#GM crops created superweed, say scientists

[Guest guest]

<http://www.guardian.co.uk/gmdebate/Story/0,2763,1535428,00.html>

 

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

 

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revolutions a

minute and man is a sick fly taking a dizzy ride on

it. Religion is

the theory that the wheel was designed and set

spinning to give him

the ride. --- H.L. Mencken (1880 - 1956)

 

 

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