Field Resistance to Potato Stem Colonization by the Black Dot Pathogen Colletotrichum coccodes

ABSTRACT Potato (Solanum tuberosum) germplasm was tested for resistance to stem colonization by the black dot pathogen Colletotrichum coccodes. Forty-six potato selections were tested in three field trials from 2006 to 2008. Resistance was determined by comparing disease severity on aboveground stems to the mean disease severity of the industry standards Russet Burbank, Ranger Russet, and Umatilla Russet. The potato selections were also tested for genotype*environment interaction to determine their genetic stability. Heritability of resistance was calculated to be 0.13 with confidence intervals between 0.00 and 0.68. The selections A0012-5, PA95B2-4, PA98NM38-1, and PO94A009-7 had less black dot than the standards in all years, and also demonstrated genetic stability. These selections also possess resistance to the root galling stage of the powdery scab pathogen Spongospora subterranea f. sp. subterranea. PA95B2-4, PA98NM38-1, and PO94009-7 were derived from an introgression program to incorporate resista...