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Distribution of Phoma sclerotioides on Alfalfa and Winter Wheat Crops in the North Central United States

May 2007 , Volume 91 , Number  5
Pages  551 - 558

J. E. Larsen , Department of Plant Pathology, University of Minnesota, St. Paul 55108 ; C. R. Hollingsworth , Northwest Research and Outreach Center and Department of Plant Pathology, University of Minnesota, Crookston 56716 ; J. Flor , Department of Plant Pathology, University of Minnesota, St. Paul 55108 ; M. R. Dornbusch , USDA-ARS-Plant Science Research, Department of Plant Pathology, University of Minnesota, St. Paul 55108 ; N. L. Simpson , Fort Valley State University, Fort Valley, GA 31030 ; and D. A. Samac , USDA-ARS-Plant Science Research, Department of Plant Pathology, University of Minnesota, St. Paul 55108



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Accepted for publication 15 November 2006.
ABSTRACT

Brown root rot of alfalfa (Medicago sativa), caused by Phoma sclerotioides, has been reported in several states in the northern United States and in western Canada. A survey was conducted to determine the distribution of the fungus in Minnesota and Wisconsin. Isolates of the pathogen were recovered from roots of alfalfa, winter wheat, and perennial ryegrass plants. The internal transcribed spacer (ITS) 1, 5.8S, and ITS2 of the rDNA of the isolates from alfalfa and wheat were identical and matched the sequences of a P. sclerotioides isolate from Wyoming. The fungus was found to be widespread in both states and was detected in roots of alfalfa plants from 17 counties in Minnesota and 14 counties in Wisconsin using polymerase chain reaction (PCR)-based assays. A real-time PCR assay was developed that increased sensitivity of detecting the pathogen from plant tissues and soil. The isolates from alfalfa caused disease on inoculated winter wheat plants. Although the fungus was previously found associated with roots of diseased cereal and turfgrass plants, this is the first demonstration of pathogenicity of P. sclerotioides on wheat.


Additional keywords: Lolium perenne, Triticum aestivum, winterkill

The American Phytopathological Society, 2007