Immunohistochemical Detection of Binding of Cryia Crystal Proteins of Bacillus thuringiensis in Highly Resistant Strains of Plutella xylostella (L.) from Hawaii

We detected binding of insecticidal crystal proteins from Bacillus thuringiensis in one susceptible strain and six resistant strains of diamondback moth, Plutella xylostella, from Hawaii. Immunohistochemical tests with tissue sections from larval midguts showed specific binding of CryIA(a), CryIA(b), and CryIA(c) to brush border membranes. CryIE, which is not toxic to P. xylostella, did not bind to midgut tissues. Larvae from one of the resistant strains ingested extremely high concentrations of a commercial formulation containing the three CryIA proteins without suffering midgut cell damage or mortality. This same resistant strain had previously been found to have greatly reduced binding o…