Government Study Finds GM 'Superweeds'

New government research in the UK has reported on the discovery of the first GM uperweed in the country. This was the result of GM oilseed rape cross-breeding with a common weed, charlock, a phenomenon that was earlier thought to be impossible.

The UK government study monitored gene flow from Bayer's herbicide resistant GM oilseed rape to related wild plants during the government-sponsored farm scale evaluations of GM crops. At one test site, the researchers found a GM version of the common weed charlock growing in the field the year after the GM trial. The plant was resistant to the weed killer used in the GM trial and was confirmed as containing the gene inserted into the GM oilseed rape. This is the first known case of such an occurrence in the UK, and overturns previous scientific assumptions that charlock was unlikely to cross-breed with GM oilseed rape, according to Friends of the Earth.

The discovery raises fears that herbicide-resistant superweeds could develop in the British countryside if GM crops were grown commercially. There is also the possible fallout for the environment as this means that more and deadlier herbicides will need to be employed to kill the GM weeds.

Currently only two countries in Europe have banned GM oilseed rape. They are France and Greece and both have been subjected to pressure to lift those bans.

The summary of the research is attached below (Item 1). The full study can be obtained at: http://www.defra.gov.uk/environment/gm/research/epg-1-5-151.htm. We also attach two news reports on the issue from The Guardian (Items 2 and 3).

Item 1

THE POTENTIAL FOR DISPERSAL OF HERBICIDE TOLERANCE GENES FROM GENETICALLY-MODIFIED, HERBICIDE-TOLERANT OILSEED RAPE CROPS TO WILD RELATIVES

Roger Daniels, Caroline Boffey, Rebecca Mogg, Joanna Bond & Ralph Clarke
CEH Dorset.
Final report to DEFRA

SUMMARY

1. The commercial growing of genetically modified, herbicide-tolerant (GMHT) oilseed rape is seen to result in the potential for the inserted gene to escape from the crop and become incorporated in the genomes of one or more related wild crucifer species, potentially giving a competitive advantage to the recipients.
2. The possibility of such gene transfer may be greatest where the wild relative is closely related to the crop, where the two grow in close proximity and where they flower at the same time.
3. Because oilseed rape is grown as either a winter-sown or a spring-sown crop, there are two flowering periods; winter rape in late March to mid-May and spring rape in June. There may be a short overlap period when some individuals in both crops are in flower at the same time. The existence of these two flowering periods extends the period over which both crop and wild relatives may be in flower together.
4. The most closely related species to oilseed rape (Brassica napus), and those which have been considered as potential recipients of herbicide tolerance are other members of the genus Brassica: B. oleracea, B. rapa, B, nigra, together with Raphanus raphanistrum and R. sativus, and two species of Sinapis, S. arvensis and S. alba.
5. As an adjunct to the Farm Scale Evaluations of GMHT oilseed rape, DEFRA funded a three-year project to examine the extent to which transfer of herbicide tolerance from the oilseed rape crops to wild relatives in the vicinity did occur. This report details the result of that study.
6. Transfer of herbicide tolerance was assessed in the field and in the laboratory. In the field, plants were tested by the application of a small quantity of glufosinate ammonium (LibertyTM) to individual leaves and observing whether any necrosis resulted. Seed collected from plants growing in or near oilseed rape fields were germinated and the resulting seedlings were sprayed with LibertyTM to assess tolerance. Any plants showing signs of tolerance to the herbicide were subjected to PCR to identify whether the gene was present.
7. The most common wild relative found in fields in the trial was Sinapis arvensis. In contrast, Brassica rapa was only found adjacent to a single field in the winter oilseed rape trial.
8. A total of 95459 seedlings of wild relatives were grown and tested. Of these, only 2 plants, of Brassica rapa showed resistance to the treatment.
9. In the year after the trial, a sub-set of fields was revisited and wild relatives growing in or around the subsequent crop were tested by herbicide application. A single plant of Sinapis arvensis showed no reaction to the application and a leaf of this plant was taken for PCR analysis. The gene construct was found to be present.
10. Because weed control is generally very efficient in cereal fields, few volunteer oilseed rape plants survive in wheat or barley fields sown following the harvest of an oilseed rape crop.
11. We examined some fields in the first and second years following the oilseed rape trials and found that volunteer populations did occur and that a proportion of the plants were tolerant of glufosinate ammonium.
12. Transfer of herbicide tolerance to wild relatives is not seen as a major problem, especially as it would not be expected to confer any selective advantage in the absence of the appropriate herbicide application.
13. The persistence of herbicide-tolerant volunteer populations of oilseed rape in subsequent crops may pose agronomic problems, especially if the same gene construct is introduced into other crop species.

Item 2
GM crops created superweed, say scientists Modified rape crosses with wild plant to create tough pesticide-resistant strain
Paul Brown, environment correspondent
The Guardian, Monday July 25, 2005
http://www.guardian.co.uk/gmdebate/Story/0,2763,1535428,00.html

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.

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 amaging 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.<P>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.

Item 3

Weed discovery brings calls for GM ban
Paul Brown, environment correspondent
The Guardian, July 26, 2005
http://politics.guardian.co.uk/green/story/0,9061,1536021,00.html

Britain cannot afford to take the risk of spreading genetically modified genes to wild plants and should ban GM crops that have wild relatives in the countryside, the former environment minister Michael Meacher said yesterday.

Mr Meacher, who was the minister responsible for introducing the farm-scale trials of GM crops in Britain to test their effect on the environment, said he was shocked yesterday at research results revealed for the first time in the Guardian.

The results showed that a related weed had picked up herbicide resistance as a result of cross-fertilisation with GM oil seed rape, something that scientists had said would not happen in the countryside.

The discovery raises fears that herbicide-resistant superweeds could develop in the British countryside if GM crops were grown commercially.

"I remember being reassured on this issue when I was minister. Now we discover that charlock, a distant relative of GM oil seed rape, has acquired resistance to herbicide," he said.

"It means we just cannot afford to take the risk that GM crops will not cross-contaminate wild plants in unpredictable and unforeseeable ways.

"If weeds are able to tolerate broad spectrum herbicides as a result of cross-pollination it means we get into uncharted territory."

He said he had been to Canada to see the plight of farmers who had encountered superweeds. They had been forced to spray them with heavy duty chemicals.

"In a small island like Britain where we have many comparatively small fields and many related species of plants, it is unrealistic to think we could have adequate separation distances between GM crops and conventional crops or their wild relatives."

It was impossible to see how organic and conventional farmers could be safeguarded from cross-contamination, or how GM crops would not gradually contaminate everything else.

Mr Meacher said French research, also highlighted by the Guardian yesterday, which showed that one herbicide resistant weed introduced into a crop had multiplied to 103,000 plants in four years, was "frightening".

"The safe option is to say simply that the risk of these GM crops is too great and we will not grow them," he said.

Brian Johnson, an ecological geneticist, head of the biotechnology group at English Nature, emphasised yesterday that the charlock was not a superweed and did not appear to be fertile, but it was possible the GM genes could be carried to other plants in the pollen.

The research did not analyse the pollen so "we could not be sure that the trait was there".

Government researchers from the Centre for Ecology and Hydrology, who had been surprised by their own findings of the transfer of a GM trait to charlock, said follow-up research was needed.

In Canada plants had evolved from GM crops which were resistant to three types of herbicide, which was why they had been called superweeds. The charlock that was found in the UK was only resistant to one.

Pete Riley, the director of Five Year Freeze, an organisation dedicated to preventing the commercial growing of GM crops for five years, said: "The news that a GM herbicide-tolerant gene has moved from oilseed rape to charlock is very surprising - previously we were told that this was impossible under field conditions.

"What a good job that there has been a moratorium to allow such unexpected events to be discovered. Who knows what the next shock finding will be?

"In our view it is high time that GM oilseed rape was quietly put to sleep. After these findings and the other field-scale trial results we will be looking for the Advisory Committee on Releases to the Environment, and ministers, to take a strong approach and ban it."