The Safety Research Of Cry1C-and Cry2A-Expressing Bt Rice On Bombyx Mori And Folsomia Candida

Transgenic Bt rice is an efficient strategy for insect pest control and planting of Bt rice can significantly reduce chemical pesticide use, thus can improve the environment. However, planting of Bt rice may has the potential to bring ecological risks. Therefore, it is necessary that the potential risks of any noval insect-resistant genetically modified (IRGM) plant to the environment must be extensively evaluated before being commercialized. An important component of the risk assessment is the potential effects of IRGM plants on nontarget organisms.Bombyx mori Linnaeus (Lepidoptera:Bombycidae) is an economically and culturally important insect in China. B. mori larvae feed exclusively on mulberry (Morus atropurpurea Roxb.) leaves. In southeast China, mulberry trees are typically planted near or around rice fields in a planting system that is referred to as mulberry-mixed cropping. Thus, once Bt rice is commercially grown in China, mulberry leaves may be covered with Bt rice pollen. It follows that B. mori larvae could be exposed to Cry proteins if they consume mulberry leaves covered with Bt rice pollen and if Cry proteins are produced in the pollen. In the current study, we developed and used a rice pollen feeding assay to assess the potential effects of Bt rice pollen containing Cry2A or Cry1C protein on B. mori larvae. In a short-term assay, B. mori larvae were fed mulberry leaves covered with different densities of pollen from Bt rice lines or their corresponding near isoline (control) for the first3d and then were fed mulberry leaves without pollen. No effect was detected on any life table parameter, even at1800pollen grains/cm2leaf, which is much higher than the mean natural density of rice pollen on leaves of mulberry trees near paddy fields. In a long-term assay, the larvae were fed Bt and control pollen in the same way but for their entire larval stage. Bt pollen densities>150grains/cm2leaf reduced14-d larval weight, increased larval development time, and reduced adult eclosion rate. Our results demonstrate that B. mori larvae are sensitive to CrylC and Cry2A proteins, the exposure levels that harmed the larvae in the current study are far greater than natural exposure levels. We therefore conclude that consumption of Bt rice pollen will pose a low to negligible risk to B. mori.Folsomia candida (Collembola:Isotomidae), is one of the most abundant and diversity soil arthropods in the soil ecosystem. It may be exposed to insecticidal proteins produced in genetically engineered (GE) plants by contact with crop residues or root exudates. In the present study, a dietary exposure assay was validated and used to assess the lethal and sublethal effects of two Bacillus thuringiensis(Bt) insecticidal proteins, Cry1C and Cry2A, on Folsomia candida. Using the insecticidal compounds potassium arsenate (PA), protease inhibitor (E-64), and Galanthus nivalis agglutinin (GNA) mixed into Baker's yeast, we show that the assay used can detect adverse effects on F. candida. Survival and development were significantly reduced when F. candida was fed a diet containing PA, E-64, and GNA at9,75, and100?g/g diet, respectively, but not when fed a diet containing 300?g/g Cry1C or600?g/g Cry2A. The activities of test antioxidant-, detoxification-, and digestion-related enzymes in F. candida were unaltered by a diet containing300?g/g Cry1C or600?g/g Cry2A, but were significantly increased by a diet containing75?g/g E-64. The results confirm that F. candida is not toxic to Cry1C and Cry2A at concentrations that are much higher than those encountered under field conditions.