miRNA-mediated insect-resistant transgenic rice poses no risk to a non-target parasitoid, Cotesia chilonis, via direct feeding or through its target host.

MicroRNAs (miRNAs) have started to play an important role in pest control, and novel miRNA-based transgenic insect-resistant plants are now emerging. However, an environmental risk assessment of these novel transgenic plants expressing insect miRNAs must be undertaken before promoting their application. Here, transgenic miR-14 rice, which has high resistance to the rice stem borer Chilo suppressalis, was used as an example for evaluation in this study. Taking the tier 1 risk assessment method in Bacillus thuringiensis (Bt) crops as a reference, the effects of the direct exposure of a non-target parasitoid, Cotesia chilonis, to a high concentration of miRNA were evaluated. The results showed that direct feeding with miR-14 at high concentration had no significant effects on the biological parameters of Co. chilonis, whereas when miR-14 was injected into Ch. suppressalis-parasitized larvae, the development duration of Co. chilonis was significantly affected. In combination with the real conditions of the rice paddy field, it could be inferred that transgenic miR-14 rice has no significant negative effects on the important non-target parasitoid, Co. chilonis. These results will provide a foundation for the establishment of a new safety evaluation system for novel RNAi-based transgenic plants.