The Return of the American Chestnut Tree

In 1904, the Chestnut blight fungus, or Cryphonectria parasitica, was imported into the United States. The fungus came into the country on some Japanese and Chinese chestnut trees that were being imported to the Bronx Zoological Park in New York City. The blight quickly spread through the air to some American chestnut trees in the park and, by the 1940s, impacted the entire range of the chestnut. The American chestnut trees, which evolved without the presence of the blight, are not resistant to the fungus and, with few exceptions, die once infected. The blight enters the chestnut tree through cracks in the bark, which usually appear once a tree is a few years old. Once under the bark, the fungus then "eats" away at the tree leaving a girdling, sunken canker. This canker prevents the tree from transporting the food it makes in its leaves through photosynthesis. Without this food, the tree then dies within a decade or so. However, the root systems are not affected by the blight and often sprout to form new chestnut trees. Once the sprouts are a few years old though, they once again become infected with the blight and die back again.

The American Chestnut Foundation (TACF), which counts Former U.S. President Jimmy Carter on its advisory board, the Pennsylvania Department of Conservation and Natural Resources (DCNR), and the Pennsylvania State University formed a core group dedicated to developing a blight resistant American chestnut. They began developing a method whereby resistance to the blight is transferred from a blight resistant Chinese chestnut to the American Chestnut. The method requires a minimum of six generations of breeding. Seedlings and seed of the fifth generation (B3F2) will compose the principal population of the orchard at the Penn State Arboretum and will total upwards of 135,000 trees. In three to four years, the trees will be challenged with blight. The survivors showing a combination of highest resistance and the growth characteristic of an American chestnut will be cross pollinated to produce seed for the sixth generation. Then the ultimate challenge: reestablishing trees in the forest ecosystems that once were composed of up to 40 percent American chestnut.

Pictured today is former Pennsylvania DCNR Secretary (and former WPC President) John C. Oliver ( left ) with Dean Steele, PSU College of Agricultural Sciences ( right ), as they plant the first B3F2 seedling at the Penn State Arboretum.

Photo courtesy of TACF.

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