Food production and tissue culture

Three routes can raise food production: agriculture based on agro-chemicals, organic agriculture, and agriculture based on genetically engineered crops.

The Green Revolution tripled the food supply, yet it still fell short of feeding a growing population. Its gains came partly from improved varieties but mainly from better management and agrochemicals (fertilisers and pesticides).

Agrochemicals are often too costly for farmers in developing countries, and conventional breeding cannot push the yield of existing varieties much higher.

Because traditional breeding could not keep pace with demand, tissue culture was developed. In the 1950s scientists learnt that a whole plant can be regenerated from an explant: any part of a plant removed and cultured in a test tube on a special nutrient medium, with everything kept sterile.

The capacity of any cell or explant to give rise to a whole plant is totipotency.

The medium must supply a carbon source such as sucrose, plus inorganic salts, vitamins, amino acids and growth regulators such as auxins and cytokinins.

Producing thousands of plants this way in a very short time is micro-propagation.

Every plant so produced is genetically identical to the parent it came from; such plants are somaclones.

Tomato, banana and apple are among the important food plants produced commercially by micro-propagation.