Effects of Transgenic Maize (Zea mays) Event DR 12-5 with Cry1Ab/cry2Aj and g10evo-epsps Genes on Silkworm (Bombyx mori)
ZHU Xuan1,2, JIANG Yuan-Yuan1, LAI Yong-Min1, CHEN Xiao-Yun1, WANG Xiao-Fu1, XU Xiao-Li1,*, XU Jun-Feng1,*
1 State Key Laboratory for Quality and Safety of Agro-products, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, China; 2 Fuyang Normal University, Fuyang 236037, China
Abstract：The possible impacts on nontarget organisms of transgenic crops are important in environmental risk assessment for genetically modified organisms (GMOs), such as Bt maize (Zea mays). Because Bombyx mori belongs to the same order as the target pests of transgenic Bt maize, i.e., the Lepidoptera, it may be affected by consuming mulberry leaves covered with pollen from nearby transgenic Bt maize. In this study, laboratory experiments were conducted to assess the potential effects of transgenic maize 'DR12-5' pollen on growth and reproduction of B. mori. In the assay, B. mori larvae were fed mulberry (Morus alba) leaves covered with different densities of pollen from 'DR12-5' or its corresponding near isoline (control). When B. mori larvae were exposed to 40 g/L (10000 grains/cm2) transgenic maize 'DR12-5' pollen, the survival rate dropped significantly, and no larvae could survive after 8 d. When the 'DR12-5' pollen concentration on the leaves of mulberry was 4 g/L or 0.4 g/L,no lethal effect was observed but the development of the neonate larvae was inhibited. The weights of different instar larvae were significantly decreased, and the development time was significantly prolonged than control larvae. However, there were no significant differences in pupation rate, emergence rate, cocoon weight, pupa weight, cocoon shell weight and oviposition between GM maize pollen and its non-transgenic cron pollen. The activity of the anti-oxidation enzyme system in 5th instar silkworms was detected, and it was found that the activities of superoxide dismutase (SOD), peroxidase (POD) and hydrogen peroxide (CAT) in 'DR 12-5'-treated silkworms were significantly increased, and the higher the pollen concentration, the higher the enzyme activity. The above results showed that 'DR 12-5' pollen densities ≥ 100 grains/cm2 leaf had negative effects on the growth of the silkworms and the adverse effect was improved with higher pollen density. In the natural conditions, the drift of maize pollen is affected by various environmental factors such as distance, weather conditions and so on. And the exposure levels are far lower than in the current study. Therefore, it is generally recognized that Bt maize pollen will pose a low risk to B. mori. This study provides a theoretical basis for evaluating the potential risks to silkworm posed by insect-resistant genetically modified maize
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