Limited ecological risk of insect-resistance transgene flow from cultivated rice to its wild ancestor based on life-cycle fitness assessment

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 F₂ hybrid descendants from crosses of two insect-resistant GE rice lines (Bt, Bt/CpTI) 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 high-insect 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/CpTI 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.