Identification of a gene associated with bit resistance in Heliothis virescens

Transgenic crops producing insecticidal toxins from Bacillus thuringiensis (Bt) are widely used for pest control. Bt-resistant insect strains have bee n studied, but the molecular basis of resistance has remained elusive. Here , we show that disruption of a cadherin-superfamily gene by retrotransposon -mediated insertion was linked to high levels of resistance to the Et toxin Cry1Ac in the cotton pest Heliothis virescens. Monitoring the early phases of Bt resistance evolution in the field has been viewed as crucial but ext remely difficult, especially when resistance is recessive. Our findings ena ble efficient DNA-based screening for resistant heterozygotes by directly d etecting the recessive allele.