Host range changes generated by heterogeneous recombination of two nucleopolyhedroviruses isolated from Spodoptera litura and Spodoptera exigua

To study the recombination characteristics between nucleopolyhedroviruses(NPVs),and reveal the rules of evolution in NPVs and explore new NPVs with expanded host range,two NPVs[Spodoptera litura NPV(SlNPV) and S.exigua NPV(SeNPV)] were used to co-infect alive host in vivo.The biological activities of NPVs before and after co-infection were determined,and the ultrastructure of polyhedra were observed under transmission electron microscope.The results showed that,oral co-infection of SlNPV and SeNPV resulted in a new strain of NPV(SlNPV-1) which could infect both S.litura and S.exigua.The lethal concentration of 50 percent individuals(LC50) of SlNPV-1 against S.litura was not significantly different from that of SlNPV.The biological activity of SlNPV-1 against S.exigua,was significantly lower than that of SeNPV.The ultrastructure of polyhedra in SlNPV-1 was not significantly different from that of SlNPV.Restriction enzyme profiles of genomic DNA from SlNPV-1 was the same as that of SlNPV.All these results indicated that co-infection of SlNPV and SeNPV in vivo could generate a new strain of NPV with an expanded host range againt both S.litura and S.exigua.