Frequency distribution of lepidopteran-specific secretory genes in indigenous Bacillus thuringiensis isolates recovered from diverse soil habitats of India

Abstract

Not Available acillus thuringiensis (Bt) is an ubiquitous entomopathogenic bacterium present in almost all environments and predominantly in soils. It produces secretory toxins during its vegetative growth phase, in addition to other virulent factors. Among these secretory proteins, the Vip3 proteins have been reported to be effective against major lepidopteran pests of several agricultural crops, thus spurring identification of Bt isolates which produce Vip proteins in different laboratories world over. Therefore, screening of Bt isolates recovered from various soil habitats in India was carried out in this study to analyze the effect of type of soil on the distribution of vip3 genes. We have observed heterogeneous distribution (20%-100%) of vip3-type genes in Bt isolates, which may be due to ecological, topographical and nutritional conditions of soil. The overall frequency of occurrence of vip3-type genes was not significantly different in Bt isolates recovered from soil samples of cropped and non-cropped areas. However, isolates recovered from forest soil were the least abundant in vip3-type genes. We have found that our collection from various soil habitats is a rich source of vip3-type genes, which can be further explored for isolation of full length unique vip3-type genes having toxicity against agriculturally important lepidopteran insects for deployment in insect pest control