Abstract: The Asian corn borer, Ostrinia furnacalis (Guenée), is one of the most important insect pests of maize in China. Transgenic Bacillus thuringiensis (Bt) maize provide an effective mean to control this insect pest. However, evolution of resistance in the target insect will be a great threat to the continued success of Bt toxins used in insecticide formulations or expressed by transgenic maize. It is theoretically and practically important to well characterize resistant strains, which will provide the only way to empirically validate proposed management strategies. A strain of O. furnacalis was selected for resistance to Cry1Ie by exposure to the toxin incorporated into artificial diet in the laboratory. The resistance development and cross-resistance to other Bt toxins such as Cry1Ab, Cry1Ac and Cry1Fa after 14 generations of selection were determined by bioassay. In addition, the changes in biology of O. furnacalis were also observed. The results indicated that the susceptibility of the selected strain to Cry1Ie toxin declined as the selection pressure increased. The selected strain developed higher than 23-fold resistance to Cry1Ie after 14 generations of selection. However, it was as susceptible to Cry1Ab, Cry1Ac, and Cry1Fa as the unselected control strain. In addition, compared with the unselected strain, the larvae of selected strain required an average 5.7 d longer duration, the pupal weight reduced by 13.7%, and the number of eggs laid per female decreased by 40.0%. These results suggest that the widespread use of transgenic Cry1Ie maize could lead to the development of resistance in target pest O. furnacalis. The lack of cross-resistance between Cry1Ie and Cry1Ab, Cry1Ac or Cry1Fa suggests that maize hybrids expressing these two toxins (Cry1Ie and Cry1Ab, Cry1Ac or Cry1F) are likely to be compatible for resistance management of O. furnacalis.

Key words: Ostrinia furnacalis, Bt toxins, selection for resistance, resistance development, biology, resistance management