Effect Of Bt Cry1Ab Protein On Non-target Food Chain Of Nilaparvata Lugens And Its Natural Enemies

Although theoretical approaches to assessing risk on non-target organisms in insect resistant transgenic crops expressing Bt toxin has been debating over last decades, Bt crops have become a major insecticide worldwide. Bt rices can effectively control lepidopteran pests under laboratory and field conditions. Before release, transgenic Bt rice need to undergo a risk assessment process to avoid harm to the environment. In the present study, we choose two non-target food chains (Bt rices—Nilaparvata lugens—Cytorhinus lividipennis and Bt rices—N. lugens—Anagrus nilaparvatae) to evaluate 1) biotransfer and bioaccumulation of Cry1 Ab toxin in a non-target food chain, and 2) the effect of Cry1 Ab on the fitness parameters of nontarget organisms. Results are as follows:1. Biotransfer and bioaccumulation of Cryl Ab on non-target food chain of Bt rices—Nilaparvata lugens—Cytorhinus lividipennisBt toxin Cryl Ab could be detected in the 6-day-old eggs. Moreover, the presence of Cry1 Ab toxin was detected in C. lividipennis nymphs after preying on Bt rice-fed N. lugens eggs, but not accumulate in C. lividipennis as the stage developed. However, no Cry1 Ab was detected in nymphs and adults of C. lividipennis after preying on Bt rice-fed N. lugens first instar nymphs.2. Effect of Bt rices on fitness parameter of N. lugens and its predatorAlthough egg developmental time of N. lugens was significantly longer when N. lugens fed on Bt rice, developmental time of C. lividipennis was not significantly different between individuals preyed eggs of N. lugens fed on Bt and non-Bt rice. Survivorship of C. lividipennis increased significantly when it preyed on eggs of N. lugens feeding on Bt rice. Furthermore, the body weight of C. lividipennis female adult increased significantly as compared to the control.3. Biotransfer and bioaccumulation of Cry1 Ab on non-target food chain of Bt rices—N. lugens—A. nilaparvatae and multi-generation effects of Bt rice on A nilaparvatae ELISA test confirmed that Cry1 Ab toxin could be detected in newly-eclosed parasitoid adults. However, no significant effect on fecundity of A. nilaparvatae was observed between Bt or non-Bt rice. Developmental times of both genders of A. nilaparvatae in both genders were significantly prolonged from first generation to second generation when host eggs laid in Bt (KMD1 and KMD2) rice lines. However, the developmental times of A. nilaparvatae on eggs in KMD1 and KMD2 were not always prolonged from third generation to eleventh generation as compared to the control rice line. Furthermore, progeny sex ratio of A. nilaparvatae from first generation to eleventh generations in three rice lines was always female-biased.4. Effect of CrylAb on the longevity of A. nilaparvataeCryl Ab protein could be detected from A. nilaparvatae adults when they reared on honey mixed with different concentrations of purified Cry1Ab protein. Longevity of male A. nilaparvatae adults were not affected by eggs of N. lugens feeding on Bt or non-Bt rice. The longevity of female A. nilaparvatae adults from eggs of N. lugens feeding on KMD2 rice were shorter than thosefrom eggs of N. lugens feeding on XS11 and KMD1 rice. Survival rate of A. nilaparvatae adults from eggs of N lugens feeding on KMD2 rice were singificantly different from those from eggs of N. lugens feeding on XS11 and KMD1 rice. No significant effects were observed on longevity and survival rate of A. nilaparvatae adults reared on honey mixed with purified Cry1Ab protein compared to those reared on honey. Different concentrations of purified CrylAb protein have no effect on longevity of A. nilaparvatae adults.5. Effect of transgenic Bt rice on population dynamics of N. lugens eggs and its natural enemy in paddy fieldThe trends of N. lugens eggs population dynamics were almost the same on three different rice lines at Zhejiang University Experiment Farm and Fuyang Experiment Farm in 2008 and 2009. The peak of number of N. lugens eggs lasted about two weeks in paddy field. The trends of prey-upon rate and parasitism rate of N. lugens eggs were basically the same on three different rice lines at Zhejiang University Experiment Farm and Fuyang Experiment Farm in 2008 and 2009.