转基因作物一开始降低农药使用量，但很快杂草抗药，使得农药比不种GMO时更多。 抗虫的转基因作物则引起其他害虫的大量繁殖，降低作物产量的同时还增加农药的用量。 同时转基因作物还对生态，和消费者的健康有负面影响。
以下是Woth网友以前的一个中文贴。 英文的文献很多。 我就只挑“科学（Science)”和“自然（Nature）”上的文章列在中文下面了。
http://blog.wenxuecity.com/myblog/40113/201005/25356.html
科学（science)杂志刊登了中国科学家关于转基因棉花导致次生害虫大爆发的文章
(2010-05-22 16:06:02) 下一个
今年5月14号的科学杂志刊登了中国科学家关于转基因棉花导致次生害虫大爆发的文章。我国是产棉大户，转基因棉花当初就是为了防止棉花的主要害虫棉铃虫而 研制的，可是这却导致了其它害虫的大量爆发。转基因棉花不能抵抗其他害虫，其结果可能就是造成棉花的减产，以及用到更多的农药。这个结果和转基因棉花当初 的“可以大量减少农药使用”的宣传完全不同啊。很多科学家都有预料到这个问题，现在中国的转基因食品是大力推广的时候么？
记得上个月的科 学杂志还刊登了一篇转基因作物对农业可能有好处的文章，有趣的是这个好处也就是上面说的可以大量减少农药使用，然后还说了其他一些可能存在的问题（说明在 转基因作物推广上还是要谨慎啊）。结果还不到一个月的时间，科学杂志就刊登了中国科学家长期研究转基因作物的结果，这说明转基因作物并不能完全解决“大量 减少农药使用”的问题，这个明显的“好处”已经出了问题了，也不知道还有没有其他的“好处”会陆续被发现有问题呢？
转基因作物对整个生态系统的影响（也包括对人类的影响）应该是长期的，因此在考虑推广这些作物的时候，尤其是长期大量食用的作物，绝对应该是谨慎，谨慎，再谨慎啊
------------------------------------------------------------------------------------------------------------------------
《科学》刊文: 中国转基因棉花盲蝽爆发（转贴）
中国农业科学院植保所在《科学》发表报告称，中国大面积种植转基因棉花造成盲蝽大爆发。
在中国北方一项长达十年的研究中发现，种植转基因棉花来杀死它的主要害虫棉铃虫，但却可能导致其它昆虫的大量爆发。上世纪90年代初期，棉铃虫爆发严重 打击了棉花的产量和经济效益，使用杀虫剂控制棉铃虫会对环境造成危害，造成每年数千例的中毒死亡事件，1997年，中国政府大力推广种植转基因棉花，它能 产生一种来自绿芽孢杆菌（Bt）的毒素，可以有效杀死棉铃虫。
现在有超过400万公顷的Bt转基因棉花在中国种植。自从这种转基因作物推广以来，中国农业科学院的昆虫学家吴孔明就带领一个团队对中国北方38个地方的害虫种群进行监控，监控面积覆盖了300万公顷棉花和2600万公顷其它各种农作物。
盲蝽是盲蝽科（Miridae）一些昆虫的统称，以前在中国北方只是一种数量较少、危害并不严重的害虫。但是，研究人员发现自从1997年以来它们的数 量增加了12倍。“现在盲蝽成了北方地区的主要害虫。”吴孔明说， “它们的数量大量增加与大规模种植Bt转基因棉花有很大的关系。”吴孔明和他的同事推测盲蝽种群数量的激增与引进Bt转基因棉花之后农田里使用广谱杀虫剂 减少有关。“盲蝽对Bt毒素并不敏感，因此当农民不再使用杀虫剂后它们就开始兴盛蔓延。”吴孔明说。他们的研究成果发表在这周的《科学》杂志上。
“盲蝽和棉铃虫一样，如果不加控制可以使棉花减产高达50%。”吴孔明补充说。这些昆虫同样也会对其他农作物形成威胁，例如青豆、谷物、蔬菜和各种水果。
盲蝽爆发
盲蝽的爆发迫使农民重新使用杀虫剂，目前他们使用杀虫剂的数量已经达到引进Bt转基因棉花前的2/3。吴孔明估计一旦盲蝽产生抗药性，农民很快就会像以前一样喷洒农药了。
两年以前，纽约科奈尔大学的经济学家大卫?贾斯特（David Just）领导的一项研究认为中国种植物Bt转基因棉花的经济效益已经被损坏了。他们把原因归结于为了对付次要害虫而大量使用杀虫剂。这个结论还存在争 议，批评者的观点主要集中在该研究采用了相对较小的样本空间和经济模型的应用。美国圣?保罗明尼苏达大学的经济学家大卫?安多（David Andow）指出，现在吴孔明的发现支持了这个早期的研究结果。
“这项调查结果再次提醒我们，转基因农作物并不是控制农业害虫百发百中的神奇子弹。” 安多表示，“他们只能作为一个整体害虫管理系统的一部分，才能保证长期的经济效益。”
硝烟背后
每当把主要害虫作为目标加以控制的时候，在同一地点其它物种就有可能迅速增加。例如，棉铃象甲曾经是世界范围内棉花的主要威胁。当农民针对棉铃象甲喷洒 杀虫剂时，棉铃虫却产生了抗药性，迅速增加成为了新主要害虫。同样的道理，自从Bt转基因棉花引进之后，在美国南部臭椿象代替棉铃虫成为了主要害虫。
随着转基因作物的大量推广，安多表示，农民需要反应害虫种群数量变化的有效系统。这需要基于对杀虫剂使用的时机、剂量和频率的研究，来应付新发生的害虫。“当让农民来决定如何控制害虫的时候，他们更倾向于过度使用杀虫剂。”安多说。
吴孔明和他的同事正在寻找利用杀虫剂的最有效的方式，并且他们在棉田附近种植害虫喜欢吃的普通作物来减少盲蝽对棉花的损害。同时中国研究人员也在试图开 发能够同时杀死棉铃虫和盲蝽的转基因棉花品种。然而，吴孔明强调害虫防控必须保持整个生态系统的视野。 “转基因作物的影响必须在环境水平上进行评估，考虑到不同生物物种的生态环境上的投入。”他说，“这是确保它们的可持续性应用的唯一方法。”
英文链接：http://www.sciencemag.org/cgi/content/abstract/science.1187881
这是复旦学者做的工作
http://www.nature.com/news/genetically-modified-crops-pass-benefits-to-weeds-1.13517
Genetically modified crops pass benefits to weeds
Herbicide resistance could confer an advantage on plants in the wild.
“自然”这篇文章也讲中国转基因棉花导致次生害虫大爆发的文章
http://www.nature.com/news/2010/100513/full/news.2010.242.html
GM crop use makes minor pests major problem
“自然”这篇专门讲中国是否应该种转基因的水稻， 负面问题比如对环境，生态的影响极大。 基本上人类从来没干过这事。 所以文中专家认为万一做错，后果不堪设想。
http://www.nature.com/news/2008/081015/full/455850a.html
Agriculture: Is China ready for GM rice?
In an effort to avoid a food crisis as the population grows, China is putting its weight behind genetically modified strains of the country's staple food crop. Jane Qiu explores the reasons for the unprecedented push.
Jane Qiu
WANG FENG
In a paddy field 30 kilometres south of Fuzhou, the capital of China's Fujian province, Wang Feng is surveying a massive green and yellow chessboard before him. Wang, a rice researcher at the Fujian Academy of Agricultural Sciences, and his colleagues have been developing genetically modified (GM) rice strains to resist pest infestation, and have been testing in these plots for a decade. Two strains from Wang's team are now awaiting regulatory approval by the agricultural ministry for commercial growth. It could represent the largest commercialization of a GM foodcrop. Rice is a staple for most of the country's 1.3 billion people and a primary source of calories for more than half the world's population.
China's population is set to top 1.45 billion by 2020, and the country needs to increase grain production by about 25%, a daunting task in the face of increasing urbanization, industrialization, farmland reduction and the efflux of rural workers to the cities. The Chinese government has latched on to transgenic plants as a solution, rolling out a major research and development initiative on GM crops for the next 12 years, including a sizeable investment of 25 billion yuan (US$3.7 billion) from the central government and additional matched funding from its provincial counterparts.
The bigger picture
Like GM initiatives elsewhere, such as in the United States, the move has drawn its share of criticism, with concerns being raised about the practicality and safety of such a push. Scientists warn that a single-minded focus on genetic engineering to enhance pest resistance misses the bigger picture of how to address agricultural production. China is the world's largest rice producer, weighing in with nearly 200 million tonnes, and several observers fear that introducing GM rice could endanger the food supply and the environment. "The consequences would be unthinkable if large-scale cultivation of GM rice were not properly regulated," says Xue Dayuan, chief scientist on biodiversity at the Nanjing Institute of Environmental Sciences. But in a country where policies are rarely a matter of open debate, government officials warn that the scale of the impending food shortage makes further delays an unaffordable luxury. "This is the only way to meet the growing food demand in China," says Huang Dafang, former director of the Biotechnology Research Institute of the Chinese Academy of Agricultural Sciences (CAAS) in Beijing.
Stem borers can limit rice yields.WANG FENG
Wang is optimistic that his group's pest-resistant GM rice will help lead the way. In April, the team planted alternating squares of conventional rice crops and crops genetically modified to produce an insecticidal toxin made by the bacterium Bacillus thuringiensis (Bt) gene and the cowpea trypsin inhibitor (CpTI) gene. In the absence of chemical pesticides, Bt/CpTI rice thrived, whereas the conventional plants withered, resulting in the chessboard pattern of alternating colours. Wang pulls the top from one of the non-transgenic plants. Unrolling its leaves and splitting its stem, he reveals the insecticides' primary target, the stem borer.
Wang says stem borers can affect 3.3 million hectares of rice fields, resulting in a 5% loss in yields at a cost of 10 billion yuan a year. According to Zhu Zhen, a geneticist at the Beijing-based Institute of Genetics and Developmental Biology, Chinese Academy of Sciences (CAS), who developed the rice strains with Bt and CpTI genes, there are no naturally occurring strains that can confer such resistance. After ten years of field testing at a dozen locations, the researchers are confident that farmers would use less pesticide with GM rice strains1.
Plagued by pests
But David Andow, an entomologist at the University of Minnesota in St Paul, says he is unconvinced. In the past few decades, the stem borer has been overtaken by another pest, the brown planthopper (Nilaparvata lugens), which wreaks havoc every spring and has become the main concern of farmers in Asia. Bt and CpTI toxins have no effect on the insect.
Moreover, many simply see GM approaches as ham-fisted in the face of complex ecologies. Kong Luen Heong, an entomologist at the International Rice Research Institute in Los Ba?os, the Philippines, calls pest-resistant GM crops a short-term fix for long-term problems caused by crop monoculture and overuse of broad-spectrum pesticides. "Pests thrive where biodiversity is at peril," says Heong. "Instead of genetic engineering, why don't we engineer the ecology by increasing biodiversity?"
Indeed, such ecological engineering has proved beneficial. Zhu Youyong, president of the Yunnan Agricultural University in Kunming, and his colleagues have found that growing a mixture of rice varieties across thousands of farms in China could greatly limit the development of rice blast — a fungal rice disease — and boost the yield2. They have also tested similar practices using different crops and found beneficial effects.
Although GM crops are, in principle, compatible with such an ecological approach, it requires management that has proved hard to achieve within China's agricultural system, which is based on small-scale cultivation, says Xue. Although Bt cotton, the biggest GM crop produced in China to date, has put the cotton bollworm (Helicoverpa armigera) under control, the population of secondary pests, such as mirids, has risen since 2001. That has led to increased pesticide use3, 4, but still at levels lower than pre-1997, when the cotton was introduced.
Safety concerns
Debates have also flared because of rice's central role in the Chinese diet. One concern has been that antibiotic-resistance marker genes used in the derivation of the transgenic plants could invariably be taken up by naturally occurring gut bacteria and lead to resistant, pathogenic strains. Both of Zhu Zhen's Bt/CpTI rice lines and other Bt strains developed elsewhere are free of such markers.
WANG FENG
The GM plants must also be shown to be non-allergenic. Composition tests and studies assessing toxicity in non-human animals allow the developers to claim that the GM rice varieties are "substantially equivalent" to unmodified counterparts apart from the target-gene expression. But for food eaten three times a day by a billion people, short-term animal studies aren't enough to measure equivalence. "If there were a health risk, we would be heading for a major disaster," warns Liu Bing, an expert on science and society in Tsinghua University in Beijing.
Another concern is the potential environmental consequences of transgenes escaping from GM rice to its unmodified crop counterparts through cross-pollination. Several escapes have occurred around the world, including releases of unapproved GM crops such as rice and corn into human consumption streams. For example, in 2006, the European Union halted imports of US rice when an unapproved strain was found in the food supply. Trade resumed, but the problem of accidental cross-pollination, which is thought to have caused the contamination, is one that has not yet been solved. The consensus seems to be that perfect prevention of such events is impossible5.
“Using GM rice is the only way to meet the growing food demand.”
Lu Baorong, a biodiversity researcher at Fudan University in Shanghai, is concerned about gene flow from GM rice to its wild or weedy relatives. Wild-rice plants are undomesticated strains, whereas weedy rice, which is characterized by its seed scattering and dormancy, is thought to originate from rice crops as a result of mutations. Lu's team and another group have shown that the rate of gene flow from GM strains to wild and weedy rice is 3–18% and 0.01–0.5%, respectively6, 7.
"What is most worrying is that such gene flow is cumulative," says Lu. Although rice crops are harvested at the end of the season, wild and weedy rice carrying transgenes would continue to reproduce, allowing the genes to spread, subject to selection.
This could threaten the biodiversity of wild rice, which provides a valuable gene pool for rice breeders (see 'The panda of the plant world') but is already at the brink of extinction in China. In addition, weedy rice with pest-resistant or other fitness genes could have a greater capacity to infest rice fields, causing yield loss. However, Lu says that these are not inevitable consequences of large-scale cultivation of GM rice. "Proper regulation is the key," he says.
A regulatory mess
But regulation, says Xue, is where the majority of problems lie. "Field testing is one thing, but the reality is quite another." Although China has had biosafety regulations for GM crops since 1996, their implementation has proved uneven — a fact that most people approached by Nature acknowledged. In some provinces, such as Xinjiang, farmers began large-scale cultivation of Bt cotton long before approval was granted, says Xue. In several cases, Bt cotton strains were grown without proper labelling, some of which were experimental strains from research institutes.
Cross pollination and labelling slip-ups could be disastrous for China's exports of rice and rice-related products. And proper regulation of GM crops is crucial for delaying the emergence of resistant pests. Many crops, such as cotton and rice, are grown as a monoculture in China, which would select pests that are resistant to the toxins. One way to avoid this from happening is to use seeds that produce high toxin levels; another way is to set aside some land near GM-crop fields for its unmodified counterparts, which would serve as a 'refuge' for insects.
Chinese researchers are working to reduce pest infestation in the paddy fields of Fujian.J. QIU
This 'high-dose and refuge' strategy, which has been widely adopted in countries that grow GM crops, is difficult to implement in China. Many Chinese farmers exchange seeds with each other or buy cheap seeds from illegal dealers, and end up growing cotton plants with low levels of Bt toxin. In addition, as agricultural practices in China are based on small-scale cultivation by individual families with limited resources, Bt cotton plants are grown without refuge areas.
Fortunately, the cotton bollworm also attacks crops such as wheat, corn, soya beans, peanuts and vegetables, which are grown next to the Bt-cotton fields and offer a safety valve against resistance8, 9. "This is unlikely to happen with Bt/CpTI rice because the stem borer feeds only on rice," says Heong. "Therefore, setting aside refuge areas is absolutely essential."
Behind closed doors
Worryingly, many of the stakeholders, including farmers, bioethicists and environmental groups, aren't being involved in the biosafety evaluation process as spearheaded by the agricultural ministry. The country hails GM rice as a magic bullet for food-production problems and few dissenting opinions are heard. "The whole process is rather opaque," says David Just, an economist at Cornell University in Ithaca, New York. "China is trying very hard to keep the lid on." Experts who express their concerns are often sidelined. Xue, for example, has been repeatedly excluded from biosafety committees that are assessing GM crops.
“The consequences would be unthinkable if larger-scale cultivation of GM rice were not properly regulated.”
Despite these concerns, China does need to find a way to feed its swelling population. Although it has instigated plans to prevent further reduction in farmlands, boosting grain production remains the key to food security. Still, the single-minded focus on genetic modification seems misguided to many. "Genetic-modification technologies just treat the symptoms rather than dealing with the causes," says Hans Herren, president of the Millennium Institute in Arlington, Virginia, and a co-chair of the International Assessment of Agricultural Knowledge, Science and Technology for Development (IAASTD). According to a report released by the IAASTD in April, the main challenges faced by agricultural development around the world are soil fertility, water management and climate change10. "Life in the soil is gone after decades of heavy use of pesticides, herbicides and chemical fertilizers," says Manuela Giovannetti, a soil microbiologist at the University of Pisa in Italy. Herren agrees: "Without a concerted global effort to restore soil fertility, genetic modification would be futile."
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Xue says he recognizes the potential of genetic modification, but is concerned that huge investment in the technologies — as with China's new initiative — would sap already dwindling attention from improving traditional plant-breeding technologies and conventional farming practices. However, GM strategies have a strong draw for keeping China competitive at the cutting edge of agriculture. A report by the International Service for the Acquisition of Agri-biotech Applications estimates that biotech rice could deliver benefits of $4 billion per year for China11.
"What is behind all this might be about who controls germ plasm and who owns intellectual-property rights," says Andow. The scale of the effect that commercial GM rice could have on China and the rest of the world argues for caution. Nevertheless, many interests within the country say that the time to act is now. Huang puts it bluntly: "We cannot afford to think too far ahead but must tackle the present issues."
Jane Qiu writes for Nature from Beijing.
? References
1. Huang, J., Hu, R., Rozelle, S. & Pray, C. Science 308, 688–690 (2005).
2. Zhu, Y. et al. Nature 406, 718–722 (2000).
3. Wang, S., Just, D. & Pinstrup-Andersen, P. Int. J. Biotechnol. 10, 113–120 (2008).
4. Wang, Z. et al. Agric. Sci. China (in the press).
5. Ledford, H. Nature 445, 132–133 (2007).
6. Wang, F. et al. Plant Biotechnol. J. 4, 667–676 (2006).
7. Shivraina, V. K. et al. Crop Protection 26, 349–356 (2007).
8. Wu, K.-M., Lu, Y.-H., Feng, H.-Q., Jiang, Y.-Y. & Zhao, J.-Z. Science 321, 1676–1678 (2008).
9. Qiu, J. Nature doi:10.1038/news.2008.1118 (2008).
10. Beintema, N. et al. International Assessment of Agricultural Knowledge, Science and Technology for Development: Global Summary for Decision Makers (IAASTD, 2008); available at http://www.agassessment.org/index.cfm?Page=IAASTD%20Reports&ItemID=2713
11. James, C. Global Status of Commercialized Biotech/GM Crops: 2007 ISAAA Brief No. 37. (ISAAA, 2007); available at http://www.isaaa.org/Resources/Publications/briefs/37/executivesummary/default.html
以下是Woth网友以前的一个中文贴。 英文的文献很多。 我就只挑“科学（Science)”和“自然（Nature）”上的文章列在中文下面了。
http://blog.wenxuecity.com/myblog/40113/201005/25356.html
科学（science)杂志刊登了中国科学家关于转基因棉花导致次生害虫大爆发的文章
(2010-05-22 16:06:02) 下一个
今年5月14号的科学杂志刊登了中国科学家关于转基因棉花导致次生害虫大爆发的文章。我国是产棉大户，转基因棉花当初就是为了防止棉花的主要害虫棉铃虫而 研制的，可是这却导致了其它害虫的大量爆发。转基因棉花不能抵抗其他害虫，其结果可能就是造成棉花的减产，以及用到更多的农药。这个结果和转基因棉花当初 的“可以大量减少农药使用”的宣传完全不同啊。很多科学家都有预料到这个问题，现在中国的转基因食品是大力推广的时候么？
记得上个月的科 学杂志还刊登了一篇转基因作物对农业可能有好处的文章，有趣的是这个好处也就是上面说的可以大量减少农药使用，然后还说了其他一些可能存在的问题（说明在 转基因作物推广上还是要谨慎啊）。结果还不到一个月的时间，科学杂志就刊登了中国科学家长期研究转基因作物的结果，这说明转基因作物并不能完全解决“大量 减少农药使用”的问题，这个明显的“好处”已经出了问题了，也不知道还有没有其他的“好处”会陆续被发现有问题呢？
转基因作物对整个生态系统的影响（也包括对人类的影响）应该是长期的，因此在考虑推广这些作物的时候，尤其是长期大量食用的作物，绝对应该是谨慎，谨慎，再谨慎啊
------------------------------------------------------------------------------------------------------------------------
《科学》刊文: 中国转基因棉花盲蝽爆发（转贴）
中国农业科学院植保所在《科学》发表报告称，中国大面积种植转基因棉花造成盲蝽大爆发。
在中国北方一项长达十年的研究中发现，种植转基因棉花来杀死它的主要害虫棉铃虫，但却可能导致其它昆虫的大量爆发。上世纪90年代初期，棉铃虫爆发严重 打击了棉花的产量和经济效益，使用杀虫剂控制棉铃虫会对环境造成危害，造成每年数千例的中毒死亡事件，1997年，中国政府大力推广种植转基因棉花，它能 产生一种来自绿芽孢杆菌（Bt）的毒素，可以有效杀死棉铃虫。
现在有超过400万公顷的Bt转基因棉花在中国种植。自从这种转基因作物推广以来，中国农业科学院的昆虫学家吴孔明就带领一个团队对中国北方38个地方的害虫种群进行监控，监控面积覆盖了300万公顷棉花和2600万公顷其它各种农作物。
盲蝽是盲蝽科（Miridae）一些昆虫的统称，以前在中国北方只是一种数量较少、危害并不严重的害虫。但是，研究人员发现自从1997年以来它们的数 量增加了12倍。“现在盲蝽成了北方地区的主要害虫。”吴孔明说， “它们的数量大量增加与大规模种植Bt转基因棉花有很大的关系。”吴孔明和他的同事推测盲蝽种群数量的激增与引进Bt转基因棉花之后农田里使用广谱杀虫剂 减少有关。“盲蝽对Bt毒素并不敏感，因此当农民不再使用杀虫剂后它们就开始兴盛蔓延。”吴孔明说。他们的研究成果发表在这周的《科学》杂志上。
“盲蝽和棉铃虫一样，如果不加控制可以使棉花减产高达50%。”吴孔明补充说。这些昆虫同样也会对其他农作物形成威胁，例如青豆、谷物、蔬菜和各种水果。
盲蝽爆发
盲蝽的爆发迫使农民重新使用杀虫剂，目前他们使用杀虫剂的数量已经达到引进Bt转基因棉花前的2/3。吴孔明估计一旦盲蝽产生抗药性，农民很快就会像以前一样喷洒农药了。
两年以前，纽约科奈尔大学的经济学家大卫?贾斯特（David Just）领导的一项研究认为中国种植物Bt转基因棉花的经济效益已经被损坏了。他们把原因归结于为了对付次要害虫而大量使用杀虫剂。这个结论还存在争 议，批评者的观点主要集中在该研究采用了相对较小的样本空间和经济模型的应用。美国圣?保罗明尼苏达大学的经济学家大卫?安多（David Andow）指出，现在吴孔明的发现支持了这个早期的研究结果。
“这项调查结果再次提醒我们，转基因农作物并不是控制农业害虫百发百中的神奇子弹。” 安多表示，“他们只能作为一个整体害虫管理系统的一部分，才能保证长期的经济效益。”
硝烟背后
每当把主要害虫作为目标加以控制的时候，在同一地点其它物种就有可能迅速增加。例如，棉铃象甲曾经是世界范围内棉花的主要威胁。当农民针对棉铃象甲喷洒 杀虫剂时，棉铃虫却产生了抗药性，迅速增加成为了新主要害虫。同样的道理，自从Bt转基因棉花引进之后，在美国南部臭椿象代替棉铃虫成为了主要害虫。
随着转基因作物的大量推广，安多表示，农民需要反应害虫种群数量变化的有效系统。这需要基于对杀虫剂使用的时机、剂量和频率的研究，来应付新发生的害虫。“当让农民来决定如何控制害虫的时候，他们更倾向于过度使用杀虫剂。”安多说。
吴孔明和他的同事正在寻找利用杀虫剂的最有效的方式，并且他们在棉田附近种植害虫喜欢吃的普通作物来减少盲蝽对棉花的损害。同时中国研究人员也在试图开 发能够同时杀死棉铃虫和盲蝽的转基因棉花品种。然而，吴孔明强调害虫防控必须保持整个生态系统的视野。 “转基因作物的影响必须在环境水平上进行评估，考虑到不同生物物种的生态环境上的投入。”他说，“这是确保它们的可持续性应用的唯一方法。”
英文链接：http://www.sciencemag.org/cgi/content/abstract/science.1187881
这是复旦学者做的工作
http://www.nature.com/news/genetically-modified-crops-pass-benefits-to-weeds-1.13517
Genetically modified crops pass benefits to weeds
Herbicide resistance could confer an advantage on plants in the wild.
“自然”这篇文章也讲中国转基因棉花导致次生害虫大爆发的文章
http://www.nature.com/news/2010/100513/full/news.2010.242.html
GM crop use makes minor pests major problem
“自然”这篇专门讲中国是否应该种转基因的水稻， 负面问题比如对环境，生态的影响极大。 基本上人类从来没干过这事。 所以文中专家认为万一做错，后果不堪设想。
http://www.nature.com/news/2008/081015/full/455850a.html
Agriculture: Is China ready for GM rice?
In an effort to avoid a food crisis as the population grows, China is putting its weight behind genetically modified strains of the country's staple food crop. Jane Qiu explores the reasons for the unprecedented push.
Jane Qiu
WANG FENG
In a paddy field 30 kilometres south of Fuzhou, the capital of China's Fujian province, Wang Feng is surveying a massive green and yellow chessboard before him. Wang, a rice researcher at the Fujian Academy of Agricultural Sciences, and his colleagues have been developing genetically modified (GM) rice strains to resist pest infestation, and have been testing in these plots for a decade. Two strains from Wang's team are now awaiting regulatory approval by the agricultural ministry for commercial growth. It could represent the largest commercialization of a GM foodcrop. Rice is a staple for most of the country's 1.3 billion people and a primary source of calories for more than half the world's population.
China's population is set to top 1.45 billion by 2020, and the country needs to increase grain production by about 25%, a daunting task in the face of increasing urbanization, industrialization, farmland reduction and the efflux of rural workers to the cities. The Chinese government has latched on to transgenic plants as a solution, rolling out a major research and development initiative on GM crops for the next 12 years, including a sizeable investment of 25 billion yuan (US$3.7 billion) from the central government and additional matched funding from its provincial counterparts.
The bigger picture
Like GM initiatives elsewhere, such as in the United States, the move has drawn its share of criticism, with concerns being raised about the practicality and safety of such a push. Scientists warn that a single-minded focus on genetic engineering to enhance pest resistance misses the bigger picture of how to address agricultural production. China is the world's largest rice producer, weighing in with nearly 200 million tonnes, and several observers fear that introducing GM rice could endanger the food supply and the environment. "The consequences would be unthinkable if large-scale cultivation of GM rice were not properly regulated," says Xue Dayuan, chief scientist on biodiversity at the Nanjing Institute of Environmental Sciences. But in a country where policies are rarely a matter of open debate, government officials warn that the scale of the impending food shortage makes further delays an unaffordable luxury. "This is the only way to meet the growing food demand in China," says Huang Dafang, former director of the Biotechnology Research Institute of the Chinese Academy of Agricultural Sciences (CAAS) in Beijing.
Stem borers can limit rice yields.WANG FENG
Wang is optimistic that his group's pest-resistant GM rice will help lead the way. In April, the team planted alternating squares of conventional rice crops and crops genetically modified to produce an insecticidal toxin made by the bacterium Bacillus thuringiensis (Bt) gene and the cowpea trypsin inhibitor (CpTI) gene. In the absence of chemical pesticides, Bt/CpTI rice thrived, whereas the conventional plants withered, resulting in the chessboard pattern of alternating colours. Wang pulls the top from one of the non-transgenic plants. Unrolling its leaves and splitting its stem, he reveals the insecticides' primary target, the stem borer.
Wang says stem borers can affect 3.3 million hectares of rice fields, resulting in a 5% loss in yields at a cost of 10 billion yuan a year. According to Zhu Zhen, a geneticist at the Beijing-based Institute of Genetics and Developmental Biology, Chinese Academy of Sciences (CAS), who developed the rice strains with Bt and CpTI genes, there are no naturally occurring strains that can confer such resistance. After ten years of field testing at a dozen locations, the researchers are confident that farmers would use less pesticide with GM rice strains1.
Plagued by pests
But David Andow, an entomologist at the University of Minnesota in St Paul, says he is unconvinced. In the past few decades, the stem borer has been overtaken by another pest, the brown planthopper (Nilaparvata lugens), which wreaks havoc every spring and has become the main concern of farmers in Asia. Bt and CpTI toxins have no effect on the insect.
Moreover, many simply see GM approaches as ham-fisted in the face of complex ecologies. Kong Luen Heong, an entomologist at the International Rice Research Institute in Los Ba?os, the Philippines, calls pest-resistant GM crops a short-term fix for long-term problems caused by crop monoculture and overuse of broad-spectrum pesticides. "Pests thrive where biodiversity is at peril," says Heong. "Instead of genetic engineering, why don't we engineer the ecology by increasing biodiversity?"
Indeed, such ecological engineering has proved beneficial. Zhu Youyong, president of the Yunnan Agricultural University in Kunming, and his colleagues have found that growing a mixture of rice varieties across thousands of farms in China could greatly limit the development of rice blast — a fungal rice disease — and boost the yield2. They have also tested similar practices using different crops and found beneficial effects.
Although GM crops are, in principle, compatible with such an ecological approach, it requires management that has proved hard to achieve within China's agricultural system, which is based on small-scale cultivation, says Xue. Although Bt cotton, the biggest GM crop produced in China to date, has put the cotton bollworm (Helicoverpa armigera) under control, the population of secondary pests, such as mirids, has risen since 2001. That has led to increased pesticide use3, 4, but still at levels lower than pre-1997, when the cotton was introduced.
Safety concerns
Debates have also flared because of rice's central role in the Chinese diet. One concern has been that antibiotic-resistance marker genes used in the derivation of the transgenic plants could invariably be taken up by naturally occurring gut bacteria and lead to resistant, pathogenic strains. Both of Zhu Zhen's Bt/CpTI rice lines and other Bt strains developed elsewhere are free of such markers.
WANG FENG
The GM plants must also be shown to be non-allergenic. Composition tests and studies assessing toxicity in non-human animals allow the developers to claim that the GM rice varieties are "substantially equivalent" to unmodified counterparts apart from the target-gene expression. But for food eaten three times a day by a billion people, short-term animal studies aren't enough to measure equivalence. "If there were a health risk, we would be heading for a major disaster," warns Liu Bing, an expert on science and society in Tsinghua University in Beijing.
Another concern is the potential environmental consequences of transgenes escaping from GM rice to its unmodified crop counterparts through cross-pollination. Several escapes have occurred around the world, including releases of unapproved GM crops such as rice and corn into human consumption streams. For example, in 2006, the European Union halted imports of US rice when an unapproved strain was found in the food supply. Trade resumed, but the problem of accidental cross-pollination, which is thought to have caused the contamination, is one that has not yet been solved. The consensus seems to be that perfect prevention of such events is impossible5.
“Using GM rice is the only way to meet the growing food demand.”
Lu Baorong, a biodiversity researcher at Fudan University in Shanghai, is concerned about gene flow from GM rice to its wild or weedy relatives. Wild-rice plants are undomesticated strains, whereas weedy rice, which is characterized by its seed scattering and dormancy, is thought to originate from rice crops as a result of mutations. Lu's team and another group have shown that the rate of gene flow from GM strains to wild and weedy rice is 3–18% and 0.01–0.5%, respectively6, 7.
"What is most worrying is that such gene flow is cumulative," says Lu. Although rice crops are harvested at the end of the season, wild and weedy rice carrying transgenes would continue to reproduce, allowing the genes to spread, subject to selection.
This could threaten the biodiversity of wild rice, which provides a valuable gene pool for rice breeders (see 'The panda of the plant world') but is already at the brink of extinction in China. In addition, weedy rice with pest-resistant or other fitness genes could have a greater capacity to infest rice fields, causing yield loss. However, Lu says that these are not inevitable consequences of large-scale cultivation of GM rice. "Proper regulation is the key," he says.
A regulatory mess
But regulation, says Xue, is where the majority of problems lie. "Field testing is one thing, but the reality is quite another." Although China has had biosafety regulations for GM crops since 1996, their implementation has proved uneven — a fact that most people approached by Nature acknowledged. In some provinces, such as Xinjiang, farmers began large-scale cultivation of Bt cotton long before approval was granted, says Xue. In several cases, Bt cotton strains were grown without proper labelling, some of which were experimental strains from research institutes.
Cross pollination and labelling slip-ups could be disastrous for China's exports of rice and rice-related products. And proper regulation of GM crops is crucial for delaying the emergence of resistant pests. Many crops, such as cotton and rice, are grown as a monoculture in China, which would select pests that are resistant to the toxins. One way to avoid this from happening is to use seeds that produce high toxin levels; another way is to set aside some land near GM-crop fields for its unmodified counterparts, which would serve as a 'refuge' for insects.
Chinese researchers are working to reduce pest infestation in the paddy fields of Fujian.J. QIU
This 'high-dose and refuge' strategy, which has been widely adopted in countries that grow GM crops, is difficult to implement in China. Many Chinese farmers exchange seeds with each other or buy cheap seeds from illegal dealers, and end up growing cotton plants with low levels of Bt toxin. In addition, as agricultural practices in China are based on small-scale cultivation by individual families with limited resources, Bt cotton plants are grown without refuge areas.
Fortunately, the cotton bollworm also attacks crops such as wheat, corn, soya beans, peanuts and vegetables, which are grown next to the Bt-cotton fields and offer a safety valve against resistance8, 9. "This is unlikely to happen with Bt/CpTI rice because the stem borer feeds only on rice," says Heong. "Therefore, setting aside refuge areas is absolutely essential."
Behind closed doors
Worryingly, many of the stakeholders, including farmers, bioethicists and environmental groups, aren't being involved in the biosafety evaluation process as spearheaded by the agricultural ministry. The country hails GM rice as a magic bullet for food-production problems and few dissenting opinions are heard. "The whole process is rather opaque," says David Just, an economist at Cornell University in Ithaca, New York. "China is trying very hard to keep the lid on." Experts who express their concerns are often sidelined. Xue, for example, has been repeatedly excluded from biosafety committees that are assessing GM crops.
“The consequences would be unthinkable if larger-scale cultivation of GM rice were not properly regulated.”
Despite these concerns, China does need to find a way to feed its swelling population. Although it has instigated plans to prevent further reduction in farmlands, boosting grain production remains the key to food security. Still, the single-minded focus on genetic modification seems misguided to many. "Genetic-modification technologies just treat the symptoms rather than dealing with the causes," says Hans Herren, president of the Millennium Institute in Arlington, Virginia, and a co-chair of the International Assessment of Agricultural Knowledge, Science and Technology for Development (IAASTD). According to a report released by the IAASTD in April, the main challenges faced by agricultural development around the world are soil fertility, water management and climate change10. "Life in the soil is gone after decades of heavy use of pesticides, herbicides and chemical fertilizers," says Manuela Giovannetti, a soil microbiologist at the University of Pisa in Italy. Herren agrees: "Without a concerted global effort to restore soil fertility, genetic modification would be futile."
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Xue says he recognizes the potential of genetic modification, but is concerned that huge investment in the technologies — as with China's new initiative — would sap already dwindling attention from improving traditional plant-breeding technologies and conventional farming practices. However, GM strategies have a strong draw for keeping China competitive at the cutting edge of agriculture. A report by the International Service for the Acquisition of Agri-biotech Applications estimates that biotech rice could deliver benefits of $4 billion per year for China11.
"What is behind all this might be about who controls germ plasm and who owns intellectual-property rights," says Andow. The scale of the effect that commercial GM rice could have on China and the rest of the world argues for caution. Nevertheless, many interests within the country say that the time to act is now. Huang puts it bluntly: "We cannot afford to think too far ahead but must tackle the present issues."
Jane Qiu writes for Nature from Beijing.
? References
1. Huang, J., Hu, R., Rozelle, S. & Pray, C. Science 308, 688–690 (2005).
2. Zhu, Y. et al. Nature 406, 718–722 (2000).
3. Wang, S., Just, D. & Pinstrup-Andersen, P. Int. J. Biotechnol. 10, 113–120 (2008).
4. Wang, Z. et al. Agric. Sci. China (in the press).
5. Ledford, H. Nature 445, 132–133 (2007).
6. Wang, F. et al. Plant Biotechnol. J. 4, 667–676 (2006).
7. Shivraina, V. K. et al. Crop Protection 26, 349–356 (2007).
8. Wu, K.-M., Lu, Y.-H., Feng, H.-Q., Jiang, Y.-Y. & Zhao, J.-Z. Science 321, 1676–1678 (2008).
9. Qiu, J. Nature doi:10.1038/news.2008.1118 (2008).
10. Beintema, N. et al. International Assessment of Agricultural Knowledge, Science and Technology for Development: Global Summary for Decision Makers (IAASTD, 2008); available at http://www.agassessment.org/index.cfm?Page=IAASTD%20Reports&ItemID=2713
11. James, C. Global Status of Commercialized Biotech/GM Crops: 2007 ISAAA Brief No. 37. (ISAAA, 2007); available at http://www.isaaa.org/Resources/Publications/briefs/37/executivesummary/default.html
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