Abstract
T2A-1 is a newly developed transgenic rice that expresses a synthesized cry2Aa gene driven by the maize ubiquitin promoter. T2A-1 exhibits high resistance against lepidopteran pests of rice. The brown planthopper, Nilapavarta lugens (Stål), is a main nontarget sap-sucking insect pest of rice, and Cyrtorhinus lividipennis (Reuter) is the major predator of the eggs and young nymphs of planthoppers. As C. lividipennis may expose to the Cry2Aa protein via N. lugens, it is therefore essential to assess the potential effects of transgenic cry2Aa rice on this predator. In the present study, three experiments were conducted to evaluate the ecological risk of transgenic cry2Aa rice to C. lividipennis: (1) a direct feeding experiment in which C. lividipennis was fed an artificial diet containing Cry2Aa at the dose of 10-time higher than that it may encounter in the realistic field condition; (2) a tritrophic experiment in which the Cry2Aa protein was delivered to C. lividipennis indirectly through prey eggs or nymphs; (3) a realistic field experiment in which the population dynamics of C. lividipennis were investigated using vacuum-suction. Both direct exposure to elevated doses of the Cry2Aa protein and prey-mediated exposure to realistic doses of the protein did not result in significant detrimental effects on the development, survival, female ratio and body weight of C. lividipennis. No significant differences in population density and population dynamics were observed between C. lividipennis in transgenic cry2Aa and nontransgenic rice fields. It may be concluded that transgenic cry2Aa rice had no detrimental effects on C. lividipennis. This study represents the first report of an assessment continuum for the effects of transgenic cry2Aa rice on C. lividipennis.
Highlights
Rice, Oryza sativa L., is the staple food of more than three billion people of Asia [1]
No significant differences were observed between the developmental time, preimaginal survival, female ratio and fresh body weight of C. lividipennis adults reared with eggs or nymphs of N. lugens fed on Bacillus thuringiensis (Bt) and non-Bt rice (P.0.05) (Tables 1, 2)
When the N. lugens nymphs fed on T2A-1 were removed from T2A-1 and the nymphs alone were provided to C. lividipennis, no Cry2Aa was detected in the predator
Summary
Oryza sativa L., is the staple food of more than three billion people of Asia [1]. More than 200 species of insect pests infest rice during its growing season [2], and this causes 15% to 25% yield losses of rice [3,4]. Among these insects, lepidopteran species such as stem borers and leaffolders are serious chronic pests and cause large annual yield losses [5,6]. Excessive or continual applications of pesticide cause environmental contamination and the resurgence of herbivores and reduce populations of the natural enemies of these herbivores [7,8]. Researchers have been encouraged to seek more effective and environmentally friendly methods to control lepidopteran pests
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