Resistant Reactions To Insecticidal Transgenic Bt Maize And Bt Cotton In Helicoverpa Armigera H(?)bner

The dynamics of temporal and spatial insecticidal activities of three different transgenic plants, transgenic maize expressing insecticidal protein from Bacillus thuringiensis (Bt), transgenic Bt cotton (one gene cotton) and transgenic cotton expressing Bt & Cowpea trypsin inhibitor (Cpu) (two-gene cotton) were studied. Two populations of the cotton bollworm (CBW), Helicoverpa armigera (Hubner) with different susceptibility to Bt were used. The survival, growth and development resistant reactions of CBW to three types of transgenic plants were also evaluated. Our experimental data are useful for managing CBW resistance to Bt in a cropping system containing both Bt cotton and Bt maize. The results showed that Bt maize has high insecticidal activity to CBW. The insecticidal activity has a dynamic change by temporal and spatial. The activity decreased with the crop growth stage development and CBW larvae growth. The order of insecticidal activities of different organs is as follows: leaves> bract > young-ear > young-grain> filament> stamen. The temporal and spatial dynamics of insecticidal activities of the two-gene cotton (Super-Goukang, SGK) and one gene cotton (Guokang 12, GK12) to CBW were also observed. SGK cotton plants could keep higher insecticidal activity to CBW in later growth stage while GK12 had low insecticidal activity, especially to the resistant CBW population. The result also showed dynamic spatial insecticidal activities of Bt cotton in different growth stages. The experimental data showed that Bt maize had high insecticidal and growth inhibition activity to CBW in whole growth season. Therefore, there was a higher selection pressure for CBW to feed on Bt maize, and it could result in quickly resistance evolution to Bt in CBW. It was proved that Bt maize has higher efficacy to susceptible CBW population than to a resistant population selected by Bt cotton. This implied that there were cross-resistance to Bt maize and Bt cotton.As a result, it was suggest6d that the planting of Bt maize and Bt cotton in thesame reagion should be avoided.