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

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.

Resistance to Root Galling Caused by the Powdery Scab Pathogen Spongospora subterranea in Potato.

Potato (Solanum tuberosum) selections (clones and commercial cultivars) were examined for resistance to root galling, caused by the powdery scab pathogen Spongospora subterranea f. sp. subterranea in seven field trials conducted between 2003 and 2007 in the states of Washington and Idaho.

Disease Potential of Soil- and Tuberborne Inocula of Colletotrichum coccodes and Black Dot Severity on Potato.

Inoculum of Colletotrichum coccodes, the cause of potato black dot, is soil- or tuberborne. Understanding the disease potential of sources of inocula is crucial for developing disease management strategies and resistance screening techniques. Two hypotheses were tested in this study: (i) soilborne inoculum causes more disease than tuberborne inoculum and (ii) black dot severity is related to the concentration of soilborne inoculum.

Postinfection Activity of Selected Late Blight Fungicides.

Two sets of experiments were done in the greenhouse with 'Russet Burbank' potatoes infected with Phytophthora infestans. The first determined the effectiveness of selected late blight fungicides in restricting lesion length and spore production when applied after stem lesions had occurred on potted plants. The second quantified the curative activity of selected fungicides applied 12 to 48 h after inoculation of excised leaves with P.

Evaluation of Mint Mutants, Hybrids, and Fertile Clones for Resistance to Verticillium dahliae.

Peppermint and spearmint clones derived from cobalt 60 gamma irradiation and peppermint seed fertile clones and hybrids were evaluated for resistance to Verticillium dahliae in inoculation tests in the greenhouse. Mutant and fertile clones and hybrids varied significantly for wilt resistance. One peppermint mutant clone, three peppermint hybrids, and four peppermint fertile clones had low but varying wilt-severity values.