One technology that deserves greater attention from both the public and policymakers is the use of tissue culture, the most widely used application of which involves creating copies of plants through a process known as micropropagation.

In essence, micropropagation involves taking tissue (known as an 'explant') from a plant and growing it on sterile media containing substances essential for growth. Once it is growing well, samples of this culture can be taken and used to grow entire plants under laboratory conditions.

The technique is currently used mainly with perennial crops that can reproduce vegetatively, producing new stems directly from the existing ones rather than needing to be pollinated and produce seeds.

It can be used to create millions of new 'clones' from a single plant, each genetically-identical to the parent plant.

The method can be used to produce large quantities of high-quality plant lines, to eliminate pathogens from infected planting materials, or to produce 'true-to-type' material from desirable plant lines.

Micropropagation has been developed over many decades, and can now be considered a 'mature' plant biotechnology. It is already widely used in developing countries, especially Asia - in particular as a result of the immense market in China for plants generated in this way.

It is relatively cheap, and has been shown in general to increase productivity (especially of root and tuber crops, such as sweet potatoes and potatoes).

Its most common application in developing countries involves producing virus-free plantlets by heat-treating the explant to kill any viruses present and then culturing cells from its 'meristem', the plant's actively growing tissue.

Because micropropagation cannot, however, guarantee that plants will be virus-free access to a virus diagnostic facility is essential.

Anther culture and embryo rescue

Another widely used tissue culture technique, 'anther culture', uses the immature pollen-producing organs of a plant to generate fertile 'haploid' plants, which have half the full set of genetic material.

These plants can later be crossed to produce pure homozygous 'diploid' plants, with identical copies of each gene, thus eliminating undesirable variation in key traits.

The technique is popular among breeders as an alternative to the numerous cycles of inbreeding or 'backcrossing' usually needed to obtain pure lines.

In vitro anther culture is now used routinely for improving vegetables, such as asparagus, sweet pepper, eggplant, watermelon and Brassica vegetables. It is also used, though to a lesser extent, for cereal crops such as rice, barley and wheat.

A further refinement of the technique is the so-called 'microspore culture'. This involved isolating and culturing the cells from which pollen grains develop, and can yield up to ten times as many haploid embryos as anther rescue.

A further tissue culture technique, known as 'embryo rescue' (or sometimes 'embryo culture') involves crossing species that are not normally sexually compatible. In nature embryos that result from such 'wide crosses' usually fail to develop. But in the laboratory, wide crosses can be used to transfer genetic traits from wild relatives of crops (i.e. secondary and tertiary gene pools) into cultivated crop plants (primary gene pools).

An example is triticale, a relatively new hybrid variety that is the result of a cross between rye and wheat.