Molecular Characterization of Southern Rice Blacked-Streaked Dwarf Virus ( SRBSDV) from Vietnam.

Southern rice black-streaked dwarf virus ( SRBSDV) is a novel putative member of the genus Fijivirus, family Reoviridae. We report here the genomic sequences of a Vietnamese isolate ( SRBSDV-V). The total genome of SRBSDV-V has 29 115 nucleotides (nt), nine nt shorter than SRBSDV- GD or - HN, but similar in organization to these two Chinese isolates. Nucleotide diversities among SRBSDV isolates were much lower than those among the corresponding ORFs of the available RBSDV isolates and there was a lower purifying selection pressure on SRBSDV than RBSDV, providing first molecular evidence for the view that SRBSDV is of recent origin. In studies of all available SRBSDV sequences, there was no obvious correlation between geographic distances and phylogenetic distribution. A high frequency of genetic recombination was found among both Chinese and Vietnam SRBSDV isolates, suggesting that recombination may play an important role in the molecular variation and evolution of SRBSDV. [ABSTRACT FROM AUTHOR]