Cloning and biological characterization of Spodoptera exigua nucleopolyhedroviruses isolated in China

Abstract

Fifteen nucleopolyhedrovirus (NPV) clones designated as SeNPV G1-G15 were derived by plaque assay from the uncloned NPV population that was isolated in China from the beet armyworm, Spodoptera exigua (Lepidoptera: Noctuidae). Restriction endonuclease analysis of genomic DNA showed that these 15 clones fell into three groups represented by G1, G3, and G4. The genomic DNAs of G1, G3, and G4 showed a similar overall restriction endonuclease pattern and a polymorphism in the size and number of restriction endonuclease fragments. Examination with seven different lepidopteran insect cell lines derived from Bombyx mori (BmN-4), Lymantria dispar (IPLB-Ld652Y), Spodoptera exigua (Se301), S. frugiperda (Sf9), S. littoralis (CLS-79), S. litura (TUAT-SpLi221), and Spilosoma imparilis (FRI-SpIm-1229) showed that Se301, Sf9 and FRI-SpIm-1229 cell lines were permissive for all the SeNPV clones obtained, in which only the Se301 cell line was able to support a high titre of SeNPV replication. Comparative biological characterization in Se301 cells showed that among the SeNPV clones, G3 had the highest potential for the production of viral DNA, budded virions, and polyhedrin in the infected cells. All the SeNPV clones caused an apoptotic-like cytopathology in a significant proportion of IPLB-Ld652Y and FRI-SpIm-1229 cells, and a maximum degree of the apoptotic-like cytopathology was observed in the cells infected with G3. These results indicate that the SeNPV clones obtained in the present study are closely related clonal variants that exhibit different biological activity due to minor genomic differences. © 2000, The Japanese Society of Sericultural Science. All rights reserved.