Insecticidal Activity of Autographa Californica Nuclear Polyhedroses Virus Expressing Different Bacillus Thuringiensis Crystal Protein Constructs

Baculoviruses are insect pathogens that cause fatal disease in many Lepidopteran larvae. The major drawback in the use of these viruses as biological insect control agents is their slow speed of action. Improvement of this property is sought by introducing an insecticidal gene in the genome of the virus. The product of this new gene should interfere at an early stage with larval metabolism. Several crystal protein gene constructs of Bacillus thuringiensis (cryIA(b)) including a minimal toxin fragment, were introduced into the plO-locus of Autographa californica nuclear polyhedrosis virus (AcNPV). This gene is dispensable for the production of non-occluded virus and contains a strong promoter. The recombinant viruses expressed the crystal protein constructs at high level. The viral crystal proteins produced via AcNPV in insect cells, were highly toxic. Polyhedra produced by these plO recombinants are being tested to measure enhancement of insecticidal action against a susceptible host (Heliothis virescens) as compared to polyhedra from wild-type virus.