Ecological impact caused by transgene flow from genetically engineered(GE) crops to their wild relatives is largely determined by the fitness effect brought by a transgene. To estimate such impact is critical for the ecological risk assessment prior to the commercialization of GE crops. We produced F1 and F2hybrid descendants from crosses of two insect-resistant GE rice lines(Bt, Bt/Cp TI)and their non-GE rice parent with a wild rice(Oryza rufipogon) population to estimate the transgenic fitness. Insect damages and life-cycle fitness of GE and non-GE crop–wild hybrid descendants as well as their wild parent were examined in a common-garden experiment. No significant differences in insect damages were observed between the wild rice parent and GE hybrid descendants under highinsect pressure. The wild parent showed significantly greater relative survival-regeneration ratios than its GE and non-GE hybrid descendants under both high- and low-insect pressure. However, more seeds were produced in GE hybrid descendants than their non-GE counterparts under high-insect pressure. Given that the introduction of Bt and Bt/Cp TI transgenes did not provide greater insect resistance to crop–wild hybrid descendants than their wild parent, we predict that transgene flow from GE insect-resistant rice to wild rice populations may not cause considerable ecological risks.
Lei LiXiao YangLei WangHuanxin YanJun SuFeng WangBao-Rong Lu
Ecological impact of transgene flow into populations of wild/weedy relatives is associated with fitness effects in hybrid progeny. Most studies assessing fitness effects focus essentially on early-generation hybrid progeny. However, whether the transgenes remain effective and durable in advanced generations of hybrid progeny remains unclear. We conducted a common garden experiment with F5–F7hybrid progeny derived from crosses between insect-resistant transgenic(Bt/Cp TI) rice and weedy rice, to examine their insect resistance and fitness effects of transgenes on progeny. Hybrid progeny were grown under different insect pressures and cultivation modes where insect damage and fitness-related traits were measured in the same growth season. Plants with transgenes showed significantly lower insect damage(10 % vs.32 %) and higher fecundity(551 vs. 392 seeds/plant) than those without transgenes in F5–F7populations, suggesting the efficacy of transgenes for insect resistance. Fitness benefits of the transgenes were similar among the F5–F7populations, indicating the stability of transgenic effects. A positive correlation between insect index and fecundity change was detected, stressing the important role of ambient insect pressures in assessing fitness effects caused by insect-resistance transgenes. Our results have importantimplications for assessing ecological impacts caused by transgene flow to wild/weedy relatives. For cost-effectiveness, the experimental estimation of fitness effects is probably sufficient based on data from hybrids in early generations. Given that fitness effects of insect-resistance transgenes are associated with ambient insect pressure,ecological risk assessment on transgene flow should consider this variable in experimental design, reasonably reflecting actual situations in wild/weedy populations.
Xiao YangLei LiXing Xing CaiFeng WangJun SuBao-Rong Lu
