转基因抗虫作物对非靶标昆虫的影响

转基因抗虫作物自 1996年被批准商业化种植以来 ,它的抗虫性和经济效益已得到了普遍肯定 ,同时 ,转基因抗虫作物对非靶标生物的影响 ,如转基因抗虫作物的长期种植 ,是否会导致次要害虫上升为主要害虫 ,是否会影响有益昆虫 ,包括重要经济昆虫、捕食性和寄生性天敌以及重要蝶类的种类及种群数量 ,已成为转基因抗虫作物生态风险评估的重要内容。一些研究结果表明 ,转基因抗虫作物在对靶标害虫有效控制的同时 ,一些对杀虫蛋白不敏感的非靶标害虫有加重危害的趋势 ,由于种植转基因抗虫作物 ,减少了化学农药的使用 ,客观上也使非靶标害虫种群数量上升 ,这对转基因抗虫作物害虫综合治理提出了新的要求。靶标害虫数量的减少直接影响了害虫天敌种群数量 ,靶标害虫取食转基因抗虫作物后发育迟缓 ,也间接影响了天敌昆虫的生长发育 ,转基因抗虫作物的花粉或花蜜是一些重要经济昆虫如蜜蜂、熊蜂和一些寄生蜂 ,甚至捕食性天敌的食物来源 ,或花粉飘落到一些鳞翅目昆虫如家蚕或重要蝶类昆虫的寄主植物上 ,直接或间接对这些昆虫造成一定影响。目前大多数研究表明转基因抗虫作物对非靶标昆虫 ,特别是对有益昆虫没有明显的不利影响 ,也有研究报道认为对某些有益昆虫有一定的不良影响。这为深入开展转基因抗虫作物的生态安全     

抗虫转基因植物对非靶标节肢动物生态影响的研究进展

重组DNA技术的发展为培育高效的抗虫作物提供了前所未有的便利条件。通过转基因技术,全世界已培育出众多转基因抗虫植物品系。其中,表达苏云金芽孢杆菌(Bt)基因的作物品系如Bt棉花和Bt玉米已在很多国家大规模种植,在害虫控制方面发挥了重要的作用。转基因抗虫作物可能带来的生态风险问题,如对农田非靶标节肢动物的潜在影响,一直受到相关研究者及民众的广泛关注。至今,已有大量研究论文发表。本文在总结、归纳前人研究的基础上,阐述了从实验室到田间多层次评价转基因抗虫作物对非靶标生物影响的一般研究程序和方法,并简要综述了Bt玉米和Bt棉花2种已商业化种植的转基因抗虫作物对农田非靶标节肢动物生态影响的研究进展。现有研究表明:当前种植的Bt作物所表达的Cry蛋白杀虫专一性非常强,对农田非靶标节肢动物没有毒性;且Bt作物的利用降低了广谱化学杀虫剂的施用量,从而提高了非专一性害虫天敌的种群密度,加强了对害虫的控制,并有效地保护了生态环境和农民健康。因此,Bt作物可以作为害虫综合防治(IPM)的一个策略,结合其他防治措施可加强对害虫的有效控制。     

转Bt抗虫稻对地上非靶标节肢动物的生态风险性

通过转入Bt基因使作物获得抗虫性,减少杀虫剂施用量,为害虫管理开辟了一条重要途径。但公众关注与担忧其环境释放可能存在生物安全与生态风险。本文在系统评述转基因抗虫水稻的生态风险、安全性评价研究内容与方法基础上,重点分析了转基因抗虫水稻对非靶标害虫、捕食性天敌、寄生蜂、中性昆虫及其在食物链上传递的生态风险与安全性,提出了未来研究发展的方向。     

Bt水稻田重要非靶标节肢动物暴露于Cry2Aa蛋白的程度分析

根据风险=危险×暴露的原理,在实验室条件下评价转基因作物对非靶标节肢动物影响时,所选择的代表性非靶标生物通常是在农田系统中较高地暴露于转基因外源杀虫蛋白的节肢动物种.为了弄清Bt稻田主要节肢动物暴露于Cry蛋白的程度,选择合适的非靶标节肢动物,用于转基因抗虫水稻的风险评价,本文采用酶联免疫技术检测了水稻不同生长期从转cry2Aa基因水稻田采集的不同节肢动物体内Cry2Aa蛋白的含量.结果表明: 不同节肢动物种体内的Cry蛋白含量差异显著.一些节肢动物体内不含Cry蛋白,而一些节肢动物体内含有较高的Cry蛋白;相对于花期后采集的节肢动物,在Bt水稻花期采集的节肢动物,特别是捕食性节肢动物体内的Cry蛋白含量较高;寄生性节肢动物体内未检测到Cry蛋白.这为在实验室条件下评价转基因水稻对农田非靶标节肢动物的影响奠定了基础.     

转基因抗虫植物对昆虫天敌的影响

东北农业大学农学院吴研、王振营（中国农科院植保研究所）、赵长山等植保研究工作人员在转基因作物给人类带来经济效益的今天,对此课题进行了试验研究,发现转基因抗虫作物对靶标害虫有很好的控制作用。对捕食性天敌和寄生天敌及其种群数量的影响为其安全评价的重要内容。[第一段]     

Bt水稻田重要非靶标节肢动物权露于Cry2Aa蛋白的程度分析

根据风险=危险×机露的原理,在实验室条件下评价转基因作物对非靶标节肢动物影响时,所选择的代表性非靶标生物通常是在农田系统中较高地关露于转基因外源杀虫蛋白的节肢动物种.为了弄清Bt稻田主要节肢动物暴露于Cry蛋白的程度,选择合适的非靶标节肢动物,用于转基因抗虫水稻的风险评价,本文采用酶联免疫技术检测了水稻不同生长期从转cry2Aa基因水稻田采集的不同节肢动物体内Cry2Aa蛋白的含量.结果表明:不同节肢动物种体内的Cry蛋白含量差异显著.一些节肢动物体内不合Cry蛋白,而一些节肢动物体内含有较高的Cry蛋白;相对于花期后采集的节肢动物,在Bt水稻花期采集的节肢动物,特别是捕食性节肢动物体内的Cry蛋白含量较高;寄生性节肢动物体内未检测到Cry蛋白.这为在实验室条件下评价转基因水稻对农田非靶标节肢动物的影响奠定了基础.     

转Bt基因抗虫作物对鳞翅目非靶标昆虫生态影响的研究进展

任何转基因作物在进入商业化应用之前都必须经过严格的环境风险评价。评价转基因作物特别是抗虫作物对农田重要非靶标节肢动物的生态影响是其中一项重要内容。当前,全球种植的转基因抗虫作物大多表达对鳞翅目害虫具有活性的Cry1或Cry2类杀虫蛋白。由于非靶标鳞翅目昆虫如斑蝶、家蚕等与靶标害虫具有较近的亲缘关系,其幼虫可能同样对这类杀虫蛋白敏感。因此,这类转基因抗虫作物对非靶标鳞翅目害虫的潜在影响引起了研究者的广泛关注。在总结国内外相关研究数据的基础上,系统分析了转基因抗虫作物对非靶标蝶类和蚕类昆虫的潜在影响,获得以下结论：虽然蚕类和蝶类昆虫对Cry1或Cry2类杀虫蛋白敏感,但在自然条件下这类非靶标昆虫暴露于Cry杀虫蛋白的水平很低,抗鳞翅目害虫转基因作物的种植不可能显著影响田间蝶类昆虫的种群密度,也不会给我国的蚕丝产业带来负面影响。     

转基因抗虫棉花和玉米与节肢动物相关的生态安全性研究进展

转基因抗虫棉花和玉米自1996年商业化种植以来,已取得显著的经济、生态和社会效益。与其相关的生态安全性,特别是其对非靶标生物的影响及靶标害虫的抗性监测和治理已成为人们普遍关注的话题。本文在大量室内和田间评价工作的基础上,系统综述了国内外研究在该领域内取得的进展。结果表明： 由于Bt棉田和玉米田杀虫剂用量的减少,某些对Bt杀虫蛋白不敏感的非靶标植食害虫种群有上升的趋势; 现阶段生产上推广种植的Bt棉花和玉米花粉对家蚕、柞蚕和蜜蜂等经济昆虫以及帝王斑蝶是安全的。杀虫剂用量的减少,降低了对天敌的杀伤力,Bt田中捕食性天敌的种类和数量均显著高于常规施药田; 但Bt田内靶标害虫数量的减少和质量的降低,在一定程度上影响了寄生性天敌的种类和数量。Bt棉花和玉米的大面积种植对农田生态系统节肢动物群落结构无明显不利影响。靶标害虫田间抗性监测结果表明,无论在以大农场单一种植经营为主的发达国家如美国或澳大利亚,还是在以小农经营为主的多种寄主作物小规模交叉混合种植模式的发展中国家如中国或印度,田间并未出现10年前人们所关注和预测的靶标害虫种群抗性上升问题。究其原因,可能与发达国家严格执行了预防性的抗性治理对策及发展中国家独特的作物种植模式有关。尽管目前在田间尚未发现害虫对Bt作物产生抗性,但应用更多年份之后,害虫对Bt作物的抗性就很可能不是“是否”发生问题,而是“何时”发生的问题。因此,今后的研究重点应放在Bt棉花和玉米长期、大面积种植后,其对非靶标生物及靶标害虫抗性发展影响的长期生态效应上。     

应用肠道内含物定量评价天敌捕食作用的方法

【目的】自然天敌在农田生态系统中发挥着重要的生物功能,明确捕食性天敌对害虫猎物的控制能力是充分发挥天敌控制作用的前提。【方法】本文基于肠道内含物分子检测方法,以华北花生与玉米组成的微景观系统中的花生/玉米-花生蚜-龟纹瓢虫为研究主线,对龟纹瓢虫Propylaeajaponica肠道内含物进行了分子检测。【结果】结合室内和大田取样两种途径,通过测定龟纹瓢虫肠道内含物中花生蚜的阳性检出率,显示龟纹瓢虫体内检测到花生蚜的扩增,阳性检出率最高时达到26.25%。【结论】基于天敌肠道内含物的分子标记技术可作为定量评价田间实际天敌控害作用的有效方法之一,玉米作为功能植物(作物)可通过涵养天敌瓢虫实现对花生蚜的控制作用。     

转基因作物对天敌的影响研究进展

随着转基因作物商业化种植的发展,人们越来越关注转基因作物对生态安全的影响,其中的一个焦点就是转基因作物对非靶标昆虫天敌的影响。转基因作物主要通过花粉和取食转基因植物的昆虫两个途径影响天敌的种群。目前国内外转基因作物对天敌影响的研究方法包括田间种群调查,室内转基因作物花粉或取食转基因作物的害虫对天敌影响研究,近年来把高浓度毒蛋白通过人工饲料喂养给天敌的Tier-1法研究也逐渐增多。大多数研究表明,转基因抗虫作物中的杀虫蛋白通过花粉和取食转基因植物的昆虫两个途径对天敌没有产生不利的影响。同样,Tier-1法研究结果,也证明浓度毒蛋白喂养对天敌并没有产生不利的影响。     

Assessment of risk of insect-resistant transgenic crops to nontarget arthropods

An international initiative is developing a scientifically rigorous approach to evaluate the potential risks to nontarget arthropods (NTAs) posed by insect-resistant, genetically modified (IRGM) crops. It adapts the tiered approach to risk assessment that is used internationally within regulatory toxicology and environmental sciences. The approach focuses on the formulation and testing of clearly stated risk hypotheses, making maximum use of available data and using formal decision guidelines to progress between testing stages (or tiers). It is intended to provide guidance to regulatory agencies that are currently developing their own NTA risk assessment guidelines for IRGM crops and to help harmonize regulatory requirements between different countries and different regions of the world.     

Non-target organism effects tests on Vip3A and their application to the ecological risk assessment for cultivation of MIR162 maize

Transgenic crops producing insecticidal proteins from Bacillus thuringiensis (Bt) provide economic, environmental and health benefits by maintaining or increasing crop yields with fewer applications of insecticide. To sustain these benefits, it is important to delay the evolution of insect resistance to the proteins, and to ensure that the proteins do not harm non-target organisms, particularly those that may control secondary pests that would otherwise flourish because of reduced insecticide applications. Vip3A is a Bt vegetative insecticidal protein that is active against lepidopterous pests. It has a different mode of action from other proteins for control of Lepidoptera in current Bt crops, and when combined with these proteins, it should help to delay the evolution of pest resistance to Bt crops. This paper presents data on the effects of Vip3A on non-target organisms, and an ecological risk assessment of MIR162 maize, which expresses Vip3Aa20. Laboratory studies indicate few adverse effects of Vip3A to non-target organisms: 11 of 12 species tested showed no adverse effects when exposed to high concentrations of Vip3A relative to estimated exposures resulting from cultivation of MIR162 maize. Daphnia magna exposed to Vip3Aa20 were unaffected in terms of survival or fecundity, but grew slightly more slowly than unexposed controls. The data indicate that cultivation of MIR162 maize poses negligible risk to non-target organisms, and that crops producing Vip3A are unlikely to adversely affect biological control organisms such that benefits from reduced insecticide applications are lost.     

Extrapolating non-target risk of Bt crops from laboratory to field

The tiered approach to assessing ecological risk of insect-resistant transgenic crops assumes that lower tier laboratory studies, which expose surrogate non-target organisms to high doses of insecticidal proteins, can detect harmful effects that might be manifested in the field. To test this assumption, we performed meta-analyses comparing results for non-target invertebrates exposed to Bacillus thuringiensis (Bt) Cry proteins in laboratory studies with results derived from independent field studies examining effects on the abundance of non-target invertebrates. For Lepidopteran-active Cry proteins, laboratory studies correctly predicted the reduced field abundance of non-target Lepidoptera. However, laboratory studies incorporating tri-trophic interactions of Bt plants, herbivores and parasitoids were better correlated with the decreased field abundance of parasitoids than were direct-exposure assays. For predators, laboratory tri-trophic studies predicted reduced abundances that were not realized in field studies and thus overestimated ecological risk. Exposure to Coleopteran-active Cry proteins did not significantly reduce the laboratory survival or field abundance of any functional group examined. Our findings support the assumption that laboratory studies of transgenic insecticidal crops show effects that are either consistent with, or more conservative than, those found in field studies, with the important caveat that laboratory studies should explore all ecologically relevant routes of exposure.     

Recommendations for the design of laboratory studies on non-target arthropods for risk assessment of genetically engineered plants

This paper provides recommendations on experimental design for early-tier laboratory studies used in risk assessments to evaluate potential adverse impacts of arthropod-resistant genetically engineered (GE) plants on non-target arthropods (NTAs). While we rely heavily on the currently used proteins from Bacillus thuringiensis (Bt) in this discussion, the concepts apply to other arthropod-active proteins. A risk may exist if the newly acquired trait of the GE plant has adverse effects on NTAs when they are exposed to the arthropod-active protein. Typically, the risk assessment follows a tiered approach that starts with laboratory studies under worst-case exposure conditions; such studies have a high ability to detect adverse effects on non-target species. Clear guidance on how such data are produced in laboratory studies assists the product developers and risk assessors. The studies should be reproducible and test clearly defined risk hypotheses. These properties contribute to the robustness of, and confidence in, environmental risk assessments for GE plants. Data from NTA studies, collected during the analysis phase of an environmental risk assessment, are critical to the outcome of the assessment and ultimately the decision taken by regulatory authorities on the release of a GE plant. Confidence in the results of early-tier laboratory studies is a precondition for the acceptance of data across regulatory jurisdictions and should encourage agencies to share useful information and thus avoid redundant testing.     

Benefits and risks of exotic biological control agents

The use of exotic (=alien) arthropods in classical and augmentative biological control programs has yielded huge economic and ecological benefits. Exotic species of arthropods have contributed to the suppression of key pests in agriculture and forestry or have aided in restoring natural systems affected by adventive species. However, adverse non-target effects of exotic biological control agents have been observed in a number of projects. Non-target effects range from very small effects, e.g. 2% parasitization on a non-target insect on a local level, to massive effects on a large scale. Until now, no consensus on how to judge the magnitude of non-target effects and whether these effects can be tolerated or are unacceptable has emerged. In this paper, we briefly review both the benefits of biological control as well as the associated risks including to human and animal health, plant health and particularly the environment. We also make an attempt at identifying the major challenges for assessing risks and for balancing benefits and risks. There is general agreement that sound risk assessment procedures should precede the release of exotic invertebrate biological control agents and a recent shift??especially for arthropod biological control??from introductions done without meaningful risk assessment studies to projects conducting thorough host range testing can be observed. However, overly stringent regulations that would preclude promising agents from being developed must be avoided.     

Ecological risk assessment of transgenic plant releases: an Austrian perspective

Some prerequisites for ecological risk assessment of transgenic plant releases are examined, with the aim of identifying research needs in Austria. Austria harbours high habitat diversity, extending from the Alps to the Pannonian continental lowlands. The Pannonian flora includes potential cross-breeding partners of several crops, which do not occur in western Europe. The border zones of major biogeographical regions contain high biodiversity, both in terms of species and habitat diversity; whether the genetic variability of widespread plant species is also increased in these areas requires further investigation. Especially in Alpine regions, transgenic grasses might eventually cause profound changes in community structure. Ecological risk assessment of transgenic crop releases should not only consider adverse effects on non-target species and ecosystems, but also their likely impact on the agroecosystems.     

Assessing the risks of insect resistant transgenic plants on entomophagous arthropods Bt-maize expressing Cry1Ab as a case study

One of the primary concerns related to theadoption of insect resistant transgenic plantsin the environment is the detrimental effectthat these may pose on non-target organisms,including entomophagous arthropods (parasitoidsfand predators) which have an important functionin regulating pests. Despite the fact thatregulatory bodies require information regardingthe potential risk of releasing transgenicplants in the environment, to date, no specificprotocols have been designed for assessing therisks of insect resistant transgenic crops onentomophagous arthropods. Here a framework forrisk assessment is proposed to evaluate theeffects of insect resistant plants onentomophagous arthropods. Using maizeexpressing the Bacillus thuringiensisgene which codes for the Cry1Ab toxin, weillustrate the procedure necessary forassessing the risks. As a first step, it isrequired to determine which entomophagousarthropods play a major role in regulatingmaize pests, and which may be at risk. Becausethe risk which transgenic plants pose toentomophagous arthropods depends on both, theirexposure, and their sensitivity to theinsecticidal protein, it is essential todetermine, as a second step, if and at whatlevel organisms are exposed to the transgenecompound. Exposure will be associated with thefeeding behaviour of phytophagous andentomophagous arthropods together with thetissue and cell specific temporal and spatialexpression of the insecticidal protein. Forthose organisms which could potentially beexposed to the insecticidal protein,sensitivity tests, as a third step, should beperformed to assess toxicity. The testingprocedure and the type of tests which should beadopted to quantify the effects of insectresistant plants on natural enemies aresubsequently illustrated. Taking the greenlacewing Chrysoperla carnea as anexample, we propose a procedure on how toperform tests and give evidence that Bt-maizeposes no risk to this predator.