Genetic Breakthrough Promises Faster Revival of Beloved American Chestnut Tree

WASHINGTON – Once a majestic presence across the eastern United States, the American chestnut tree dominated the landscape with its towering height and abundant nut production. So prolific were these trees that chestnuts were transported by train, and their legacy is immortalized in the classic Christmas song about roasting chestnuts over an open fire.

However, by the 1950s, this iconic tree had nearly vanished due to a devastating fungal blight and aggressive root rot. In a promising turn of events, a study published Thursday in the journal Science suggests that genetic testing may hold the key to reviving these trees. Researchers have found that identifying trees with a natural resistance to disease and a propensity for growth could significantly reduce the time required to cultivate a more resilient generation of American chestnuts.

The ability to shorten the generational cycle could pave the way for a resurgence of disease-resistant chestnut trees across Eastern forests, potentially within the next few decades.

“What’s groundbreaking here is the system we’re establishing for restoration,” explained Jared Westbrook, the study’s lead author and director of science at The American Chestnut Foundation. The foundation aims to restore the tree across its historical range, which once extended from Maine to Mississippi.

Nicknamed the “redwood of the East,” the American chestnut is known for its rapid growth, reaching heights of over 100 feet (approximately 30 meters). It produces a wealth of nutritious chestnuts and is sought after for its straight-grained, durable wood.

But it had little defense against foreign-introduced blight and root rot. Another type of chestnut, however, had evolved alongside those diseases. The Chinese chestnut had been introduced for its valuable nuts and it could resist diseases. But it isn’t as tall or competitive in U.S. forests, nor has it served the same critical role supporting other species.

So, the authors want a tree with the characteristics of the American chestnut and the disease resistance of the Chinese chestnut.

That goal is not new — scientists have been reaching for it for decades and made some progress.

But it has been difficult because the American chestnut’s desirable traits are scattered across multiple spots along its genome, the DNA string that tells the tree how to develop and function.

“It’s a very complex trait, and in that case, you can’t just select on one thing because you’ll select on linked things that are negative,” said John Lovell, senior author and researcher at the HudsonAlpha Genome Sequencing Center.

Breed for disease resistance alone and the trees get shorter, less competitive.

To deal with this, the authors sequenced the genome of multiple types of chestnuts and found the many places that correlated with the desired traits. They can then use that information to breed trees that are more likely to have desirable traits while maintaining high amounts of American chestnut DNA — roughly 70% to 85%.

And genetic testing allows the process to move faster, revealing the best offspring years before their traits would be demonstrated by natural growth and encountering disease. The closer the gap between generations, the faster gains accumulate.

Steven Strauss, a professor of forest biotechnology at Oregon State University who wasn’t involved in the study, said the paper identified some promising genes. He wants scientists to be able to edit the genes themselves, a possibly faster, more precise path to a better tree. In an accompanying commentary piece in Science, he says regulations can bog down these ideas for years.

“People just won’t consider biotech because it is on the other side of this social, legal barrier” and that’s shortsighted, he said.

For people who have closely studied the American chestnut, the work begs an almost existential question: How much can the American chestnut be changed and still be an American chestnut?

“The American chestnut has a unique evolutionary history, it has a specific place in the North American ecosystem,” said Donald Edward Davis, author of the American chestnut, an environmental history. “Having that tree and no other trees would be sort of the gold standard.”

He said the tree was a keystone species, useful to humans and vital to bigger populations of squirrels, chipmunks and black bears — hybrids might not be as majestic or effective. He was pleased that the authors included some surviving American chestnuts in their proposal, but favored an approach that relied on them more heavily.

“Not that the hybrid approach is itself bad, it is just that why not try to get the wild American trees back in the forest, back in the ecosystem, and exhaust all possibilities from doing that before we move on to some of these other methods?” he said.

Lovells said resurrecting the species requires introducing genetic diversity from outside the traditional pool of American chestnut trees. The study authors’ goal is tall, resilient trees and they are optimistic.

“I think if we only select American chestnut (tree genes), period, there’s going to be too small of a pool and we’re going to end up with a genetic bottleneck that will lead to extinction in the future,” said Lovell.

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