American chestnut trees were once one of the most important trees in eastern US forests. Some of these trees reached heights of over 100 feet with trunk diameters up to 14 feet. Billions of American chestnuts once stretched from Georgia and Alabama to Michigan and Maine before disease nearly wiped out the trees, which are now considered to be “functionally extinct.” But there is now hope that American chestnuts can be revived thanks to trees that have been genetically modified to make them resistant to the blight that wiped them out.
An estimated 4 billion American chestnuts once populated the forests of the eastern US. The reddish brown wood was highly valued for its rot-resistance and used in a variety of ways. For three centuries many barns and homes near the Appalachian Mountains were made from American chestnut. Its straight-grained wood did not shrink or warp so was also ideal for building furniture and caskets. The fruit that fell to the ground was an important cash crop and food source. Many native animals fed on chestnuts, and they were widely used for livestock feed. The bark and wood were also rich in tannic acid, which provided tannins for use in the tanning of leather.
In the early 1900s, a fungus called “chestnut blight” arrived in New York via infected plants, which nearly wiped out what remained of the trees. The disease enters through wounds on susceptible trees, growing in and beneath the bark and eventually killing the tree. However, the root collar and root system of the chestnut tree have some resistance to blight infection. As a result, an estimated 430 million small American chestnut trees still exist as shoots growing from existing root bases. Most of them are 1″ in diameter or smaller though, and are usually killed by the fungus before reaching the sexually reproductive stage.
After decades of research, scientists at the SUNY College of Environmental Science and Forestry in Syracuse, N.Y., have engineered American chestnut trees to host a gene from wheat that disarms the fungal invader, breaking the production of an acid required for infection. This strategy allows the tree and the fungus to live together without sacrificing the tree. It also enables the preservation of the native chestnut’s genetics by avoiding hybridization with other chestnut species.
The US Department of Agriculture is now in the process of seeking deregulation of the GE American chestnut variety, known as “Darling 58,” after numerous studies concluded that the trees do not represent novel risks to the environment. This would allow for the widespread planting of the trees as opposed to just a handful of authorized locations currently. If approved, the tree would be the first genetically engineered plant released with the purpose of spreading freely into the wild. USDA is still seeking public input on the decision, which can be submitted HERE.
Bill Powell, director of SUNY ESF’s American Chestnut Research and Restoration Project, is hopeful that approval of Darling 58 will spur similar efforts among geneticists. “It’s going to spark a lot of other research on trees that people basically wanted to do but couldn’t do because they had that brick wall in front of them,” he said. Already, Powell’s team is investigating ways to insert blight-resistant genes into chinkapins, a tree closely related to American chestnuts, and to engineer elms that can resist elm yellows, a bacterial disease with no known cure. (Sources: Wall Street Journal, Washington Post, Genetic Literacy Project)