VIEW ARTICLE

Research.

Races of Puccinia graminis in the United States During 1993. A. P. Roelfs, Research Plant Pathologist, Cereal Rust Laboratory, USDA, Agricultural Research Service, University of Minnesota, St. Paul 55108. D. L. Long, Plant Pathologist, Cereal Rust Laboratory, USDA, Agricultural Research Service, University of Minnesota, St. Paul 55108; and J. J. Roberts, Research Plant Pathologist, USDA, Agricultural Research Service, Georgia Agricultural Experiment Station, Experiment 30212. Plant Dis. 79:969-972. Accepted for publication 18 May 1995. 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, 1995. DOI: 10.1094/PD-79-0969.

Wheat stem rust overwintered in southern Texas, southern Louisiana, and southern Georgia. Yield losses in wheat to stem rust were traces, but several hundred hectares southwest of Houston were destroyed. Race Pgt-TPMK was the most common race overall, making up 61% of the 895 isolates from 311 collections. From Hordeum spp., 112 collections were made, in which the most common race was Pgt-QCCJ, comprising 56% of the isolates. Eighty-eight percent of the isolates of QCCJ were from cultivated barley, and 56% of all isolates from cultivated barley were race QCCJ. No virulence was found to wheat lines with "single" genes Srl3, 22, 24, 25, 26, 27, 29, 30, 31, 32, 33, 37, Gt, or Wld-1. Little oat stem rust overwintered in the southern states in 1993. Yield losses in 1993 were negligible. Race NA-27, virulent to Pg-l, -2, -3, -4, and -8, was again the predominant race in the United States, comprising 81% of the 93 isolates from 33 collections. NA-5 and NA-10 were the other races isolated, comprising 9 and 11% of the population, respectively. No virulence to Pg-9, -13, -16, or -a was found in the 1993 oat stem rust population.