Molecular and insecticidal characterization of Vip3A protein producing Bacillus thuringiensis strains toxic against Helicoverpa armigera (Lepidoptera: Noctuidae)

Vegetative insecticidal proteins (Vip) represent the second generation of insecticidal proteins produced by Bacillus thuringiensis (Bt) during the vegetative growth stage of growth. Bt based biopesticides are recognized as viable alternatives to chemical insecticides, the latter cause environmental pollution and lead to emergence of pest resistance. In order to perform a systematic study of vip genes encoding toxic proteins a total of 30 soil samples were collected from diverse locations of Kashmir valley, India and characterized by molecular and analytical methods. 86 colonies showing Bacillus like morphology were selected. Scanning Electron Microscopy observations confirmed the presence of different crystal shapes, PCR analysis of insecticidal genes revealed predominance of lepidopteran specific vip3 (43.18%) followed by coleopteran specific vip1 (22.72%) and vip2 (15.90%) genes in the isolates tested. Multi-alignment of the deduced amino acid sequences revealed that vip3 sequences were highly conserved whereas vip1 and vip2 showed adequate differences in amino acid sequences compared to already reported sequences. Screening for toxicity against Helicoverpa armigera larvae was performed using partially purified soluble fractions containing Vip3A protein, mortality levels observed ranged between 70% and 96.6% in the isolates. LC50 values of two of the native isolates JK37 and JK88 against H. armigera was found to be at par with that of Bt kurstaki HD1, suggesting that these isolates could be developed as effective biopesticides against H. armigera.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author