Molecular characterization and PCR-based screening of cry genes from Bacillus thuringiensis strains

Novel cry genes are potential candidates for resistance management strategies, due to their different structures and modes of action. Therefore, it is desirable to clone and express novel cry genes from several new isolates of Bacillus thuringiensis (Bt). In the present study, 28 Bt strains were characterized at morphological and molecular level. All these strains are Gram positive, endospore forming and had shown different crystal morphologies when viewed under the microscope. The ARDRA (16S rDNA PCR-RFLP technique) with AluI, HaeIII, HinfI and TaqI produced unique and distinguishable restriction patterns used for the molecular characterization of these isolates. Based on UPGMA clustering analysis, Bt strains showed significant molecular diversity and the dendrogram obtained differentiated 28 Bt strains into 1 major cluster at a similarity coefficient 0.56. PCR analysis demonstrated that the Bt strains showed diverse cry gene profiles with several genes per strain. The Bt strain G3C1 showed the presence of maximum cry-type genes by PCR. The toxicological characterization of these cry genes will have huge importance in transgenic technology and will be useful in transgenesis of crop plants for better resistance management.