Seeds more risky than pollen for GM escape
Seeds more risky than pollen for GM escape
00:01 18 June 03
NewScientist.com news service
Seeds are more likely than pollen to spread genes from genetically-modified sugar beet into wild relatives, researchers have warned. Previously, concern about the leakage of genes from GM crops into the environment has focused on pollen, which can blow for long distances on the wind. But new research in France reveals that the transport of seeds may present a greater risk.
Jean-FranÃ§ois Arnaud, head of the research team at Lille University, says: "Accidental transport of seeds within soils carried on motor vehicles, or by other normal agricultural activities provide the best explanation."
Arnaud's team used molecular markers to track different types of sugar beet, including the weedy hybrids of commercial and wild sugar beet that commonly form in fields. The team found that the weedy hybrids, which produce more seeds that the commercial sugar beets, had somehow migrated 1500 metres from the fields and were mingling with wild sea beet. The far-flung hybrids must have come from seed because they had maternal genes, rather than the paternal ones carried by pollen.
Arnaud thinks that soil transported from beet growing areas to assist with dyke reconstruction might have carried the seeds, or that seeds might have been dropped in dirt from lorries transporting harvested beet to factories.
No GM varieties were Arnaud's research, but the principle would be the same. The implication is that the inadvertent transport of seeds might have been overlooked when assessing the risks posed by GM sugar beet.
"Our result was unexpected," the team write in Proceedings of the Royal Society B, "since most studies involving the assessment of transgene escape generally focus only on pollen dispersal."
Arnaud warns that care should therefore be taken in choosing where to grow sugar beet. Furthermore, farmers growing GM sugar beet might need to dig up the weedy hybrids in their fields to stop them producing seeds that could then be dispersed.
Jeremy Sweet of NIAB, a crop research company in Cambridge, UK, goes further: "The research means that if you put any gene into sugar beet, it would get into wild beet - it's inevitable. But it is taken into account when risk assessments are conducted on GM beet."
He says that the environmental impact on the wild sea beet would therefore depend on whether the gene significantly alters the behaviour or ecology of that plant.
Journal reference: Proceedings of the Royal Society B (DOI: 10.1098/rspb.2003.2407)
Humans may spread GM seeds
Study suggests intrepid beet weed seeds could spread crop genes into wild relatives.
18 June 2003
Hitch-hiking on farm machinery, the seeds of sugar-beet weeds can travel more than a kilometre from the field where they were born. In theory, such seeds could spread genes from genetically modified (GM) crops into their wild relatives.
But the finding, some of the first evidence of gene flow from crops through seeds, rather than pollen, should not increase worries over the environmental impact of growing GM foods, researchers say.
"You can't contain genes," says ecologist Alan Gray of the Centre for Ecology and Hydrology in Dorset, UK. "The concern is to identify possible hazards from gene flow - we must be very careful about the sort of genes we put in." Gray chairs the UK government's Advisory Committee on Releases to the Environment.
The study suggests that, in managing GM crops, farming practices will be as important as technology. To minimize gene flow, domestic and wild beets need to be well separated, and fields must be carefully weeded.
The problem is neither the crops nor the wild plants themselves, but crosses between the two. Domestic sugar beet breeds with its wild relative, sea beet (Beta vulgaris ssp. maritima). The resulting hybrids are potent weeds, producing thousands of seeds in their first year.
These weedy beets' seeds get around, Joel Cuguen of the University of Lille in France and colleagues have found1. Once the weeds are alongside their wild relatives, they breed with the wild plants.
The researchers DNA fingerprinted weeds in a sugar-beet field in northern France, and those growing alongside a river 1.5 kilometres away, where sea beet also grows.
The river weeds were descended from those in the field. They must have been transported there as seeds - in soil on agricultural equipment, for example, says Cuguen. "Gene flow through seeds is too often underestimated."
"If you grow beets near the coast, escape is possible," agrees ecologist Detlef Bartsch of the Robert Koch Institute, Berlin. Gene escape is even more likely in southern Europe, where the crop is grown for seed, he warns. The herbicide-tolerant beet varieties being grown in the United States and on trial in Europe will have no advantage over wild plants - although herbicide-resistant weeds might give farmers a problem.
But possible future varieties, such as insect- or disease-resistant strains, might cause environmental damage. "Gene escape will take place - the question is what the genes are," says Bartsch.