Bloodier oranges, more purple tomatoes, fishier vegetable oils and zinc-rich rice. Those are some of the latest genetic modification projects under way in UK plant laboratories, aimed at producing healthier food – and a response to those who say that the GM foods commercialised so far may benefit farmers but offer nothing to consumers.
The GM orange project follows nutritional research showing that juice from blood oranges gives additional health benefits compared with ordinary “blond” orange juice. One study, for instance, found that when a “full English” fried breakfast was washed down with a glass of blood orange juice this reduced the harmful cardiovascular effects of the fatty food.
The bloody pigmentation, which is believed to confer the fruit’s health benefits, comes from natural anti-oxidant compounds called anthocyanins. Now scientists at the John Innes Centre in Norwich have identified the gene responsible for producing anthocyanin pigmentation – which they call Ruby – and worked out how it is switched on.
Their research, published in The Plant Cell journal, explains why blood oranges can only be grown reliably on a commercial scale in eastern Sicily. The Ruby gene is controlled by genetic switches that are activated by cold stress. The Sicilian climate gives just the right combination of sunny days and cold nights as the fruit is growing, without destructive frosts. Attempts to produce blood oranges in the citrus growing areas of Florida, Brazil and South Africa, for example, often give weak and unreliable pigmentation.
“Our results offer little hope of conventionally breeding or identifying new varieties of blood orange that are free from cold dependency,” says Cathie Martin, the project leader. “We are now experimenting with hooking the Ruby gene up with a specific fruit [gene] promoter so it can be induced in another way.”
Some experimental GM orange seedlings, with the Ruby gene activated in this way, are growing near Valencia in Spain but they are still too young to bear fruit. If new fruit varieties capable of turning red in any weather can be commercialised, then the world’s citrus farmers will be able to produce far greater volumes of healthy blood orange juice.
A related project, also led by Martin, is beefing up the anthocyanin content in tomatoes. In contrast to the blood oranges, where the researchers switched on an existing gene that is usually inactive, they have inserted a new anthocyanin gene into the tomato plants – obtained from garden snapdragons. The purple tomatoes need now to be developed into commercial strains. Martin hopes a field trial will begin in the US in 2013-14.
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