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By
Paul Brown
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
beets 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 forever
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 soy 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.
The
Guardian August 15, 2002
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