Races of Puccinia graminis f. sp. avenae in the United States and Mexico During 1981. A. P. Roelfs, Research Plant Pathologist, Cereal Rust Laboratory, ARS, USDA, University of Minnesota, St. Paul 55108. D. L. Long, Plant Pathologist, and D. H. Casper, Research Technician, Cereal Rust Laboratory, ARS, USDA, University of Minnesota, St. Paul 55108. Plant Dis. 67:986-987. Accepted for publication 10 March 1983. 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, 1983. DOI: 10.1094/PD-67-986.

Overwintering oat stem rust in southern Texas in 1981 produced a large quantity of inoculum. Subsequent infections occurred earlier in the year than normal in the north central states, but earlier than normal planting dates nullified much of the effect of an early disease onset. The 1,530 isolates from 555 uredial collections from the United States consisted of North American (NA) races NA-27, 95%; NA-16, 3%; and NA-5, 1%. No virulence was detected for oat lines with genes Pg-13, -16, and -a or the host lines Saia, S.E.S. Selection No. 52, Kyto, CI9221, and X-1588-2 in the United States.