轉基因作物一開始降低農藥使用量，但很快雜草抗藥，使得農藥用得比原來更多

轉基因作物一開始降低農藥使用量，但很快雜草抗藥，使得農藥比不種GMO時更多。 抗蟲的轉基因作物則引起其他害蟲的大量繁殖，降低作物產量的同時還增加農藥的用量。 同時轉基因作物還對生態，和消費者的健康有負麵影響。

以下是Woth網友以前的一個中文貼。 英文的文獻很多。 我就隻挑“科學（Science)”和“自然（Nature）”上的文章列在中文下麵了。

http://blog.wenxuecity.com/myblog/40113/201005/25356.html

科學（science)雜誌刊登了中國科學家關於轉基因棉花導致次生害蟲大爆發的文章
(2010-05-22 16:06:02) 下一個
今年5月14號的科學雜誌刊登了中國科學家關於轉基因棉花導致次生害蟲大爆發的文章。我國是產棉大戶，轉基因棉花當初就是為了防止棉花的主要害蟲棉鈴蟲而 研製的，可是這卻導致了其它害蟲的大量爆發。轉基因棉花不能抵抗其他害蟲，其結果可能就是造成棉花的減產，以及用到更多的農藥。這個結果和轉基因棉花當初 的“可以大量減少農藥使用”的宣傳完全不同啊。很多科學家都有預料到這個問題，現在中國的轉基因食品是大力推廣的時候麽？

記得上個月的科 學雜誌還刊登了一篇轉基因作物對農業可能有好處的文章，有趣的是這個好處也就是上麵說的可以大量減少農藥使用，然後還說了其他一些可能存在的問題（說明在 轉基因作物推廣上還是要謹慎啊）。結果還不到一個月的時間，科學雜誌就刊登了中國科學家長期研究轉基因作物的結果，這說明轉基因作物並不能完全解決“大量 減少農藥使用”的問題，這個明顯的“好處”已經出了問題了，也不知道還有沒有其他的“好處”會陸續被發現有問題呢？

轉基因作物對整個生態係統的影響（也包括對人類的影響）應該是長期的，因此在考慮推廣這些作物的時候，尤其是長期大量食用的作物，絕對應該是謹慎，謹慎，再謹慎啊

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《科學》刊文: 中國轉基因棉花盲蝽爆發（轉貼）
中國農業科學院植保所在《科學》發表報告稱，中國大麵積種植轉基因棉花造成盲蝽大爆發。
在中國北方一項長達十年的研究中發現，種植轉基因棉花來殺死它的主要害蟲棉鈴蟲，但卻可能導致其它昆蟲的大量爆發。上世紀90年代初期，棉鈴蟲爆發嚴重 打擊了棉花的產量和經濟效益，使用殺蟲劑控製棉鈴蟲會對環境造成危害，造成每年數千例的中毒死亡事件，1997年，中國政府大力推廣種植轉基因棉花，它能 產生一種來自綠芽孢杆菌（Bt）的毒素，可以有效殺死棉鈴蟲。
現在有超過400萬公頃的Bt轉基因棉花在中國種植。自從這種轉基因作物推廣以來，中國農業科學院的昆蟲學家吳孔明就帶領一個團隊對中國北方38個地方的害蟲種群進行監控，監控麵積覆蓋了300萬公頃棉花和2600萬公頃其它各種農作物。
盲蝽是盲蝽科（Miridae）一些昆蟲的統稱，以前在中國北方隻是一種數量較少、危害並不嚴重的害蟲。但是，研究人員發現自從1997年以來它們的數 量增加了12倍。“現在盲蝽成了北方地區的主要害蟲。”吳孔明說， “它們的數量大量增加與大規模種植Bt轉基因棉花有很大的關係。”吳孔明和他的同事推測盲蝽種群數量的激增與引進Bt轉基因棉花之後農田裏使用廣譜殺蟲劑 減少有關。“盲蝽對Bt毒素並不敏感，因此當農民不再使用殺蟲劑後它們就開始興盛蔓延。”吳孔明說。他們的研究成果發表在這周的《科學》雜誌上。
“盲蝽和棉鈴蟲一樣，如果不加控製可以使棉花減產高達50%。”吳孔明補充說。這些昆蟲同樣也會對其他農作物形成威脅，例如青豆、穀物、蔬菜和各種水果。
盲蝽爆發
盲蝽的爆發迫使農民重新使用殺蟲劑，目前他們使用殺蟲劑的數量已經達到引進Bt轉基因棉花前的2/3。吳孔明估計一旦盲蝽產生抗藥性，農民很快就會像以前一樣噴灑農藥了。
兩年以前，紐約科奈爾大學的經濟學家大衛?賈斯特（David Just）領導的一項研究認為中國種植物Bt轉基因棉花的經濟效益已經被損壞了。他們把原因歸結於為了對付次要害蟲而大量使用殺蟲劑。這個結論還存在爭 議，批評者的觀點主要集中在該研究采用了相對較小的樣本空間和經濟模型的應用。美國聖?保羅明尼蘇達大學的經濟學家大衛?安多（David Andow）指出，現在吳孔明的發現支持了這個早期的研究結果。
“這項調查結果再次提醒我們，轉基因農作物並不是控製農業害蟲百發百中的神奇子彈。” 安多表示，“他們隻能作為一個整體害蟲管理係統的一部分，才能保證長期的經濟效益。”
硝煙背後
每當把主要害蟲作為目標加以控製的時候，在同一地點其它物種就有可能迅速增加。例如，棉鈴象甲曾經是世界範圍內棉花的主要威脅。當農民針對棉鈴象甲噴灑 殺蟲劑時，棉鈴蟲卻產生了抗藥性，迅速增加成為了新主要害蟲。同樣的道理，自從Bt轉基因棉花引進之後，在美國南部臭椿象代替棉鈴蟲成為了主要害蟲。
隨著轉基因作物的大量推廣，安多表示，農民需要反應害蟲種群數量變化的有效係統。這需要基於對殺蟲劑使用的時機、劑量和頻率的研究，來應付新發生的害蟲。“當讓農民來決定如何控製害蟲的時候，他們更傾向於過度使用殺蟲劑。”安多說。
吳孔明和他的同事正在尋找利用殺蟲劑的最有效的方式，並且他們在棉田附近種植害蟲喜歡吃的普通作物來減少盲蝽對棉花的損害。同時中國研究人員也在試圖開 發能夠同時殺死棉鈴蟲和盲蝽的轉基因棉花品種。然而，吳孔明強調害蟲防控必須保持整個生態係統的視野。 “轉基因作物的影響必須在環境水平上進行評估，考慮到不同生物物種的生態環境上的投入。”他說，“這是確保它們的可持續性應用的唯一方法。”
英文鏈接：http://www.sciencemag.org/cgi/content/abstract/science.1187881

這是複旦學者做的工作

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”這篇文章也講中國轉基因棉花導致次生害蟲大爆發的文章
http://www.nature.com/news/2010/100513/full/news.2010.242.html

GM crop use makes minor pests major problem


“自然”這篇專門講中國是否應該種轉基因的水稻， 負麵問題比如對環境，生態的影響極大。 基本上人類從來沒幹過這事。 所以文中專家認為萬一做錯，後果不堪設想。
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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