Races of Puccinia graminis in the United States and Mexico During 1983. A. P. Roelfs, Research Plant Pathologist, Cereal Rust Laboratory, ARS, USDA, University of Minnesota, St. Paul 55108. D. H. Casper, Research Technician, and D. L. Long, Plant Pathologist, Cereal Rust Laboratory, ARS, USDA, University of Minnesota, St. Paul 55108.. Plant Dis. 68:902-905. Accepted for publication 23 April 1984. 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, 1984. DOI: 10.1094/PD-68-902.

Oat stem rust was present in trace amounts in the southern United States in 1983. Disease development was generally a week later than the 40-yr average. Losses were light throughout the United States. No isolates were obtained from Mexico. The principal race was NA-27, virulent on host genes Pg-1, -2, -3, -4, and -8, making up 88% of the isolates. No virulence was found in oat stem rust for host genes Pg-13, 16, or -a. Wheat stem rust was found in trace amounts in southern Texas in mid-March. Stem rust spread northward into the northern Great Plains by mid-June. Although moderate severities occurred in some hard red spring wheat fields, the cultivars had adequate resistance to prevent the massive inoculum levels of the mid-1950s and losses were minimal. Race 15-TNM, virulent on Sr17, was the most common virulence combination, making up 70% of the 1,295 isolates from 466 collections. The second most common race was Sr17 avirulent on 15 TNM, which made up 24% of the isolates. No virulence was found on wheat lines with genes Sr13, 22, 24, 25, 26, 27, 29, 31, 32, 33, 37, Gt, and Wld-1.

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