Virulence of Puccinia recondita f. sp. tritici in the United States in 1987. D. L. Long, Plant Pathologist, Cereal Rust Laboratory, USDA-ARS, Department of Plant Pathology, University of Minnesota, St. Paul 55108. J. F. Schafer, A. P. Roelfs, and J. J. Roberts. Collaborator, Research Plant Pathologist, Cereal Rust Laboratory, USDA-ARS, Department of Plant Pathology, University of Minnesota, St. Paul 55108, and Research Plant Pathologist, USDA-ARS, Georgia Agricultural Experiment Station, Experiment 30212. Plant Dis. 73:294-297. Accepted for publication 2 November 1988. 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, 1989. DOI: 10.1094/PD-73-0294.

Isolates of Puccinia recondita f. sp. tritici were obtained from wheat leaf collections made by cooperators and from field rust surveys conducted by the authors in the Great Plains, Ohio Valley, and Gulf Coast states in 1987. Testing of 947 isolates for virulence to 14 single-gene differentially resistant test lines showed 44 virulence/avirulence phenotypes, categorized into nine Unified Numeration races. An increased frequency of virulence to Lr1, 24, and 26 over recent years was found, and combined virulence to Lr16 and 26 was observed for the first time. No virulence was found to 15 of 24 additional entries in a resistant test series. Regional race distribution patterns again suggested that the central United States was a single epidemiological unit.

Keyword(s): plant disease monitoring, rust epidemiology, wheat leaf rust.