The world's first genetically modified crop that has been deliberately engineered to emit a repellent-smelling substance against insect pests is now growing in a small patch of land in the Hertfordshire countryside. Scientists have created the "whiffy" wheat in an effort to combat aphid attacks that can cause upwards of £120m of damage each year to the UK's most important cereal crop, which has an annual value of £1.2bn – and rising.
The field trial, however, is also one of several "second generation" GM crops that scientists hope will be more acceptable to the British public who resoundingly rejected the first generation of commercial GM crops – such as herbicide-tolerant cereals – which are nevertheless grown extensively outside Europe.
The first commercial GM crop was developed in the early 1990s. It was a tomato that would remain fresh after picking and although consumed in the United States, it was never sold in the UK.
Monsanto, the multinational agrochemicals company based in St Louis, Missouri, then came up with a herbicide-tolerant soybean plant. The crop could grow even if sprayed by a weedkiller, which was conveniently made by the same company.
For many people, GM technology was not seen as a socially useful scientific development but a means for companies to increase their market share and profits. The death knell for GM in Britain probably came at the end of the 1990s when a scientist working at a UK research institute claimed to have shown that GM potatoes were poisonous to laboratory rats – even though the research methodology was widely condemned as flawed.
The green movement jumped on GM as anti-environment, while anti-capitalists claimed it was designed to maximise profits at the expense of the people. Meanwhile the Daily Mail came out against "Frankenfood" as unwarranted meddling with the food chain.
But now scientists believe the time has come to fight back. They believe that time is running out for new ways to feed a growing human population, exacerbated by the growing number of wealthy people of the developing world who want to eat to a protein-rich, meat-based diet. Scientists view GM technology as a way of extending the successful "green revolution" of the late 20th Century into the 21st Century.
This is the background to the GM wheat trial in Hertfordshire.
The GM wheat contains an added, synthetic gene that causes the plant to exude an insect pheromone on its leaves which is naturally produced by "frightened" aphids as a warning signal to other aphids. Although the pheromone released by the GM wheat plants will be undetectable to the human nose, the scientists hope that it will deter species of cereal aphids which spread harmful plant viruses as well as sucking energy from the crop.
However, the aphid's "fear" pheromone – known as farnesene – has the opposite effect on beneficial insects, such as ladybirds and parasitic wasps that feed on aphids, because they are attracted to the smell.
The scientists hope these predators will visit the GM crop early enough in the growing season to prevent aphid infestations.
The small-scale field trial, at the government-funded Rothamsted Research station near Harpenden, is designed to test whether the GM wheat variety is able to repel significant numbers of aphids as well as attract the beneficial insects that feed on them, said Rothamsted's director, Professor Maurice Moloney.
"GM has traditionally been associated with killing something. Either killing the weeds or killing the insects. In this case what we are doing is putting a 'no parking' sign on every leaf of the plant.
"It's a very different strategy from what's been done so far and I think it will open up many avenues that will allow us to use natural mechanisms and allow to respond to concerns from the public about the amount of pesticides that are used."
The field trial has been approved by the Government's Advisory Committee on Releases to the Environment, which has to oversee all outdoor GM experiments and field trials. Among the many preconditions was the stipulation that the GM wheat would not be eaten by humans or animals at the end of the experiment.
The committee also stipulated that the movement of pollen and seeds from the crop should be controlled with biological barriers and weed killer. A tall metal fence will protect the site from unauthorised people as well as birds, hedgehogs, rabbits and other large animals. Professor John Pickett, the scientist in charge of the experiment, said that there is still likely to be some opposition to the trial, even though it has been discussed in detail with people and organisations opposed to GM crops.
"We've had meetings with the public and anti-GM lobby groups, and we've found there is common ground because I think there is a lot of common interest in improving the sustainability of agriculture and in using natural processes," Professor Pickett said. "We do feel there is a better view of GM technology from the public at large but we recognise there are some individuals who are strongly against this kind of thing and they may seek to disrupt it by direct action," he said.
The idea behind the experiment dates back to the mid-1980s but it was only in 2006 that Rothamsted scientists demonstrated that it was possible to isolate the gene for the farnesene pheromone and insert into an experimental plant.
"We've done a lot of work in the lab and it works really well. It repels the aphids and attracts in the parasitic wasps brilliantly – better than our wildest dreams," Professor Pickett said.
Many wild flowers have evolved the same pheromone gene as a natural defence against aphids, so the scientists went to the peppermint plant as the source of the gene that they engineered and inserted into the wheat plant. Professor Moloney said that the study of "chemical ecology" is about understanding the substances that are continually being passed between organisms and using them in a way that can control pests in a more natural way that is less harmful to the environment than some pesticides.
"When we breed for plants, we breed for things like yield and disease resistance – and sometimes what's lost in the process is some ancient natural mechanisms the plant uses to protect itself," Professor Moloney said.
"Quite often we find it's the weeds out there that are protected against aphid attack, as opposed to crop plants. So what we've done is go back to these wild plants to see if we can reconstruct mechanisms that they probably would have had earlier in their evolution."
However, many wild plants produce a mixture of volatile substances that allow aphids to distinguish the plant-produced substance from the genuine insect fear pheromone. The difficult trick was to create a GM wheat plant that produces copious quantities of pure pheromone, said Professor John Napier, who led genetics team behind the work.
The idea eventually would be to produce GM wheat varieties that do not need to be sprayed with harmful pesticides. The scientists believe that preventing aphid infestations would benefit the wider environment, including the songbirds that feed on aphids.
The new GM: Latest crop of ideas
Cereals with a "zinc sink"
Scientists hope to produce genetically modified grains such as cereals and rice with higher levels of zinc, which is essential for many vital enzymes. A third of the world's population is estimated to have a zinc-deficient diet.
Fish oil in plants
The genes for long-chain omega 3, an ingredient of fish oil with proven benefits for human health, are being inserted into plants in the hope of producing GM oilseed rape with medicinal properties.
Genetically modified tomatoes have already been created with extra genes for boosting the red pigments found in snapdragon plants. These antioxidants, which are also found in blueberries and blackberries, could help to prevent cancer.