American Chestnut Cooperators Foundation
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The American Chestnut Cooperators Foundation (ACCF) is a 501(c)(3) non-profit scientific and educational foundation, organized in 1984, dedicated to restoring the American chestnut (Castanea dentata) to its former place in our Eastern hardwood forests. Priorities include the development of blight resistant all-American chestnuts and economical biological control measures against chestnut blight in the forest environment. ACCF supports American chestnut research and engages senior citizens and school children, volunteers and professionals in planting, grafting and managing the fruits of this research.
Breeding for blight resistance is currently pursued by two separate foundations: The American Chestnut Foundation (TACF) is developing advanced hybrids, building on the work of earlier breeders to improve tree form while enhancing resistance; the American Chestnut Cooperators Foundation is not using Oriental genes for blight resistance, but intercrossing among American chestnuts selected for native resistance to the blight.
"All-American intercrosses" defines the breeding strategy of the ACCF; John Rush Elkins, a research chemist and professor emeritus of chemistry at Concord University, and Gary Griffin, professor of plant pathology at Virginia Tech, think there may be several different characteristics which favor blight resistance. By making intercrosses among resistant American chestnuts from many locations, they expect to improve upon the levels of blight resistance to make an American chestnut that can compete in the forest.
Griffin developed a scale for assessing levels of blight resistance, which made it possible to make selections scientifically. He inoculated five-year-old chestnuts with a standard lethal strain of the blight fungus and measured growth of the cankers. Chestnuts with no resistance to blight make rapid-growing, sunken cankers that are deep and kill tissue right to the wood. Resistant chestnuts make slow-growing, swollen cankers that are superficial: live tissue can be recovered under these cankers. The level of blight resistance is judged by periodic measurement of cankers.
Grafts from large survivors of the blight epidemic were evaluated following inoculations, and controlled crosses among resistant Americans were made beginning in 1980. The first all-American intercrosses are planted in Virginia Tech's Martin American Chestnut Planting in Giles County, VA, and in Beckley, WV. They were inoculated in 1990 and evaluated in 1991 & 1992. Nine of them showed resistance equal to their parents, and four of these had resistance comparable to hybrids in the same test.
It appears that inheritance of resistance requires genes of two trees with good combining ability from each source location. Thus, more generations of controlled crosses may be required to make American chestnuts produce blight resistance that is regularly inherited by seednuts. It takes at least 7 years for an American chestnut to produce nuts, and new trees must be at least 5 years old before their resistance can be tested by inoculation; the test requires 2 years for evaluation. Some of this time may be saved by utilizing grafts, and further progress may result from Elkins' studies underway, to locate chemical markers for resistance. In the meanwhile, ACCF plantings of all-American intercrosses are producing, from open pollinations, large nut crops.
Meanwhile, the potential for significant blight resistance to be randomly expressed in the nuts ACCF sends out has increased, following the culling of large numbers of mature trees which did not pass resistance tests in their largest orchard. The ACCF is always in need of more good cooperating growers, to help carry on the all-American breeding program, by raising nuts and seedlings and reporting their progress to a central data base.
Many ACCF chestnuts have expressed blight resistance equal to an original blight survivor but so far, only a handful have demonstrated superior, durable blight control. Time will tell if the progeny of these best chestnuts exhibit durable blight resistance in different stress environments.