Races of Puccinia graminis f. sp. avenae in the United States and Mexico in 1980. A. P. Roelfs, Research Plant Pathologist, Cereal Rust Laboratory, Agricultural Research Service, U.S. Department of Agriculture, University of Minnesota, St. Paul 55108. D. L. Long, Plant Pathologist, and D. H. Casper, Research Technician, Cereal Rust Laboratory, Agricultural Research Service, U.S. Department of Agriculture, University of Minnesota, St. Paul 55108. Plant Dis. 66:208-209. Accepted for publication 5 June 1981. 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, 1982. DOI: 10.1094/PD-66-208.

The only known overwintering site for oat stem rust in the United States in 1980 was in a Beeville, TX, nursery. Surveys of Mexico in April and May found little rust in commercial fields. Disease incidence increased in Texas nurseries, and rust appeared earlier in the year than normal in the north central states; however, the earlier than normal plant maturity negated the effect of the early initial infections. The 1,150 isolates from 434 uredial collections from the United States consisted of 78% race NA-27, 11% NA-16, and 9% NA-5. No virulence for oat lines with genes Pg-9, -13, -16, and -a and the host lines Saia, CI 9221, S.E.S. Selection No. 52, X-1588-2, Kyto, or CI 9139 was found in Mexico or the United States in 1980.

Keyword(s): specific resistance.