In Food Today 11, we examined the ways in which scientists are looking to improve crops by genetic modification. This article looks at some of the fruits (and vegetables!) of their research.

Plant viruses are a major problem in agriculture throughout the world. By introducing genetic protection into crop plants, they are made resistant to virus attack and there is the added benefit that farmers require less chemical spray to control the spread of disease.

Around the world, many virus resistant cereals, fruits and vegetables have already been introduced either commercially or in field trials. These include tomatoes, potatoes, melon, sweet pepper, papaya and several others. Resistance to insects and herbicides has also been introduced into many important crops by genetic modification. This is described in Food Today 9.

Another vital goal is to enhance food quality by genetic modification. One of the first developments was a tomato that could be left on the vine longer to allow the development of flavour, without becoming over-ripe and spoiled. This was achieved using a technique which involves switching off the gene in the plant which is responsible for the production of an enzyme that attacked cell walls of tomatoes, causing them to rot. Similar methods are being applied to other fruits such as bananas, strawberries, peaches, and melons. Sweet potatoes, an important crop in many poorer countries of the tropics, have been nutritionally improved by inserting a synthetic gene coding for a storage protein. This protein has a high content of so-called essential amino acids, ones that the human body cannot make for itself. The crop could be extremely useful in parts of the world where high -quality protein is scarce. Although not yet in commercial production, trials of the sweet potatoes have proved very promising.

Biotechnology can be used to increase the quantity of vitamins in foods. As well as working to enhance vitamin C & E contents of several kinds of fruit and vegetables, scientists are seeking to increase the amount of vitamin A in varieties of potatoes, bananas and tomatoes. This again is of significance for the developing world where vitamin A deficiency is relatively common and leads to impaired vision. Interest in food with health-promoting or medicinal properties also includes the development plants that will produce edible vaccines for human consumption.

Diarrhoea-causing organisms such as E.coli, a major cause of infant mortality, have been one focus of attention. In one set of experiments, researchers introduced the gene for an E.coli protein into potatoes, which made the protein. When human volunteers ate these potatoes they induced the production of antibodies to the protein. The next step will be to test the immunised volunteers with E.coli to see if the antibodies can protect against diarrhoea. Some further work suggests that it might even be possible to use genetically modified plants to produce an edible form of the hormone insulin. Plants may also be used to mass-produce expensive monoclonal antibodies to treat various diseases.

FOOD TODAY 03/1999