Diversity of Bacillus thuringiensis cry genes in soils of Andhra Pradesh, India

Abstract

A total of 61 bacterial strains was isolated in soils from Chittoor and Kadapa districts of Andhra Pradesh, India using sodium acetate selection method and preliminarily identified as Bacillus thuringiensis based on Gram's staining, endospore staining and crystal protein study. These strains were tested against the insect, Spodoptera litura under laboratory conditions and found 18 strains with ≥ 50% insect mortality. Further, these eighteen strains were analyzed for the insecticidal crystal protein composition with fourteen cry specific primers. The results indicated that, among all 14 cry genes, cry1I was the observed in 11 strains, followed by cry1Aa in 10 strains. At the same time a strain, F493 collected from Talakona area identified an effective against S. litura with 100 per cent larval death and which was also identified with 8 different crystal protein encoding genes (cry1Aa, cry1Ac, cry1Fa1, cry1I, cry2, cry2A(a)1, cry8, cry9Ca1).