Maine Chapter of The 
  American Chestnut Foundation
   at the Merryspring Orchard
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Planting Merryspring B3F2 seeds in the seed orchard in Stetson on the property of Penobscot County Conservation Association in May 2012.   (photo courtesy of Penobscot County Conservation Association).

The Merryspring orchard in the summer of  2011 is pictured before the first harvest of B3F2 seeds.  The seeds were planted in the first seed orchard plantings in May 2012.  (photo by Eric Evans)

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American Chestnut Blight-Resistance Trial

by the Maine Chapter of The American Chestnut Foundation

Have you noticed the “band-aids” on the trunks of the trees in the American chestnut breeding orchard in Merryspring Park?  In June 2007, a team of 15 volunteers from the Maine Chapter of The American Chestnut Foundation injected live blight fungus into two small holes in the trunk of each of the 200 trees, the first step to evaluate their resistance to Asian chestnut blight.

American Chestnuts, once the most abundant and ecologically and economically important forest trees in Appalachia, were nearly driven to extinction by the Asian Chestnut Blight in the first half of the 20th century. This fungal disease of the bark spread through Maine in the 1920s and 30s. American chestnuts –– not related to “horse” chestnuts –– were prized for their fast-growing rot-resistant wood, high-tannin bark for leather processing, and abundant reliable crops of sweet chestnuts for people and wildlife.

After government-sponsored efforts to develop blight-resistant chestnuts were abandoned in the 1950s, several plant breeders who had been leaders of the agricultural “Green Revolution” in the 1970s founded The American Chestnut Foundation (TACF) to conduct a back-cross breeding program to introduce blight-resistance genes from Chinese chestnuts into the remaining populations of American chestnuts throughout their original range. Currently TACF is coordinating this breeding program in a dozen states, with research and breeding headquarters in Meadowview, Virginia.

The Maine Chapter of TACF planted its first third-backcross seedlings in this Merryspring orchard in 1999. Now they are big enough to have their blight-resistance tested. According to our best understanding of the genetics, one-eighth of these trees have inherited enough partial blight-resistance from their Chinese great-great-grand-parent to be used in the next generation of the breeding program. We will determine which ones to save by comparing the blight infections this Spring, and the rest will be cut down. The selected trees will probably out-grow their blight infections, and will be crossed with each other for several years. We will plant the seeds from those crosses –– and similar crosses in the ten other chestnut breeding orchards in Maine –– in new orchards, and some of those new trees will be fully blight-resistant. Preliminary results from Virginia and the Pennsylvania Chapter have verified this hypothesis. We expect to start harvesting fully blight-resistant American chestnuts in Maine about 10 years from now.

The Maine Chapter of TACF is very grateful to Merryspring Park for providing the space for this project. For more information about American chestnuts and how to participate in our program, contact: Eric Evans     207-236-9635   

The article below appears courtesy of the Maine Chapter of The American Chestnut Foundations’ website: