Distribution and Toxicity of Bacillus Thuringiensis (berliner) Strains from Different Crop Rhizosphere in Indo-Gangetic Plains Against Polyphagous Lepidopteran Pests

Rhizobacterial diversity is an indicator of soil health and in turn it is influenced by the host crops, edaphic factors and weather. The present investigation reports the diversity of endospore forming, gram positive rhizobacteria ( Bacillus megaterium , B. thuringiensis , B. cereus and Lysinibacillus spp.) inhabiting 11 different agricultural crops in the IGP of India. Twelve Bacillus thuringensis ( Bt ) isolates were identified by screening 62 g positive bacterial isolates from 63 rhizosperic soil samples collected from 6 districts of IGP. The highest Bt index was recorded from Bhopal (0.25) followed by Fatehpur (0.17), Kanpur dehat (0.10), Jalaun (0.08) and Hamirpur (0.06). The bacterial isolates were characterized based on the 16SrRNA gene and phylogenetically grouped into 3 clades. The spore crystal mixture of 12 Bt isolates were subjected to insect bioassay and it revealed, F8.IIPR has highest toxicity against Spilosoma obliqua Walker (100%), Olepa ricini Fabricius (91.67%) and Helicoverpa armigera Hubner (100%) larva. Survival analysis (ST 50 ) showed that the S . obliqua is highly susceptible than O . ricini and H . armigera to F8.IIPR. Crystal staining and protein profiling showed the presence of cry 1 (135 kDa) and cry 2 (65 kDa) genes in 5 Bt isolates. PCR amplification of vip3A gene confirmed its presence in five Bt isolates. To conclude F8.IIPR and Ak2.IIPR has the potential as a promising biopesticide for controlling the three lepidopteran insects tested.