For nearly a decade, Jared Westbrook has worked on resurrecting the American chestnut, an iconic tree that nearly vanished from the United States a century ago.
The American Chestnut Foundation, a nonprofit where Westbrook is director of science, has poured years of work into a line of chestnuts genetically engineered to endure a deadly disease infecting them, an effort meant to be one of the best hopes for its survival. Then an October visit to a chestnut field in Indiana delivered a blow to that vision.
Looking out at the modified trees, Westbrook knew something wasn’t right. He saw one tall tree next to one shorter than normal. Another tall, another short. It meant some may not be able to compete for sunlight if placed in the wild.
Andrew Newhouse walks through a grove of American chestnut trees at a field research station in Syracuse, N.Y., in July 2022. Newhouse is the director of chestnut restoration at the State University of New York College of Environmental Science and Forestry. Lauren Petracca or The Washington Post
The team was meant to be working with a tree dubbed Darling 58, developed by the State University of New York College of Environmental Science and Forestry (SUNY ESF). But Westbrook and others would soon discover that many of the trees they were working with were not Darling 58 trees at all. They were a different variety of chestnut – with the gene inserted into the wrong spot.
The mistake would prove to be the latest in a series of concerns, driving the American Chestnut Foundation to pull its support this month for the Darling line. It’s a development that has sent a rift through the passionate community and left still-unanswered questions about the fate of a long-standing, high-tech effort. The disagreement threatens to delay or derail plans for restoring the trees.
“Virtually every month we turn around, we’re getting even more red flags,” said Sara Fern Fitzsimmons, the American Chestnut Foundation’s chief conservation officer. “There’s no way we would have pulled this if we weren’t really concerned.”
“It’s a science-based decision,” she added.
But Andrew Newhouse, director of chestnut restoration at SUNY ESF, said his team is moving forward with seeking federal approval to begin distributing seeds to the public – but without the 5,000-member foundation as its longtime partner and financial backer.
Concerns over how the trees are growing in the field, he said, are overblown or can be overcome. The school is awaiting the green light from the Agriculture Department and Environmental Protection Agency.
“We are very interested in moving forward and doing good science, and we don’t think that completely pulling the application is justified,” Newhouse said. “We haven’t seen risks, we haven’t seen harm to other organisms, and we think it’s very important to keep studying this, to keep learning about it. And further study will really clarify some of these concerns.”
AN ICONIC TREE
Billions of American chestnuts once presided over canopies from Maine to Mississippi, drizzling the forest floor with nuts for people and animals to eat and providing straight-grained, rot-resistant wood for building the young American nation.
But toward the beginning of the 20th century, an invasive fungus nearly eradicated the trees, pocking their bark with cankers that cut off circulation. Today, with some chestnuts still sprouting in the wild but rarely reaching maturity, scientists consider the tree “functionally extinct.”
After years of fruitless efforts to use traditional breeding to produce blight-resistant American chestnuts, SUNY ESF scientists developed a series of genetically engineered trees meant to do so. About a decade ago, the team started inserting into the chestnuts’ DNA a gene that produced an enzyme to neutralize a chemical secreted by the fungus that helps it kill and eat tree tissue.
Linda McGuigan, tissue culture lab manager, records data as Hana Wood, an undergraduate research aide, pollinates flowers on an American chestnut tree at a SUNY ESF field research station in Syracuse, N.Y., in July 2022. Lauren Petracca for The Washington Post
SUNY ESF moved forward with one line, called Darling 58, where the gene was added to a part of the genome without any known function. Over the past several years, the team distributed the modified chestnuts to other labs to study.
“I was thinking for years this is going to work,” Westbrook said.
But more recently, some outside researchers began to notice problems with the Darling trees they were growing, according to the American Chestnut Foundation. Some were lagging in height compared with regular chestnuts. Others showed lower resistance to infection than expected. Yet others sprouted curling, brown leaves. And in some plots, the genetically modified trees had higher mortality rates.
“I would have considered it a blip if not for the mounting evidence from other trials,” said Jason Holliday, a Virginia Tech professor whose transgenic chestnuts died at a higher rate.
The American Chestnut Foundation grew concerned, too, about SUNY ESF’s interest to use a for-profit company to eventually grow seeds, a move the school meant to help scale up distribution but one that ran counter to the foundation’s nonprofit mission.
At the University of New England, Thomas Klak was “speed breeding” the transgenic chestnuts under grow lights but was having trouble producing many plants with two copies of the gene to fight the blight.
After he enlisted the help of Ek Han Tan, a geneticist at the University of Maine, to analyze the chestnut’s genome, they made their discovery this fall: The plants they were working on were, in fact, not Darling 58 trees.
Instead, they found they were working with a different chestnut line – called the Darling 54 – where the gene was inserted in another chromosome entirely, potentially corrupting one of the tree’s existing genes. Klak called Westbrook in late October with the news.
“It was in some ways to me a little sad because I knew so much work was poured into 58,” Tan said. “I was glad that we were able to figure it out before anyone else, and before deregulation” by the federal government.
Tan teaches a course on genetic engineering and sees it as a promising solution for bringing back chestnuts, but he understands how controversial the technology can be.
“The success as well as the failure, if you want to say failure, of the technology hinges upon public opinion, right? So we cannot say something is not what it is.”
“Science never is smooth,” Klak added. “Two steps forward, one step back is normal in science, but you just keep pressing on.”
In a phone interview, Newhouse, the SUNY ESF director, acknowledged the mix-up but said he wasn’t sure what transpired.
“As far as exactly how it happened, we don’t know,” he said. “It must have been a label swap between these two trees that we were working with at the same time” in or around 2016.
‘THIS IS SCIENCE’
At this point, no one is sure what exactly is behind the performance issues – whether it has to do with where the genes were inserted or just the presence of the new genes themselves. But the American Chestnut Foundation isn’t turning away from genetic engineering as a potential solution for chestnut restoration.
“This is science,” Fitzsimmons said. “Stuff happens.” But she is frustrated with the lack of candor from SUNY ESF. The foundation learned of the variety mix-up not from SUNY ESF but from the researchers in Maine.
“It’s not that the mistake was made,” she said. “It’s that we weren’t told about it.”
James R. McKenna, a retired U.S. Forest Service tree breeder who maintained the chestnut plot in Indiana that Westbrook visited, still thinks the Darling line as a whole has promise to preserving the tree’s genetic diversity.
“There’s a fatal flaw in the 54,” McKenna said. “All [the discovery] means really is we cool our jets. We don’t want that widely distributed.”
SUNY ESF said it has notified regulators and is amending the documents it filed for approval. Newhouse said experiments his team has already done show Darling 54 nuts are safe to eat. His team is testing its own trees to how many true Darling 58 trees it has, estimating the school has “dozens” left.
USDA spokesman Richard Coker said officials “have paused work until we receive additional information from SUNY.”
Newhouse added that he hasn’t observed higher mortality in his plots, but he acknowledged the transgenic trees were shorter. He said that traditional breeding methods could yield taller transgenic trees.
“It might bring up a question of whether it’s better to have short trees or dead trees,” he said. “If the trees are resistant to blight and can keep growing, then the height might not matter as much.”
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