Genetically modified wheat which gives off an odour that repels aphids has been grown for the first time by British scientists.
The crop has been manipulated to give off chemicals that aphids release to warn one another of danger. Scientists hope this can protect the plants by tricking the insects into staying away.
It is believed to be the world's first GM crop that repels insects instead of killing them, which experts say will reduce the chances of the pests developing immunity to it. Following successful lab tests, the first batches of seeds were planted last week at Rothamsted Research in Harpenden, and will be monitored throughout the summer.
The crop was designed purely for testing and not for commercial use, but if it proves effective the scientists running the project hope ultimately to develop an aphid-resistant strain of wheat that could be sold to farmers.
Prof Maurice Moloney, the director of Rothamsted Research, said: "Generally GM has been used in a mode whereby you have got to kill something. In this case what we are really doing is putting a no-parking zone on the leaf of the plant saying 'don't come here.'"
Wheat is one of Britain's major crops, with 15?million tons produced each year at a total value of about pounds 1.2?billion. Farmers are forced to use pesticides to protect their fields against pests, chiefly aphids, which would each year destroy wheat worth up to pounds 120?million by sucking out sugars and spreading viruses.
Concerns about the widespread use of pesticides, which are lethal to a variety of insects, and the risk of pests developing immunity to them led to the need for an alternative solution, the researchers said.
The solution, they believe, lies in a pheromone or chemical signal that aphids use to spread warnings of danger, for example the arrival of a predator such as a ladybird.
The chemical, known as (E)-beta-farnesene, is produced naturally in peppermint but not in sufficiently concentrated amounts to scare off pests.
By removing the gene which produces the chemical, adding it to the wheat and manipulating it so it is released in quantities that match those given off by aphids, the scientists believe they can make the pests seek out other food sources.
The pheromone is too mild to be smelled by humans and has the added benefit of attracting a tiny breed of parasitic wasp which reduces the aphid population by laying its eggs inside their bodies, the scientists said.
Prof John Pickett, who is leading the project, said: "We are using a natural process to control aphids but because it is a very difficult process that the aphids have evolved to use, we have had to use another living organism, which is the crop itself, to do this.
"We don't believe there is an alternative, but we are providing a new way of controlling the pests that doesn't rely on toxic modes of action. We believe in the long term all crops need to be protected through the genetics in the seed."
