Races of Puccinia graminis in the United States in 1989. A. P. Roelfs, Research Plant Pathologist, Cereal Rust Laboratory, Agricultural Research Service, U.S. Department of Agriculture, University of Minnesota, St. Paul 55108. D. H. Casper, D. L. Long, and J. J. Roberts. Research Technician; Plant Pathologist; and Research Plant Pathologist, Cereal Rust Laboratory, Agricultural Research Service, U.S. Department of Agriculture, University of Minnesota, St. Paul 55108. Plant Dis. 75:1127-1130. Accepted for publication 25 April 1991. 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, 1991. DOI: 10.1094/PD-75-1127.

Oat stem rust was present in light amounts throughout most of the United States in 1989, and yield losses were nil. Disease onset was 1 mo later than the 40-yr average. The principal race in the United States was NA-27, virulent to resistance genes Pg-1, -2, -3, -4, and -8. NA-27, NA-5, and NA-16, respectively, made up 97, 1, and 1% of the isolates from the United States. No virulence was found for Pg-9, Pg-13, Pg-a, or Pg-16 in the 1989 oat stem rust population. Wheat stem rust overwintered in trace amounts from southern Texas to southern Alabama. A probable overwintering site on winter wheat was found in a northeastern North Dakota plot leeward of a shelterbelt. Stem rust inoculum spread northward, but little disease developed because of a severe drought throughout the central and northern Great Plains. No stem rust was found in fields of hard red spring or durum wheat cultivars. Race Pgt-TPM was the most common virulence combination, making up 53% of the 686 isolates from 247 collections. However, if only collections made from wheat were considered, it made up 73% of the isolates. Race Pgt-QCC made up 62% of the isolates from barley and 19% of all isolates. No virulence was found for wheat lines with “single” genes Sr13, 22, 24, 25, 26, 27, 29, 30, 31, 32, 33, 37, Gt, or Wld-1.