Genetic Breakthrough Promises Faster Comeback for Iconic American Chestnut Tree

WASHINGTON – Once, the eastern United States was blanketed with towering American chestnut trees, their nuts so plentiful they were transported by train. Immortalized in the classic holiday song about chestnuts roasting on an open fire, these trees were a symbol of the region’s natural abundance.

However, by the mid-20th century, the American chestnut had nearly vanished, decimated by a devastating airborne fungal blight and lethal root rot. A recent study published in Science offers a glimmer of hope for the tree’s revival. The research suggests that genetic testing can identify trees most likely to resist disease and thrive, potentially accelerating the planting of a stronger generation.

This advancement could significantly reduce the time needed to cultivate a robust population of disease-resistant trees, capable of reclaiming their place in Eastern forests. Researchers are optimistic that this resurgence could happen within the next few decades.

“The innovation here is the framework we’re building for restoration,” explained Jared Westbrook, the study’s lead author and director of science at The American Chestnut Foundation. The foundation aims to reintroduce the tree across its historical range, which once stretched from Maine to Mississippi.

Nicknamed the “redwood of the East,” the American chestnut can grow rapidly, reaching heights over 100 feet (30 meters). It yields an abundant supply of nutritious chestnuts and provides high-quality lumber known for its straight grain and durability.

Unfortunately, the American chestnut lacked defenses against invasive blight and root rot. In contrast, the Chinese chestnut, introduced for its nuts, had evolved to withstand these ailments. Yet, it falls short in height and competitiveness within U.S. forests and doesn’t fulfill the same ecological roles as its American counterpart.

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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