Characterization of the inheritance of the Cry1A.105 resistance in Helicoverpa zea

Cry1A.105 is an engineered Bacillus thuringiensis (Bt) protein, with domains from natural donors of the Cry1Ab, Cry1Ac, and Cry1F. As of the two Bt proteins in the corn event MON 89034, Cry1A.105 has been commercially planted since 2010 to control some above-ground lepidopteran pests, including the corn earworm (CEW) Helicoverpa zea. Recent studies have shown that Cry1A.105 resistance in CEW has widely occurred in the field in the United States. The objective of this study was to characterize the inheritance of the Cry1A.105 resistance in a population selected from field collections in Louisiana. The Cry1A.105 susceptibilities of a known Bt susceptible strain (BZ-SS), a Cry1A.105-resistant strain (Cry1A.105-RR), F1 hybrids of the reciprocal crosses between BZ-SS and Cry1A.105-RR, F2 populations, and backcrossed populations were assayed using a diet over-laying bioassay. The results showed that the Cry1A.105-resistance in CEW was controlled by a single autosomal and non-recessive gene. The non-recessive property of the resistance documented in this study should have played an important role in the wide occurrence of the resistance of the insect to Cry1A.105 in the United States.