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Variation in Double-Stranded RNA from Isolates of Pyricularia oryzae. Penny L. Hunst, Research associate, Department of Plant Pathology, Physiology & Weed Science, Virginia Polytechnic Institute & State University, Blacksburg 24061; Frances M. Latterell(2), and Albert E. Rossi(3). (2)(3)Research plant pathologist and biologist, respectively, USDA-ARS Plant Disease Research Laboratory, Frederick, MD 21701. Phytopathology 76:674-678. Accepted for publication 6 January 1986. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/Phyto-76-674.

Mycelial extracts of 29 isolates of Pyricularia oryzae representing 21 physiologic races from worldwide sources were analyzed for double-stranded RNA (dsRNA) content. Among the 20 isolates found to contain dsRNA, 15 distinct dsRNA electrophoretic patterns were observed. A number of isolates related by host specificity and/or genealogy had common dsRNA bands as well as unique bands. Virus particles about 35 nm in diameter were partially purified from mycelial extracts of isolates 455 (race IA-65) and 793 (IB-49) and were observed by transmission electron microscopy. Upon dissociation, the particles were found to contain dsRNA, which comigrated with the dsRNA extracted from the mycelium. Dot-blot hybridization analysis revealed sequence homology between the dsRNA of isolate 455 of race IA-65 and several other isolates of related races. Evidence of a relationship between dsRNA content and pathogenicity of P. oryzae, however, was inconclusive.