Races of Puccinia graminis in the United States and Mexico During 1985. 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. 70:1010-1013. Accepted for publication 1 July 1986. 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, 1986. DOI: 10.1094/PD-70-1010.

Oat stem rust was present in light amounts throughout most of the United States in 1985, and yield losses were small. Disease development was generally more than a week later than the 40-yr average. The principal race in the United States and Mexico was NA-27, virulent on hosts with resistance genes Pg-1, -2, -3, -4, and -8. NA-27 comprised 96 and 100% of the isolates from the United States and Mexico, respectively. No virulence was found in oat stem rust for Pg-9, -13, -16, or -a. Wheat stem rust was found in trace amounts in trap plots near Beeville and Victoria in southern Texas in early April. Additional overwintering sites were found in nurseries from Florida through Louisiana and northward into central Arkansas. Stem rust spread northward into the northern Great Plains by early July. Although stem rust occurred on some hard red spring wheat cultivars, they had adequate resistance and losses were nil. Race 15-TNM, virulent on plants with Sr17, was the most common virulence combination, making up 77% of the 616 isolates from 225 collections. The second most common race was 15-TDM, which made up 4% of the isolates. No virulence was found for wheat lines with genes Sr13, 22, 24, 25, 26, 27, 29, 30, 31, 32, 33, 37, Gt, and Wld-1.