"...Agricultural botanists in France have now shown that genes for herbicide resistance engineered into oilseed rape can persist for several generations in hybrids between the transgenic rape and wild radishes. Meanwhile, British researchers have found that potatoes engineered to resist attack by aphids can also harm ladybirds, the pests' natural predators.

While experts stress that neither finding poses a major environmental threat, industry sources fear that the new results will further undermine public acceptance of genetically engineered crops.

The escape of genes into wild plants has always been the main worry surrounding transgenic crops. To study this, Anne-Marie Chèvre and her colleagues at INRA, France's national agricultural research agency, based near Rennes, planted plots of wild radish, Raphanus raphanistrum, next to transgenic oilseed rape, Brassica napus. The rape was engineered to carry a gene for resistance to the herbicide glufosinate ammonium and did not produce pollen.

The researchers had found previously that the rape produced hybrids carrying 28 chromosomes, 19 from the rape, 9 from the radish. In this week's Nature (vol 389, p 924), they describe experiments in which the hybrids were planted surrounded by wild radishes, and followed through four generations.

Subsequent generations of the hybrids had variable numbers of chromosomes--anywhere between 20 and 60. "We never found a stable variety," says Frédérique Eber, the team's chromosome specialist. Even in the fourth generation, however, 20 per cent of the hybrids retained the gene for herbicide resistance.

Although the results suggest that the gene might be lost eventually, botanists note that the hybrids studied by the French team are more persistent than many crosses between different species, which frequently don't survive beyond the first generation. "Often things will die out at that stage," says Philip Dale of the John Innes Centre in Norwich.

John Beringer of the University of Bristol, who chairs Britain's Advisory Committee on Releases to the Environment, believes that there is no cause for public alarm. But hybrid weeds could remain in fields and sprout despite herbicide spraying. "It is more of a problem for farmers than an environmental problem." "