The American chestnut (Castanea dentata), once known as The King of the Forest in the Appalachian Mountains of the eastern United States and southeastern Canada, has been all but extirpated by chestnut blight disease caused by an Asiatic bark fungus, Cryphonectria parasitica. A group of scientists at The American Chestnut Foundation has been working since 1983 to develop blight resistant American chestnut by inter-species backcross breeding with the relatively resistant Chinese chestnut (Castanea mollissima). In an effort to facilitate this breeding program we have initiated cytogenetic studies of these two species and their F1 and backcross hybrids. Here we report our successes in preparing somatic chromosomes using enzymatic digestion of American chestnut seedling root tips and demonstrate the quality of the chromosome spreads using fluorescent in situ hybridization with ribosomal DNA probes. Our results show two 18S-28S rDNA sites, one major and one minor, and one 5S rDNA site in American chestnut. This is the first such report for American chestnut and our preliminary results appear similar for Chinese chestnut.
ribosomal DNA 18S-28S rDNA 5S rDNA FISH Chinese chestnut backcross breeding
U.S.Forest Service,Southern Institute of Forest Genetics,Forest Tree Molecular Cytogenetics Laborato U.S.Forest Service,Southern Institute of Forest Genetics,Harrison Experimental Forest,23332 Old Miss Headquarters Office,The American Chestnut Foundation,160 Zillicoa Street,Suite D,Asheville,NC 28801, Meadowview Research Farm,The American Chestnut Foundation,14005 Glenbrook Avenue,Meadowview,VA 24361 Department of Agronomy and Plant Genetics,University of Minnesota,1991 Upper Buford Circle,411 Borla