Races of Puccinia graminis in the United States During 1991. A. P. Roelfs, Research Plant Pathologist, Cereal Rust Laboratory, USDA, Agricultural Research Service, University of Minnesota, St. Paul 55108. D. L. Long, and J. J. Roberts. Plant Pathologist, Cereal Rust Laboratory, USDA, Agricultural Research Service, University of Minnesota, St. Paul 55108; and Research Plant Pathologist, USDA, Agricultural Research Service, Georgia Agricultural Experiment Station, Experiment 30212. Plant Dis. 77:129-132. Accepted for publication 29 September 1992. 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, 1993. DOI: 10.1094/PD-77-0129.

Wheat stem rust overwintered in southern Texas, southern Louisiana, and southwestern Georgia. Yield losses caused by stem rust in wheat and barley were light, although losses up to 10% occurred in some barley fields in east central North Dakota. Race Pgt-QCCJ was the most common race, making up 68% of the 1,279 isolates from 487 collections. However, when only collections made from wheat were considered, the most common races were QCCJ, TPMK, and QFCS, comprising 38, 36, and 25% of the isolates, respectively. Of the isolates of race Pgt-QCCJ, 67% were from cultivated barley. No virulence was found for wheat lines with “single” genes Sr13, 22, 24, 25, 26, 27, 29, 30, 31, 32, 33, 37, Gt, and Wld-1. Oat stem rust was present in light amounts, occurring only in the Gulf Coast area, northern Great Plains, and California (an isolated population). Yield losses were negligible. The principal race was NA-27, virulent to resistance genes Pg-1, -2, -3, -4, and -8. NA-27, NA-16, and NA-5 made up 94, 4, and 2%, respectively, of the isolates from the United States. No virulence to Pg-9, -13, -16, or -a was found in the 1991 oat stem rust population.