Abstract: In this paper, we investigated five Bacillus thuringiensis (Bt) strains from four major manufacturers of Bt products in China for the endotoxin components by PCR and SDS-PAGE. All five strains harbour cry 1Aa and/or c, and/or d, and/or e genes, only the Bt+Virus strain has cry1Ab gene. The cry1A class of genes encodes for insecticidal crystal proteins with MW of 130 kD and toxic to Lepidoptera. The JS-Bt C strain contains the cry1B gene, which encodes for a 138 kD crystal protein, potentially toxic to both Lepidoptera and Coleoptera. Four of the five strains (HB-Bt P, Bt+Virus, JS-Bt P, and JS-Bt C) harbour the cry2Aa and/or b genes, which encode 70 kD crystal proteins toxic to Lepidoptera. All of the five strains have the cry1I gene which appears to be cryptic in all the strains. None of the five strains harbours the cry1C and cry1D genes.

Key words: Bacillus thuringiensis, insecticidal crystal proteins, genes, PCR, SDSPAGE