Analysis of defective genomes of bombyx mori nucleopolyhedrovirus generated by serial undiluted passage in cell culture.

Viral DNA was extracted from cells infected with bombyx mori nucleopolyhedrovirus (BmNPV) D1 strain after 34 serial undiluted passages (P34). P34 DNA was subjected to restriction analysis and Southern blot hybridisation using standard D1 DNA and P34 DNA of BmNPV as probes. Based on hybridisation profiles, the BmNPV DNA regions retained in the P34 DNA were localised on HindIII and PstI restriction maps. Two regions of BmNPV DNA located at 0-12.8 and 40.2-65.0 map unit (m.u.) were highly conserved in P34 DNA. These regions contained two of three interspersed homologous sequences (ihss), but only one of five homologous regions (hrs). This suggests that ihss may have an essential role in BmNPV replication.