Screening of Bacillus thuringiensis Isolates Recovered from Diverse Habitats in India for Crystal Toxin Genes Predicting Toxicity Against Three Insect Orders: Lepidoptera, Coleoptera, and Hemiptera

Entomopathogenic Bacillus thuringiensis ( Bt ) has emerged as a sustainable alternative to chemical pesticides due to its selective action against insect pests and negligible effects on non-target organisms. However, the increasing occurrence of resistance to conventional cry genes poses a significant threat to their efficacy. It underscores the immediate need to identify novel cry genes with unique modes of action and toxicity profiles. To address this, our study investigated the frequency of recently discovered neoteric cry genes in Indian Bt isolates, known for their diverse range of insecticidal cry genes. We screened seventy-nine indigenous Bt isolates collected from diverse agroclimatic zones and natural habitats across India for novel cry genes with activity against Lepidoptera, Coleoptera, and Hemiptera orders. PCR-based analysis confirmed the presence of various insect-specific cry genes, revealing notable diversity among the isolates. Twenty-seven isolates carried single or multiple cry genes, with conventional cry7/8 genes being more prevalent than neoteric genes. Among the latter, cry30Fa was the most abundant, followed by cry30Ga, cry15Aa, cry64Ca, cry79Aa1, cry78Aa , and cry78Ba . Remarkably, isolates SK-768, SK-979, SK-110, and SK-949 harbored cry genes active against two or three insect orders. These findings highlight the importance of region-specific Bt strains in formulating effective biocontrol strategies.