Isolation of a Virus from Virulent Strains of Rhizoctonia solani

Abstract
Summary Double-stranded RNA viruses were detected in virulent strains of Rhizoctonia solani. The virus particles were 33 nm in diameter, contained two or three major segments of dsRNA (mol. wt. 1.6 × 106, 1.45 × 106 and 1.25 × 106), had a density of 1.34 g/ml and had an estimated sedimentation coefficient of 161S. The major coat protein had a mol. wt. of 46000. An RNA-dependent RNA polymerase activity was associated with the viral capsids. Native hypovirulent strains of R. solani were devoid of these viruses and attenuation of virulent strains to hypovirulence appeared to be correlated with the loss of some or all of the segments of dsRNA. Transmission of dsRNA from a virulent to a hypovirulent strain by heterokaryon formation was associated with the transmission of virulence.