Abstract: 【Aim】 This study aims to further reveal genotypic polymorphism of Spodoptera litura nucleopolyhedrovirus (SpltNPV) in the wild based on genome sequences. 【Methods】 The virus clones A5, F1, X3 and X15 were isolated from SpltNPV Egypt stock, Fukuyama stock and Ogasawara stock by in vivo cloning technique, respectively. According to the complete genome sequence of SpltNPV (GenBank accession no.: NC_003102) and some SpliNPV gene sequences (GenBank accession no.: X99377, X99376 and X98924), primers were designed. Polyhedrin and ORF18-ORF23 of A5, F1, X3 and X15 were obtained by PCR amplification. 【Results】 According to the polyhedrin sequence, A5 and F1 belong to SpliNPV type, while X3 and X15 belong to SpltNPV type. The homologous comparisons of ORF18-ORF23 were done between A5, F1, X3, X15 and SpltNPV or SpliNPV. The results showed that F1 shares high nucleotide identity with SpliNPV, and X3 shares high nucleotide identity with SpltNPV, but only 387 bp is deleted at 172-558 nt of ORF20. Though X15 belongs to SpltNPV type according to the polyhedrin sequence, ORF18-ORF23 all share high nucleotide identities to those of SpliNPV, and as a SpltNPV-unique ORF, ORF22 is deleted in X15 genome. A5 belongs to SpliNPV type, and the corresponding ORF18-ORF20 share high nucleotide identities with SpliNPV, but ORF21 shares 100% nucleotide identity with that of SpltNPV. As a SpltNPVunique ORF, ORF22, however, appears in A5 genome, and shares 100% nucleotide identity with that of SpltNPV. Furthermore, ORF23 shares high nucleotide identity with that of SpliNPV. 【Conclusion】 These results indicate that SpltNPV in the wild possesses genotypic polymorphisms, and moreover, the genomes of these virus clones with the same genotype have significant differences. The natural heterogeneity can be exploited to develop NPV strains suitable for the control of S. litura.

Key words: Spodoptera litura nucleopolyhedrovirus (SpltNPV), virus clones, genotype, genome;polymorphism