Modified genes from crops in a genetically modified (GM) crop trial have transferred into local wild plants, creating a form of herbicide-resistant ‘superweedâ€.
The cross-fertilisation between GM oilseed rape and a distantly related plant, charlock, had been discounted as virtually impossible by scientists with the British government’s environment department. It was found during a follow-up to the government’s three-year trials of GM crops, which ended two years ago.
The new form of charlock was growing among others in a field that had been used to grow GM rape. When scientists treated it with lethal herbicide it showed no ill-effects.
The scientists also collected seeds from other weeds in the oilseed rape field and grew them in the laboratory. They found that two, both wild turnips, were herbicide resistant.
Brian Johnson, an ecological geneticist and member of the government’s specialist scientific group, which assessed the farm trials, has no doubt of the significance. ‘You only need one event in several million. As soon as it has taken place, the new plant has a huge, selective advantage. That plant will multiply rapidly.”
Johnson, who is head of the biotechnology advisory unit and head of the land management technologies group at English Nature, the government’s nature advisers, said: ‘I am not surprised by this. If you apply herbicide to plants, which is lethal, eventually a resistant survivor will turn up.”
It is not clear whether the charlock was fertile. Scientists collected eight seeds from the plant but they failed to germinate them and concluded that the plant was ‘not viableâ€.
But Johnson points out that the plant was very large and produced many flowers. ‘The GM trait could be in the plant’s pollen and, thus, be carried to other charlock in the neighbourhood, spreading the GM genes. This is, after all, how the cross-fertilisation between the rape and charlock must have occurred in the first place.”
Since charlock seeds can remain in the soil for 20 to 30 years before germinating, once GM plants have produced seeds it would be almost impossible to eliminate them.
The discovery that herbicide-resistant genes have transferred to farm weeds from GM crops is the second blow to the hopes of bio-tech companies to introduce their crops into Britain. Following farm scale trials, there was already scientific evidence that herbicide-tolerant oilseed rape and GM sugar beet were bad for biodiversity.
Farmers the world over are always troubled by what they call ‘volunteers†— crop plants that grow from seeds spilled from the previous harvest, of which oilseed rape is probably the greatest offender. Thousands of oilseed rape plants grow uninvited amid crops of wheat or barley in the English countryside, and in great swathes by the roadside where the ‘small greasy ballbearings†of seeds have spilled from lorries.
Farmers in Canada soon found that ‘volunteers†were resistant to at least one herbicide, and became impossible to kill with two or three applications of different weedkillers after a succession of various GM crops were grown. The new plants were dubbed superweeds. —