USDA Approves Bioengineered American Chestnut Tree That Could Bring Them Back From Near-Extinction

The United States Department of Agriculture deregulated Darling 54, a genetically modified variety of American chestnut designed to resist the tree-killing chestnut blight. Does this mean that the restoration of this iconic tree to America’s forests can soon begin? Maybe, but some researchers have their doubts.

The chestnut blight fungus was identified at the Bronx Zoo in 1904, likely introduced by chestnut trees imported from East Asia. Numbering around 4 billion trees, American chestnuts once dominated North American forests from Ontario to Mississippi. The rapid spread of the blight killed all of the native trees by the 1950s.

Developed by researchers at the State University of New York College of Environmental Science and Forestry (ESF), the Darling 54 has been modified by adding a gene from wheat that confers blight resistance by expressing oxalate oxidase, an enzyme that degrades the tree-killing oxalate produced by the fungus.

The U.S. Department of Agriculture’s (USDA) Animal and Plant Health Inspection Service (APHIS) determined last week that the Darling 54 variety is “unlikely to pose a greater plant pest risk than the nonmodified comparator and therefore is no longer subject to our regulations.” In other words, Darling 54 trees are ecologically as safe as native trees except that they are better able to resist the blight.

Andrew Newhouse, director of ESF’s American Chestnut Research and Restoration Project, said in a statement, “Our ‘Darling’ chestnuts are an important step in the big picture of chestnut reintroduction. They tolerate blight better than any other fully American chestnuts we’ve tested, so they can help restore some of the ecological relationships that were lost to this disease.” The next step before the trees can be released to the public is approval by the Environmental Protection Agency.

“The disease resistant American Chestnut is the first genetically engineered organism with the goal of ecological restoration to be deregulated by USDA,” explains Dr. Emma Kovak, senior analyst at the Breakthrough Institute in a press release. “This decision sets a precedent for other genetically engineered organisms developed for release into the wild rather than agricultural use.”

That’s really good news.

However, other researchers who are also been seeking to return chestnuts to America’s forests have some reservations about the Darling 54. For example, in 2023 the American Chestnut Foundation (TACF), which had initially applauded ESF’s genetic engineering efforts, withdrew its support of the project. In its comments to APHIS, TACF notes that the introduced wheat gene disrupted another gene that has apparently resulted in reduced growth and survival rates of the modified trees. TACF also suggests that the Darling 54 trees have not been tested long enough to determine whether their bioengineered blight resistance is sufficient for long-term survival. “The growth and survival penalties are likely to negatively impact the long-term forest competitiveness of Darling 54 progeny,” note TACF researchers.

Asked about the Darling 54 deregulation, TACF’s Director of Science Jared Westbrook said, “We support the use of any genetic technologies that will be effective at restoring blight resistance.” Still, Westbrook worries that the failure of ESF’s chestnuts to thrive in the wild would bolster anti-biotech activist campaigns against future bioengineered trees.

In the meantime, TACF continues its decades-long project of chestnut restoration via cross breeding American with blight resistant Chinese chestnuts. The process of breeding increasingly blight-resistant trees is sped up using recurrent genomic selection. TACF researchers thus identify genetic markers of disease resistance conferred by genes from the Chinese varieties while retaining high American chestnut ancestry in the hybrids.

Since TACF chestnuts are being created via traditional breeding methods, they will not need federal regulatory approval prior to release. When pressed, Westbrook reluctantly offered that TACF trees could be available for restoration planting in seven to 10 years.

Here’s hoping that ESF’s trees are a rousing success in the wild. In the meantime, let a thousand efforts to restore chestnuts to America’s forests bloom.

Disclosure: I am a long-time small donor to the American Chestnut Foundation.