TENNESSEE – The Southern Research Station has partnered with The American Chestnut Foundation, The University of Tennessee’s Tree Improvement Program, and the Southern Region of the National Forest System, to test 1100 chestnut seedlings planted in the Cherokee, Jefferson, and Nantahala National Forests.
The American chestnut (Castanea dentata) was an iconic keystone tree species that dominated forests in the eastern U.S. from Maine to Georgia. Chestnut blight (Cryphonectria parasitica), a fungal disease that was accidently imported from Asia in the early 20th century, reduced dominant overstory chestnuts to remnant understory sprouts.
Over many decades, a breeding program was developed to produce hybrid seedlings with blight resistant genes from the Chinese chestnut (C. mollissima) and growth characteristics of the American chestnut. Southern Research Station research forester Stacy Clark evaluated blight resistance after eight-years of field testing in silviculturally treated forests, and results are presented in a recent publication.
Clark and her team conduct yearly evaluations, measuring tree size at the time of planting, growth rates after planting, and of course, blight resistance, with the assistance of Richard Baird, a pathologist at Mississippi State University. The fungus harbors on native oaks and chestnut sprouts, and will naturally invade a site over time. No studies to date had examined when and where on the tree blight infection occurs.
After eight years, blight infected 40 percent of trees, and was more likely to infect trees after they grew 3 to 5 inches in size. Hybrids were more resistant than pure American chestnut, but hybrids were less resistant than Chinese chestnut in plantings where blight disease was most pervasive. Blight most often developed near the tree’s base, but was found as high as 13 feet in the canopy.
This long-term research directly supports the USDA Forest Service priorities to sustain our nation’s forests and deliver benefits to the public by providing guidance on restoration of an extirpated species that had many ecological benefits and was highly valued by the public. If restored, the American chestnut would return one of the most reliable and nutritious hard mast producers to the eastern U.S.