Virulence of Puccinia recondita f. sp. tritici in the United States in 1986. 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. Research Plant Pathologists, 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. 72:22-24. Accepted for publication 23 September 1987. 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, 1988. DOI: 10.1094/PD-72-0022.

Isolates of Puccinia recondita f. sp. tritici were obtained from wheat leaf collections made by cooperators throughout the United States and from cereal rust field surveys of the Great Plains and Gulf Coast states in 1986. Testing of 972 isolates for virulence to 14 single-gene differentially resistant test lines showed 44 virulence/avirulence phenotypes, which were categorized into 11 Unified Numeration (UN) races. An increased frequency of virulence to Lr24 over recent years was found, and combined virulence to Lr24 and 26 was observed for the first time. No virulence was found to 11 of 21 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.