One of the major risks posited for transgenic crop releases has 
been their potential to "go feral" and become weedy.

A long-term study in the UK provides quantitative evidence that, 
under UK conditions, the current releases of maize, oilseed rape, 
sugarbeet and potato show no tendency to become invasive.

Best wishes
 

David Duthie

***************************************************************************
Crawley, M. J., Brown, S. L., Hails, R. S., Kohn, D. D. & Rees, M. 
(2001)   Transgenic crops in natural habitats. Nature 409, 682–683

Summary by JOHN WHITFIELD

A ten-year survey of genetically modified (GM) crops has found that 
they do not survive well in the wild, and are no more likely to invade 
other habitats than their unmodified counterparts. The study will 
help to allay fears that GM plants will be super-weeds, either in 
their own right or by breeding with unmodified plants. 

"Problem plants have attributes that are totally different from crop 
plants," says Michael Crawley, an ecologist at Imperial College, 
London, and the leader of the team that conducted the experiment. 
"No matter what you do to an oilseed rape or wheat plant, it won't 
become a problem." 
 

In 1990, Crawley's team planted experimental plots of all the GM 
crop plants available: maize, sugar beet and oilseed rape varieties 
that had been made resistant to pesticides, and two varieties of 
potato modified to be insect-resistant. The researchers grew 
modified and unmodified crops alongside one another at 12 sites in 
the United Kingdom. 
 

The plants did not become self-seeding, self-sustaining 
populations, nor did they spread onto neighbouring unplanted 
areas. GM and non-GM plants both did equally badly — within four 
years all plots of maize, beet and rape had died out. Only one plot 
of potatoes lasted the full decade, and all the survivors are 
unmodified. 
 

"Approval of GM crops is based on the assumption that crop plants 
don't survive well without the attentions of farmers," says John 
Beringer, a microbiologist at the University of Bristol, UK, and 
former chairman of the UK government's Advisory Committee on 
Releases to the Environment. "It's nice to see that these 
expectations have been met." 
 

As for the possibility that GM traits might spread via hybrids, this 
is a "non-problem" says Crawley. "Gene flow out of crops is 
irrelevant if the hybrid isn't more competitive than it otherwise would 
have been," he says. 
 

But the researchers caution that plants genetically modified in the 
future for traits such as drought tolerance or pest resistance could 
be better at surviving on their own, and will need to be tested as 
they are developed. "Our results do not mean that other genetic
modifications could not increase weediness," they write. 
 

Beringer concurs that it is the trait that is introduced that matters, 
and not the fact of modification itself. "The concept that GM is 
intrinsically harmful will have to change," he says. 
 

Dr David Duthie (Programme Co-ordinator)
UNEP/GEF Biodiversity Planning Support Programme
T-133
PO Box 30552
Gigiri
Nairobi
KENYA

Tel: +254-2-623717
Fax: +254-2-624268/623162
E-mail: david.duthie@unep.org
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