Dual Insecticidal Activity of Spodoptera-Toxic Bacillus thuringiensis Strain Transformed with Lepidopteran-Specific Cry Toxin

The E. coli-B. thuringiensis shuttle vector for expression of cry1Ac, pHT1K-1Ac plasmid was introduced into acrystalliferous B. thuringiensis Cry−B and Spodoptera toxic STB-3 strain. The presence of a recombinant plasmid in transformants after electroporation was confirmed by PCR. The 1K-1Ac/Cry−B(Cry−B transformant) and 1K-1Ac/STB-3 (STB-3 transformant) produced bipyramidal-shaped parasporal inclusion that was 130 kDa in size as like B. thuringiensis subsp. kurstaki HD-73. In P. xylostella bioassay, these transformants showed significantly high toxicity than the wild-type recipients and further, in case of B. thuringiensis STB-3 transformant still had original Spodoptera toxicity. These results suggested that the pHT1K could be successfully applied for generating individual B. thuringiensis strains that produce various combinations of insecticidal proteins to expand their host spectrum and enhance insecticidal activity.