Variation in Double-Stranded RNA from Isolates ofPyricularia oryzae

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Abstract
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.