Races of Puccinia graminis in the United States in 1988. 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. 74:555-557. Accepted for publication 25 January 1990. 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, 1990. DOI: 10.1094/PD-74-0555.

Oat stem rust was present in light amounts throughout most of the United States in 1988, and yield losses were nil. Disease development was a month later than the 40-yr average. The principal race of the pathogen was NA-27, which is virulent on hosts having resistance genes Pg-1, -2, -3, -4, and -8. NA-27 accounted for 83% of the isolates and NA-16 for 7%. No virulence was found for Pg-a or Pg-16 in the 1988 oat stem rust population. Wheat stem rust overwintered in trace amounts from southern Texas to southern Georgia. A probable overwintering site was found in a plot in northeastern North Dakota 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 92% of the 148 isolates from 54 collections. 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.