OPPORTUNITIES FOR FINDING NEW BACILLUS-THURINGIENSIS STRAINS

There has been much effort, particularly by various companies, to isolate new strains of Bacillus thuringiensis (Bt) with increased potency to target insect pests and/or a wider host range. This is with a view to the production of microbial insecticides or transgenic plants expressing the Bt insecticidal protein. Bt can be isolated readily from insects, stored product material, sericulture environments, the phylloplane, and it is also a ubiquitous soil bacterium. New strains have been characterised by unusual crystal morphology or protein profile, DNA probes, reactivity with crystal antisera and insecticidal activity. Recently new strains have been found with activity against New Zealand grass grub, southern corn rootworm, Mexican bean beetle, root lesion and animal parasitic nematodes, mushroom flies, Australian sheep blowfly, and the sheep body louse. The opportunity for finding new Bt strains will depend on screening isolates against new insect pests or large-scale screening to find isolates with increased toxicity.