THIRD WORLD NETWORK BIOSAFETY INFORMATION SERVICE
Dear Friends and Colleagues
Re: Fitter GM-weedy rice hybrid raises concerns
A new study in China has found that a weedy rice cross-bred with a genetically modified (GM) variety made resistant to the herbicide glyphosate (commonly sold as Roundup) has demonstrated unexpected improved fitness. Second-generation hybrids had higher rates of photosynthesis, grew more shoots and flowers, and produced 48–125% more seeds per plant than non-transgenic hybrids, all in the absence of glyphosate.
This finding raises concerns as it is contrary to scientific expectation that such a hybrid would actually be less competitive. Should such a transgene pass on to weedy or wild relatives, this could create risks to the environment. Having weedy rice that is more competietive will exacerbate the problems the it causes farmers while a more competitive wild rice species could out-compete normal wild species, threatenening genetic diversity.
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Third World Network
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Item 1
Genetically modified crops pass benefits to weeds
Jane Qiu
Nature News, 16 August 2013
http://www.nature.com/news/genetically-modified-crops-pass-benefits-to-weeds-1.13517
*Herbicide resistance could confer an advantage on plants in the wild.
A genetic-modification technique used widely to make crops herbicide resistant has been shown to confer advantages on a wild form of rice, even in the absence of the herbicide. The finding suggests that the effects of such modification have the potential to extend beyond farms and into the wild.
Several types of crops have been genetically modified to be resistant to glyphosate, an herbicide first marketed under the trade name Roundup. This glyphosate resistance enables farmers to wipe out most weeds from the fields without damaging their crops.
Glyphosate inhibits plant growth by blocking an enzyme known as EPSP synthase, which is involved in the production of certain amino acids and other molecules that account for as much as 35% of a plant’s mass. The genetic-modification technique — used, for instance, in the Roundup Ready crops made by the biotechnology giant Monsanto, based in St Louis, Missouri — typically involves inserting genes into a crop’s genome to boost EPSP-synthase production. The genes are usually derived from bacteria that infect plants.
The extra EPSP synthase lets the plant withstand the effects of glyphosate. Biotechnology labs have also attempted to use genes from plants rather than bacteria to boost EPSP-synthase production, in part to exploit a loophole in US law that facilitates regulatory approval of organisms carrying transgenes not derived from bacterial pests.
Few studies have tested whether transgenes such as those that confer glyphosate resistance can — once they get into weedy or wild relatives through cross-pollination — make those plants more competitive in survival and reproduction. “The traditional expectation is that any sort of transgene will confer disadvantage in the wild in the absence of selection pressure, because the extra machinery would reduce the fitness,” says Norman Ellstrand, a plant geneticist at the University of California in Riverside.
But now a study led by Lu Baorong, an ecologist at Fudan University in Shanghai, challenges that view: it shows that a weedy form of the common rice crop, Oryza sativa, gets a significant fitness boost from glyphosate resistance, even when glyphosate is not applied.
In their study, published this month in New Phytologist, Lu and his colleagues genetically modified the cultivated rice species to overexpress its own EPSP synthase and cross-bred the modified rice with a weedy relative.
The team then allowed the cross-bred offspring to breed with one another, creating second-generation hybrids that were genetically identical to one another except in the number of copies of the gene encoding EPSP synthase. As expected, those with more copies expressed higher levels of the enzyme and produced more of the amino acid tryptophan than their unmodified counterparts.
The researchers also found that the transgenic hybrids had higher rates of photosynthesis, grew more shoots and flowers and produced 48–125% more seeds per plant than non-transgenic hybrids — in the absence of glyphosate.
Making weedy rice more competitive could exacerbate the problems it causes for farmers around the world whose plots are invaded by the pest, Lu says, Lu says.
“If the EPSP-synthase gene gets into the wild rice species, their genetic diversity, which is really important to conserve, could be threatened because the genotype with the transgene would outcompete the normal species,” says Brian Ford-Lloyd, a plant geneticist at the University of Birmingham, UK. “This is one of the most clear examples of extremely plausible damaging effects [of GM crops] on the environment.”
The study also challenges the public perception that genetically modified crops carrying extra copies of their own genes are safer than those containing genes from microorganisms. “Our study shows that this is not necessarily the case,” says Lu.
The finding calls for a rethinking of future regulation of genetically modified crops, some researchers say. “Some people are now saying that biosafety regulation can be relaxed because we have a high level of comfort with two decades of genetic engineering,” says Ellstrand. “But the study shows that novel products still need careful evaluation.”
Nature doi:10.1038/nature.2013.13517
References
Wang, W. et al. New Phytol. http://dx.doi.org/10.1111/nph.12428 (2013).
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Item 2
http://www.wired.co.uk/news/archive/2013-08/19/gm-crops-weed-risk
Weeds get ‘fitness’ boost from genetic modification
Kadhim Shubber, Wired UK
22 August 2013
Genetically modified (GM) crops could give harmful weeds a significant growth boost if their modifications are transferred into the wild.
Rice weeds with a herbicide-resistant genetic modification produced up to 125 percent more seeds and had photosynthesised at rates up to 109 percent higher than control plants.
The research from the Fudan University in Shanghai, published in New Phytologist, suggests that an experimental gene modification that protects against the widely-used glyphosate herbicide also confers significant fitness benefits to weeds.
"Originally, this epsps transgene was developed to confer resistance to glyphosate," write the authors. "But it also appears to provide profound and previously unrecognised benefits for plant growth and seed production."
The transfer of genetic modifications into the wild is a thorny issue, with cases of herbicide-resistant weeds stoking the debate about whether GM crops should be used or not. This study lends some credence to fears that certain genetic modifications can have unintended consequences on other plants, but it should be noted that the researchers passed the modification to the weeds by hand and the modification that they passed is not currently used.
"There’s a risk when you have closely-related wild versions," says Wendy Harwood of The John Innes Centre. But that’s why we take those risks into account when considering where and how to plant GM crops, she added.
The genetic modification transferred in this study concerns epsps, a key enzyme in plants, which permits the production of vital amino acids and other substances. Decreased levels of epsps results in the death of a plant. Glyphosate blocks the function of epsps, making it a powerful and widely-used herbicide.
One-way, therefore, of ensuring that your herbicide kills the plants you hate — the weeds — but leaves alone the plants you love — your crops — is by altering the epsps enzyme so that it isn’t affected by glyphosate. This is done by either changing the enzyme directly, or by forcing the plant to over-produce epsps, so that the glyphosate is overwhelmed.
It is this second route, which is not used commercially, that the Fudan University researchers investigated. By breeding GM and non-GM weeds from the same lineage, they were able to show that this genetic modification resulted in "dramatic changes in fitness-related traits". They were unable to conclusively rule out the unlikely possibility that other factors, like the placement of the genes, had caused the changes.
"The location of a gene can influence its impact," says Harwood.
GM crops are a contentious area for debate. Most recently, a group of Filipino farmers destroyed a field of "Golden Rice", which is genetically modified to encourage vitamin A production in humans.
Harwood said that the study was interesting, and that it would certainly be looked at carefully by other researchers in the field, but warned against drawing broad conclusions from a single study. "One report can’t be applied to GM generally," she said, noting that each crop and each genetic modification has to be looked at on a case by case basis.