Analysis of Cry1Ab toxin bioaccumulation in a food chain of Bt rice, an herbivore and a predator.

Lessons from organophosphorus pesticides, which could be bioaccumulated in non-target organisms at different trophic levels and caused unexpected negative impacts, necessitate a study of the possibility of biotransfer and bioaccumulation of Bacillus thuringiensis (Bt) insecticidal toxin(s) expressed in Bt plants. Using ELISA, we evaluated the transfer of Cry1Ab toxin in a food chain of Bt rice (KMD1 and KMD2), the target insect, Cnaphalocrocis medinalis, and its predator, Pirata subpiraticus. Cry1Ab was detected in C. medinalis and P. subpiraticus. However, the concentration of Cry1Ab detected from C. medinalis and P. subpiraticus did not increase as feeding or preying time increased. A binding study of Cry1Ab to the brush border membrane vesicle of C. medinalis and P. subpiraticus indicated that P. subpiraticus does not have binding receptors in its midgut to Cry1Ab, while C. medinalis does. Survivorship and fecundity of P. subpiraticus preying on Bt rice-fed C. medinalis were not significantly different from those preying on non-Bt rice-fed C. medinalis. Developmental time of P. subpiraticus was significantly longer when it preyed on Bt rice-fed C. medinalis than on non-Bt rice-fed prey. However, a 3-year field trial indicated that Bt rice did not significantly affect the density of P. subpiraticus.