State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China,
Ecotoxicology. 2013 Nov;22(9):1413-21. doi: 10.1007/s10646-013-1127-0. Epub 2013 Sep 22.
To assess the potential effects of Cry2Aa-expressing insect-resistant Bt rice on Chrysoperla sinica larvae, we conducted two tritrophic bioassays using a non-target (Laodelphax striatellus) and a target herbivore (Chilo suppressalis) as prey. None of the tested life-table parameters of C. sinica did differ when fed with L. striatellus nymphs reared on either Bt or control rice plants. Similarly, C. sinica larval survival and development were not affected when fed C. suppressalis larvae that were reared on Cry2Aa-contained artificial diet compared to those fed control diet. However, the 7-day larval weight was significantly decreased in the Bt treatment and none of the C. sinica larvae developed to the adult stage. To clarify whether the observed effects were due to the direct toxicity of Cry2Aa or prey-quality mediated, we conducted a dietary exposure assay in which the toxicity of Cry2Aa to C. sinica larvae was tested. Potassium arsenate (PA) was included as a positive control. None of the tested life-table parameters of C. sinica was adversely affected when fed Cry2Aa at 500 μg/ml sucrose solution. In contrast, C. sinica larvae were adversely affected by feeding on sucrose solution containing PA. In the feeding assays, exposure of C. sinica larvae to Cry2Aa was confirmed by ELISA. Our results demonstrate that C. sinica larvae are not sensitive to Cry2Aa at concentrations exceeding the levels that the larvae may encounter in Bt rice fields. Consequently the detrimental effects observed in the tritrophic studies using Bt rice-fed C. suppressalis as prey can be attributed to the decreased prey quality due to the sensitivity of C. suppressalis larvae to Cry2Aa.
为了评估 Cry2Aa 表达的抗虫 Bt 水稻对中华通草蛉幼虫的潜在影响，我们进行了两项三营养生物测定，使用非靶标（褐飞虱）和靶标草食性昆虫（二化螟）作为猎物。当以 Bt 或对照水稻植株上饲养的褐飞虱若虫为食时，中华通草蛉的所有测试生命表参数均无差异。同样，当以含有 Cry2Aa 的人工饲料饲养的二化螟幼虫为食时，与对照饲料相比，中华通草蛉幼虫的存活率和发育没有受到影响。然而，Bt 处理组的 7 天幼虫体重显著下降，且没有一只中华通草蛉幼虫发育为成虫。为了澄清观察到的影响是由于 Cry2Aa 的直接毒性还是由于猎物质量介导的，我们进行了饮食暴露测定，其中测试了 Cry2Aa 对中华通草蛉幼虫的毒性。砷酸氢钾（PA）被用作阳性对照。当以 500μg/ml 蔗糖溶液喂养时，Cry2Aa 对中华通草蛉的所有测试生命表参数均无不良影响。相比之下，中华通草蛉幼虫在喂食含有 PA 的蔗糖溶液时受到不利影响。在喂养试验中，通过 ELISA 确认了中华通草蛉幼虫暴露于 Cry2Aa。我们的结果表明，当幼虫可能在 Bt 稻田中遇到的浓度超过时，Cry2Aa 对中华通草蛉幼虫不敏感。因此，在使用以 Bt 水稻为食的二化螟作为猎物的三营养研究中观察到的有害影响可归因于二化螟幼虫对 Cry2Aa 的敏感性导致的猎物质量下降。
