PCR-based detection of cry genes in local Bacillus thuringiensis DOR Bt-1 isolate

Abstract

A sporulating culture of Bacillus thuringiensis ssp. kurstaki strain DOR Bt-1 was isolated from castor semilooper (Achaea janata L.) cadavers from a castor bean (Ricinus communis L.) field at Kothakota mandal of Mahaboobnagar district, Andhra Pradesh, India. This strain has shown high toxicity against many insect pests and the wettable power formulation of this strain obtained through solid-state fermentation has been registered with the Central Insecticides Board (CIB), India under section 9 (3b). Based on the bioassay results and the efficacy of the formulation on different Lepidopteran insects, it was concluded that the strain must be carrying diverse cry genes. Therefore, to understand the cry gene profile of this strain, a PCR-based assay was carried out. Genomic PCR analysis of the DOR Bt-1 isolate with universal primers specific to cry gene classes indicated the presence of both cry1 and cry2 class-specific genes. Further, PCR analysis with cry gene-specific primers revealed the presence of cry1Aa, cry1Ab, cry1Ac, cry2Aa and cry2Ab genes. Thus, DOR Bt-1 iso-late harbors a combination of different cry genes, such as Lepidoptera-active cry1Aa, cry1Ab and cry1Ac, and Lepidoptera-Diptera-active cry2Aa and cry2Ab genes, indicating that this isolate has the potential to be effective against both Lepidopteran and Dipteran insect pests.