UK gardening - Re: GM crops created superweed, say scientists

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Re: GM crops created superweed, say scientists

John

2005-07-26, 3:21 pm

On Mon, 25 Jul 2005 23:01:50 +0200, marcus@myrealbox.com wrote:

>
>GM crops created superweed, say scientists
>
>Modified rape crosses with wild plant to create tough pesticide-resistant
>strain
>
>Paul Brown, environment correspondent
>Monday July 25, 2005
>The Guardian
>
>Modified genes from crops in a GM crop trial have transferred into local wild
>plants, creating a form of herbicide-resistant "superweed", the Guardian can
>reveal.
>
>The cross-fertilisation between GM oilseed rape, a brassica, and a distantly
>related plant, charlock, had been discounted as virtually impossible by
>scientists with the environment department. It was found during a follow up to
>the government's three-year trials of GM crops which ended two years ago.
>
>The new form of charlock was growing among many others in a field which had
>been used to grow GM rape. When scientists treated it with lethal herbicide it
>showed no ill-effects.
>
>Article continues
>Unlike the results of the original trials, which were the subject of
>large-scale press briefings from scientists, the discovery of hybrid plants
>that could cause a serious problem to farmers has not been announced.
>
>The scientists also collected seeds from other weeds in the oilseed rape field
>and grew them in the laboratory. They found that two - both wild turnips - were
>herbicide resistant.
>
>The five scientists from the Centre for Ecology and Hydrology, the government
>research station at Winfrith in Dorset, placed their findings on the
>department's website last week.
>
>A reviewer of the paper has appended to its front page: "The frequency of such
>an event [the cross-fertilisation of charlock] in the field is likely to be
>very low, as highlighted by the fact it has never been detected in numerous
>previous assessments."
>
>However, he adds: "This unusual occurrence merits further study in order to
>adequately assess any potential risk of gene transfer."
>
>Brian Johnson, an ecological geneticist and member of the government's
>specialist scientific group which assessed the farm trials, has no doubt of the
>significance. "You only need one event in several million. As soon as it has
>taken place the new plant has a huge selective advantage. That plant will
>multiply rapidly."
>
>Dr Johnson, who is head of the biotechnology advisory unit and head of the land
>management technologies group at English Nature, the government nature
>advisers, said: "Unlike the researchers I am not surprised by this. If you
>apply herbicide to plants which is lethal, eventually a resistant survivor will
>turn up."
>
>The glufosinate-ammonium herbicide used in this case put "huge selective
>pressure likely to cause rapid evolution of resistance".
>
>To assess the potential of herbicide-resistant weeds as a danger to crops, a
>French researcher placed a single triazine-resistant weed, known as fat hen, in
>maize fields where atrazine was being used to control weeds. After four years
>the plants had multiplied to an average of 103,000 plants, Dr Johnson said.
>
>What is not clear in the English case is whether the charlock was fertile.
>Scientists collected eight seeds from the plant but they failed to germinate
>them and concluded the plant was "not viable".
>
>But Dr Johnson points out that the plant was very large and produced many
>flowers.
>
>He said: "There is every reason to suppose that the GM trait could be in the
>plant's pollen and thus be carried to other charlock in the neighbourhood,
>spreading the GM genes in that way. This is after all how the
>cross-fertilisation between the rape and charlock must have occurred in the
>first place."
>
>Since charlock seeds can remain in the soil for 20 to 30 years before they
>germinate, once GM plants have produced seeds it would be almost impossible to
>eliminate them.
>
>Although the government has never conceded that gene transfer was a problem, it
>was fear of this that led the French and Greek governments to seek to ban GM
>rape.
>
>Emily Diamond, a Friends of the Earth GM researcher, said: "I was shocked when
>I saw this paper. This is what we were reassured could not happen - and yet now
>it has happened the finding has been hidden away. This is exactly what the
>French and Greeks were afraid of when they opposed the introduction of GM
>rape."
>
>The findings will now have to be assessed by the government's Advisory
>Committee on Releases to the Environment (Acre). The question is whether it is
>safe to release GM crops into the UK environment when there are wild relatives
>that might become superweeds and pose a serious threat to farm productivity.
>This has already occurred in Canada.
>
>The discovery that herbicide-resistant genes have transferred to farm weeds
>from GM crops is the second blow to the hopes of bio-tech companies to
>introduce their crops into Britain. Following farm scale trials there was
>already scientific evidence that herbicide-tolerant oilseed rape and GM sugar
>beet were bad for biodiversity because the herbicide used to kill the weeds
>around the crops wiped out more wildlife than with conventionally grown crops.
>Now this new research, a follow-up on the original trials, shows that a second
>undesirable potential result is a race of superweeds.
>
>The findings mirror the Canadian experience with GM crops, which has seen
>farmers and the environment plagued with severe problems.
>
>Farmers the world over are always troubled by what they call "volunteers" -
>crop plants which grow from seeds spilled from the previous harvest, of which
>oilseed rape is probably the greatest offender, Anyone familiar with the
>British countryside, or even the verges of motorways, will recognise thousands
>of oilseed rape plants growing uninvited amid crops of wheat or barley, and in
>great swaths by the roadside where the "small greasy ballbearings" of seeds
>have spilled from lorries.
>
>Farmers in Canada soon found that these volunteers were resistant to at least
>one herbicide, and became impossible to kill with two or three applications of
>different weedkillers after a succession of various GM crops were grown.
>
>The new plants were dubbed superweeds because they proved resistant to three
>herbicides while the crops they were growing among had been genetically
>engineered to be resistant to only one.
>
>To stop their farm crops being overwhelmed with superweeds, farmers had to
>resort to using older, much stronger varieties of "dirty" herbicide long since
>outlawed as seriously damaging to biodiversity.
>
>Q&A: What the discovery means for UK farmers
>
>What's the GM situation in the UK?
>
>No GM crops are currently grown commercially in the UK. Companies who wish to
>introduce them face a series of licensing hurdles in Britain and Europe and
>interest has waned in recent years amid public opposition.
>
>Other firms have dropped applications in the wake of the government field scale
>trials that showed growing two GM varieties - oilseed rape and sugar beet - was
>bad for biodiversity.
>
>The EU has approved several GM varieties and the UK government insists that
>applications will be considered on a case-by-case basis.
>
>Where are GM crops grown?
>
>Extensively in the wide open spaces of the US, Canada and Argentina. In Europe,
>Portugal, France and Germany have all dabbled with GM insect-resistant maize.
>Spain plants about 100,000 hectares (250,000 acres) of it each year for animal
>feed.
>
>What is a superweed?
>
>Many GM crop varieties are given genes that allow them to resist a specific
>herbicide, which farmers can then apply to kill the weeds while allowing the GM
>crop to thrive.
>
>Environmental campaigners have long feared that if pollen from the GM crop
>fertilised a related weed, it could transfer the resistance and create a
>superweed. This "gene transfer" is what appears to have happened at the field
>scale trial site. It raises the prospect of farmers who grow some GM crops
>being forced to use stronger herbicides on their fields to deal with the
>upstart weeds.
>
>Is it a big problem?
>
>Not yet. Farmers in the UK do not grow GM crops commercially. If they did, then
>the scale of possible superweed contamination depends on two things: whether
>the hybrid superweed can reproduce (many hybrids are sterile) and, if it could,
>how well its offspring could compete with other plants. Herbicide-resistant
>weeds could potentially grow very well in agricultural fields where the
>relevant herbicide is applied. Most experts say superweeds would be unlikely to
>sweep across the UK countryside as, without the herbicide being used to kill
>their competitors, their GM status offers no advantage.
>
>Some GM crops, such as maize, have no wild relatives in the UK, making gene
>transfer and the creation of a superweed from them impossible.
>
>Is it a surprise?
>
>On one level no, gene flow and hybridisation are as old as plants themselves.
>Short of creating sterile male plants, it's simply impossible to stop crops
>releasing pollen to fertilise related neighbours. But government scientists had
>thought that GM oilseed rape and charlock were too distantly related for it to
>occur.
>
>The dangers of hybridisation where it does happen are well documented - experts
>from the Dorset centre behind the latest research published a high-profile
>paper in 2003 in the US journal Science showing widespread gene flow from
>non-GM oilseed rape to wild flowers.
>
>Have superweeds surfaced elsewhere?
>
>Farmers in Canada and Argentina growing GM soya beans have large problems with
>herbicide-resistant weeds, though these have arisen through natural selection
>and not gene flow through hybridisation. Experiments in Germany have shown
>sugar beets genetically modified to resist one herbicide accidentally acquired
>the genes to resist another - so called "gene stacking", which has also been
>observed in oilseed rape grown in Canada.
>
>· David Adam
>
>http://www.guardian.co.uk/gmdebate/...1535428,00.html
>

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