Physiologic Specialization of Puccinia graminis f. sp. secalis in North America. B. J. Steffenson, Graduate Research Assistant, Department of Plant Pathology, University of Minnesota, St. Paul 55108. R. D. Wilcoxson, Professor, Department of Plant Pathology, University of Minnesota, St. Paul 55108; I. A. Watson, Professor Emeritus, University of Sydney, Sydney, N.S.W., Australia; and A. P. Roelfs, Research Plant Pathologist, Cereal Rust Laboratory, USDA, ARS, University of Minnesota, St. Paul 55108. Plant Dis. 67:1262-1264. Accepted for publication 23 May 1983. Copyright 1983 American Phytopathological Society. DOI: 10.1094/PD-67-1262.

Twelve physiologic races of Puccinia graminis f. sp. secalis were found in North America using single-gene differentials of rye. The prevalent races were HR, comprising 48% of 52 isolates; HT, 14%; HQ, 12%; KT, 10%; and GR, 4%, respectively. Races HH, HK, HM, KH, KR, GM, and GQ were also found. Virulence phenotypes of isolates derived from sexually and asexually reproducing populations were compared. The sexually reproducing population was more variable in virulence phenotypes than the asexually reproducing population.