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The first research plantings of third-generation, third-backcross American chestnut (Castanea dentate) in the southeastern United States

Clark, S.L., Schlarbaum, S.E., Hebard, F.V.
Acta horticulturae 2014 no.1019 pp. 39-44
Castanea dentata, Cryphonectria parasitica, Cyrtepistomus castaneus, Dryocosmus kuriphilus, Odocoileus virginianus, Phytophthora cinnamomi, backcrossing, browsing, chestnuts, deer, defoliation, field experimentation, forests, fungi, genetic transformation, national forests, pathogens, planting, root rot, sawflies, seedlings
Production of American chestnut (Castanea dentate) resistant to the chestnut blight fungus (Cryphonectria parasitica) is being conducted currently through traditional breeding and genetic transformation. Sufficient material for field testing is currently available from The American Chestnut Foundation’s backcross breeding program. We planted approximately 4500 chestnut seedlings into forest test plantings on three National Forests over three years, beginning in 2009. Early survival and growth was dependent on disease pressure from exotic pathogens, primarily, root rot caused by Phytophthora cinnamomi. Plantings that contained seedlings not exhibiting symptoms of this disease had high survival (>75%) and fast rates of height growth (0.5 m/yr). We documented other non-native pests negatively affecting chestnuts including Asiatic oak weevil (Cyrtepistomus castaneus) and the Asian chestnut gall wasp (Dryocosmus kuriphilus). Native pest problems included browsing of the terminal leader by deer (Odocoileus virginianus) and defoliation caused by the chestnut sawfly (Craesus castaneae). Restoration of American chestnut will require not only blight-resistance, but adaptation to forest environments with intense vegetation competition and strategies to address other native and exotic insects and pathogens.