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Access to Blight Resistant Chestnut Trees

Forest biologists are seeking federal approval from the FDA, USDA and EPA to reintroduce an almost-extinct species — the American chestnut — back into the forests of the eastern United States. The scientists have genetically modified the trees to resist the devastating Chestnut blight that over the last 100 years has almost killed every nut-bearing American chestnut tree on the planet.

William Powell, Charles Maynard and their colleagues from the State University of New York College of Environmental Science and Forestry (SUNY-ESF), have taken genes from wheat, Asian chestnuts, grapes, peppers and other plants to create hundreds of transgenic trees that are almost 100 percent genetically identical to wild American chestnut trees yet immune to the chestnut blight, or Cryphonectria parasitica. 

Over the next 5 years, the team expects to grow 10,000 blight-resistant American chestnut trees and, with the help of volunteers and landowners, reintroduce them into private and public woodlands of New York and the rest of eastern United States, reclaiming mine sites, populating historic sites, and making them available to the public.

Before the early 1900s, one in every four hardwood trees in North America’s eastern forest was an American chestnut. An important source of food, shelter, and naturally rot-resistant timber, the American chestnut was considered a “keystone” species, providing critical and valuable habitat.

Starting in the late 1800s, an exotic blight pathogen from Asia killed 3 to 5 billion American chestnut trees, nearly wiping out the tree that had shaped the Eastern U.S. forest ecosystem for centuries. The fungus releases oxalic acid that kills nearby tree tissue, providing a conducive environment for the fungus to spread further. The dead tissues, called cankers, essentially strangle the tree.

“The wheat gene in the transgenic trees codes for an enzyme that detoxifies oxalic acid. Without the acid to kill the tissue, the fungus can’t move in,” says Powell. “If you eat wheat, you’re eating oxidate oxalic genes and you’re most likely also eating the enzyme that it produces.” Powell notes that genetically engineered chestnut trees do not kill the fungus, but are better able to defend themselves against the fungus.

The SUNY-ESF team does not intend to patent the transgenic trees, nor will they profit from their reintroduction. In several years, Powell hopes the chestnut trees will be deregulated, ready to plant and eat.

Update 3/15/17 by Joan Conrow

Researchers are seeking broad public engagement as they guide the first genetically engineered forest tree — a blight-resistant American chestnut— through the federal regulatory process.

They’re currently in the midst of their second crowd-funding campaign, this time raising money to create a 120-acre restoration forest near Tully, New York, that will offer research, education, and public recreation opportunities.

A birds-eye view of the American chestnut forest restoration site.

Scientists will use the site to study different approaches to forest restoration and blight-resistant tree production, as well as assess the environmental impacts, if any, of the transgenic chestnut trees.

“We’re calling it a century study, because theoretically, the trees could be out there for 100 years,” said William A. Powell, director of the American Chestnut Research & Restoration Project at the State University of New York (SUNY) College of Environmental Science & Forestry (ESF).

Researchers will plant four types of chestnut trees: the transgenic, blight-resistant variety; trees bred through conventional backcross methods; hybrids that cross the American chestnut with an Asian variety; and the wild chestnut, which has been devastated by a pathogen inadvertently introduced from Asia more than a century ago.

Blight has killed some 3 to 5 billion American chestnut trees, driving the keystone Eastern forest tree nearly to extinction. The fungal pathogen functions by colonizing a wound in the bark and producing oxalic acid, which creates a canker that girdles the trunk, killing the trees within 10 years.

Powell and his co-researcher, Charles Maynard, identified a gene from bread wheat that detoxifies the oxalic acid, providing an effective defense against chestnut blight. A team of 100 university scientists and students at ESF assisted the work.

Over the coming decades, researchers will compare the vigor, blight-resistant qualities, and overall health of the various types of trees, as well as different planting methods: orchard, reclamation, and shelter wood cut. One area will be left unplanted as a control. They will also be investigating the distance that chestnut pollen can travel, and conducting bumble bee feeding, leaf litter, and other studies.

“It’s a very big project,” Powell said. “I’ve been thinking about this for over a year now. It’s very complicated.”

He hopes the restoration forest will attract other research projects. “We do a lot of collaboration, he said, noting that ESF landscape architecture students are designing trails and interpretive elements for school field trips and recreational hikers.

“We want people to go out and see the trees and touch the trees and see that the transgenic trees are just like other trees,” Powell said.

The American Chestnut Project has integrated public engagement and outreach into its research work from the onset.

Its first crowd-funding effort raised money to produce 10,000 transgenic chestnut seedlings, which will be distributed to the public once the regulatory process is complete and the federal government issues its approval. The ultimate goal is to get the transgenic trees into backyards and forests, where they will eventually confer genetic resistance to blight in the remaining wild populations and help restore the tree to its historic range.

Though the restoration forest isn’t required for the deregulation process, it fits into what Powell calls a “stewardship plan” for assessing all the potential benefits and risks of using a transgenic tree species in ecosystem restoration.

“Everything [transgenic] produced in the past has been for agriculture,” Powell explained. “This is the first time we’re doing something for restoration.”

Previously, regulators have focused on how to keep genetically modified organisms from spreading into the natural environment.

“But we want this transgenic tree to get out there in the forest because that’s what’s going to save the American chestnut tree,” Powell said. “It’s a whole new paradigm for the regulators to think about.”

Powell and his collaborators are proceeding carefully and thoughtfully, well aware that they’re blazing trail in both the scientific and regulatory arenas. “These studies will help others who want to do this in the future,” he said.

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