LAUSR

BACKGROUND The potential risk of insecticidal proteins produced by genetically engineered (GE) plants to non-target organisms have long been an ecotoxicological concern. Apanteles chilonis, an important endoparasitoid of rice pest Chilo suppressalis, is potentially exposed to Bacillus thuringiensis (Bt) endotoxins through a food chain of transgenic Bt rice - C. suppressalis - A. chilonis, thus, a rigorous risk assessment is urgently needed. Here we combined a tri-trophic bioassay system with high dose exposure approach using C. suppressalis hemolymph as the carrier of insecticidal protein to evaluate the biosafety of Cry1Ca to A. chilonis. RESULTS Cry1Ca protein could be transmitted and retained along the food chain and remains bioactive in the hemolymph of C. suppressalis during the pre-adult duration of A. chilonis. No significant differences in pre-adult period, male and female longevity, adult fecundity and weight, emergence rate, and sex ratio were observed when A. chilonis parasitized C. suppressalis feeding on cry1Ca rice compared to control treatment. However, the pupal period and weight were significantly prolonged and decreased. When A. chilonis parasitized on C. suppressalis injected with a high dosage of Cry1Ca protein, no adverse effects on the life-history parameters, peroxidase (POD), superoxide dismutase (SOD), and glutathione reductase (GR) of A. chilonis were observed, demonstrating that the host quality mediates adverse effects during the food chain. CONCLUSIONS We confirmed that Cry1Ca posed no ecological risk to the non-target endoparasitoid A. chilonis. This study may serve as an example for future risk assessment of transgenic crops to non-target endoparasitoids. This article is protected by copyright. All rights reserved.