Specific binding of Bacillus thuringiensis Cry1Ea toxin, and Cry1Ac and Cry1Fa competition analyses in Anticarsia gemmatalis and Chrysodeixis includens.

Anticarsia gemmatalis (velvetbean caterpillar) and Chrysodeixis includens (soybean looper) are two important defoliation pests of soybeans. In the present study, we have investigated the susceptibility and brush border membrane-binding properties of both species to Bacillus thuringiensis Cry1Ea toxin. Bioassays performed in first-instar larvae demonstrated potent activity against both soybean pests in terms of mortality or practical mortality. Competition-binding studies carried out with Iodine-labelled Cry1Ea, demonstrated the presence of specific binding sites on the midgut brush border membrane vesicles (BBMV) of both insect species. Heterologous competition-binding experiments indicated that Cry1Ea does not share binding sites with Cry1Ac or Cry1Fa in either soybean pest. This study contributes to the knowledge of Cry1Ea toxicity and midgut binding sites in A. gemmatalis and C. includens and sheds light on the cross-resistance potential of Cry1Ea with other Bt proteins aimed at controlling lepidopteran pests in soybeans.