Potato

Potato, edible starchy tuber (underground food-storing stem). It is produced by certain plants of a genus of the nightshade family, especially the common white potato. The name is also applied to the plants themselves. The tuber of the white potato is a staple food in most countries of the temperate regions of the world. The plant is grown as an annual herb. The stem attains a length up to almost 1 m (3 ft), erect or prostrate, with pointed leaves and white to purple flowers. The fruit is a many-seeded berry about the size of a cherry. Like the stems and the foliage, the fruit contains significant amounts of solanin, a poisonous alkaloid characteristic of the genus. Three to six tubers form on the underground stem, although in some varieties there may be as many as 10 to 20. The tuber skin varies from brownish-white to purple. The plant, native to the Peruvian Andes, was probably first taken to Europe in the mid-16th century by Spanish explorers and was probably introduced to Britain by English explorers sailing from the New World only a few years later. The cultivation of the potato spread rapidly, especially in the temperate regions, and early in the 18th century the plant was introduced into North America.

In ordinary cultivation, propagation is accomplished by planting the tuber or a section of the tuber containing an eye, which is an undeveloped bud. New varieties are developed from seed produced after controlled pollination. Improved varieties may be propagated rapidly by using cuttings from the sprouts. There are hundreds of varieties of potatoes. Rich, sandy loams are most suitable for producing the light, mealy types favoured by British and American tastes; heavy, moist soils produce the firm type preferred by other Europeans. The most popular varieties in Britain are “King Edwards”, “Pentland Crown”, and “Maris Piper”. Freshly dug potatoes contain 78 per cent water, 18 per cent starch, 2.2 per cent protein, 1 per cent ash (inorganic constituents), and 0.1 per cent fat. About 75 per cent of the dry weight is carbohydrate. The potato is an important source of starch for the manufacture of adhesives and alcohol. Potatoes also contain many vitamins, including riboflavin, niacin, and vitamin C, and a number of minerals.

The most important disease of the potato is late blight (Phytophthora infestans), caused by a fungus that rots leaves, stems, and tubers. It was the late blight which caused the widespread failure of potato crops in Ireland in the 1840s, causing the Irish Famine. The early blight, caused by a different fungus, is not so destructive but causes lesions that permit entry of the various forms of bacterial rot. Several forms of mosaic disease and leaf curl are caused by infection with viruses. (See Diseases of Plants.) The Colorado potato beetle is the most destructive of the insect pests. See also Sweet Potato.

Scientific classification: Potatoes are produced by plants of the genus Solanum, of the family Solanaceae. The common white potato is classified as Solanum tuberosum.