Effects Of Cryiab/Cryiac On The Tachinid Fly,Exorista Civilis (Rondani) And Combined Effects On Oriental Armyworm, Mythimna Separata (Walker)

In recent years, there is much concern on the safety of genetically modified crops,(GMCs), especially for Bt crops. One of the major concerns of deployment of Bt crops is their effects on the non-target organisms and the natural enemy. However, there is little study regarding the relationship of Bt crops-M. separata-E. civilis. Thus, in our research, we explored whether the Bt toxin and E. civilis would affect the development, immune and flight of M. separate. Indirect and direct effects of Bt on E. civilis were also investigated. Our data will contribute to ecological risk assessment of GM crops for regulatory purposes.Combined effects of CrylAb/Ac and E. civilis on M. separate. We have developed a bioassay to test the effects of CrylAb/Ac and E. civilis on survival, development and reproduction of M. separate. The6th instar parasitized hosts were fed with different concentrations (3.125μg/g、6.25μg/g、12.5μg/g、25μg/g) artificial diets in6holes cell culture plate individually. Two other treatments were set, namely, unparasitized (CK) and parasitized (Oug/g) hosts fed with artificial diet without Bt. The exposure to CrylAb/Ac artificial diets and E. civilis had significant differences on the larval mortality, pupation rate and emergence rate of M. separate (P<0.05). Larvae of CK treatment were in better conditions than the other treatments. What’s more, the pupal weight was increased along with the concentration of CrylAb/Ac increasing. But it did not affect the pupal duration (P>0.05). It showed that3.125μg/g of Cry1Ab and12.5μg/g of Cry1Ac treatments has the combined effects with E. civilis to control M. separate. However, there were significant differences in pupal weight, preoviposition period and fecundity (P＜0.05). These data indicate that there are combined control effects of Cry1Ab/Ac and E. civilis against M. separate in the laboratory.Combined effects of CrylAb with sub-lethal dose and E. civilis on M. separate. We studied the effects of CrylAb and E. civilis on cuticular colour and total hemocytes of6th instar M. separate. The relationship between immunization and potential flight capacity were also investigated. We set1.56μg/g as the sub-lethal dose of Cry1Ab. The6th instar M. separate were reared on fresh maize leaves (un-parasitized/parasitized), artificial diet without Bt (un-parasitized/parasitized) and artificial diet with Cry1Ab (un-parasitized/parasitized),6treatments in total. It turned out that cuticular colour and total hemocytes of M. separate were affected by E. civilis and Bt after48h. Cuticular colour decides oplical density (OD), and they are derict ratio. The order of OD was as follows:maize leaves unparasitized> maize leaves parasitized> artificial diet without Bt unparasitized> artificial diet without Bt parasitized> CrylAb unparasitized> Cry1Ab parasitized. Because cuticular colour was depended on hemocytes, the order of total hemocytes was similar. Besides, larval mortality, pupation rate and emergence rate of different treatment were also affected significantly (P<0.05). But no obviously combined effects were found between the sub-lethal dose Cry1Ab and E. civilis. Flight potential capacity including flight distance, flight duration and flight velocity of adult M. separate after emergence1d was tested. There were no significant differences among the treatments (P>0.05). The results of this investigation showed that sub-lethal dose of CrylAb and E. civilis could affect immune defense system and development but not affected flight potential capacity of M. separate. This work need to be complemented by focusing on the relationship among Bt crop, host and parasitoids in landscape.Indirect effects of CrylAb on E. civilis. We examined the effect of CrylAb toxin on the preference and performance of adult E. civilis and recorded the life-history parameters of E. civilis by which their hosts were fed on CrylAb. The6th instar M. separata larva fed on artificial diets containing3.125μg、6.25μg/g、12.5μg/g、25μg/g of Cry1Ab toxin, respectively, after parasitized by its tachinid fly E. civilis. The results of our study showed that feeding last instar M. separata with the Cry1Ab toxin did not affect the utilization of subsequently parasitoid, since it did not vary significantly on the parasitoid rate and egg number between CK and treatments (P＞0.05). In addition, there were no significant effects on egg-larval duration, puparium duration, adult emergence rate and sex ratio of E. civilis (P>0.05). No significant differences were observed in preoviposition period and life time fecundity of female fly either (P>0.05). There were significant differences in the pupal weight because hosts that were fed Cry1Ab toxin were under poor conditions (P<0.05). However, the treatment of3.125μg/g had the most pupae (P＜0.05). It is suggested that the Cryl Ab toxin had no negative effects on the growth and development of E. civilis, but on the potential ability of parasitizing. Furthermore, it was beneficial to the population of E. civilis under the applicable concentration of Cry1Ab. We suggest that using Bt crops would likely lead to similar conclusions about the safety of the presently used Bt proteins on parasitoids.Direct effects of CrylAb on E. civilis. The experiment was conducted to determine whether adult fly and the development of offspring (F2) were affected by CrylAb in the laboratory. Flies were fed with honey solutions containing a range of CrylAb concentrations, reaching3.125μg/ml、6.25μg/ml、12.5μg/ml and25μg/ml were treated by direct ingestion. The control treatments consisted of starvation (S), water solution (W) and honey solution (H). CrylAb did not affect the longevity separately of female or male flies significantly from the treatment of3.125μg/g to25μg/g, and also not significantly affected the longevity of female or male flies compared to the flies fed on honey solution (H)(P>0.05). However, longevity of treatment S or W decreased significantly, less than5days. Egg-larval duration of the offspring of adults fed on Bt-solutions and honey solution (H) were not prolonged significantly (P>0.05). There were also no significant differences compared to H in biological characteristics for the offspring, including pupation rate, puparium duration, pupal weight, emergence rate and adults weight, and sex ratio. Although at highest concentration (25μg/ml), pupal weight was lighter and pupal duration showed a slight prolongation compared to treatment H (P>0.05). Our results indicated that there were no negative direct effects of CrylAb on E. civilis. To complement this study, future investigations will perform in a more realistic scenario than in a laboratory situation.