Biochemistry and genetics of insect resistance to Bacillus thuringiensis insecticidal crystal proteins

Abstract Current knowledge of biochemical mechanisms of insect resistance to Bacillus thuringiensis is reviewed. Available information on resistance inheritance and on patterns of cross-resistance is included. Modification of the binding sites for B. thuringiensis insecticidal crystal proteins has been found in different populations of three insect species. This resistance mechanism seems to be inherited as a single recessive or partially recessive major gene, and the resistance levels reached are high. Altered proteolytic processing of B. thuringiensis crystal proteins has been suggested to be involved in one case of resistance. From the available data it seems that binding site modification is the most significant resistance mechanism under field conditions.