Development and relative fitness of Cry1C resistance in Chilo suppressalis

Abstract BACKGROUND Chilo suppressalis is an important lepidopteran rice pest in the rice‐growing areas of China, and the development of transgenic rice expressing the Cry1C insecticidal protein has provided a useful strategy for controlling this pest. However, insect resistance is a major threat to the durability of cry1C rice. Thus, evaluation of the risk of insect resistance before the commercial use of cry1C rice is crucial. RESULTS This study investigated the development of C. suppressalis resistance to Cry1C protein and the relative fitness of Cry1C‐resistant and ‐susceptible strains on different Bt rice lines. The LC 50 value of the Cry1C‐resistant strain increased 42.6‐fold after 41 generations of selection, and the estimated realized heritability ( h 2 ) of Cry1C resistance was 0.096 in C. suppressalis . Moreover, the Cry1C‐resistant strain displayed high fitness on the cry1C line, but not on the cry1Ab and cry1Ab + cry1C lines and was not cross‐resistant to Cry1Ab. CONCLUSIONS These findings suggest that C. suppressalis has the potential to develop resistance to Cry1C, although the rate of evolution is low. The pyramiding of the cry1A and cry1C genes in Bt rice is an effective strategy for delaying the evolution of resistance in C. suppressalis and sustainably maintaining the utility of Bt rice. © 2017 Society of Chemical Industry