant trees,” he said. “But none have been successful back out into the wild.”

Developing the GMO American Chestnut

William Powell with GMO chestnut seedlings

William Powell planting a genetically modified American chestnut at a holding plot where trees are grown for later use. Photo courtesy of SUNY College of Environmental Science and Forestry

So Powell and his colleagues turned to genetic engineering. They figured out that a gene in the wheat plant enhances resistance to the fungus that causes the blight, and they’ve added that gene to the cells of the American chestnut.

“The gene makes an enzyme that actually detoxifies the acid that the fungus throws at the plant,”  Powell explained. “By giving the tree the ability to make this enzyme, you basically take away or neutralize the weapon of the fungus. Therefore, the fungus and the tree can coexist.”

Powell said that genetic engineering is more precise than hybridizing American chestnuts with other varieties. He points to studies that show traditional breeding of plants can change the genome ten to 100 fold more than genetic engineering.

Genetically engineered American Chestnuts

These trees, shown here in 2017, are an earlier version of the GMO trees, planted at the NY Botanical Garden. They were coppiced (cut near to ground level) in 2019 because they became too big to cut off all the flowers, as required by USDA permit. If USDA deregulates the trees, Powell’s team can do longer-term studies. Photo: SUNY College of Environmental Science and Forestry

“If you’re interested in conservation and you want to maintain the integrity of the original species, genetic engineering is actually better than a lot of the traditional techniques,” he said.

Powell and his team have successfully grown test plots of genetically engineered American chestnuts in New York, Pennsylvania, and Virginia. Currently, these GMO trees are federally regulated, and are required to be cut before they flower. Powell has petitioned USDA to deregulate them, and the agency is currently accepting public comments

If deregulated, the trees would be allowed to mature. They would be the first genetically engineered trees released into the wild for ecological restoration. Powell said the deregulation process has taken five years, much longer than he anticipated. 

“I get emails all the time, people wanting these trees,” he said. “They want to plant them on their property, and I just have to keep telling them, once we get through the process, then you’ll be able to get to the trees.”

Opposition to GMO Trees

It’s just so reckless,” said Anne Petermann, director of the Global Justice Ecology Project, “What’s the rush?”

Her group has developed a coalition of hundreds of groups worldwide opposed to genetically engineered trees. They say these trees, developed for industrial timber production, creates a monoculture that can displace people and native forests around the world, and can create problems in the ecosystem if they escape tree plantations. 

For example, a freeze-tolerant eucalyptus for biofuels is being developed to survive in the southeastern U.S. But in places like California, eucalyptus is considered invasive and has become fuel for wildfires.

Unlike trees developed as crops, the genetically modified American chestnut is meant to be grown in forests. “What will be the impact on the future generations of these genetically engineered trees?” Powell asked. “No one knows.”

In the USDA petition, Powell and his colleagues described ecological studies they’ve done to assess the impact of the GMO, also called transgenic, chestnut trees on insects, bumble bees, wood frog tadpoles feeding on leaf litter, and the chemical composition of the nuts. 

In all cases, the blight-tolerant transgenic American chestnut trees were shown to be equivalent to wild-type American or traditionally bred hybrid chestnuts,” the petition states.

A Trojan Horse for More GMO Trees?

Some funding for Powell’s work has come from Monsanto (now Bayer), Duke Energy, and ArborGen, a biotech tree company. Petermann said these companies are using Powell’s effort as a Trojan horse for other GMO trees. Powell’s American chestnut would be the first GMO tree to be deregulated by USDA. “That precedent, of course, then makes it a lot easier to get other genetically engineered trees approved,” she said.

Powell countered that industry has provided little of the project’s total funding, and their work will not be patented, so anyone could plant at the trees.

“People say this is a rubber stamp for other species. It’s not,” said Sara Fitzsimmons, director of restoration for The American Chestnut Foundation (TACF) and a research technologist at Penn State University.

“The USDA takes two or more years for every application to carefully consider all the consequences of a decision that it makes,” she said.

TACF plants hybrids throughout the eastern US, including Pennsylvania, but Fitzsimmons said their efforts have not been enough to restore the tree. So, TACF supports the genetically engineered American chestnut. 

“I am not of the opinion that [genetically engineered] American chestnuts are going to save and restore the species on its own. It needs to be coupled with other techniques,” she said. “But it is an incredibly important tool, not just for the American chestnut, but for other native species.”

Some Native American groups see genetic engineering is another example of humans trying to dominate nature. Their ancestors used the chestnut’s bark to build longhouses, the leaves for medicine, and the nuts for flour.

We need to leave the forest alone as much as possible. The forest will recover — these ecosystems will recover if we quit taking things from these forests that we absolutely do not need,” said BJ McManama of the Indigenous Environmental Network.

But American chestnut enthusiast Mike Aucott thinks the ecosystem will continue to decline if people don’t use all the available tools. 

“They’re not going to get better if we just let nature take its course, because I think the days of doing that unfortunately are over,” he said.

The USDA is accepting public comment on the genetically engineered American chestnut until October 19. There will be more opportunity for the public to weigh in as the proposal winds its way through several federal agencies. 

Top Photo: American chestnuts harvested in 2018 from wild-type trees pollinated with transgenic pollen. Each of the nuts has a 50/50 chance of containing the OxO transgene that enhances blight tolerance. Photo courtesy of SUNY College of Environmental Science and Forestry