London, April 2: Swedish plant ecologists have found that genetically modified oilseed rape can survive and produce plants as much as a decade after being sown.

Tina D'Hertefeldt of Lund University, who led the study leading to this discovery, says that she and her colleagues studied seedlings found growing at Lonnstorp Experimental Farm, where the biotech firm Plant Genetic Systems sowed a plot of various transgenic oilseed rape strains, including a herbicide-resistant variety, in 1995 as part of a trial.

Since 1996, the plot has been used to grow wheat, barley and sugar beet instead.

When the researchers collected seedlings from the plot in 2005, they found 38 oilseed rape plants growing amongst the modern crops.

Upon testing the plants with herbicides, the researchers found that 15 of such plants were resistant, and so came from seeds left by the transgenic plants.

After this discovery, the researchers now need to solve the problem as to how to monitor genetically modified crops, so that genes designed to pump out pharmaceuticals, for example, don't wind up in food, and crops labelled as 'organic' are pure enough to satisfy consumers and regulators.

The European Union rules that food labelled 'organic' should contain no more than 0.9 per cent of its material from genetically modified sources.

D'Hertefeldt admits that she does not have any way to tell whether the level of contamination her team found would exceed the European Union's limits in fields sown with GM oilseed rape and then used for food production.

"We found quite a low number of plants," Nature magazine quoted her as saying.

She said that persistence might not be such an issue with other transgenic crops, especially ones that can be prevented from producing seeds, like the high-starch potatoes being trailed in Germany.

However, she conceded, engineering oilseed rape not to produce flowers was out of the question.

"With oilseed rape the crop you're after is the oil, and the oil is in the seeds," D'Hertefeldt said.

A report on the study has been published in the journal Biology Letters. (ANI)