Several crop plants have been enhanced by genetic modification and so far the modifications that have worked best have been the simplest; those that can be accomplished by introducing just one gene into a plant with minimal effects on its physiology. Many more candidates await introduction and as techniques improve, more ambitious modifications may become reality.

What do they do?

So far the work on genetically engineered crop plants have been varieties that are better able to cope with environmental stresses such as disease or herbicides. Many virus and herbicide resistant crops have successfully been introduced. More complicated projects such as engineering nitrogen-fixing cereals, the "holy grail" of plant biotechnology, have yet to be tackled. The complexity of the relationship between nitrogen-fixing bacteria and the host plant is unlikely to be re-created artificially in the near future. Nonetheless production of cereals such as rice has doubled over the last generation and international collaborative efforts should ensure that biotechnology will help scientists continue to improve the quality and quantity of yields. This is essential if the demands of an increasingly numerous and affluent world population are to be met and the challenges of decreasing available land area and water supply are to be overcome.

Although research has concentrated on characteristics that are governed only by a single gene, longer- term research on more complicated traits controlled by several genes, is underway. This includes the possibility of building accurate, automatic indicators into plants. These would signal to the farmer what is needed in terms of fertiliser and water treatments and precisely when they should be applied. In this way, wasteful quantities of expensive and limited resources will be avoided, with applications only being made when the crop indicates there is a need for them. Efforts being made to engineer drought resistant crops would bring obvious advantages to farmers in areas of low rainfall. As techniques become increasingly sophisticated, there will also be a shift towards plants modified for nutritional or health-promoting qualities. Traditional foods and feed that have been marketed specifically as commodity products will be endowed with specific traits to serve particular markets. These improved products will be designed for health, nutrition, taste and new processing methods. The R&D pipeline is full of promising new products.

Specific developments include the reduction of allerginicity in foods as well as reducing the level of mycotoxins - potent toxins, often immune suppressors - which are deposited in grains by fungi during the growing season. At Nagoya University in Japan for example, researchers have managed to reduce levels of the major allergenic protein in rice by 70 to 80 per cent by inserting a so-called anti-sense gene to block the protein's production in the plant. Producers also want to reduce other molecules produced by the plant that can be anti-nutritive or toxic.

Further work focussed on increasing the nutritional content of foods involves modifying the oil, protein and carbohydrate properties as well as the vitamin and mineral content (for example vitamins C&E and beta carotene in fruit and vegetables). Priorities also include increasing digestibility and foods that contribute to disease prevention- both infectious and physiological diseases. Foods with additional health benefits will figure prominently. For example, food-incorporated vaccines that reduce cholesterol levels or reduce the chance of cancer are likely to be developed.

A criticism of food biotechnology is that few, if any, of the crops that have emerged so far have benefited farmers in the developing world. Several innovations in the pipeline might help. For example, fodder crops are being developed that contain more calories leading to more efficient livestock production. Also crops which are staples of the poor, such as sweet potato and cassava will be engineered to be virus resistant. Some could also be nutritionally improved. Another expected short-term development is rice that has an improved protein profile to include higher levels of the essential amino acid, lysine. This may help reduce childhood blindness in China caused by lysine deficiency.

FOOD TODAY 02/1999