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Virulence of Puccinia recondita f. sp. tritici in the United States During 19881990. D. L. Long, Plant Pathologist, Cereal Rust Laboratory, Agricultural Research Service, U.S. Department of Agriculture, Department of Plant Pathology, University of Minnesota, St. Paul 55108. A. P. Roelfs, and J. J. Roberts. Research Plant Pathologist, Cereal Rust Laboratory, Agricultural Research Service, U.S. Department of Agriculture, Department of Plant Pathology, University of Minnesota, St. Paul 55108; and Research Plant Pathologist, Agricultural Research Service, U.S. Department of Agriculture, Georgia Agricultural Experiment Station, Experiment 30212. Plant Dis. 76:495-499. Accepted for publication 3 January 1992. 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, 1992. DOI: 10.1094/PD-76-0495.

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, Ohio Valley, and Gulf Coast states in 1988, 1989, and 1990. Forty-one virulence/avirulence phenotypes were found among 618 isolates in 1988, 45 among 983 isolates in 1989, and 53 among 906 isolates in 1990 on 14 host lines with single designated genes for leaf rust resistance. The frequencies of virulence to lines with Lr11 and Lr26 during 19881990 were greater than in previous years. Isolates were tested on 14 additional entries selected for potentially useful resistance to common races of P. r. tritici. No virulence was found to 12 of these 14 entries during 19881990. Regional race distribution patterns again suggested the central United States is a single epidemiological unit distinct from the eastern United States.

Keyword(s): wheat leaf rust.