Exploiting the smell of genetically modified fear

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Biotechnology is back on the political agenda today with the launch of a field trial designed to assess a new variety of aphid repelling GM wheat.

Scientists have used genetic engineering to add a peppermint plant gene to wheat that expresses an alarm pheromone that aphids associate with danger.

It's the same smell that aphids themselves produce when they're under attack from a predator - warning other bugs to keep clear. And in one of those twists so often found in nature, the odour also attracts the aphids' natural predators - parasitic wasps and labybirds - resulting in a double whammy of fewer pests and more predators homing in on the crop.

Aphids are a major pest problem for cereal crops across northern Europe, causing £80m to £120m worth of losses to UK farmers every year. Millions more are spent on expensive, highly toxic and carbon intensive pesticides to protect against infestation. By exploiting the natural defences some plants have evolved to combat the threat, the scientists (based at the Rothamsted Research Station in Hertfordshire), hope to boost cereal production and cut costs in an ecologically-friendly way.

"It's a very clever combination of biotechnology, chemistry and natural ecology" according to Professor Maurice Maloney the Director of Rothamsted Research. "Using GM as a tool to enhance natural defence mechanisms is a big step forward for crop protection that also benefits the environment".

The pheromone, E-beta-Farnesene, is produced by aphids as a chemical distress signal that's released when they come under attack from predators. It acts as a deterrent, warning other aphids to stay away, but in the continuing arms race of natural selection some plants - including some species of peppermint - have evolved the ability to mimic the smell, expressing their own versions of E-beta-Farnesene.

The job of engineering the pheromone producing gene into a high performance wheat variety - cadenza - was taken on by Professor Johnathan Napier in the 1980's.

"Although the basic idea is quite simple," he says, "it's taken the best part of 20 years to refine and perfect the transfer. The problem is getting the plant to express the aphid alarm pheromone at appropriate levels and in a very pure form. You want the aphid to pick up on the scent of another terrified aphid, not just that the plant is a bit smelly."

Image caption The peppermint plant odour attracts aphid predators, including ladybirds

The science may be clever, but it's already attracting the kind of criticism levelled at earlier trials of genetically modified crops. Pete Riley from the anti-GM campaign group GM Freeze says there are a number of unpredictable risks attached to conducting research in the open countryside.

"Insects adapt quickly," he says, "and if you expose them to this pheromone for any length of time they're likely to get habituated to it and ignore it. There are also safety concerns about whether this gene will change the chemistry of wheat in ways we can't predict".

Speaking on the programme this morning Professor John Pickett, who leads the research on new approaches to pest control at Rothamsted, said they had conducted extensive safety tests in the laboratory ahead of the field trial, and that although the risk of something unforseen could never be completely eliminated, that had to be weighed against the potential benefits to society.

It remains to be seen whether this new, more subtle, approach to genetic engineering that relies on exploiting and enhancing a plant's natural defences will re-ignite the GM wars.