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Virulence Genes of the Wheat Powdery Mildew Fungus, Erysiphe graminis f. sp. tritici, in North Carolina. S. Leath, USDA-ARS, Department of Plant Pathology, North Carolina State University, Raleigh 27695. J. P. Murphy, Department of Crop Science, North Carolina State University, Raleigh 27695. Plant Dis. 69:905. Accepted for publication 13 June 1985. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/PD-69-905e.

In April 1985, 60 mobile wheat (Triticum aestivum L.) nurseries were placed across North Carolina in fields of cvs. Coker 747, Coker 983, and Saluda and in areas at least 1.5 km distant from wheat, for 1224 hr, to trap spores of Erysiphe graminis DC. ex Merat, f. sp. tritici Em. Marchal. Nurseries consisted of cv. Chancellor and 11 near-isogenic lines, each with a different mildew resistance gene. Virulence was detected for all genes tested: Pm1, Pm2, Pm2(+), Pm3a, Pm3b, Pm3c, Pm4, Pm6, Pm7, Pm8, and a gene considered to be from cv. Michigan Amber. Virulence to Pm1, Pm3b, Pm4, Pm7, and Pm8 was detected less often (P ≤0.05) than was virulence to other host genes. Frequent occurrence of virulence to Pm3a differs from results of studies completed in Pennsylvania and Ontario. From east to west, this survey covered an aerial distance of 651 km and an elevation change of 1,762 m.