Altering food crops

Plant breeders use a range of methods to produce varieties with particular qualities, such as traditional crop breeding and, more recently, chemicals and radiation.

The traditional method of cross-breeding to produce hybrid plants has been used for generations. This involves breeding different combinations of plants repeatedly to encourage sought-after characteristics and breed out the less desirable ones. However, through this method large amounts of genetic material are passed between plant varieties. This makes it more difficult to develop specific characteristics without incorporating other unwanted ones, such as susceptibility to disease.

Before precise genetic modification techniques were developed, plant breeders used a variety of methods to try to generate useful genetic alterations that had not appeared in the plant naturally. For example, one method that became popular in the 'nuclear age' after the Second World War was using radiation to alter the genes of crop and horticultural plants. The rice variety ‘Calrose 76' was produced using gamma rays to create a shorter plant, and ‘Alamo-X’ oats were produced using X-rays to give it resistance to blight.

A type of barley called 'Golden Promise' was also developed using gamma rays. This caused a genetic change in a particular variety of barley so that it produced a shorter plant with a high yield and good malting qualities – important for brewing. Originally sold in 1966, Golden Promise was the main variety grown in Scotland during the 1970s and 1980s. For information on crops that have been developed using radiation, see the International Atomic Energy Agency website.

Chemicals such as sodium azide and ethyl methanesulphate have also been used to alter plant genes. In the 1970s, this type of breeding was particularly popular in the USA and sometimes new varieties are still created using chemicals or radiation, especially in developing countries. However, these methods can take a long time to achieve desirable results because the genetic alterations they create are random. In fact, most of the genetic alterations generated by these methods are not useful for plant breeders. In contrast, genetic modification technology creates specific changes.

The first GM plants were created in 1983. Since then, a range of different crop plants, including soya beans, maize and rice have been created with characteristics such as herbicide tolerance and the ability to resist attack by insects and viruses.

The impulse to develop and improve crops, which has led to genetic modification technology, can be traced all the way back to the earliest farming communities, however. Why not take a look at our Time Tour to trace these developments?

Scientists are working to create crops with added nutritional value by changing the fat, protein or vitamin content of the plant.

For example, a type of rice called ‘Golden Rice’ is being developed with higher levels of beta carotene, which the body converts into vitamin A. This is intended for use in parts of the developing world where vitamin A deficiency is common. Lack of vitamin A can lead to permanent blindness and leave the body less able to fight off illness.

Another example is a potato that has been genetically modified with a gene from an amaranth plant to create a potato that has a third more protein than usual. Amaranth is a South American plant that was originally used by the Aztecs to make flour. Its leaves are sometimes used as a vegetable.

Researchers are also working on the following:

• Producing crops to grow on land that would typically be unsuitable. For example, one project is working towards producing tomatoes that can grow on soil containing high levels of salt'
• Removing the elements of a plant that trigger allergy or illness in some people. For example, a type of protein in rice can cause dermatitis, but switching off the gene should produce a variety of rice that is much less likely to trigger an allergic reaction.
• Developing ways of protecting plants against disease, such as mould.

Visit our eatwell website from more information on how GM is used in food production.

You can read more in the How is it being used section of our eatwell website.