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Rice lines genetically modified with the crystal toxin genes from Bacillus thuringiensis (Bt) have experienced rapid development, with biosafety certificates for two Bt rice lines issued in 2009. There has still been no commercial release of these lines yet due to public concerns about human health and environmental risks. Some studies confirmed that Bt rice was as safe as conventional rice to non-target organisms when pesticides were not applied, however, pesticides are still required in Bt rice to control non-lepidopteran pests. In this study, we assessed the environmental effects of two Bt rice lines expressing either the cry1Ab/1Ac or cry2A genes, respectively, by using zooplanktons as indicator species under normal field management practices using pesticides when required. In the whole rice growing season, non-Bt rice was sprayed 5 times while Bt rice was sprayed 2 times, which ensured both rice achieved a normal yield. Field investigations showed that rice type (Bt and non-Bt) significantly influenced zooplankton abundance and diversity, which were up to 95% and 80% lower in non-Bt rice fields than Bt rice fields. Laboratory rearing showed that water from non-Bt rice fields was significantly less suitable for the survival and reproduction of Daphnia magna and Paramecium caudatum in comparison with water from Bt rice fields. Higher pesticide residues were detected in the water from non-Bt than Bt rice fields, accounting for the bad performance of zooplankton in non-Bt field water. Our results demonstrate that Bt rice is safer to aquatic ecosystems than non-Bt rice, and its commercialization will be beneficial for biodiversity restoration in rice-based ecosystems. [ABSTRACT FROM AUTHOR]

Abstract: Genetically modified (GM) rice expressing Bt toxins is at the edge of commercial release in China. However, little information is available concerning the impact of Bt rice on aquatic organisms which are abundant in paddy field. A two-year study was conducted to assess the effects of two GM rice lines expressing a fusion protein Cry1Ab/1Ac (Bt rice) on three groups of zooplankton, rotifers, cladocerans and copepods in field conditions. Multi-factor ANOVA revealed that the population densities of rotifers, cladocerans and copepods in paddy field varied significantly between years and rice developmental stages, but did not differ significantly between Bt and non-Bt rice treatments. In all the field investigations, only one significant difference was found on copepods in the tillering stage of 2009, but the difference was not related to the presence of the Cry toxin. Under open-air conditions, we simulated the farming practice of straw mulch, using Bt rice straw as a food source for the water flea Daphnia hyalina. After one and two months of culture, the density of D. hyalina did not differ between Bt rice treatments and non-Bt rice treatments. A laboratory experiment found that purified Bt toxins Cry1Ab and Cry1Ac had no toxic effect on D. hyalina even in the treatment in which the Bt toxin concentration was as high as 2500ng/ml. Those above results indicate that the two Bt rice lines have no negative effect on the three groups of zooplankton. However, further studies are needed to compare the effects of Bt rice and non-Bt rice on the paddy zooplankton community in the context of integrated pest management which includes the use of pesticides. [Copyright &y& Elsevier]

Abstract: Bt rice may become the first commercially released staple food crop transformed with insecticidal genes derived from Bacillus thuringiensis (Bt). However, little information is available concerning the insecticidal protein released from Bt rice into the environment. A 3-year study was conducted to determine the amount, persistence and movement of Cry1Ab/1Ac protein released from Bt-Minghui63 (Bt-MH63) and Bt-Shanyou63 rice (Bt-SY63) using an enzyme-linked immunosorbent assay. The Cry1Ab/1Ac protein was detected in the water of Bt rice fields during the growth stage (below 0.03 ng ml−1 water), but it was not detected in the water of non-Bt fields. A basal level of Cry1Ab/1Ac protein was found in the rhizosphere soil of non-Bt rice (about 0.75 ng g−1 dried soil), and the amount of Cry1Ab/1Ac protein in the rhizosphere soil of Bt rice (about 1.49 ng g−1 dried soil) was significantly higher than that at the basal level. The amount of Cry1Ab/1Ac protein in soil did not significantly differ between non-Bt fields irrigated using water from Bt fields or from a reservoir. In the surface and 10 cm deep soil, the amount of Cry1Ab/1Ac protein differed significantly between Bt and non-Bt rice fields during the harvest period. The amount of Cry1Ab/1Ac protein in the rhizosphere soil of Bt rice was only significantly higher than the basal level during the first two months after harvest. Under hydroponic conditions, Bt rice released detectable Cry1Ab/1Ac protein to the nutrient solution, but artificial wounding in roots did not enhance the releasing of this protein. Based on the above results, we conclude that Bt-MH63 and Bt-SY63 rice can release detectable amounts of Cry1Ab/1Ac protein into soil and field water in the growth period but that the Bt protein does not move into adjacent paddies along with the irrigating water and does not persist in the soil for more than two months. [Copyright &y& Elsevier]

Abstract: Although dozens of transgenic Bacillus thuringiensis (Bt) rice lines have been developed, none of them has been released to farmers. Under field conditions, we evaluated the influence of a hybrid Bt rice on the primary rice insect pests and rice yield in 2005 and 2006. Four treatments were evaluated, including Bt and non-Bt rice treated with insecticides when necessary, and unprotected Bt and non-Bt rice. Unprotected Bt rice exhibited stable and high control of the three primary lepidopteran pests, Chilo suppressalis Walker, Tryporyza incertulas Walker and Cnaphalocrocis edinalis Güenée. Under unprotected conditions, larval densities of these three pests in Bt plots decreased by 87.5–100% compared to those in non-Bt plots, and percentages of damaged stems and leaves remained less than 0.6% during the entire rice growing season. In early rice growth stages, populations of two important planthoppers, Nilaparvata lugens Stål and Sogatella furcifera Hovarth, were significantly affected only by protection level (protected vs unprotected). However, in late rice growth stages (filling and maturing), densities of planthoppers were significantly affected both by protection level and by rice type (Bt vs non-Bt), and densities of N. lugens were significantly higher in Bt plots than in non-Bt plots under unprotected conditions. Pesticide sprays were reduced by 60 and 50% in protected Bt vs protected non-Bt plots in 2005 and 2006, respectively. Yield of unprotected Bt rice increased by 60–65% compared to unprotected non-Bt rice, but decreased by 28–36% compared to protected Bt rice. These results show that Bt rice increased yield greatly, but still required pesticide sprays to avoid losses caused by non-target insect pests. [Copyright &y& Elsevier]