Published online 8 February 2001 | Nature | doi:10.1038/news010208-9


GM plants make weedy weeds

Genetically modified crops are no better suited to life in the wild than their unmodified counterparts.

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.1

"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. 

  • References

    1. Crawley,M.J.,Brown, S.L.,Hails, R.S.,Kohn, D.D.& Rees, M. Transgenic crops in natural habitats. Nature 409,682 - 6832001. | Article | PubMed | ISI | ChemPort |