Diversity of Bacillus thuringiensis Isolates Native to Uttarakhand Himalayas, India and Their Bioefficacy Against Selected Insect Pests

Abstract

The huge family status and diversified agricultural applications of Bacillus thuringiesnsis (Bt) Berliner made the bacterium, a highly specialized bio-insecticide with worldwide commercial usage. Novel strains and cry genes always expand potential usage of the bacterium. In the present investigation, the authors isolated 45 candidate strains of Bt from a unique ecological niche of Indian subcontinent, i.e., Uttarakhand state belongs to North Western Himalayas of India. All the isolates were characterized for light microscopy, PCR, SDS-PAGE and bioassays against major insect pests. The diversity in collection is manifested by existence of two major crystal shapes (Bipyramidal and spherical) and 21 different cry gene profiles with predominance of cry1 (cry1Aa, cry1Ab, cry1Ac, cry1B, cry1C, cry1D, cry1I) family genes followed by cry2 (cry2A, cry2B) and cry26. Interestingly, coleopteran specific genes were governed by cry8 not the cry3. The sequencing of major cry genes showed preferential divergence of cry2A genes and led to partial identification of novel cry1D gene from UKBt13. Majority of the isolates showed existence of 68 and 130 kDa crystal toxins. The bioefficacy studies presented here led us to identify putative novel strains with potential applications in pest management programs and associated toxicological diversity of Bt in Uttarakhand Himalayas.