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Assessment of Genetic Relatedness Among Double-Stranded RNAs from Isolates of Rhizoctonia solani from Diverse Geographic Origins. N. Bharathan, Former graduate assistant, Department of Plant Biology and Pathology, University of Maine, Orono 04469-0118, Present address: University of Florida, Institute of Food and Agricultural Sciences, 18905 SW 280 Street, Homestead 33031; S. M. Tavantzis, associate professor, Department of Plant Biology and Pathology, University of Maine, Orono 04469-0118 Phytopathology 81:411-415. Accepted for publication 5 November 1990. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/Phyto-81-411.

The degree of genetic relatedness among double-stranded RNA (dsRNA) components from 51 isolates of Rhizoctonia solani of diverse geographic origins was analyzed by RNA-RNA hybridization. The cultures included in this study were classified into five anastomosis groups (AGs 15), and originated from different geographic locations in the United States, Japan, and Israel. Radioisotope-labeled total dsRNA from eight Japanese cultures (AGs 1, 2, 4, and 5) did not hybridize to northern blots of total dsRNA from American cultures of the corresponding AGs. By contrast, total dsRNA from a Japanese AG 3 isolate hybridized to dsRNA from two of the nine North American cultures tested. Isolates of the same AG and obtained from the same field contained dsRNAs, some of which had the same size; only a few of these dsRNAs cross-hybridized. Quantitative analysis of hybridizing dot-spots showed that sequence homology among cross-hybridizing dsRNAs from isolates of the same AG but different geographic locations ranged from 32 to 80%.