Consumption of Bt rice pollen expressing Cry2Aa does not cause adverse effects on adult Chrysoperla sinica Tjeder (Neuroptera: Chrysopidae)

Adults of Chrysoperla sinica Tjeder are prevalent pollen feeders in rice fields in China. They are therefore exposed to insecticidal proteins when foraging insect-resistant genetically engineered rice pollen containing Bacillus thuringiensis (Bt) proteins. Laboratory bioassays were conducted to evaluate the potential impacts of Cry2Aa-expressing transgenic rice (T2A-1) pollen on fitness of adult C. sinica. Survival, pre-oviposition period, fecundity and adult dry weight did not differ between lacewings that had consumed Bt or non-Bt rice pollen. To ensure lacewing adults were not sensitive to Cry2Aa protein independent from the plant background and to add certainty to the toxicity assessment, C. sinica adults were fed with an artificial diet containing Cry2Aa protein at an approximately 10 times higher concentration than in rice pollen. Artificial diet containing potassium arsenate (PA) was included as a positive control. No difference was detected for any of the life-table parameters tested between Cry2Aa-containing and pure diet. In contrast, the pre-oviposition, fecundity and dry weight of C. sinica were significantly adversely affected by feeding on PA-containing diet. In both bioassays, the uptake of Cry protein by adult C. sinica and the bioactivity of Cry protein in the food sources were confirmed by ELISA measurements and sensitive insect bioassays, respectively. These results indicate that adults of C. sinica are not affected by Cry2Aa-expressing rice pollen and are not sensitive to Cry2Aa protein at concentrations exceeding the levels in pollen, thus demonstrating that growing Bt rice expressing Cry2Aa protein will pose a negligible risk to adult C. sinica.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► We developed a model assessing potential impacts of Bt rice pollen on Chrysoperla sinica. ► C. sinica adults are not negatively affected by ingestion of Bt rice pollen. ► C. sinica adults are not sensitive to Cry2Aa protein at high levels. ► Growing Bt rice expressing Cry2Aa poses a negligible risk to adult C. sinica.