PHYLOGENETIC-RELATIONSHIPS BETWEEN RICE DWARF PHYTOREOVIRUS ISOLATES FROM 5 COUNTRIES

Rice dwarf virus isolates were collected from several locations in Jap an, the Philippines, China, Nepal and Korea. Genomic dsRNA segment pro files in polyacrylamide gel electrophoresis differed among the isolate s. There were less differences in the profiles between isolates from J apan and Korea than in those between these two Countries and others. N ucleic acid hybridization was used to examine the extent of genomic va riation. Full-length cDNAs to all genomic segments encoding non-struct ural proteins (S4, S6, S9, S10, S11 and S12) were synthesized from two Japanese isolates, and were used for dot-blot hybridization. Hybridiz ations using probes generated from the full-length cDNA clones failed to differentiate isolates from different geographical areas. However, cDNA probes covering a variable region of S12 were able to distinguish Japanese and Korean isolates from those of other countries. Phylogene tic tree analysis based on the amino acid sequence of P12 encoded by S 12 grouped Japanese and Korean isolates together. The Chinese isolates from two different locations (Yunnan and Fujian) were closely related to each other, and were the most distantly related to Japanese and Ko rean isolates.