Abstract
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.
Highlights
Rice (Oryza sativa L.) is a staple food for more than three billion people [1], and more than 90% of total rice is produced and consumed in Asia [2]
We evaluated the environmental effects of two Bacillus thuringiensis (Bt) rice lines, one of which has been granted a safety certificate by the China Ministry of Agriculture (CMOA), using paddy zooplanktons as indicator species
Special permits for the field studies were obtained from Science and Technology Department of Huazhong Agricultural University (HZAU) which executes the function of GMO management under the supervision of China National Agricultural GMO Safety Committee (CNAGSC)
Summary
Rice (Oryza sativa L.) is a staple food for more than three billion people [1], and more than 90% of total rice is produced and consumed in Asia [2]. Rice has been successfully modified to express the cry genes derived from the Bacillus thuringiensis (Bt) bacterium, and several Bt rice lines with high resistance to lepidopteran pests have been developed over the past 15 years in China [4]. The China Ministry of Agriculture (CMOA) has confirmed that safety certificates were issued in November 2009 for two Bt rice lines, Huahui no. The safety certificates did not lead to final commercial release because there were fierce public debates on the health and environmental risks of Bt rice [6]. There is an urgent need to provide the public with scientifically based knowledge of the actual environmental effects of genetically modified rice
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