| Transgenic Bt Rice opens a new chapter for agricultural development and environmental management.However,there are widespread concerns about whether transgenic rice will damage the natural environment and affect the original ecological balance and other environmental issues.In farmland environment,natural enemy insects,as an important part of biological control of pests,can be indirectly exposed to the Bt protein expressed by Bt rice by feeding on target insects,so whether Bt rice has any effect on them is an important part of safety evaluation of transgenic rice.In the traditional assessment of environmental safety,the growth and development of target insects are inhibited by feeding on transgenic insect-resistant crops,which may be detrimental to the development and reproduction of parasitic natural enemies,i.e.the“Host quality-mediated effect”.This effect will cause deviation to the result of safety evaluation.These effects can be avoided by exposure to the hemolymph of the target insect injected with Bt protein as a parasitoid.Transgenic insect-resistant rice T1C-19 expressed Cry1C* gene,which showed good resistance to borer pests.Apanteles chilonis is an endoparasitous natural enemy and dominant parasitoid of Chilo suppressalis,the main target pest of T1C-19 rice.Therefore,the evaluation of Cry1Ca protein on the security of A.chilonis is of great significance.In this study,the effects of Cry1Ca protein on vital life table parameters and enzyme activities of A.chilonis were evaluated from two aspects: Firstly,microinjection of Bt protein into the haemolymph of the C.suppressalis,and exposure of the A.chilonis to high doses of Cry1Ca protein.Secondly,based on the food chain of transgenic rice T1C-19-C.suppressalis-A.chilonis to simulate the actual situation of field transmission.The results are as follows:1.Safety evaluation of Apanteles chilonis exposed to high dose of Cry1Ca proteinAfter C.suppressalis eating T1C-19 rice for three days,the content of Cry1Ca protein in the hemolymph was 2.29 ± 0.46 ng/g,which was the actual exposure of the A.chilonis.After 1.5 ng/n L,1000 n L Cry1Ca protein was injected into the hemolymph of C.suppressalis,the Cry1Ca protein showed a tendency of degradation in the hemolymph of C.suppressalis within 12 days,however,the content of Cry1Ca protein was 10 times higher than the actual exposure of A.chilonis.After parasitized by A.chilonis,the Cry1Ca protein also showed a degradation trend in hemolymph of C.suppressalis,but the concentration of Cry1Ca protein(270.93 ± 41.30 ng/g)at the 12 th day was more than 10 times higher than the actual exposure,it can meet the requirement of Tier-1 system for evaluating the safety of Cry1Ca proein to A.chilonis.The injection system of Cry1Ca protein was established.The females of A.chilonis after mating were inoculated with the 4th-5th instar larvae of C.suppressalis newly injected with Cry1Ca protein to lay eggs.When the egg is laid,the wasp is removed.Using bovine serum albumin(BSA)and Galanthus nivalis agglutinin(GNA)as negative control and positive control,the life table parameters of A.chilonis were recorded and compared.The results showed that compared with negative control,high concentration of Cry1Ca protein affected the developmental duration and sex ratio,pupa weight,adult weight,fecundity,adult male and female longevity,emergence rate and enzyme activity(t-Pro,SOD,POD,GR)of A.chilonis were not significantly affected.Positive control GNA had significant effects on fecundity,adult longevity,pupal weight,adult weight and enzyme activity(t-Pro,SOD,POD,GR).2.Safety evaluation of transgenic rice with Cry1C* gene based on tri-trophic food chain to A.chilonisThe safety of Cry1Ca protein expressed in T1C-19 rice to A.chilonis was evaluated by a tri-trophic bioassay test.The results showed that the pupal stage(7.48 ±0.10 d)and pupal weight(4.57 ± 0.16 mg)of A.chilonis parasitized on the larvae of C.suppressalis fed on T1C-19 rice for 3 days were significantly longer than those of the control,the adult weight(2.94 ± 0.18 mg)was slightly less than that of the control group,but not significant.There were no significant differences in sex ratio,fecundity,emergence rate,egg + larval duration,adult longevity.In this study,the results of tri-trophic bioassay test showed that Cry1Ca protein could affect the biological parameters of A.chilonis through the host,while the high dose exposure of Cry1Ca protein had no effect on important life table parameters of A.chilonis.The results of the two studies is different,which confirmed the existence of host quality-mediated effect and avoided the interference of prey quality-mediated effect by high-dose injection.The results showed that Cry1Ca protein had no negative effect on A.chilonis and provided data for safety evaluation of T1C-19 rice. |
