转基因作物对环境影响的讨论

随着转基因作物的不断推广，转基因作物对环境的影响受到越来越多的关注，其中包括转基因作物潜在的侵袭力，基因漂移，对生物多样性的冲击，对农业生产的影响等等。这些议题具有跨学科性和高度的复杂性，要正确评价它们，就必须设定一个合适的标准作为参照。通过传统育种方法培育的新品种对环境的影响成为最合适的参照，这些新品种被广为认可，是现代农业重要的组成部分。在许多实例当中。转基因作物对环境的影响与通过传统育种方式所得到的新品种对环境的影响非常相似。通过比较对转基因作物进行恰当评价，会使植物转基因技术更好的发挥作用。     

Improving the management of coexistence between GM and non-GM maize with a spatially explicit model of cross-pollination

The European Commission have established the concept of coexistence, according to which, farmers should be able to grow whatever type of agricultural crops they wish (genetically modified (GM), conventional or organic), provided that they comply with the legal obligations for labeling and/or purity standards. In the case of maize, the main factor conditioning the feasibility of coexistence is gene flow from GM fields to other types of production. The distance between fields has been identified as a key factor governing this gene flow. As a consequence, the existing regulations mostly concern the maintenance of a fixed isolation distance between GM fields and the closest non-GM field. However, other factors, such as temporal dynamics of pollen shedding, wind, relative field sizes and shapes and the spatial distribution of the different types of fields, may greatly modulate the effect of distance. Moreover, uniform distance-based rules create a “domino effect”, in which it is difficult for GM crops and non-GM crops to co-exist at the landscape scale. In this study, we hypothesized that the use of a spatially explicit gene-flow model, MAPOD^®, would result in a significant gain in proportionality and freedom of choice for the farmer over uniform distance-based rules. To test this hypothesis, we performed a global sensitivity analysis on this process-based model but, instead of exploring a random set of situations, the sensitivity analysis was carried out on a subset of realistic scenarios based on farmers’ strategies. To select those scenarios, we constructed a multicriteria decision-making model describing the decision process used by farmers when deciding whether or not to grow GM maize, and used this model to generate realistic allocation scenarios for GM, non-GM conventional and organic maize cultivation. We showed that the coexistence method based on the MAPOD^® model allowed the presence of a higher percentage of GM maize in the landscape than the distance-based method. This made it possible to follow the farmer’s field intended allocations more closely, whilst complying with the legal threshold requirements. This gain in proportionality was greater at high maize densities, for which the distance-based method allowed almost no cultivation of GM crops. However, in case of high proportions of organic fields, our study indicated that coexistence between GM maize and organic maize at the landscape level is difficult, if not impossible in case of farm-saved seeds, without a spatial aggregation of fields, leading de facto to separate non-GM and GM zones. Finally, the use of MAPOD^® resulted in better discrimination between acceptable and risky situations, and greater flexibility, which is crucial for the implementation of an efficient coexistence strategy.     

转基因作物的生物安全：基因漂移及其潜在生态风险的研究和管控

转基因作物品种在商业化推广的20多年间发展迅猛,在保障食品供应、拓展农业功能、缓解资源约束、保护生态环境等方面做出了卓越贡献。在创造巨大经济、环境和社会效益的同时,转基因作物的生物安全问题也引起了全球的广泛关注和讨论。其中,难以准确预见的外源基因通过基因漂移逃逸至非转基因作物及其野生近缘种,进而导致潜在的生态风险就是国内外学者的研究热点。围绕基因漂移的机制及其生态风险、风险评估、控制措施等问题进行介绍和讨论,并展望转基因生物技术的发展趋势。     

利用微滴式数字PCR技术分析转基因玉米抗除草剂标记基因EPSP拷贝数

基于微滴式数字PCR(Droplet digital PCR,ddPCR)平台,以转基因玉米为例,建立了转基因作物(Genetically modified crops,GM crops)外源基因拷贝数分析方法,对待测样品进行了快速鉴定,并从T_0转基因玉米株系中鉴定出多个单拷贝单株。对该方法与实时荧光定量PCR(Quantitative real-time PCR,qRT-PCR)方法在分析结果的准确性方面进行了比较,从试验数据可以看出,2种检测方法的结果比较一致,单拷贝检测结果高度一致;但是ddPCR试验操作更加简便,试验结果可重复性强,试验数据更加准确可靠。研究表明,ddPCR方法是一种更加便捷、快速和准确的外源基因拷贝数分析新方法,基于其在准确性和灵敏度方面的显著优势,将会在转基因作物的外源基因拷贝数分析中得到广泛的应用。     

几种除草剂对当茬玉米生长发育的影响

除草剂为作物产量提供保障的同时,对作物造成的药害也频繁发生。为此,本文以目前陇东旱塬区主栽玉米品种为试验材料,选用对恶性杂草具有良好防除效果的除草剂,明确了75%二氯吡啶酸SG、90%莠去津WG和56% 2甲4氯钠盐SP 3个单剂及其2个混配配方对玉米主要农艺性状及产量的影响,以期为玉米的安全生产提供依据。结果表明：参试除草剂在药后0~7天及不同生育期对玉米生长均无直观影响。75%二氯吡啶酸SG、90%莠去津WG、75%二氯吡啶酸SG+90%莠去津WG对苗期玉米株高稍有影响,但随着玉米自身防御能力的增强,除草剂对之后各生育期的玉米株高无显著抑制作用。不同除草剂对各生育期玉米茎粗无抑制作用,玉米果穗粗、果穗有效长、穗粒数和百粒重无显著差异。各除草剂处理后玉米产量较空白对照增加21.93%~30.22%,较人工除草对照增加-2.91%~3.69%。可见,供试除草剂对玉米安全性高,可应用于玉米田的杂草防除。     

Towards an optimal management regime to facilitate the coexistence of GM herbicide tolerant and non-GM oilseed rape

Although a national strategy for the coexistence of GM and conventional/organic crops in Ireland has been published (McGill et al., 2005), measures pertaining to the coexistence of GM and non-GM oilseed rape (OSR) crops was omitted pending the completion of regional specific research. As the evaluation of gene flow between coexisting OSR varieties cannot be solely studied through field experiments and to assist policy makers in the generation of coexistence guidelines for GM herbicide tolerant (HT) OSR, the present work utilized the gene flow model GeneSys to simulate the influence of management strategies on gene escape from GM OSR across the Irish agri-environment. The model predicted that the incorporation of GMHT OSR into an existing winter wheat-based rotation without a complimentary modification to the cropping regime would rapidly compromise coexistence, recorded as the % harvest impurities in non-GM OSR crops at the silo and the % of non-GM OSR fields whose harvest exceeded the European Union labelling threshold of 0.9% GM content. Enhanced herbicide efficacy, the application of spring weed control, the inclusion of a single spring crop (potato, barley, maize) post-OSR, reduced regional harvest impurities in non-GM OSR crops below the 0.9% threshold. The simulations showed that the establishment of GM zones by clustering of GMHT OSR fields presents for early adopters a viable mechanism to achieve coexistence with neighboring non-GM OSR sites. By incorporating a 50 m non-OSR (GM/non-GM) buffer zone to circumvent each GM cluster, the simulations concluded that regional harvest purity can be assured with up to 6 separate clusters accommodating up to 10% regional GM adoption across the landscape. Significantly, these simulations were completed using GMHT OSR as a break crop in the standard winter wheat rotation, which in previous simulations was deemed to be impractical for coexistence purposes. Organizing cultivation through GM clusters, presents a workable option to those early adopters who will seek to investigate the potential of the technology by (i) concentrating the necessity for intensive volunteer control in a specific, localised area (ii) increasing the potential for allocating machinery via GM/non-GM purposes and (iii) facilitating regulatory requirements in regards to farmer-to-farmer communication.     

Controlling the release of pollen from genetically modified maize and increasing its grain yield by growing mixtures of male-sterile and male-fertile plants

There is public concern about the consequences of pollen dispersal from genetically modified (GM) crops. There lease of viable pollen from GM maize can be controlled by growing mixtures of cytoplasmic male-sterile plants and male-fertile non-transformed pollinator plants. Our experiments indicate that such associations can bring about grain yields as high or even higher than those produced by pure male-fertile maize crops, especially when the male-sterile component is pollinated non-isogenically. The grain yield benefits from cytoplasmic malesterility and xenia as well as the fact that seed of male-sterile varieties can be produced cheaply and reliably in large quantities would facilitate the implementation of the proposed system in agricultural practice. This revised version was published online in July 2006 with corrections to the Cover Date.     

Developmental expression of glutathione-S-transferase in maize and its possible connection with herbicide tolerance

Summary Crop improvement for tolerance to specific herbicides is an important breeding target, since molecules performing well with regard to environmental safety are frequently not completely selective for crops. The glutathione (GSH)/glutathione-S-transferase (GST) system is a general mechanism of detoxification that in higher plants may confer tolerance to some herbicides. GSH level and GST activity were measured in different maize inbred lines, in the absence or in the presence of EPTC (a thiocarbamate) and of Alachlor (a chloroacetanilide); a wide genetic variability was observed for these parameters, which appear to be involved in plant tolerance to herbicides. Isozyme analysis was performed on roots, leaves, scutellum, pollen, coleoptile, mesocotyl of the same inbreds: it revealed the presence of many GST forms in maize, showing high polymorphism; they are controlled by at least five genes, the expression of which is developmentally regulated in the different tissues analyzed.     

Sunflower allelopathy for weed control in agriculture systems

Recent developments in weed science and allied aspects have involved several interdisciplinary approaches. In this context, indiscriminate use of herbicides for weed control has become a questionable subject, which besides controlling the weeds, the chemical herbicides are harmful in many ways to soil, crops, other plants and the environment as a whole. Taking into consideration ecologically sound weed management, in modern days the reliance on chemical herbicides has decreased and a shift towards naturally occurring biological herbicides has received great attention throughout the world. Sunflower is an annual dicotyledonous plant, herbaceous, erect, and a native of North America. It is thermo and photo-insensitive, hence it can be grown year round in sub-tropical and tropical countries. Only two spp. Helianthus annuus L. and Helianthus tuberosum are cultivated for food, the remaining spp., are ornamentals weeds and wild plants. However, H. annuus is allelopathic and inhibits the growth and development of other plants thus reducing their productivity. Sunflower is a major oil-yielding crop in India and its cultivation in northwest India started 25 to 30 years ago in areas located in the plains. In this region, rice-wheat rotation became very popular owing to its high yields; however, these crops are highly infested by weeds, thus farmers use herbicides for their control. Hence, this rotation consumes a maximum quantity of herbicides in this region, which has resulted in several problems viz., environmental pollution, human health hazards, and development of herbicide resistance in weeds. Thus, serious ecological questions about the reliance on herbicides for weed control in this rotation have been raised. One of the alternatives to overcome these problems is with the use of allelopathic strategies, including the use of weed-smothering crops for weed management and for the sustainability of agriculture. The field, pot culture, and laboratory studies have shown that inclusion of sunflower crops in rotation and intercropping considerably reduced the weed population in the current and succeeding crops. Rhizosphere soil of sunflower drastically smothered the weed germination, population, and biomass. The residual suppression effect of sunflower also persisted in the next crop up to 75 days. Thus, it is conceptualized that the inclusion of such oilseed crops before the rice crop in the rice-wheat rotation may provide satisfactory weed control in the succeeding rice crops and may minimize the use of herbicides. Likewise, the replacement of sorghum by summer sunflower oilseed crops may also help in the control of summer as well as winter weeds. More studies in this direction may provide avenues for satisfactory weed management in agro-ecosystems and may help to minimize the use of herbicides and thereby pave the way to develop sustainable agricultural practices for biodiversity conservation and enhancing biological integrity.     

Herbicide-tolerant crops in agriculture: oilseed rape as a case study

Oilseed rape has been modified extensively by conventional breeding for the production of varieties useful for human consumption (blended vegetable oil and margarine) and industrial processes (rubber additives and high‐temperature lubricants). Because much is now known about its genetic and biochemical composition, it has been an obvious choice for genetic modification and is now at the forefront of the commercial development of genetically modified (GM) or transgenic crops. Around the world, the increase in commercial plantings of all transgenic crops has been rapid. In 1996, 1.7 million hectares were planted, but by 1998 this figure had jumped to 27.8 million ha. The area in the year 2001 is likely to be about 50 million ha. With the possible introduction of transgenic varieties into European agriculture, it is essential that the associated farming practices employed are appropriate for their growth, both from a commercial and an environmental viewpoint. Some of the first transgenic crops are those carrying agronomic traits, e.g. herbicide tolerance transgenes. However, before full commercialization occurs, important agronomic and environmental questions need to be answered. How are these new crops to be incorporated into existing cropping practices? How will this change the current herbicide use profile for a given crop? Do herbicide‐tolerant varieties enhance or impede integrated pest management schemes? What is the likely uptake of such crops in agriculture? What are the ecological implications of their introduction? Are there effective measures to control the spread of transgenes to wild relatives? This paper addresses these questions, with special emphasis on oilseed rape production in the UK, but includes examples from other crops and countries where appropriate.     

The Exploitation of Crop Allelopathy in Sustainable Agricultural Production

Crop allelopathy may be useful to minimize serious problems in the present agricultural production such as environmental pollution, unsafe products, human health concerns, depletion of crop diversity, soil sickness and reduction of crop productivity. Several crops including alfalfa, buckwheat, maize, rice, rye, sorghum, sunflower, wheat, etc. are affected either by their own toxicity or phytotoxin exudates when their residues decompose in the soil, that show strong suppression on weed emergences. Allelopathic crops when used as cover crop, mulch, smother crops, green manures, or grown in rotational sequences are helpful in reducing noxious weeds and plant pathogen, improve soil quality and crop yield. Those crop plants, particularly the legumes, incorporated at 1–2 tons ha⁻¹ (alfalfa, buckwheat, rice by-products), which can give weed reduction and increase of rice yield by 70 and 20 %, respectively, are suggested for use as natural herbicides. Allelochemicals from allelopathic crops may aid in the development of biological herbicides and pesticides. Cultivating a system with allelopathic crops plays an important role in the establishment of sustainable agriculture. The introduction of allelopathic traits from accessions with strong allelopathic potential to the target crops will enhance the efficacy of crop allelopathy in future agricultural production.     

Maize mesocotyl: Role in response to stress and deep-sowing tolerance

Maize (Zea mays L.) is one of the most important crops worldwide and is a model organism among cereal crops. Abiotic and biotic stresses are often present simultaneously and severely influence maize production, causing great yield losses worldwide. Therefore, the selection and cultivation of stress-tolerant maize lines that adapt to various stresses is instrumental in addressing the problem of yield losses caused by stress. The maize mesocotyl is the crucial organ that pushes shoots out of deep water or soil after seed germination. It has a simple anatomy and exhibits rapid growth in the dark. In this article, we reviewed the studies on the elongation of the maize mesocotyl and the actions of phytohormones, especially under deep-sowing conditions, and emphasized the role of the maize mesocotyl in response to environmental stress and deep-sowing tolerance. We propose that the maize mesocotyl can serve as a selection organ for evaluating stress tolerance at the early seedling stage. We also identify future research fields that need further investigation in studies of the maize mesocotyl.     

Coexistence Between GM and Non-GM Maize Crops – Tested in 2004 at the Field Scale Level (Erprobungsanbau 2004)

The objective of the study was to test the feasibility of coexistence between genetically modified (GM) and non‐GM maize under real‐life agronomical conditions. GM hybrid maize with the event MON810 (Bt maize) was drilled at 30 sites in fields surrounded by near isogenic conventional maize, although only 27 sites could be finally evaluated. Field sizes of Bt maize varied between 0.3 and 23 ha, and the flowering period of the Bt and conventional maize was synchronous. At some sites, different planting dates of GM and non‐GM maize or an earlier ripening conventional maize were tested in additional strips to obtain altered flowering and thereby reduce cross‐pollination. The overlapping of flowering periods was successfully avoided only at two sites where non‐GM maize was planted 25 or 28 days later. During harvest, samples were taken from the conventional maize in strips at distances of 0–10, 20–30, and 50–60 m to the Bt maize fields to assess the GM DNA content as a function of distance. Sampled materials included chaffed plant material intended for silage (18 sites), grains (eight sites), or crushed husks and cobs (one site). Wind effects were taken into account by sampling in all four compass directions. Quantitative PCR was used to detect the event specific MON810 DNA sequence in sampled materials. The analysis was conducted by two certified independent diagnostic testing companies selected in a pre‐test. Taking averages over all compass directions and the two laboratories no samples collected beyond 10 m had levels of GM above the threshold of 0.9 %. In conclusion, the data indicate that coexistence of GM and conventional maize is possible under real‐life large‐scale agronomical conditions. Levels of GM DNA in harvested grain resulting from outcrossing can be managed to levels below 0.9 % by simply planting 20 m of conventional maize as a pollen barrier between adjacent fields.     

Research and field monitoring on transgenic crops by the Centro Internacional de Mejoramiento de Maíz y Trigo (CIMMYT)

The International Maize and Wheat Improvement Center (CIMMYT) aims to genetically enhance both crops and generate public sector-provided products for the resource poor, e.g., drought tolerant wheat and insect resistant maize, and through international–national partnerships facilitate the acquisition of improved germplasm for non-mandate crops in the cropping systems where maize and wheat thrives; e.g., GM-papaya through a national food security undertaking in Bangladesh. The Center also engages in public awareness campaigns in projects such as Insect Resistance Maize for Africa (IRMA), which includes food, feed and environmental safety, monitoring of resistance and establishment of refugia, non-target effects and gene flow. Monitoring of genetic resources is a wide concern among the centers of the Consultative Group on International Agricultural Research (CGIAR), with an emphasis on the quality of gene banks. Decisions, policies and procedures about monitoring should be science-based, and this requires education, an area where CIMMYT and other CGIAR centers can play an important role. There will be a need to continue to evaluate the need for, and type of monitoring, as new (and unique) products are developed and released in the emergent economies of the world.     

Cover crops and interrow tillage for weed control in short season maize (Zea mays)

Weed competition can cause substantial maize (Zea mays L.) yield reductions. Interseeding maize with cover crops or a combination of interrow cultivation and interseeded cover crops are possible alternative methods of weed control. This study was conducted to examine the potential of interrow cultivation plus cover crops to reduce weed density in maize without reducing the grain yield. Field experiments were conducted in 1993 and 1994 at two sites in Québec to determine the effects of planting 12 cover crops with maize on weed control. Fall rye (Secale cereal L.), hairy vetch (Vicia villosa Roth), a mixture of red clover (Trifolium pratense L.) and ryegrass (Lolium multiflorum Lam), a mixture of white clover (Trifolium repens L.) and ryegrass, subterranean clover (Trifolium subterraneum L.), yellow sweet clover (Meliotus officinalis Lam), black medic (Medicago lupulina L.), Persian clover (Trifolium resupinatum L.), strawberry clover (Trifolium fragiferum L.), crimson clover (Trifolium incarnatum L.), alfalfa (Medicago sativa L.), and berseem clover (Trifolium alexandrinum L.) were seeded at two planting dates, 10 and 20 days after maize emergence. Interrow cultivation was carried out weekly until forage seeding, with a final cultivation being conducted just prior to cover crop seeding. Cover crop planting date did not affect maize yields or the ability of interrow tillage plus cover crops to suppress the development of weed populations. Maize yield was less affected by the interseeded cover crops under conditions of adequate rainfall. Corn planted in fields heavily infested with weeds resulted in substantial yield reductions even when rainfall was adequate. Except for 1993 at l'Assomption interrow tillage plus cover crop treatments had consistently lower weed biomass when compared to the weedy control. Most of the weed control was due to the interrow cultivation performed prior to seeding of the cover crops. The lowest weed density occurred in the herbicide treated plots. The ability of interrow tillage plus cover crops to suppress the development of weeds was affected by the level of weed infestation, the growing conditions and location. The cover crops provide additional weed control but the interrrow tillage or some herbicide application may still be necessary.     

秸秆还田研究进展及内蒙古玉米秸秆深翻还田现状

秸秆是培肥土壤重要的可再生资源,秸秆还田是培肥和改良土壤最为经济有效的技术措施,同时可解决田间焚烧秸秆所带来的大气污染问题。本文系统总结了秸秆还田的技术模式和培肥机理,阐述了秸秆还田对土壤理化性状、土壤养分与养分有效性、土壤酶活性与微生物、土壤温室气体减排和作物产量的影响,重点概述了内蒙古玉米秸秆深翻还田的研究进展,并对今后研究方向进行了展望。针对内蒙古平原灌区玉米生产现有的自然环境和农业栽培技术措施,以秸秆培肥土壤为切入点,提出了与农田生态环境相适应的秸秆深翻还田培肥模式。     

An overview of general features of risk assessments of genetically modified crops

The intentional introduction into the environment or market of genetically modified organisms (GMOs) is nearly always governed by a framework of science-based risk assessment and risk management measures. This is usually implemented through the integration of hazard identification and characterisation of all of the elements of risk associated with a new GM crop or derived product. Typical categories of hazards arising from the introduction of transgenic crops include: possible unintended negative health effects in a susceptible subgroup of the consumer (target) population; the evolution of resistance in the targeted pest/pathogen populations when the transgene confers resistance to a pest or pathogen; non-target hazards associated directly or indirectly with the transgenic plant or transgene product outside the plant; and those associated with the integration and subsequent expression of the transgene in a different organism or species following gene flow. The consequences of likely exposure to these and other hazards are considered in this introduction to the main issues raised when evaluating the possible risks arising from the importation or cultivation of genetically modified crops.     

玉米与旱地作物间作套种研究进展

玉米是重要的谷类作物之一,其丰产与否将对中国的粮食安全起着举足轻重的作用。实践证明,作物合理的间作套种具有充分利用资源和大幅度增加产量的特点。本文总结了旱地种植玉米与豆科作物、小麦、蔬菜以及其他一些旱地作物的间作套种的研究进展及一些实施成效。通过文献综合分析得出,玉米与旱地作物间作或套种的生产模式与单作栽培模式相比,不仅有利于提高作物产量与品质,而且有利于提高资源利用率。提出如何拓展与深化系统研究,着力构建技术体系与栽培标准,无疑是至关重要的,并且认为要将研究成果转化为能够应用于大面积实际生产的技术规范和栽培方法,服务于当今现代旱地农业生产是必要的也是亟待要探讨的。     

Determining indicators,methods and sites for monitoring potential adverse effects of genetically modified plants to the environment: the legal and conceptional framework for implementation

According to Directive 2001/18/EC commercial cultivation of genetically modified plants (GMPs) have to be monitored. The aim of the monitoring is to identify potential adverse effects of the GMPs and their use on human health and the environment. There are few concepts showing how GMP monitoring may be implemented. This article indicates monitoring requirements with a focus on environmental issues. GMP monitoring has to be appropriate to detect direct and indirect, immediate and long-term as well as unforeseen effects. For choosing suitable monitoring indicators and methods, we propose a case-by-case approach, which is hypothesis-driven and related to specified protection targets. We present criteria for selecting suitable monitoring sites and demonstrate possibilities to integrate GMP monitoring with existing environmental monitoring programmes. To ensure comparability, interpretability and quality of GMP monitoring data a harmonisation on both national and international level is proposed.     

基于尺度推绎方法的生态脆弱区耕作适宜性研究——以山西省寿阳县为例

以山西寿阳县的玉米和小麦为研究对象,应用尺度推绎方法开展机械化与传统耕作方式下区域粮食作物耕作适宜性的对比研究。结果表明：（1）传统耕作方式下玉米与小麦适宜种植面积皆要大于机械化耕作方式下两种作物适宜种植面积,而无论是机械化种植还是传统耕作小麦适宜种植区面积皆大于玉米种植适宜区.（2）两种作物种植适宜区空间分布呈两极化特征,即高度适宜区与永久非适宜区占据研究区绝大部分区域.（3）两种粮食作物高度种植适宜区基本集中在寿阳县北部黄土高原的塬、沟地貌区及坡度较小的山区。建议在机械化种植与传统耕作方式下皆是中、高度种植适宜区域采取机械化种植方式,而在仅适宜传统耕作的种植适宜区采取传统方式耕作。