Distribution and diversity analysis of Bacillus thuringiensis cry genes in different soil types and geographical regions of India.

Molecular characterization of 117 Bacillus thuringiensis (Bt) isolates from various geographical locations was previously done by PCR amplification of cry genes. In present investigation, diversity of cry genes from different soil types and climatic environments was studied using rarefaction method. Presence of cry1, cry2, cry3, 7, 8, cry4, cry5, 12, 14, 21, cry11, cry13 and cyt1 genes from Bt strains isolated from various regions of India was determined by PCR amplification. A varied distribution of cry genes and their profiles was found in four soil types. The cry1 gene was the most abundant in the isolates from four soil types and geographical regions. A higher degree of cry gene diversity was observed in isolates from alluvial soil. Rarefaction analysis indicated that more cry genes could be found from various soil types. Distribution of cry genes in semi arid, subtropical humid and tropical dry regions was varied but the degree of cry gene diversity determined by rarefaction analysis was similar. No major difference in distribution and diversity of cry genes was found in agricultural and non-agricultural samples except the absence of cry3 and cry13 genes in isolates of non-agricultural samples. We report the utility of rarefaction analysis to compare cry gene diversity from different geographical regions.