6533b871fe1ef96bd12d1819

RESEARCH PRODUCT

Lack of cross‐resistance to otherBacillus thuringiensiscrystal proteins in a population ofPlutella xylostellahighly resistant to cryia(b)

subject

description

Competition experiments were performed with brush border membrane vesicles of diamondback moth larvae using 125I‐labelled CryIA(b) and unlabelled CryIA(a), CryIA(b) and CryIA(c). The results suggested a model with a single binding site for CryIA(b). Heterologous competition showed that CryIA(c) competed as effectively as CryIA(b) for the CryIA(b) binding site, whereas CryIA(a) competed less effectively. Toxicity tests were performed on third instar larvae with trypsin‐activated insecticidal crystal proteins (ICPs) and a commercial formulation of Bacillus thuringiensis (Bt) (Dipel). A laboratory colony was found to be susceptible to all four ICPs tested and to Dipel. CryIA(b), CryIA(c) and CryIB were approximately equally toxic, and CryIA(a) was less toxic than the other ICPs by one order of magnitude. In contrast, a recently collected insect population from the Philippines was 236 times less susceptible to CryIA(b) than the control colony. However, for the other ICPs no significant differences were found ...