Molecular Screening and Bioactivity of Native Bacillus thuringiensis Isolates

Bacillus thuringiensis strains were isolated from various soil samples collected from different regions of Kahramanmaraş in Turkey and were characterized by their colony morphology, PCR method with cryIAb/Ac, cryID, cry2 and cyt2 primers, and SDS-PAGE of crystal proteins with 130-140 and 60-70 kDa molecular weights. Plasmid profiles of selected isolates were also analyzed. Among the cry genes studied, cry1Ab/Ac was found to be the most common one (60%) in local isolates. Bioactivity tests were carried out under laboratory conditions to assess the efficacy of isolates against the third instar larvae of the stored product insects; Anagasta kuehniella and Plodia interpunctella. Toxicity values of the isolates varied between 20.00-53.33% for A. kuehniella and 20.00-55.56% for P. interpunctella at 1,000 µg g-1 concentration. Out of 55 isolates, ST13.1 was found to be the most effective against A. kuehniella. Also, ST7.2, ST7.3, and ST8.2 isolates yielded remarkable control against P. interpunctella. Further research is recommended to investigate the efficacy of these promising Bt isolates against other pest insect species.