The Changes Of Secondary Substances In Transgenic Insect-resistant Corn And Its Effect On The Larval Parasitoids Macrocentrus Cingulum Of The Asian Corn Borer

Volatiles extracted from whorl leaves, young tassels and fresh silks of Bt maize DK647BTY expressing Cry1Ab and X1111TX expressing Cry1F toxin and their non-Bt controls were identified through GC-MS. Results showed that main compounds of volatiles were terpenes which molecular weight were from 136 to 282, among whichα-ylangene andβ-caryophyllene were dominant chemicals emited in all development statges of maize. There were no difference in the relative amount ofα-ylangene andβ-caryophyllene between Bt maize and their counterpart control in silk. In the tassels, there were no significant difference between Bt maize and their counterpart control in the relative amount ofα-ylangene. The relative amount ofβ-caryophyllene was significantly lower in DK647BTY than its control, however, there was no significant difference between X1111TX and its control. In the whorl leaves, there were no significant differences in the relative amount ofα-ylangene between DK647BTY and its control. However, the relative amount ofβ-caryophyllene was significantly lower in DK647BTY than its control; There were significant differences in the relative amount ofα-ylangene andβ-caryophyllene between X1111TX and the control; The relative amount of these two volatiles changed between Bt maize and their counterpart control when infested by the Asian corn borer (ACB).Results from the extraction and identification of secondary compounds from Bt maize DK647BTY and X1111TX amd their counterpart controls in the different developmental stages (whorl, tasseling and silking stages) showed that there were no significant differences in the relative amount of dimboa, isoorientin and maysin in the whorl leaves, tassels and silks between the Bt maize and their counterpart controls.A technique for Macrocentrus cingulum for mass rearing was established based on selection of different carrier, host instar and parasitic duration. The best host age was 48 h old feeding on artificial diet after hatching.There were not side effects for parasiting behaviour of M. cingulum on ACB by Bt maize. M. cingulum could parasitize ACB larvae on either stalk of Bt maize or its controls, and there were no significant differences in parasitism could be found. However, the fecundity of M. cingulum would be decreased when the parasited ACB larvae feeding on the Bt maize, this was because ACB larvae could not develop well on Bt maize.When M. cingulum parasited on the laboratory selected Cry1Ab resistant ACB larvae, the parasitism, pupal weight, number of cocoons per larva, and emergence rate would be not significant between the larvae feeding on Bt maize and on their control after parasitization if the the larvae evolved higher level of resistance to Cry1Ab toxin. When the ACB has lower level of resistance to Cry1Ab, the larvae could not develop normally on Bt maize, and the larvae weight were lower, there would resulted in the decrease of parasitism by M. cingulum and the fecundity of M. cingulum was also reduced.There were not significant different in parasitism, pupal weight, number of cocoons per lavae, and emergence rate when M. cingulum fed on suspension of pollen of Bt maize or non-Bt maize. Although the average longevity of M. cingulum male was significantly longer when they fed on suspension of pollen of Bt maize than which of non-Bt maize, there were not significant in longevity of female M. cingulum when fed on suspension of pollen of Bt maize or non-Bt maize. No Cry1Ab protein was detected in wasps of M. cingulum which fed on suspension of pollen of Bt maize.