Modified crops could erase wild counterparts, study says (25/7/2003)

"There has been a lot of hand waving about the effects" of genetically modified organisms on wild populations of plants, said Don Waller, professor of botany and environmental studies at UW-Madison. "But this is solid evidence using a rigorous model" to show that these fears are founded.

Interesting that this research was published in a Royal Society journal that this research has received so little publicity, unlike the dubious "skylark" research which the RS hyped to the skies!
Modified crops could erase wild counterparts, study says
July 24, 2003

In an evolutionary blink of an eye, wild populations of agricultural crops could be obliterated by their genetically altered descendants.  Like an army of plant barbarians, these high-tech crops have the potential to invade, pillage - and possibly recruit - neighboring populations of ancestral crops by repeatedly blasting them with their DNA.

And according to researchers at the University of Wisconsin-Madison and the University of Minnesota-Twin Cities, relic populations of wild crops could be erased or transformed in just a matter of a few generations - possibly in less than a decade.

This is a concern not only for basic species conservation, but it could also mean the loss of an important reservoir of genetic diversity and information, said Hugh Iltis, a retired UW botany professor who discovered one of the earliest forms of wild corn.

"Wild plants are very precious," said Iltis, who did not contribute to this study. "You lose them and you lose a treasure of information."

In addition, the study indicates that genes designed for insect and pest resistance could potentially jump from agricultural crops to related weed species - spawning an army of weed warriors.

"There has been a lot of hand waving about the effects" of genetically modified organisms on wild populations of plants, said Don Waller, professor of botany and environmental studies at UW-Madison. "But this is solid evidence using a rigorous model" to show that these fears are founded.

The research, which appeared in this week's edition of the Proceedings of the Royal Society of London, is based on mathematical models that predict the rate of gene transfer between neighboring plant populations.

The model doesn't apply just to genetically modified crops, it's more universal, said Ralph Haygood, a zoology post-doctoral fellow at UW-Madison and an author of the paper.

The findings could spur research on the effects of genetically modified organisms on their wild, weedy progenitors - a hot topic in biotechnology and environmental studies.

Of particular concern are genes created using both plant and animal DNA. While humans have been combining plant DNA for thousands of years, no one knows the long-term effects of splicing plant and bacterial DNA.

Haygood's team built a model based on the laws of population genetics, paying close attention to the manner and speed that genes move between related plants.  They looked specifically at two evolutionary processes: genetic assimilation - crop genes replacing the wild plants' genes - and demographic swamping.

Swamping occurs after genetic assimilation. As the wild population picks up genes from surrounding crops, the small native patch begins to shrink. The patch eventually becomes so inundated with mongrel pollen that "migrational meltdown" occurs, and the wild population is erased, Haygood said.

It's like a 50-gallon tub of spring water bobbing along an ocean surface. As the spring water spills out and ocean spray comes in, it's just a matter of time before the tub is filled with water that looks, smells and tastes like the ocean around it.

And that's what the researchers predict will happen to these islands of wild plants - they'll be drowned out of existence in a very short time.

The study's model, unlike earlier models, assumes that the altered crop will be planted every year, just as corn is, said David Andow, co-author and professor of entomology at Minnesota. The crop plants would provide an unrelenting onslaught of high-tech pollen to the small wild population.

"The consequence of making that assumption is quite dramatic," said Andow, because it means that a gene could more rapidly spread into the wild than previously thought - even if it isn't beneficial.

Model criticized

Carol Mallory-Smith, a professor of weed science at Oregon State University, hesitates to embrace their model.

"While I think their conclusions are correct, there's no new biology here," she said. "For as long as people have been cultivating plants, this has been happening."

In any case, she said, the most critical threat to wild plants is not crop invasion, but habitat destruction and deforestation.

But to professor Waller of UW, it's a weak argument.

"That's like saying you shouldn't be worried about logging old-growth forests in the Pacific Northwest" because loggers will just find other forests to cut down, he said. The problem is the genes escaping into the wild, creating weed-warrior species.

In any case, William Tracy, a UW professor of agronomy, said that while habitat degradation and overpopulation drive wild populations to the brink, gene flow simply "pushes them over the edge," with dire consequences.

Continental divide

In terms of a super-weed scenario, North America is lucky. Most of the major crops grown here are far removed from their related species. For instance, corn originated in the highlands of Mexico, and wheat is from the Middle East.

But it could become a North American problem if sunflowers, pumpkin, squash, blueberry, cranberry and some rice varieties are tinkered with.

"Both the EPA and the USDA do look at crops that cross-pollinate to study for the potential of movement to weedy relatives," said Lisa Dry, the communications director at Biotechnology Industry Organization, which represents over 1,100 biotech firms.

She said that the Environmental Protection Agency has established buffer zones "to ensure that crops are not going to places they should not be going."

Some universities have seed banks, repositories of native DNA, providing insurance.

"The problem with plants is they aren't animals; they don't move," said Iltis. So you may not know what you've already run over.
GM crops gene leakage 'could wipe out wild relatives'

Genetically modified crops could easily spread their genes and threaten the survival of related wild plants, according to a study.  Computer models show that pollen from crop fields can rapidly contaminate wild relatives, even under normal conditions.

As a result, wild species may be swamped by weak hybrids that reproduce poorly and cause their population size to shrink. At the same time, potentially valuable genetic traits could be lost for ever.

Dr Ralph Haygood, from the University of Wisconsin-Madison, who led the research, said: "You don't need high rates of pollen flow or strongly favoured traits. Crop genes, even deleterious ones, can easily become common in wild populations within 10 to 20 generations."

The findings apply to crops developed by cross-breeding as well as genetic engineering. But they are especially relevant to GM crops, which have prompted the most concern about gene leakage.

Some scientists fear GM crops containing herbicide-resistant genes might give rise to resistant superweeds, or damage the environment in other ways. Dr Haygood said growers around the world had already planted 145 million acres of genetically modified crops.

GM experts in the UK said on Monday there was no scientific case for ruling out all genetically modified crops and their products. The GM Science Review Panel published a report which followed an inquiry chaired by the Government's Chief Scientific Adviser Sir David King.

It was criticised by green lobby groups and former Environment Minister  Michael Meacher described it as a "public scandal".

Dr Haygood's team found that crop genes rapidly took over wild populations. Sometimes just a small increase in the rate at which pollen was blown on the wind or carried by insects made a big difference to gene spread.

Researchers say affected wild plants could have their genetic make-up changed for the worse, or suffer a population meltdown.

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