November 6, 2020

The revival of the American Chestnut

When my husband first told me of the chestnut trees planted at Panther Creek State Park, I hadn’t realized it was part of a much larger movement. Still, I was curious about the new trees, so we took our kids to see them and read the plaque near the freshly planted grove. 

Later, I discovered that the six trees are one of five demonstration groves in state parks across Tennessee as part of a decades-long project to restore the American Chestnut Tree. These groves have two each of pure American Chestnut, Chinese Chestnut, and a crossbreed between the two. 

Tower_Hill_Botanic_Garden_-_American_chestnuts

Restoration Chestnuts, as they’ve been dubbed, took years to breed. Starting with a 50/50 crossbreed between American and Chinese Chestnuts, researchers bred that combination with the pure American Chestnut. This process was repeated until they got a tree that is 15/16 American Chestnut and 1/16 Chinese Chestnut. The hope is that the small amount of Chinese Chestnut bred in will give the crossbreed immunity to the Chestnut blight, enabling them to flourish while retaining the characteristics of the American Chestnut.

It will still be several years before we know how successful the Restoration Chestnuts are. Fortunately, there’s another project being worked on to help fight the blight. When Chestnut Blight attacks a tree, infected cankers form on the trunk. At the edge of these cankers, the blight produces high amounts of oxalate, which kills the tree’s tissues. This enables the infection to expand through the weakened tree. 

Several other plants are known for being attacked with oxalate. Wheat, one of these plants, has developed a defensive enzyme called oxalate oxidase. This gene takes oxalic acid, released by the oxalate, and converts it into carbon dioxide and hydrogen peroxide. Scientists are working on inserting that gene into the American Chestnut to help it fight off damage from the blight.  


 

This method has some bonuses. First, while the trees will be able to mitigate the damage caused by the blight, the blight will still be able to infect them and spread. That sounds like a massive negative, right? Well, it’s actually beneficial because since the survival of the blight won’t be put in jeopardy, it won’t need to evolve to survive. This means that the risk of the blight becoming more damaging and in return undoing years of work, is relatively low.  

Secondly, the hydrogen peroxide by-product has the potential to strengthen the lignin inside the cell walls of the trunk, raising its chances of surviving infection even more. And, lastly, the chestnut that grows will be completely genetically American Chestnut, instead of a crossbreed. 

Still, if it means the return of such a mighty tree, does it matter if it is “only” 96% American Chestnut? 

linkedin facebook pinterest youtube rss twitter instagram facebook-blank rss-blank linkedin-blank pinterest youtube twitter instagram