Pollen from a genetically modified grass has been shown to travel up to 21km away from the site where it was orginally planted.
The grass could see use on golf course putting greens
This may be the longest recorded distance travelled by any GM pollen, US researchers have claimed.
They tracked the spread of genes from creeping bentgrass engineered to resist popular herbicides and which could be used on golf-course putting greens.
Details appear in the Proceedings of the National Academy of Sciences.
Lidia Watrud and colleagues at the US Environmental Protection Agency tracked the flow of creeping bentgrass (Agrostis stolonifera L) pollen from an area containing an experimental crop in central Oregon, US.
After the pollination season, they gathered and raised seeds from wild and potted "sentinel" plants growing several km around the test plot.
Seedlings that had survived exposure to the herbicide Roundup were then checked to determine their genetic signatures.
The researchers found that plants growing within about 2km of the test plot were extensively contaminated with genes from the GM grasses.
But the team also found evidence of transgenic seed formation up to 21km downwind in potted sentinels and up to 14km away in wild plants.
The results are likely to heighten concerns about the unintentional spread of genes from GM crops.