Editing American chestnut (section)

===Intercrossing surviving American chestnuts===
{{main|American Chestnut Cooperators' Foundation}}

[[File:Floyda.jpg|thumb|upright|Large surviving blight-resistant American chestnut in its natural range. Surviving trees passing resistance tests are used in ACCF's All American Breeding program.]]
[[American Chestnut Cooperators' Foundation]] (ACCF) is not using crosses with Asian species for blight resistance, but [[Hybrid (biology)|intercrossing]] among American chestnuts selected for native resistance to the blight, a breeding strategy described by the ACCF as "All-American intercrosses". 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. Both Elkins and Griffin have written extensively about the American chestnut.<ref name=griffin>[http://www.accf-online.org/biblio.html "Bibliography."] {{Webarchive|url=https://web.archive.org/web/20160305080130/http://www.accf-online.org/biblio.html |date=March 5, 2016 }} ''www.accf-online.org.'' Retrieved January 11, 2016.</ref> They believe that by making intercrosses among resistant American chestnuts from many locations, they will continue to improve upon the levels of blight resistance to make an American chestnut that can compete in the forest. Griffin, who has been involved with American chestnut restoration for many years,<ref name=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 American chestnut trees were made beginning in 1980. The first "All-American intercrosses" were planted in Virginia Tech's Martin American Chestnut Planting in [[Giles County, Virginia]], and in [[Beckley, West Virginia]]. They were inoculated in 1990 and evaluated in 1991 and 1992. Nine of the trees showed resistance equal to their parents, and four of these had resistance comparable to hybrids in the same test.<ref name=griffin/><ref name="elkins">Griffin, G. J., J. R. Elkins, D. McCurdy, and S. L. Griffin. [http://ecosystems.psu.edu/research/chestnut/information/conference-2004/conference/griffin "Integrated use of resistance, hypovirulence, and forest management to control blight on American chestnut."] ''www.ecosystems.psu.edu'', 2005.</ref><ref name=integrated>[https://archive.org/stream/restorationofame00stei/restorationofame00stei_djvu.txt "Restoration of American Chestnut to Forest Lands: Proceedings of a Conference and Workshop Held May 4-6, 2004 at The North Carolina Arboretum."] ''www.archive.org.'' Retrieved January 22, 2016.</ref><ref name="resist">[http://www.accf-online.org/breed.html "Breeding for Blight Resistance."] {{Webarchive|url=https://web.archive.org/web/20160304215224/http://www.accf-online.org/breed.html |date=March 4, 2016 }} ''www.accf-online.org.'' Retrieved January 11, 2016.</ref> Many ACCF chestnuts have expressed blight resistance equal to or greater than 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.<ref>[http://www.accf-online.org/news.html "American Chestnut Cooperators' Foundation 2015 Newsletter: Grower Reports."] {{Webarchive|url=https://web.archive.org/web/20160122062941/http://www.accf-online.org/news.html |date=January 22, 2016 }} ''www.accf-online.org.'' Retrieved January 11, 2015.</ref>