Evaluation of recombinant diamondback moth baculovirus in selected lepidopteran cell lines and larvae

The diamondback moth (DBM), Plutella xylostella (L.) is one of the most important pests of the cabbage family, as well as other vegetable crops throughout the world. Its control by chemical insecticides as well as the biopesticide Bacillus thuringiensis has become more difficult due to the development of resistance to these agents. The present study was initiated to evaluate the replication of a recombinant baculovirus of DBM (PxMNPV- AaIT) developed by BASF (formerly American Cyanamid Company) from the parental wild type baculovirus in insect cell lines, as well as to test its pathogenicity against several lepidopteran species. Cell lines evaluated in this study were derived from Helicoverpa zea (HZ-FB33), Heliothis virescens (HV-OV), Trichoplusia ni (TN-CL1), Spodoptera frugiperda (SF-TS) and S. exigua (SE-E4). Twenty-four hour old larvae of H. subflexa, H. virescens, H. zea, T. ni and P. xylostella were tested for their susceptibility to the recombinant virus employing the lethal concentration fifty( LC50) bioassay. The SE-E4 cell line produced the highest titer of 6.7 ± 0.06 x 105 TCID50/ml, whereas the greatest number of occlusion bodies (OB) of 1. 1 ± 12.05 x 107/ml was produced by SF-TS. Of the five lepidopteran species of insects investigated, H. virescens was the most susceptible, with an LC500 of 0.452 OB/cm2. The LT50 was 2.69 d for PxMNPV-AalT as compared with 4.39 d for wild-type PxMNPV. (Résumé d'auteur