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Sources of Resistance in Barley to Rhynchosporium secalis. R. K. Webster, Professor, Department of Plant Pathology, University of California, Davis 95616. L. F. Jackson, Assistant Professor, University of Florida, Gainesville 32601; and C. W. Schaller, Professor, Department of Agronomy and Range Science, University of California, Davis 95616. Plant Dis. 64:88-90. Accepted for publication 5 March 1979. Copyright 1980 American Phytopathological Society. DOI: 10.1094/PD-64-88.

Nearly 18,000 entries from the USDA world barley collection were evaluated in the field for resistance to Rhynchosporium secalis. Maximum disease exposure was provided by repeated inoculations of a mixture of five California isolates with known combined abilities of pathogenicity on previously identified sources of resistance. No distinct pattern of origin of resistance was revealed. Nine entries from six countries (France, Japan, USA, Israel, Ethiopia, and Wales) showed no symptoms, but 273 entries with representatives of three species (Hordeum distichum L. emend Lam, H. vulgare L. emend Lam, and H. irregulare åberg and Wiebe) showed high levels of resistance. All other entries were susceptible to the range of pathogenicity of the inoculum employed. Resistant entries included two-rowed and six-rowed spring, winter, and facultative types. Results nearly identical to those in the field were obtained when more than 2,000 of the entries were evaluated in the greenhouse. Use of newly identified sources of resistance should include consideration of the presence and frequency of specific races, because these differ throughout the world.