Abstract: Cytoplasmic polyhedrosis viruses (CPVs) (Reoviridae: Cypovirus) are icosahedral particles with a segmented double-stranded RNA genome. CPVs were divided into at least 15 distinct electrophoretypes on the basis of variations in the electrophoretic migration patterns of the genome segments. Attempts to define the evolutionary relationships and origins of cypoviruses have been hampered by the lack of enough genetic information. This is mainly due to the fact that the various methods used in the past for sequencing dsRNA genomes are technically difficult, time consuming and require large amounts of viral RNA. Among CPVs, complete nucleotide sequences of genome dsRNA segments have already been reported for two type 1 CPVs from Bombyx mori (strains I and H ) and Lymantria dispar, respectively, a type 14 CPV from Lymantria dispar, and a type 15 CPV from Trichoplusia ni.

Key words: insect cytoplasmic polyhedrosis viruses, double-stranded RNA, electrophoretype, homology of nucleotide and amino acid sequence