Published online 6 August 2010 | Nature | doi:10.1038/news.2010.393

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Transgenic canola found growing freely in North Dakota.

If GM crops with herbicide resistance spread beyond farmland, they could become problematic weeds. IStockphoto

A genetically modified (GM) crop has been found thriving in the wild for the first time in the United States. Transgenic canola is growing freely in parts of North Dakota, researchers told the Ecological Society of America conference in Pittsburgh, Pennsylvania, today.

The scientists behind the discovery say this highlights a lack of proper monitoring and control of GM crops in the United States.

US farmers have dramatically increased their use of GM crops since the plants were introduced in the early 1990s. Last year, nearly half the world's transgenic crops were grown in US soil — Brazil, the world's second heaviest user, grew just 16%. GM crops have broken free from cultivated land in several countries, including Canada, the United Kingdom and Japan, but they have not previously been found in uncultivated land in the United States.

"The extent of the escape is unprecedented," says Cynthia Sagers, an ecologist at the University of Arkansas in Fayetteville, who led the research team that found the canola (Brassica napus, also known as rapeseed).

Sagers and her team found two varieties of transgenic canola in the wild — one modified to be resistant to Monsanto's Roundup herbicide (glyphosate), and one resistant to Bayer Crop Science's Liberty herbicide (gluphosinate). They also found some plants that were resistant to both herbicides, showing that the different GM plants had bred to produce a plant with a new trait that did not exist anywhere else.

Sagers says the previous discoveries in other countries of transgenic canola populations growing outside of cultivation were often in or near fields used for commercial transgenic canola production. By contrast, her research team found feral populations of herbicide-resistant canola growing along roads, near petrol stations and grocery stores, often at large distances from areas of agricultural production.

The researchers took samples of plants at 8-kilometre intervals along roads in North Dakota from 4 June to 23 July 2010. The number of B. napus plants in each sample plot was counted, and one plant was collected and tested for the presence of proteins that could give it resistance to either of the herbicides.

The team found B. napus at nearly half of the 288 sites tested. Of these, 80% had at least one herbicide-resistant transgene (41% were resistant to Roundup and 40% resistant to Liberty). They also found two plants that contained both transgenes.

Feral generations

Sagers says the discovery of plants that are resistant to both herbicides shows that "these feral populations of canola have been part of the landscape for several generations". Further studies are needed to establish whether these escaped GM canola plants have any ecological consequences. But those that have evolved resistance to both herbicides could become a weed problem for farmers, adds Sagers.

"The regulatory protocols designed to reduce or prevent escape and proliferation of feral transgenic crops are ineffective. Current tracking and monitoring of GM organisms are insufficient," she says. Sagers blames the delay in discovering escaped populations of transgenic plants in the United States largely on the lack of funding for research in this area.

Tom Nickson, head of environmental policy at Monsanto in St Louis, Missouri, told Nature, "Those familiar with canola know that these plants are readily found on roadsides and in areas near farmers' fields. This was true prior to the introduction of GM canola, and a common source is seed that has scattered during harvest and fallen off a truck during transport."

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Sagers agrees that feral populations could have become established after trucks carrying cultivated GM seeds spilled some of their load during transportation. She notes that the frequency and population density of GM canola that they found may be biased as they only sampled along roadsides.

Alison Snow, an ecologist at Ohio State University in Columbus, says it is not surprising that escaped transgenic plants have now been found in the United States, given that this has already happened elsewhere. The escaped populations "could be a problem if you are worried about herbicide use", she says. A major advantages of herbicide-resistant crops is that non-selective herbicides can be used, reducing the number of applications needed. But if transgenic crops escape and breed with related weed species, then that advantage could be eroded, and different and more herbicides might have to be used.