Plant reoviruses are classified in three genera in the family Reoviridae: Phytoreovirus, Fijivirus , and Oryzavirus . Fifteen viruses, including possible members, are described (1 ). With two exceptions, all of them infect plants in gramineae . They possess 10–12 segmented double-stranded RNAs (dsRNAs) as a genome and are transmitted propagatively by leafhoppers or planthoppers. Rice dwarf Phytoreovirus (RDV) is the only plant reovirus whose complete nucleotide sequence is known (2 ). Rice dwarf virus has 12 genomic segments separated by PAGE. They are numbered from S1 to S12, from the slowest migrating segment, and all the structural and nonstructural proteins of RDV have been assigned (3 ) (Fig. 1 ). Genome characterization of other plant reoviruses is reviewed by Uyeda et al. (4 ).