Races of Puccinia graminis f. sp. tritici in the United States and Mexico in 1980. A. P. Roelfs, Research Plant Pathologist, Cereal Rust Laboratory, Agricultural Research Service, U.S. Department of Agriculture, University of Minnesota, St. Paul 55108. D. L. Long, Plant Pathologist, and D. H. Casper, Research Technician, Cereal Rust Laboratory, Agricultural Research Service, U.S. Department of Agriculture, University of Minnesota, St. Paul 55108. Plant Dis. 66:205-207. Accepted for publication 5 June 1981. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1982. DOI: 10.1094/PD-66-205.

No wheat stem rust was found to have overwintered in the United States. A survey of Mexico during the spring revealed no stem rust outside of wheat breeding plots and trap nurseries. The disease appeared late in the season in the United States and in amounts too sparse to threaten the wheat crop. This was the least amount of rust found in the United States since the rust survey began in 1918. Race 15-TNM was the most frequently identified, or 43% of the 143 isolates studied. Race 151-QFB constituted 26% of the isolates. The two most commonly isolated races in Mexico, 113-RPQ and 151-QSH, were not found in the United States. No virulence was found for seedlings with Sr genes 13, 22, 24, 25, 26, 27, 29, 30, Gt, Tt2, and Wld-1.

Keyword(s): specific resistance.