by Paul Brown,
environment correspondent
Weeds have become
stronger and fitter by cross-breeding with genetically modified crops,
leading to fears that superweeds which are difficult or impossible to
control may invade farms growing standard crops.
Two separate teams,
one working on sunflowers in the US and the other on sugar beet in France,
have shown weeds and GM food crops readily swapping genes.
In the case of wild
sunflowers, classed as "weed" varieties in America, specimens
became hardier and produced 50% more seeds if they were crossed with
GM sunflowers which had been programmed to be resistant to seed-nibbling
moth larvae.
Allison Snow, who
headed the team at Ohio State University, confessed in New Scientist
that she was "shocked" by the results. "It does not prove
all GM crops are dangerous," she said. "I just think we need
to be careful because genes can be very valuable for a weed and persist
for ever once they are out there."
Pioneer Hi-Bred,
which developed the GM sunflower, has abandoned the idea of selling
the strain commercially.
The sugar beet results
show that wild and GM varieties swapped genes, sometimes to the advantage
of the wild varieties and the detriment of the GM plants, which produced
lower yields. Writing in the Journal of Applied Ecology, the University
of Lille team said they had underestimated the likelihood of GM beets
swapping genes with the beet weeds that grow among them.
The two sets of
results add to the fears of environmental groups and organic farmers
that normal crops could be contaminated by GM varieties - and make weeds
impossible to control. This is less of a problem in countries where
crops have been introduced, for instance soya grown the US, because
no native weed varieties exist. But in Europe, particularly in Britain,
where weed species of both beet and oil seed rape exist, the risk is
potentially serious.
Adrian Bebb, GM
campaigner at the environmental group Friends of the Earth, said GM
beet was now being grown at 16 farm-scale trial sites in England. "Once
again scientists are discovering new impacts of GM crops," he said.
"The government always emphasises the importance of a sound scientific
approach to GM crop safety, so they should look at this research seriously
and question whether or not we should be testing GM crops out of doors."
Two years ago government
research reported that GM crops could cross-pollinate with ordinary
crops over larger distances than had been thought. The government is
in its final year of trials to investigate the effect of growing GM
crops on the countryside.
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