2-Plants: Weeds get boost from GM crops

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TITLE:  Weeds get boost from GM crops
SOURCE: The New Scientists, UK, by Andy Coghlan
        http://www.newscientist.com/news/news.jsp?id=ns99992671
DATE:   Aug 15, 2002

------------------ archive: http://www.gene.ch/genet.html ------------------


Weeds get boost from GM crops

Weeds become stronger and fitter by cross-breeding with genetically 
engineered crops, US researchers have shown for the first time. And at the 
same time, a team in France has demonstrated how easily weeds might be able 
to swap genes with the GM strains of sugar beet already in field trials.

The findings emphasise the need for developers of GM crops to be cautious 
about which traits they introduce into plants, in case they spread 
irreversibly to weeds.

They also strengthen the case for using technologies that would prevent 
gene spread altogether, argues Jeremy Sweet of the National Institute for 
Agricultural Botany in Cambridge, UK. "If you're worried about a gene which 
alters the fitness of wild populations, then stopping the GM plant breeding 
has got to be a good thing," he says.

Allison Snow's team at Ohio State University showed in controlled tests 
that wild sunflowers, considered a weed by many farmers in the US, become 
hardier and produce 50 per cent more seeds if they are crossed with a GM 
sunflower resistant to seed-nibbling moth larvae. "We were shocked," says 
Snow.

However, Pioneer Hi-Bred of Iowa, which developed the GM sunflower, says it 
has no plans to sell the strain commercially.


Wild relatives

Snow, whose results were presented to a conference last week, cautions 
against overstating the significance of the results. "It doesn't prove all 
GM crops are dangerous," she says. "I just think we need to be careful 
because genes can be very valuable for a weed and persist for ever once 
they're out there."

Pioneer Hi-Bred spokesman Doyle Karr adds that existing GM crops such as 
soybeans and maize do not have any wild relatives in the US. And although 
GM canola, or oilseed rape, is related to wild mustard, the only spread of 
genes so far has been to commercial non-GM rape, especially in Canada.

"It's all gene- and crop-specific," he says. "You ask beforehand what the 
implications are if there's crossover, and that's been true all along."


Gene flow

However, various companies are developing GM sugar beets. Studies of normal 
beet fields by Henk van Dijk and his colleagues at the University of Lille 
in France suggest that they have underestimated the likelihood of GM beets 
swapping genes with the beet weeds that grow among them. "We found gene 
flow to be possible between all forms," they write in the Journal of 
Applied Ecology.

The situation with beet is particularly complicated because there is a two-
way flow, with weed genes often polluting farm strains and reducing yields. 
The beet weeds could become even more of a nuisance to farmers if they pick 
up herbicide-resistance genes.

Van Dijk says that while tricks such as doubling the number of chromosomes 
in GM strains could reduce the chance of gene spread, they would not 
eliminate it. "It's almost inevitable," he says. But despite the risk, he 
still believes GM strains could help farmers.

Journal reference: Journal of Applied Ecology (vol 39, p 561)



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