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Virulence of Blumeria graminis f. sp. tritici on Winter Wheat in the Eastern United States

January 1998 , Volume 82 , Number  1
Pages  64 - 68

A. S. Niewoehner , Former Graduate Student ; and S. Leath , USDA-ARS and Associate Professor, Department of Plant Pathology, North Carolina State University, Raleigh 27695

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Accepted for publication 16 September 1997.

Samples of perithecia of Blumeria graminis f. sp. tritici from senescing wheat leaves were collected by cooperators from 17 states. Ascospores were discharged from perithecia and single-spore isolates were characterized for virulence genes using a differential host series containing 15 known resistance genes. A total of 520 isolates from 17 states were characterized in 1993 and 1994. Virulence frequencies and complexity and racial composition were examined. The data were analyzed for associations among sets of virulence genes and the geographical distribution of phenotypes. Virulence to Pm3c, Pm3f, pm5, Pm6, and Pm7 was present in all states surveyed. Since 1990, virulence to Pm3a has increased in the northeast, and virulence to Pm1, Pm4b, Pm8, and Pm17 has increased across the area surveyed. The resistance genes Pm12 and Pm16 remain highly effective in the southeastern United States. An increase in virulence frequencies and complexity of isolates was observed.

Additional keywords: population genetics, Triticum aestivum

The American Phytopathological Society, 1998