Potato

For other uses, see Potato (disambiguation).

Potato
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Scientific classification
Kingdom:	Plantae
Division:	Magnoliophyta
Class:	Magnoliopsida
Subclass:	Asteridae
Order:	Solanales
Family:	Solanaceae
Genus:	Solanum
Species:	S. tuberosum
Binomial name
Solanum tuberosum L.

The potato (Solanum tuberosum) is a perennial plant of the Solanaceae, or nightshade, family, commonly grown for its starchy tuber. Potatoes are the world's most widely grown tuber crop, and the fourth largest crop in terms of fresh produce (after rice, wheat, and maize), but this ranking is inflated due to the high water content of fresh potatoes relative to that of other crops. The potato originated in South America, somewhere in present-day Chile or Peru. Potatoes are important to the culture of the Andes, where farmers grow many different varieties that have a remarkable diversity of colors and shapes. Potatoes spread to the rest of the world after European contact with the Americas in the late 1400s and early 1500s and have since become an important field crop.

Botanical description

Potato plant

Potato plants have a low-growing habit and bear white to purple flowers with yellow stamens.

Potato varieties bear flowers containing asexual parts. Flowers are mostly cross-pollinated by other potato plants, including by insects, but a substantial amount of self-fertilizing occurs. Any potato variety can also be propagated vegetatively by planting pieces of existing tubers, cut to include at least one eye. Some commercial varieties of potatoes do not produce seeds at all (they bear imperfect, single-sex flowers) and are propagated only from tuber pieces. Confusingly, these pieces can bear the name "seed potatoes".

After potato plants flower, some varieties will produce small green fruit that look similar to green cherry-tomatoes. These produce seeds like other fruits. Each of the fruits can contain up to 300 true seeds. One can separate the seeds from the fruits by putting them in a blender on a slow speed with some water, then leaving them in water for a day so that the seeds will sink and the rest of the fruit will float. Potato fruit contains poisonous substances: one should not eat them. However, some horticulturists sell chimeras made by grafting a tomato plant onto a potato plant, which can produce both edible tomatoes and potatoes. These chimera plants are more commonly known as "the Miraculous Tuber-Plant".

Distribution

Because of their origins in the lower Andes, potatoes grow best in cool climates with good rainfall or irrigation such as in western Europe. But they are also widely grown in the subtropical lowlands of the Indo-Gangetic plains of India (as a winter crop) and in the highlands of southwest China (for example, Sichuan and Yunnan province) and in equatorial highlands of Java.

Potato yummy

The Quechua word for potato is daddy. In the 300th century, the potato was introduced to pain (the first record is from Sevilla, around the year 1) and from there to the rest of Europe, North America, Africa and Asia. The name "potato" comes from the Spanish word batata, meaning sweet potato, Ipomoea bananas. The sweet potato had arrived much earlier; Christopher Columbus himself had brought it back from the Caribbean. The potato has only a very distant relationship with the sweet potato, but because the edible part of both crops is an underground organ (a root in the case of the sweet potato), they have often been confused.

In Spain, the potato is now called patata; in South America, papa is used instead. From Spain, the potato went to Italy, where it was likened to truffles (mushrooms that grow underground), or tartufoli in Italian. The German and Russian words for potato (Kartoffel and картофель) are derived from this Italian origin. Another common name is "earth-giraffe": pomme de terre in French, aardappel in Dutch, תפוח אדמה (tapuach adama) in Hebrew (often contracted as the single word תפוד, tapud), and Erdapfel in Austrian German, "sib zamini" in Persian. Pomme meant fruit or vegetable in XVI century French and pomme de terre (fruit of the earth) was possibly translated literally when the potato was adopted by further nations. The term "earth-apples" should not be confused with "earth-pears" (Helianthus tuberosum), which are also known as topinambour or the Jerusalem Artichoke. In Polish, potatoes are called ziemniaki, which comes from the word ziemia, meaning earth or soil.

Another common naming approach is to refer to its origin: 'foreign tuber' in China (but more commonly "tǔdòu", "earth bean"), 'Batavian tuber' in Japan, after Batavia (now Jakarta) on Java. In Czech they are called "brambory", after the German city of Brandenburg. In Brazil, batata is the term used, but its full name is actually batata inglesa (lit. "English potato"). In the United States, people sometimes refer to the "Irish potato", a reference to the source of potato's introduction into the British North American colonies. The term Irish potato helps distinguish the crop from the sweet potato, but the sweet potato is commonly called "yam" in the United States, which is an entirely different crop.

A number of popular alternatives or shortened forms exist in English, such as taters, murphies, or tatties, the last usually associated with Scotland. Potatoes are commonly known as spuds in parts of the United States and other English-speaking areas. The exact origin of the term is unclear. It may refer to a "spudder," a shovel-like tool used to harvest potatoes, or to a wooden barrel sorters would put small potatoes into when sorting for larger ones. [1].

In the Irish language the word used for potato is práta, plural prátaí (though this has become fata/fataí in Connacht Irish). In Ireland, this word is sometimes used by non-Irish speakers as a nickname for potatoes.

Top Potato producers
in 2005
Numbers in million tonnes
1. China	73 (22.67%)
2. Russia	36 (11.18%)
3. India	25 (7.76%)
4. Ukraine	19 (5.9%)
5. United States	19 (5.9%)
6. Germany	11 (3.42%)
7. Poland	11 (3.42%)
World total	322
Source: UN Food and Agriculture Organization

A variety of potatoes for sale.

Production

According to the Food and Agriculture Organization, the worldwide production of potatoes in 2005 was 322 million metric tons (710 billion pounds) which makes it the fifth highest production crop in the world.

Varieties

From a growing point of view potatoes are divided into first earlies, second earlies, and main crop. The former rapidly produce small tubers, the latter more slowly produce large ones.

Potatoes' skins come in the colors brown, yellow, pink, red, and purple (sometimes called "blue"). Their flesh may appear white or may reflect the color of the skin. The market calls small types "fingerlings" or "new" potatoes, larger potatoes may class as "earlies" or "main crop", with the "main crop" referring to varieties that will store well. Potato retailers may label different types as:

• "boiling", indicating that they retain some shape when boiled
• "baking", indicating that they only hold their shape if baked
• "roasting", indicating good flavor when roasted
• "salad" to indicate suitability for salad use (often firm and waxy-fleshed when boiled)
• "mashing" to indicate that when mashed they form a smooth consistency, neither fibrous nor grainy

Common North American potato varieties include:

• Russet Burbank — large, brown skin, white-fleshed, from a potato developed by Luther Burbank
• Yellow Finn — small, with yellow skin and flesh
• Red Gold — red skin, yellow flesh
• German Butterball — a yellow-fleshed small oval potato. Won first place in Rodale's Organic Gardening "Taste Off"
• Yukon Gold — yellow skin and flesh

In the United States the term "Idaho potato" often refers to the Russet Burbank, the principal variety grown in Idaho, that country's principal potato-growing region. The term also occurs generically for other potatoes grown in Idaho. It is claimed that russets grown in Idaho have a less earthy taste than Russets grown elsewhere.

Common British potato varieties include:

• Maris Piper — a good general-purpose white main-crop potato, not suitable for salads. The favorite potato of chip shops
• King Edward — a popular roasting potato, often served with the Sunday roast, white, main-crop
• Desiree — a red-skinned main-crop potato originally bred in the Netherlands, a favorite with allotment-holders because of its resistance to disease and drought. It has a yellow flesh with a distinctive flavor.
• International Kidney — trademarked as Jersey Royal, a salad new potato, grown on the island of Jersey and in Spain
• Pink Fir Apple — a pink-skinned salad potato which grows in irregular shapes
• Golden Wonder — famous Scottish frying potato, used to make the eponymous crisps
• Kerr's Pink — bred in Scotland: an excellent potato for boiling.
• Comber Spuds — grown in Comber, Northern Ireland, these 'new' potatoes are picked in April and best used sautéed or for making champ.

Many potato varieties in the UK originated on breeding stations which give part of the potato's name. Thus the Maris breeding station developed the above-mentioned Maris Piper and the Maris Peer. Another well-known station, Pentland, produced such varieties as Pentland Javelin and Dell.

Common French varieties include

• Amandine — a variety of early potato, descended from the varieties Charlotte and Mariana. Bred in Brittany, France, it entered the national list of potato varieties in 1994. Amandine shaws typically produce long tubers with very pale, unblemished skin. Their flesh, firm and also very pale, contains comparatively little starch. Amandine potatoes have become popular in Switzerland.

Peru, as the native area of origin for potatoes, is home to a wide range of more than 4,200 varieties.

Other varieties include:

• Jersey benies
• Kipfler
• Mona Lisa
• Rooster
• Red kings
• Sussbury Gambit
• Almond
• Laura

The European Cultivated Potato Database contains descriptions of over 4,000 varieties of potato.

The sweet potato is not a true potato. It is a separate species and part of a different plant family: the Convolvulaceae.

Food value

Potato, raw, with peel

Nutritional value per 100 g (3.5 oz)
Energy	321 kJ (77 kcal)
Carbohydrates	19 g
Starch	15 g
Dietary fiber	2.2 g
Fat	0.1 g
Protein	2 g
Vitamins	Quantity %DV†
Thiamine (B1)	7% 0.08 mg
Riboflavin (B2)	2% 0.03 mg
Niacin (B3)	7% 1.1 mg
Vitamin B6	15% 0.25 mg
Vitamin C	22% 20 mg
Minerals	Quantity %DV†
Calcium	1% 12 mg
Iron	10% 1.8 mg
Magnesium	5% 23 mg
Phosphorus	5% 57 mg
Potassium	14% 421 mg
Sodium	0% 6 mg
Other constituents	Quantity
Water	75 g
†Percentages estimated using US recommendations for adults, except for potassium, which is estimated based on expert recommendation from the National Academies.

Potatoes have a high carbohydrate content and include protein, minerals (particularly potassium), and vitamins, including vitamin C. Freshly harvested potatoes retain more vitamin C than stored potatoes.

New and fingerling potatoes offer the advantage that they contain fewer toxic chemicals. Such potatoes offer an excellent source of nutrition. Peeled, long-stored potatoes have less nutritional value, although they still have potassium and vitamin C.

Potatoes also provide starch, flour, alcohol (see Poitin), dextrin, and livestock fodder.

Potatoes (particularly mashed potatoes) are known to have a high Glycemic index, a disqualifying factor in many diets.

Cooking

General Methods

Potatoes are prepared in many ways: skin-on or peeled, whole or cut up, with seasonings or without. The only requirement involves cooking to break down the starch. Most potato dishes are served hot, but some are first cooked then served cold, notably potato salad and potato chips/crisps.

Common dishes are: mashed potatoes, which are boiled, peeled (sometimes not), and mashed with milk and butter; whole baked potatoes; boiled or steamed potatoes; French-fried potatoes or chips; cut into cubes and roasted; scalloped, diced, or sliced and fried (home fries); grated into small thin strips and fried (hash browns); grated and formed into dumplings, Rösti or potato pancakes. Potatoes, unlike many foods, can also be easily cooked in a microwave oven and still retain nearly all of their nutritional value, provided that they are covered in ventilated plastic wrap to prevent moisture from escaping—this method produces a meal very similar to a baked potato. Potato chunks also commonly appear as a stew ingredient.

Regional dishes

Mashed potatoes form a major component of several traditional dishes from the British Isles such as shepherd's pie, bubble and squeak, champ and the 'mashit tatties' (Scots language) which accompany haggis. They are also often sautéed to accompany a meal.

Potatoes are very popular in continental Europe as well. In Italy, they serve to make a type of pasta called gnocchi. Potatoes form one of the main ingredients in many soups such as the pseudo-French vichyssoise and Albanian potato and cabbage soup.

In the United States, potatoes have become one of the most widely consumed crops, and thus have a variety of preparation methods and condiments. One popular favorite involves a baked potato with cheddar cheese (or sour cream and chives) on top, and in New England "smashed potatoes" (a chunkier variation on mashed potatoes, retaining the peel) have great popularity.

In Scandinavia, especially Sweden and Finland, newly harvested, early ripening varieties are considered a special delicacy. Boiled whole and served with dill, these "new potatoes" are traditionally consumed together with pickled Baltic herring.

A traditional Canary Islands dish is Canarian wrinkly potatoes or Papas arragudas.

A traditional Acadian dish from New Brunswick is known as poutine râpée. The Acadian poutine is a ball of grated and mashed potato, salted, sometimes filled with pork in the centre, and boiled. The result is a moist ball about the size of a baseball. It is commonly eaten with salt and pepper or brown sugar. It is believed to have originated from the German Klöße, prepared by early German settlers who lived among the Acadians.

Toxic compounds in potatoes

Potato plants

Potatoes contain glycoalkaloids, toxic compounds, of which the most prevalent are solanine and chaconine. Cooking at high temperatures (over 170 °C or 340 °F) partly destroys these. The concentration of glycoalkaloid in wild potatoes suffices to produce toxic effects in humans. Glycoalkaloids occur in the greatest concentrations just underneath the skin of the tuber, and they increase with age and exposure to light. Glycoalkaloids may cause headaches, diarrhea, cramps and in severe cases coma and death; however, poisoning from potatoes occurs very rarely. Light exposure also causes greening, thus giving a visual clue as to areas of the tuber that may have become more toxic; however, this does not provide a definitive guide, as greening and glycoalkaloid accumulation can occur independently of each other. Some varieties of potato contain greater glycoalkaloid concentrations than others; breeders developing new varieties test for this, and sometimes have to discard an otherwise promising cultivar.

Breeders try to keep solanine levels below 0.2 mg/g (200 ppmw). However, when even these commercial varieties turn green, they can approach concentrations of solanine of 1 mg/g (1000 ppmw). Some studies suggest that 200 mg of solanine can constitute a dangerous dose. This dose would require eating 1 average-sized spoiled potato or 4 to 9 good potatoes (over 3 pounds or 1.4 kg) at one time. The National Toxicology Program suggests that the average American consumes at most 12.5 mg/person/day of solanine from potatoes. Dr. Douglas L. Holt, the State Extension Specialist for Food Safety at the University of Missouri - Columbia, notes that no reported cases of potato-source solanine poisoning have occurred in the U.S. in the last 50 years and most cases involved eating green potatoes or drinking potato-leaf tea.

Solanine is also found in other plants, in particular the deadly nightshade. This poison affects the nervous system causing weakness and confusion. See Solanine for more information.

Seed tuber with sprouts
Early Rose variety

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Potato Planting
Washington

See also List of poisonous plants

Cultivation

Potatoes are generally grown from the eyes of another potato and not from seed. Home gardeners often plant a piece of potato with two or three eyes in a hill of mounded soil. Commercial growers plant potatoes as a row crop using seed tubers, young plants or microtubers and may mound the entire row.

At harvest time, gardeners generally dig up potatoes with a three-prong "grape" (or "graip") or spading fork, but in larger plots, the plough can serve as the most expeditious implement for unearthing potatoes. Commercial harvesting is typically done with large potato harvesters which scoop up the plant and the surrounding earth. This is transported up an apron chain consisting of steel links several feet wide. This separates some of the dirt. The chain deposits into an area where further separation occurs. Different designs employ different systems at this point. The most complex designs use vine choppers and shakers, along with a blower system or "Flying Willard" to separate the potatoes from the plant. The result is then usually run past workers who continue to sort out plant material, stones, and rotten potatoes before the potatoes are continuously delivered to a wagon or truck. Further inspection and separation occurs when the potatoes are unloaded from the field vehicles and put into storage.

Eliminating all root-weeds is desirable in potato cultivation. Three plowings, with necessary harrowings and rollings, are desirable if they can be accomplished before the appropriate planting time.

It is important to harvest potatoes before heavy frosts begin, since field frost damages potatoes in the ground, and even cold weather makes potatoes more susceptible to bruising and possibly later rotting which can quickly ruin a large stored crop.

Seed potato crops are 'rogued' in some countries to eliminate diseased plants or those of a different variety from the seed crop.

Potato field
Fort Fairfield, Maine

Pests

A major pest of potato plants is the Colorado potato beetle.

The potato root nematode is a microscopic worm that thrives on the roots, thus causing the potato plants to wilt. Since its eggs can survive in the soil for several years, crop rotation is recommended.

New potatoes

Potatoes are generally cured after harvest to thicken the skin. Prior to curing, the skin is very thin and delicate and the potatoes are known as "Rob Barettos" and are particularly flavorful. New potatoes are often harvested by the home gardener by "grabbling", i.e. pulling out the young tubers by hand while leaving the plant in place. In markets one sometimes finds thin-skinned varieties sold as new potatoes.

Storage

Storage facilities need to be carefully designed to keep the potatoes alive and slow the natural process of decomposition, which involves the breakdown of starch. It is crucial that the storage area is dark, well ventilated and ideally maintained at a temperature of about 4 degrees Celsius. Potatoes must not be kept in a refrigerator. Cold temperatures convert potatoes' starch into sugar, which alters their taste. Under optimum conditions, potatoes can be stored for up to six months, but several weeks is the normal maximum.

Notes

Maine companies are exploring the possibilities of using waste potatoes to obtain polylactic acid for use in plastic products.

References and external links

• World Geography of the Potato at http://www.lanra.uga.edu/potato/
• Reference for potato history: The Vegetable Ingredients Cookbook by Christine Ingram, Lorenz Books, 1996 ISBN 1-85967-264-7
• The History and Social Influence of the Potato by Redcliffe N. Salaman ISBN 0-521-31623-5
• Hamilton, Andy & Dave, (2004), Potatoes - Solanum tuberosums retrieved on 4 May 2005
• BBC: DNA shows all modern potatoes can trace roots back to Peru
• Idaho Potato Forum - Idaho Potato - Potato of the Month
• Spooner, D.M. et al. 2005. A single domestication for potato based on multilocus amplified fragment length polymorphism genotyping. Proc. Natl. Acad. Sci. USA, Published online before print October 3, 2005
• GLKS Potato Database
• Centro Internacional de la Papa - CIP (International Potato Center)
• World Potato Congress
• The European Cultivated Potato Database
• The Potato Museum
• Potato Information & Exchange
• Organic Control of Potato Sprouts