Construction of a potent strain of Bacillus thuringiensis against the cotton leaf worm Spodoptera littoralis

This work has been carried out in order to construct a potent Bacillus thuringiensis (Bt) strain active against the Egyptian cotton leaf worm S. littoralis. Toward this target, the delta-endotoxin crystal protein genes cry1C (that encodes an insecticidal protein highly specific to S. littoralis) and cry1Ag (1Ac like) were used. Hindlll digested cry1C was ligated into the Hindlll site of the shuttle vector pHT7593 yielding the plasmid pHTNC3. Hincll digested cry1Ag was ligated into Smal site of pHT7593 and into Smal site of pHTNC3. The three plasmid constructs were used to transform E. coli strain JM109. Colonies likely to contain these recombinant plasmids were screened for the production of toxin proteins. Positively identified transformants produced the expected size protein, detected by partial purification of protein, and is truncated upon trypsin digestion.