关键词: Bt水稻, Cry1Ab杀虫蛋白, 褐飞虱, 拟水狼蛛, 食物链, 生物富集, 解毒

Abstract: The concentration of Cry1Ab insecticidal protein expressed in two homozygous transgenic Bacillus thuringiensis (Bt) rice lines, KMD1 and KMD2, were determined by enzyme immunosorbent assay (ELISA) with the PathoScreen kit for Bt cry1Ab/Ac protein (Agdia, USA). The results showed that the concentration of Cry1Ab expressed both in KMD1 and KMD2 at the heading and maturing stage were significantly lower than that at the seedling, tillering and booting stage. CrylAb protein could be transferred from   transgenic rice plants to its nontarget pest brown planthopper (BPH), Nilaparvata lugens (Stal), and from N. lugens to its natural enemy wolf spider (WS),Pirata subpiraticus (Boesenberg et Strand) in the food chain by preying. The quantitative cycle of Cry1Ab insecticidal protein in the food chain was analyzed using the kit. After being fed on KMD1 or KMD2 rice plants for 2 days, Cry1Ab protein could be detected in the N. lugens  body. However, after continuous feeding on Bt rice plants for 2, 4, 6, 8 and 10 days, the content of Cry1Ab remaining in the N. lugens body did not show the expected tendency of increase. Also, Cry1Ab protein could be detected in the P. subpiraticus body by preying on the N. lugens reared on KMD1 or KMD2 rice plants for 2, 4, 6, 8 or 10 days, while their contents were significantly higher than those of N. lugens  fed on KMD1 or KMD2 for the same time. Although the inoculation time was increased from 2 to 4, 6, 8 and 10 days, the level of Cry1Ab detected in P. subpiraticus did not show any increase.  Additionally, there were no significant differences among the predatory consumptions of P. subpiraticus preying on N. lugens reared on KMD1, KMD2 or on the non-transgenic parental rice line Xiushui11. No clear bioaccumulation pattern of Cry1Ab protein was observed in N. lugens and P. subpiraticus. More than 50 percent of Cry1Ab was degraded by the crude protease extract from the midgut of P. subpiraticus at 37℃ without light for 2 hours. However, as the exposure time increased from 2 to 4, 8, 12 and 24 hours, the detoxification function of the crude protease extract did not show a tendency to increase.

Key words: Bt rice, Cry1Ab insecticidal protein, Nilaparvata lugens;Pirata subpiraticus, food chain, bioaccumulation, detoxification