Role of Spores in the Insecticidal Activity of Bacillus thuringiensis Delta-endotoxin

Effect of spores on enhancing the insecticidal activity of Bacillus thuringiensis (Bt) delta-endotoxin (refer to toxin) has been reported to vary depending on the species of insect and variety of Bt, procedure of toxin preparation, bioassay methods and so oil. Some studies have demonstrated a remarkable synergistic effect of spores on the insecticidal activity of toxin, but others have not. These discrepancies have raised the following questions: Are spores necessary for the insecticidal activity of Bt toxin? Why is there so much variation in synergistic action between spores and toxins? What problems are there with the bioassay method for judging synergism? To address these questions, we reviewed Studies Oil the interaction between spores and toxins in the insecticidal action of Bt and outlined the problems which Should be clarified further to elucidate the role of spores in the insecticidal activity of Bt toxin.