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Ecology and Epidemiology

Dissemination of Virulent and Hypovirulent Forms of a Marked Strain of Endothia parasitica in Michigan. S. Westveer Garrod, Graduate research assistant, Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824-1312; D. W. Fulbright(2), and A. V. Ravenscroft(3). Associate professor, and senior research technician, respectively, Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824-1312. Phytopathology 75:533-538. Accepted for publication 20 November 1984. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/Phyto-75-533.

The infection and spread of a virulent and a hypovirulent form of a pentachloronitrobenzene-resistant strain of Endothia parasitica was examined in an American chestnut (Castanea dentata) grove. After electrophoresis in polyacrylamide gels, the hypovirulent form exhibited a unique dsRNA banding pattern that enabled monitoring the spread of specific dsRNA segments. Spread of virulent strains and hypovirulent strains (carrying the specific dsRNA bands) was detected within and among trees. Conversion in situ of virulent strains to hypovirulent strains occurred on some trees. Wounds located 10- 110 cm from inoculum sources were infected equally at the end of 15 mo.