Eventually, the plantlets can be transferred into soil. So far this technology has been used to produce commercial crops aimed at the farmer. The other main approach has been to develop crops that are resistant to herbicides, allowing farmers to apply chemical sprays that kill weeds not crops. The next product of the biotech revolution, at least in the US, is likely to be genetically modified wheat. Monsanto's spring-sown variety has been engineered to confer resistance to Monsanto's Roundup weedkiller.
Field trials are now underway in North and South Dakota, Montana and Minnesota.
As a staple part of the diet of millions of people around the world, the advent of the GM loaf is likely to be a particularly sensitive issue for consumers. And there are signs that the US wheat industry is being very cautious about deciding whether or not to go forward with the technology. The first such foods are likely to appear on the supermarket shelves in the next few years. Golden rice One of the first examples is being kept under lock and key in a grenade-proof greenhouse on the outskirts of Zurich, Switzerland. Unlike any other rice, this genetically modified variety contains a gene from a daffodil that enables it to produce beta-carotene in seeds.