Cultivated potatoes:

Nutritious tubers

Erdapfel, Erdbirne, Kantüffel, Krumbeer and Tüfte – the regional names used to describe the potato are almost as diverse as the varieties available. The potato belongs to the nightshade family (solanaceae), which also includes tomatoes, tobacco, deadly nightshade and datura (thorn-apple). The sweet potato, however, is not related to our traditional potato.

The potato is one of the most important food crops in the world, and it is healthy. It contains valuable plant protein, the essential amino acid lysine, high levels of potassium and other minerals (calcium magnesium, phosphorous, iron and zinc) as well as vitamin C and vitamins from the B group. In addition, the fat content of the potato is very low, at around 0.1 %.

Potato constituents
Source: aid

Cultivated areas world-wide 2010
Source: FAO, Agrarmärkte 2010, LEL Schwäbisch Gmünd

Potatoes harvested
world-wide 2010

Source: FAO, Agrarmärkte 2011, LEL Schwäbisch Gmünd

Berries on a potato plan

The parts of the potato plant growing above ground are poisonous

The potato originates from the South American Andes, where it was used as a food even by the Incas. Some potato varieties can even grow at altitudes of 2000 metres. Today potatoes are grown throughout the world, from temperate regions to the subtropics. Whilst there are more than 200 botanical species of potato in South America, seven of which are cultivated, the only species to be grown in Europe is Solanum tuberosum. According to the Food and Agriculture Organization, about 320 million tonnes of potatoes were harvested worldwide in 2010. The leading potato-growing countries are China, India, Russia, USA and the Ukraine, in the European Union potatoes are mostly cultivated in Poland, Germany and Romania.

Vegetative propagation via tubers

Potato flowers may be reddish purple, bluish purple, or white, depending on the variety. Since the flower is hermaphroditic, fertilisation generally takes place via self-pollination. Potatoes grown in the field are propagated only vegetatively via tubers, as that is the only way to preserve the traits valued by retailers and consumers. New shoots emerge from the ‘eyes’ of the mother tuber, making the ensuing daughter tuber a clone of the mother, in other words it is genetically identical. The flowers develop into green, cherry-like berries containing up to 150 seeds. Potato plants can be grown from seed in protected conditions in a greenhouse. These plants that are the result of generative propagation, produce plum-sized ‘seed potatoes’, which are used only for growing purposes. All parts of the potato plant growing above the ground are poisonous: they contain the alkaloid solanin.

The cultivated potato is tetraploid, i.e. it has four sets of chromosomes and therefore a highly complex inheritance pattern. This makes it very difficult to cross one, let alone several, desired traits, especially since several genes are usually responsible for a single trait.

Potato varieties: global diversity

The International Potato Institute in Lima (Peru) is home to the largest gene databank in the world, with around 100 wild potato varieties and 3,800 varieties traditionally cultivated in the Andes. There are around 5,000 potato varieties worldwide. The common European catalogue of varieties contains more than 1400 varieties, and in Germany more than 200 varieties of potato are approved. Depending on the variety, the flesh of the potato may be whitish, yellow or, as in the case of the truffle potato, dark purple.

Potato varieties in Germany are registered in the National List of Plant Varieties at the Federal Office of Plant Varieties in Hanover. Breeders can also apply for variety protection rights for new varieties. This means that growers have to pay royalties to the breeder concerned for a 30-year period. This can cause conflict with suppliers, if, for example, established varieties are taken off the market when the term of protection expires. This then prohibits free trade, as was the case with the potato variety Linda.