DEVELOPMENT OF RESISTANCE TO Bacillus thuringiensis

Abstract

This paper analyzes information about insect pests resistant to the toxins of Bacillus thuringiensis (Bt). So far, a total of six lepidopteran species, two mosquitoes, and one coleopteran species have been reported with varying resistant levels, to the three known pathotypes of Bt. Only four lepidopterans have developed resistance under commercial conditions (two of them showing very low resistance levels). The remaining species have developed resistance only under laboratory conditions, through high selection pressures. It is clear that only two cases of resistance are relevant: the Indian meal moth (Plodia interpunctella) and the diamondback moth (Plutella xylostella). According to the analysis of the Bt?s mode of action and the preliminary evidence on the resistance mechanism, a change of receptors of the midgut epithelial cells is the basis of this mechanism. Furthermore, the theoretical basis of resistance development is reviewed, in order to suggest appropriate management strategies. These strategies are described for the use of Bt as bioinsecticide or in transgenic plants.