Molecular Identification and Pathological Characteristics of NPV Isolated from Spodoptera litura (Fabricius) in Pakistan

Abstract

The cotton army worm Spodoptera litura Fabricius (Lepidoptera: Noctuidae) is a destructive pest of various field crops and vegetables in Pakistan. Development of biopesticide is an attractive strategy to minimize the problems of pest resistance, environmental pollution and human health concerns. The isolates of S. litura nucleopolyhedroviruses (SltNPV) were collected from infected larvae fed on natural cotton crops. The NPV was isolated from the larvae and viral occlusion bodies (VOBs) were detected using a light microscope. The toxicity of native isolates against S. litura also studied by testing different concentrations (1 x 102 POB (Polyhedral occlusion bodies) mL-1- 1 x 1010 POB mL-1) from the occlusion bodies produced from NPV isolates against 2nd, 3rd, 4th and 5th instar larvae of S. litura. The rapid and sensitive polymerase chain reaction (PCR) technique was used for the molecular detection of NPV gene from native NPV diseased insect. Multiple sequence alignment and phylogenetic analysis were performed to compare SlNPV- FSD15 based on Lef-8 with other Lef-8 genes sequences clearly showed that our SlNPV-FSD15 isolate belongs to Spodoptera litura associated NPVs. The biological activities of this NPV isolates were investigated under laboratory condition. The highest mortality of S. litura was observed at early instars. Against second instars of S. litura, LC50 values of NPV isolate ranged from 1.92×103 to 3.64×103OB/ml with LT50 values of 69.30 h to 72.80 h, respectively. This study showed highly effectiveness and provides an opportunity to cut down the use of synthetic approaches and develop safe biological/microbial insecticides from NPV isolates, which in future may effectively control S. litura.