Abstract: Biological and molecular characteristics of three strains (K-3, G1-2 and G-10) of Spodoptera litura multicapsid nucleopolyhedrovirus (SpltMNPV), isolated from Honshu, Kyushu and Shikoku, Japan, which had strong pesticide activity to S. litura, were primarily studied using the cultured cell strain of S. litura. The polyhedrin genes of the three strains was cloned and sequenced. The results showed that: (1) the three Japanese strains K-3, G1-2 and G10-3 had different restriction fragmentation patterns and belonged to the nucleic acid type A, B and C of SpltMNPV respectively. (2) There are differences in the outputs of budded virus (BV) and polyhedron between the three strains. According to the analysis of immunological blotting, the molecular weights of polyhedrin in the three strains were different. (3) The polyhedrin gene of the Japanese SpltMNPV is composed of 747 nucleic acids, which codes a peptide of 249 amino acids. The nucleic acid sequences homology is as high as 98.9% compared with the Chinese strain, and 61.7%-74.2% with other six NPVs compared. However, in the 5' upstream sequence (nt-1-100), SpltMNPV differs significantly with AcMNPV and BmNPV. There are 2 point mutations in the sequence with 8 highly conservative nucleic acids (nt-44-51), which is the domain of the promoter. Interestingly, in spite of only one mutation occurred in the polyhedron open reading frame of SpltMNPV C type, the western blot result showed that the molecular weight of polyhedron of SpltMNPV C type is apparently different from that of A type and B type.

Key words: Spodoptera litura, nucleopolyhedrovirus, polyhedrin gene, sequence