Isolation and Characterization of Native Isolates of Bacillus thuringiensis from Vidarbha Region

The present investigation was undertaken for the isolation and characterization of B. thuringiensis strains from different habitats based on the morphology, staining properties and biochemical characters. Fifty four samples including soil samples (30), phylloplane (21), insect cadaver (2) and stored grain dusts (1) were collected from cultivated and barren lands not having Bt history. Total 154 Bt isolates obtained from different sources comprising 89, 59 and 6 from soil, phylloplane and insect cadaver respectively, whereas, none of the single isolate was obtained from seed dust. The local Bt isolates showed positive morphological characters as that of standard strain Bacillus thuringiensis kurstaki HD -1 (Btk HD-1). Phase contrast microscopic evaluation showed that, more than 75% of the total 154 isolates lead significant resemblance with standard strain. Further characterization of the probable native Bt isolates was carried out biochemically with different tests such as IMViC tests and for the presence of enzymes like catalase, urease, and nitrate reductase utilization which showed that 70-80% of the total probable Bt isolates has positive characters as standard strain. Bt isolation index suggested that soil had highest background Bt population followed by insect cadaver and leaves.