科学家揭露草甘膦毒害农作物和土壤

            遗传修饰（转基因）崩溃续

科学家们继续向公众制造由抗草甘膦作物产生的对生态系统造成毁灭性的影响，而美国农业部保持沉默。侯美婉博士

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世界最广泛使用的除草剂造成的可怕后果

抗草甘膦（GT）农作物自1996年美国推出以来，已经在世界各地迅速传播，现在种植面积占全球转基因（GM）农作物种植面积的85% [1]。同时，草甘膦（商品名农达）被作为对健康和环境安全的除草剂而推广使用，成为世界上最广泛使用的除草剂。

但抗草甘膦作物对生态和健康的不利影响迅速曝光，并且多年来不断恶化而监管层视而不见（见[2, 3] Roundup Ready Sudden Death, Superweeds, Allergens..., SiS 28; Ban Glyphosate Herbicides Now, SiS 43）。

草甘膦结合烯醇丙酮酸莽草酸-3-磷酸合酶（EPSPS）并使其失活，烯醇丙酮酸莽草酸-3-磷酸合酶是植物莽草酸合成途径中的关键酶，是合成芳香族氨基酸所必需的，包括必需氨基酸苯丙氨酸，色氨酸和酪氨酸，以及下游产物诸如植物生长促进剂——吲哚乙酸和植物防御化合物——植物抗毒素[4]。但草甘膦具有许多副作用，对作物健康和产量的增效作用，远远超出了工厂排入土壤生态系统和更广泛的环境的不利影响。

抗草甘膦（GT）性状依赖于GT引入了土壤农杆菌的EPSPS，它对草甘膦不敏感，因此草甘膦被抗草甘膦作物吸收并被转运至根和茎的生长部分，甚至从根际（根系周围的土壤）渗出，因此它会影响到土壤中的微生物群落以及随后种植在该土壤中的农作物。

两名美国高级科学家，十年来在一直研究草甘膦的生态影响和“农达”作物生态系统。他们警告： “可怕的农业后果，如土壤贫瘠，农作物非生产性和植物营养不足。”

草甘膦——诱发植物疾病和毒素的一个最重要的因素

最近从美国普渡大学退休的Don Huber，与合著者G.S. Johal——就职于普渡大学的植物学和植物病理学系，2009年10月在《欧洲农学杂志》上发表的一篇论文指出，草甘膦在美国广泛使用能“大大增加各种植物疾病的严重程度，损害植物防御病原体和疾病的体系，并且固定不动的土壤和植物养分使它们无法被植物利用。”

此外，草甘膦刺激真菌生长并增强病原体的毒性，如镰刀霉， “可对一个范围广泛的敏感作物可持续生产造成严重后果。”他们警告说，“忽略潜在的非目标的任何化学品的有害副作用，特别是如草甘膦的严重使用，有可能对农业造成可怕后果如土壤贫瘠，作物非生产性，植物营养不足。“

在《有机及非转基因生物报告》的一次采访中[5]，Huber说，他已经研究了草甘膦20年，当他发现小麦真菌疾病持续上升时，开始注意到草甘膦的使用问题，当时草甘膦早些年已被应用于控制杂草。他发现草甘膦会使植物中锰含量减少，锰是许多植物对疾病和环境压力的防御反应所必需的。草甘膦固定植物的营养成分，如锰，铜，钾铁，镁，钙和锌，因此，他们不再具备营养功能。基本上，草甘膦完全削弱了植物，使其容易受到土壤传播的真菌病原体的感染。 “这就是为什么我们看到植物疾病在增加的原因，”他说。

在过去的15至18年里有一些植物疾病呈现增长趋势。四种主要的土壤真菌，镰刀霉，腐霉，丝核菌和疫霉，在使用草甘膦后更具活力；并且，这些真菌引起的疾病增加，如玉米赤霉病，或大豆烂根，甜菜冠腐病。赤霉病，影响谷类作物，产生的毒枝菌素，会进入食物链。

有超过40种疾病被报告在使用草甘膦后发生，而且数目随着人们的认识而不断增加，Huber说。

当被问及草甘膦是否如支持者所宣称德那样对”环境友好”，他回答：“绝对不会。那是彻头彻尾的错误概念。草甘膦是诱发植物疾病和植物毒素的最重要农艺因素。这些毒素对动物和人类健康造成严重影响。”

 “产生的毒素能够感染植物根部和顶部，并转移到植物的其余部位。” Huber解释道。 “秸秆的毒素水平可以高到足以使牛和猪不育。”

草甘膦影响人体健康的一个途径是“微量元素如锰，铜，钾，铁，镁，钙和锌，是人体必不可少的。他们都可被草甘膦而减少利用率，所以草甘膦处理GT植物及其他暴露于草甘膦的植物矿质营养较少。 “我们看到在我们的食物营养品质减少。”

“在[农达]基因会减少微量营养素锌和锰含量高达百分之五十的...这也说明了报道的抗草甘膦大豆产量滞后的原因。”

“不幸的是，大多数研究人员都不得在该领域做工作。他们没有获得同基因系的途径[常规和抗草甘膦株系在其他遗传方面完全相同的]，这些材料拒绝提供给研究人员。“

Huber和Johal劝告使用尽可能少的草甘膦。

不幸的是，降低了草甘膦剂量，不足以杀死杂草，尤其是众多的杂草正在变成高抗除草剂的杂草（见[6] GM Crops Facing Meltdown in the USA, SiS 46)

抗草甘膦系统改变了整个土壤生物学

Robert Kreme是USDA-ARS（美国农业部农业研究服务部）微生物学家，并且是密苏里大学植物科学部兼职教授。他从1997年开始研究新孟山都公司抗草甘膦系统（农达除草剂和GT种植）如何改变大豆线虫的水平。他的研究小组开始在根部寻找，看到根部的微生物群落，并怀疑是草甘膦产生了影响。似乎是根部真菌的问题导致猝死综合症。

事实上，该系统 “改变了整个土壤生物学。” Kremer告诉《有机及非转基因生物报告》[7]。 "我们看到植物根部细菌的不同和养分供应的改变。许多研究表明，草甘膦对[一些]微生物有毒性作用，能刺激[其他一些]微生物孢子萌发，在植物根部生成菌落。其他研究人员显示，草甘膦可固定锰，一种重要的植物微量营养素。"

草甘膦对益菌如固氮菌——根瘤菌有毒，但会增加病原微生物如镰刀霉的发生。 “有些甚至不使用草甘膦的抗草甘膦品种，往往更容易被镰刀霉感染，”可能是基因改造意想不到的效果。

如果土壤充满磷酸盐（当禽畜粪便作为肥料使用），草甘膦会渗入地下水（毒害其他野生动植物物和人类）。

“我们看到了农达生态系统中这些真菌在增加，包括大豆和玉米。” Kremer说。

这些论文描述了他的研究小组的工作，在《欧洲农学杂志》上发表[8]没有被美国接收。Kremer说，[7]："我正在在USDA-ARS工作，对这些研究要发表新闻稿。我极力向管理员推荐，但他们不愿意把一些东西公开。他们的想法是，如果农民使用该（草甘膦）技术，美国农业部并不希望关于它的负面信息被释放。这是怎样的。我认为要发布的新闻仍然放在某人的办公桌上。"

Kremer作出结论[7]："我们正在寻找一些方法可用于克服负面影响，如果我们继续使用农达作物，如叶面喷施营养补充物”但他补充说，“我对可持续农业更感兴趣。更多的农民对利用覆盖种植，以保持土壤质量和其他有机修正感兴趣。但对他们来说是一个曲折的学习过程。"

Scientists Reveal Glyphosate Poisons Crops and Soil

GM Meltdown Continues

Scientists go public on devastating ecological impacts of Roundup Ready cropping systems while USDA keeps mum Dr. Mae-Wan Ho

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Dire consequences from the most widely used herbicide in the world

Glyphosate-tolerant (GT) crops have spread rapidly around the world since they were introduced in the US in 1996, and are now planted on 85 percent of the global area growing genetically modified (GM) crops [1]. Concomitantly, glyphosate (commercial formulation Roundup), promoted as safe for health and the environment, became the most widely used herbicide in the world.

But ecological and health impacts of the GT cropping system soon came to light, and have been worsening relentlessly over the years while regulators turn a blind eye (see [2, 3] Roundup Ready Sudden Death, Superweeds, Allergens..., SiS 28; Ban Glyphosate Herbicides Now, SiS 43).

Glyphosate binds with and inactivates EPSPS, the critical enzyme in the shikimate pathway required for the synthesis of aromatic plant metabolites including essential amino acids phenylalanine, tryptophan and tyrosine, as well as downstream products such as plant growth promoter, indoylacetic acid and plant defence compounds, phytoalexins [4]. But glyphosate has multiple adverse effects that act synergistically on crop health and productivity that extends well beyond the plant into the soil ecosystem and the wider environment. 

The GT trait depends on incorporating an EPSPS from the soil bacterium Agrobacterium tumefaciens that is insensitive to glyphosate, hence glyphosate is taken up by GT plants and translocated to the growing parts of roots and shoots, and even exuded into the rhizosphere (soil surrounding the roots) so it can affect the soil community of microorganisms and also subsequent crops planted in the soil. Two senior scientists in the US who have been investigating the ecological impacts of glyphosate and the Roundup Ready cropping system for decades are warning of “dire consequences for agriculture such as rendering soils infertile, crops non-productive, and plants less nutritious.”

Glyphosate the single most important factor predisposing plants to diseases and toxins

Don Huber, recently retired from Purdue University, and co-author, at Purdue’s Dept of Botany and Plant Pathology, stated in a paper published in the October 2009 issue of European Journal of Agronomy that the widespread use of glyphosate in the US can “significantly increase the severity of various plants diseases, impair plant defense to pathogens and diseases, and immobilize soil and plant nutrients rendering them unavailable for plant use.”

Further, glyphosate stimulates the growth of fungi and enhances the virulence of pathogens such as Fusarium, and “can have serious consequences for sustainable production of a wide range of susceptible crops.” They warn that “Ignoring potential non-target detrimental side effects of any chemical, especially used as heavily as glyphosate, may have dire consequences for agriculture such as rendering soils infertile, crops non-productive, and plants less nutritious.”

In an interview [5] with the Organic & Non-GMO Report, Huber said he has been researching glyphosate for 20 years, and began noticing problems when he saw a consistent increase in “take-all”, a fungal disease of wheat, when glyphosate had been applied in a previous year to control weeds. He found glyphosate reduced manganese in plants, which is essential to many plant defence reactions against disease and environmental stress. Glyphosate can immobilize plant nutrients such as manganese, copper, potassium iron, magnesium, calcium, and zinc, so they are no longer nutritionally functional. Basically, glyphosate completely weakens the plant, making it susceptible to soil-borne fungal pathogens. “That is one reason why we see an increase in plant diseases,” he said.

There has been a general increase in the number of plant diseases in the past 15 to 18 years. Four primary soil fungi,  Fusarium, Phythium, Rhizoctonia, and Phytophthora, have become more active with the use of glyphosate; and concomitantly, diseases caused by these fungi have increased, such as head scab in corn, or root rot in soybeans, crown rot in sugar beets. Fusarium head blight, which affects cereal crops, is a disease that produces a mycotoxin that could enter the food chain.

There are more than 40 diseases reported with the use of glyphosate, and the number keeps growing as people recognize the association, Huber said.

When asked if glyphosate is “environmentally benign” as claimed by proponents, he answered “Absolutely not. That’s an outright mistaken notion. Glyphosate is the single most important agronomic factor predisposing some plants to both disease and toxins. These toxins can produce a serious impact on the health of animals and humans.

 “Toxins produced can infect the roots and head of the plant and be transferred to the rest of the plant.” Huber explained. “The toxin levels in straw can be high enough to make cattle and pigs infertile.”

One way in which glyphosate can affect human health is that “micronutrients such as manganese, copper, potassium, iron, magnesium, calcium, and zinc are essential to humans. All of them can be reduced in availability by glyphosate; so glyphosate treated GT plants as well as other plants exposed to glyphosate have less mineral nutrients. “We are seeing a reduction in nutrient quality [in our food].”

 “The [Roundup Ready] gene will reduce micronutrient efficiency up to 50 percent for zinc and manganese…This could also account for the yield drag [reported for GT soybeans].”

“Unfortunately, most researchers are forbidden to do work in the area. They don’t have access to isogenic lines [conventional and Roundup Ready plant lines that are otherwise genetically identical], the materials are denied to researchers.”

Huber and Johal recommend using as little glyphosate as possible.

Unfortunately, reducing the dose of glyphosate will be insufficient for killing weeds, particularly as numerous weeds are becoming highly resistant to the herbicide (see [6] GM Crops Facing Meltdown in the USA, SiS 46)

Roundup Ready system alters the whole soil biology

Robert Kremer is a microbiologist with the USDA-ARS (US Department of Agriculture- Agricultural Research Service) and an adjunct professor in the Division of Plant Sciences at the University of Missouri. He started in 1997 to investigate how the new Monsanto Roundup Ready system (Roundup herbicide and GT cropping) would change the level of nematodes in soybean. His research team began looking at the roots and saw microorganisms colonizing the roots, and suspected that glyphosate was having an impact. There was a root fungi problem that seemed to encourage sudden death syndrome.

In fact, the system is “altering the whole soil biology.” Kremer told The Organic & Non-GM Report [7]. “We are seeing differences in bacteria in plant roots and changes in nutrient availability. Many studies show that glyphosate can have toxic effects on [some] microorganisms and can stimulate [others] to germinate spores and colonize roots systems. Other researchers are showing that glyphosate can immobilize manganese, an essential plant micronutrient.”

Glyphosate is toxic to beneficial bacteria like rhiozbia, which fixes nitrogen, but increases the incidence of pathogens like Fusarium. “Some Roundup Ready varieties even without using glyphosate, tend to be more susceptible to Fusarium,” possibly an unintended effect of genetic modification.

If the soil is full of phosphate (as when livestock manure is used as a fertilizer), glyphosate could leach into ground water (and poison other wild-life and human beings).

“We saw the increase of these fungi in the Roundup Ready system, both soybeans and corn.” Kremer said.

The papers describing the work of his research team, published in the European Journal of Agronomy [8] received no publicity in the US.  Kremer said [7]: “I was working with USDA-ARS to publish a news release about these studies. I’ve gone all the way to the administrators, but they are reluctant to put something out. Their thinking is that if farmers are using this (Roundup Ready) technology, USDA doesn’t want negative information being released about it. This is how it is. I think the news release is still sitting on someone’s desk.”

Kremer concluded [7]: “We’re looking at some methods that could be used to overcome negative effects if we continue to use Roundup Ready crops, such as supplementation of nutrients by foliar application,” but added, “I’m more interested in sustainable agriculture. More farmers are interested in using cover cropping to maintain soil quality and other organic amendments. But it’s a steep learning curve for them.”

References

1. Yamada T. Kremer RJ. De Carmargo e Castro and Wood BW. Glyphosate interactions with physiology, nutrition, and diseases of plants: threats to agricultural sustainability? Europ J Agronomy 2009 31, 111-3

2. Ho MW and Cummins J. Roundup Ready sudden death, superweeds, allergens…time to wipe GM crops off the globe. Science in Society 28, 26-27, 2005.

3. Ho MW. Ban glyphosate herbicides now. Science in Society 43, 34-35, 2009.

4. Johal GS and Huber DM. Glyphosate effects on diseases of plants. Eur J Agron 2009, 144-52.

5.  “Scientist warns of dire consequences with widespread use of glyphosate”, The Organic & Non-GMO Report, May 2010, http://www.non-gmoreport.com/articles/may10/consequenceso_widespread_glyphosate_use.php

6. Ho MW. GM crops facing meltdown in the USA. Science in Society 46 (in press).

7. “Scientist finding many negative impacts of Roundup Ready GM crops, USDA doesn’t want to publicize studies showing negative impact2, The Organic & Non-GMO Report, January 2010, http://www.non-gmoreport.com/articles/jan10/scientists_find_negative_impacts_of_GM_crops.php

8. Kremer RJ and Means NE. Glyphosate and glyphosate-resistant crop interactions with rhizosphere microorganisms. European Journal of Agronomy 2009, 31, 153-61.

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