Abstract: As the growing area of Bacillus thuringiensis （Bt) transgenic cotton has been extending increasingly, the development of resistance to Bt in the cotton bollworm （CBW), Helicoverpa armigera （Hübner), has become a decisive problem that should not be overlooked. To develop polygenic genetically modified plants is the most effective measure for delaying the resistance of insect pest to Bt transgenic plants and Bt insecticide. In this study, a resistant strain of CBW which had been selected for more than 100 generations and had more than 2 000-fold resistance to Bt insecticide （a product of B. thuringiensis subspecies kurstaki （Btk) including a variety of toxin proteins) was used to test the inheritance mode by bioassays and various hybridizations. The objective of this study is to provide the theoretical basis for the resistance management strategy of Bt commercial formulation, and provide the reference for establishing the resistance management strategy of CBW to the polygenic genetically modified plants. The two progenies of reciprocal parental crosses between the resistant and the susceptible strains responded alike in bioassays. The resistance ratios for FSR and FRS reached 22.2 and 24.6-fold, respectively; the degrees of dominance for FSR and FRS were less than 0 （from -0.20 to -0.17), and the resistance was autosomal and incompletely recessive inheritance. Analysis of progenies from four backcrosses of F1 with the susceptible strain and two F1 by F1 crosses showed that significant deviation occurred between the observed and the expected mortality, suggesting that the resistance is controlled by more than one locus.

Key words: Helicoverpa armigera, Bacillus thuringiensis （Bt) transgenic cotton, Bacillus thuringiensis （Bt) insecticide, inheritance, resistance, resistance management