Biology:Potato

Short description: Staple food, root tuber, starchy

Potato
Potato cultivars appear in a variety of colors, shapes, and sizes.
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Eudicots
Clade:	Asterids
Order:	Solanales
Family:	Solanaceae
Genus:	Solanum
Species:	S. tuberosum
Binomial name
Solanum tuberosum L.

The potato /pəˈteɪtoʊ/ is a starchy root vegetable native to the Americas that is consumed as a staple food in many parts of the world. Potatoes are tubers of the plant Solanum tuberosum, a perennial in the nightshade family Solanaceae.

Wild potato species can be found from the southern United States to southern Chile. The potato was originally believed to have been domesticated by Native Americans independently in multiple locations, but later genetic studies traced a single origin, in the area of present-day southern Peru and extreme northwestern Bolivia. Potatoes were domesticated there about 7,000–10,000 years ago from a species in the S. brevicaule complex. Many varieties of the potato are cultivated in the Andes region of South America, where the species is indigenous.

The Spanish introduced potatoes to Europe in the second half of the 16th century. They are a staple food in many parts of the world and an integral part of much of the world's food supply. Following millennia of selective breeding, there are now over 5,000 different varieties of potatoes. Over 99% of potatoes presently cultivated worldwide descend from varieties that originated in the lowlands of south-central Chile. The importance of the potato as a food source and culinary ingredient varies by region and is still changing. It remains an essential crop in Europe, especially Northern and Eastern Europe, where per capita production is still the highest in the world, while the most rapid expansion in production during the 21st century was in southern and eastern Asia, with China and India leading the world production of 376 million tonnes (370,000,000 long tons; 414,000,000 short tons) as of 2021.

Like the tomato, the potato is a nightshade in the genus Solanum, and the vegetative and fruiting parts of the potato contain the toxin solanine which is dangerous for human consumption. Normal potato tubers that have been grown and stored properly produce glycoalkaloids in negligible amounts, but, if green sections of the plant (namely sprouts and skins) are exposed to light, the tuber can accumulate a high enough concentration of glycoalkaloids to affect human health.

Etymology

The English word "potato" comes from Spanish patata (the name used in Spain). The Royal Spanish Academy says the Spanish word is a hybrid of the Taíno batata (sweet potato) and the Quechua papa (potato). The name originally referred to the sweet potato although the two plants are not biologically closely related, despite their similar appearance. The 16th-century English herbalist John Gerard referred to sweet potatoes as "common potatoes", and used the terms "bastard potatoes" and "Virginia potatoes" for the species now known as potato. In many of the chronicles detailing agriculture and plants no distinction is made between the two. Potatoes are occasionally referred to as "Irish potatoes" or "white potatoes" in the United States to distinguish them from sweet potatoes.

The name "spud" for a potato comes from the digging of soil (or a hole) prior to the planting of potatoes. The word has an unknown origin and was originally (c. 1440) used as a term for a short knife or dagger, probably related to the Latin spad-, a word root meaning "sword"; compare Spanish espada, English "spade", and "spadroon". It subsequently transferred over to a variety of digging tools. Around 1845, the name transferred to the tuber itself, the first record of this usage being in New Zealand English. The origin of the word spud has erroneously been attributed to an 18th-century activist group dedicated to keeping the potato out of Britain, calling itself the Society for the Prevention of Unwholesome Diet (SPUD), for whose existence there is no evidence. Mario Pei's 1949 The Story of Language was responsible for the word's false etymology; he wrote "the potato, for its part, was in disrepute some centuries ago. Some Englishmen who did not fancy potatoes formed a Society for the Prevention of Unwholesome Diet. The initials of the main words in this title gave rise to spud." Like many other claimed pre-20th century acronymic origins, this is false.

At least six languages—Afrikaans, Dutch, French, (West) Frisian, Hebrew, Persian and some variants of German—are known to use a term for "potato" that translates roughly (or literally) into English as "earth apple" or "ground apple".

Plant description

Potato plants are herbaceous perennials that grow about 60 centimetres (24 inches) high, depending on variety, with the leaves dying back after flowering, fruiting and tuber formation. They bear white, pink, red, blue, or purple flowers with yellow stamens. Potatoes are mostly cross-pollinated by insects such as bumblebees, which carry pollen from other potato plants, though a substantial amount of self-fertilizing occurs as well. Tubers form in response to decreasing day length, although this tendency has been minimized in commercial varieties.

After flowering, potato plants produce small green fruits that resemble green cherry tomatoes, each containing about 300 seeds. Like all parts of the plant except the tubers, the fruit contain the toxic alkaloid solanine and are therefore unsuitable for consumption. All new potato varieties are grown from seeds, also called "true potato seed", "TPS" or "botanical seed" to distinguish it from seed tubers. New varieties grown from seed can be propagated vegetatively by planting tubers, pieces of tubers cut to include at least one or two eyes, or cuttings, a practice used in greenhouses for the production of healthy seed tubers. Plants propagated from tubers are clones of the parent, whereas those propagated from seed produce a range of different varieties.

Breeding

Potatoes, both S. tuberosum and most of its wild relatives, are self-incompatible: they bear no useful fruit when self-pollinated. This trait is problematic for crop breeding, as all sexually-produced plants must be hybrids. The gene responsible for its trait as well as mutations to disable it are now known. Self-compatibility has successfully been introduced both to diploid potatoes (including a special line of S. tuberosum) by CRISPR-Cas9. Plants having a 'Sli' gene produce pollen which is compatible to its own parent and plants with similar S genes. This gene was recently cloned by Wageningen University and Solynta in 2021, which would allow for faster and more focused breeding.

Diploid hybrid potato breeding is a recent area of potato genetics supported by the finding that simultaneous homozygosity and fixation of donor alleles is possible. Wild potato species useful for breeding may include Solanum desmissum and S. stoloniferum, among others.

Biosynthesis of starch

Sucrose is a product of photosynthesis. Ferreira et al. (2010) found that the genes for starch biosynthesis start to be transcribed at the same time as sucrose synthase activity begins. This transcription – including starch synthase – also shows a diurnal rhythm, correlating with the sucrose supply arriving from the leaves.

Taxonomic synonyms

Solanum tuberosum has 438 Synonyms.

This list is incomplete; you can help by expanding it.

Cultivation

History

Production of potatoes (2019)

Potato production – 2021
Country	Production (millions of tonnes)
China	94.3
India	54.2
Ukraine	21.4
United States	18.6
Russia	18.3
World	376
Source: FAOSTAT of the United Nations

World map of potato and cassava cultivation, 1907

The potato was first domesticated in the region of modern-day southern Peru and northwestern Bolivia by pre-Columbian farmers, around Lake Titicaca. It has since spread around the world and become a staple crop in many countries.

The earliest archaeologically verified potato tuber remains have been found at the coastal site of Ancon (central Peru), dating to 2500 BC. The most widely cultivated variety, Solanum tuberosum tuberosum, is indigenous to the Chiloé Archipelago, and has been cultivated by the local indigenous people since before the Spanish conquest.

According to conservative estimates, the introduction of the potato was responsible for a quarter of the growth in Old World population and urbanization between 1700 and 1900. In the Altiplano, potatoes provided the principal energy source for the Inca civilization, its predecessors, and its Spanish successor. Following the Spanish conquest of the Inca Empire, the Spanish introduced the potato to Europe in the second half of the 16th century, part of the Columbian exchange. The staple was subsequently conveyed by European (possibly including Russian) mariners to territories and ports throughout the world, especially their colonies. The potato was slow to be adopted by European and colonial farmers, but after 1750 it became an important food staple and field crop and played a major role in the European 19th century population boom. However, lack of genetic diversity, due to the very limited number of varieties initially introduced, left the crop vulnerable to disease. In 1845, a plant disease known as late blight, caused by the fungus-like oomycete Phytophthora infestans, spread rapidly through the poorer communities of western Ireland as well as parts of the Scottish Highlands, resulting in the crop failures that led to the Great Irish Famine.

Modern cultivation

There are about 5,000 potato varieties worldwide, 3,000 of which are found in the Andes alone—mainly in Peru, Bolivia, Ecuador, Chile, and Colombia. Over 100 cultivars might be found in a single valley, and a dozen or more might be maintained by a single agricultural household. The varieties belong to eight or nine species, depending on the taxonomic school. Apart from the 5,000 cultivated varieties, there are about 200 wild species and subspecies, many of which can be cross-bred with cultivated varieties. Cross-breeding has been done repeatedly to transfer resistances to certain pests and diseases from the gene pool of wild species to the gene pool of cultivated potato species.

Russets

The major species grown worldwide is S. tuberosum (a tetraploid with 48 chromosomes), and modern varieties of this species are the most widely cultivated. There are also four diploid species (with 24 chromosomes): S. stenotomum, S. phureja, S. goniocalyx, and S. ajanhuiri. There are two triploid species (with 36 chromosomes): S. chaucha and S. juzepczukii. There is one pentaploid cultivated species (with 60 chromosomes): S. curtilobum. There are two major subspecies of S. tuberosum: andigena, or Andean; and tuberosum, or Chilean. The Andean potato is adapted to the short-day conditions prevalent in the mountainous equatorial and tropical regions where it originated; the Chilean potato, however, native to the Chiloé Archipelago, is adapted to the long-day conditions prevalent in the higher latitude region of southern Chile.

The International Potato Center, based in Lima, Peru, holds 4,870 types of potato germplasm, most of which are traditional landrace cultivars. The international Potato Genome Sequencing Consortium announced in 2009 that they had achieved a draft sequence of the potato genome, containing 12 chromosomes and 860 million base pairs, making it a medium-sized plant genome. More than 99% of all current varieties of potatoes currently grown are direct descendants of a subspecies that once grew in the lowlands of south-central Chile. Nonetheless, genetic testing of the wide variety of cultivars and wild species affirms that all potato subspecies derive from a single origin in the area of present-day southern Peru and extreme Northwestern Bolivia (from a species in the S. brevicaule complex).

Most modern potatoes grown in North America arrived through European settlement and not independently from the South American sources, although at least one wild potato species, S. fendleri, occurs in North America, where it is used in breeding for resistance to a nematode species that attacks cultivated potatoes. A secondary center of genetic variability of the potato is Mexico, where important wild species that have been used extensively in modern breeding are found, such as the hexaploid S. demissum, as a source of resistance to the devastating late blight disease (Phytophthora infestans). Another relative native to this region, Solanum bulbocastanum, has been used to genetically engineer the potato to resist potato blight. Many such wild relatives are useful for breeding resistance to P. infestans.

Little of the diversity found in Solanum ancestral and wild relative is found outside of the original South American range. This makes these South American species highly valuable in breeding.

Varieties

Further information: Biology:List of potato cultivars

There are close to 4,000 varieties of potatoes, each of which has specific agricultural or culinary attributes. Around 80 varieties are commercially available in the UK. In general, varieties are categorized into a few main groups based on common characteristics, such as russet potatoes (rough brown skin), red potatoes, white potatoes, yellow potatoes (also called Yukon potatoes) and purple potatoes.

A thin section of a potato under light microscopy. It has been treated with an iodine based dye that binds to starch, turning it purple, showing the high starch content.

For culinary purposes, varieties are often differentiated by their waxiness: floury or mealy baking potatoes have more starch (20–22%) than waxy boiling potatoes (16–18%). The distinction may also arise from variation in the comparative ratio of two different potato starch compounds: amylose and amylopectin. Amylose, a long-chain molecule, diffuses from the starch granule when cooked in water, and lends itself to dishes where the potato is mashed. Varieties that contain a slightly higher amylopectin content, which is a highly branched molecule, help the potato retain its shape after being boiled in water. Potatoes that are good for making potato chips or potato crisps are sometimes called "chipping potatoes", which means they meet the basic requirements of similar varietal characteristics, being firm, fairly clean, and fairly well-shaped.

Immature potatoes may be sold fresh from the field as "creamer" or "new" potatoes and are particularly valued for their taste. They are typically small in size and tender, with a loose skin, and flesh containing a lower level of starch than other potatoes. In the United States they are generally either a Yukon Gold potato or a red potato, called gold creamers or red creamers respectively. In the UK, the Jersey Royal is a famous type of new potato. They are distinct from "baby", "salad" or "fingerling" potatoes, which are small and tend to have waxy flesh, but are grown to maturity and can be stored for months before being sold.

The European Cultivated Potato Database is an online collaborative database of potato variety descriptions updated and maintained by the Scottish Agricultural Science Agency within the framework of the European Cooperative Programme for Crop Genetic Resources Networks—which is run by the International Plant Genetic Resources Institute.

Pigmentation

Potatoes with different pigmentation

Dozens of potato cultivars have been selectively bred specifically for their skin or, more commonly, flesh color, including gold, red, and blue varieties that contain varying amounts of phytochemicals, including carotenoids for gold/yellow or polyphenols for red or blue cultivars. Carotenoid compounds include provitamin A alpha-carotene and beta-carotene, which are converted to the essential nutrient, vitamin A, during digestion. Anthocyanins mainly responsible for red or blue pigmentation in potato cultivars do not have nutritional significance, but are used for visual variety and consumer appeal. In 2010, potatoes were bioengineered specifically for these pigmentation traits.

Genetically engineered potatoes

Genetic research has produced several genetically modified varieties. 'New Leaf', owned by Monsanto Company, incorporates genes from Bacillus thuringiensis (source of most Bt toxins in transcrop use), which confers resistance to the Colorado potato beetle; 'New Leaf Plus' and 'New Leaf Y', approved by US regulatory agencies during the 1990s, also include resistance to viruses. McDonald's, Burger King, Frito-Lay, and Procter & Gamble announced they would not use genetically modified potatoes, and Monsanto published its intent to discontinue the line in March 2001.

Potato starch contains two types of glucan, amylose and amylopectin, the latter of which is most industrially useful. Waxy potato varieties produce waxy potato starch, which is almost entirely amylopectin, with little or no amylose. BASF developed the 'Amflora' potato, which was modified to express antisense RNA to inactivate the gene for granule bound starch synthase, an enzyme which catalyzes the formation of amylose. 'Amflora' potatoes therefore produce starch consisting almost entirely of amylopectin, and are thus more useful for the starch industry. In 2010, the European Commission cleared the way for 'Amflora' to be grown in the European Union for industrial purposes only—not for food. Nevertheless, under EU rules, individual countries have the right to decide whether they will allow this potato to be grown on their territory. Commercial planting of 'Amflora' was expected in the Czech Republic and Germany in the spring of 2010, and Sweden and the Netherlands in subsequent years. Another GM potato variety developed by BASF is 'Fortuna' which was made resistant to late blight by adding two resistance genes, blb1 and blb2, which originate from the Mexican wild potato S. bulbocastanum. In October 2011 BASF requested cultivation and marketing approval as a feed and food from the EFSA. In 2012, GMO development in Europe was stopped by BASF. In November 2014, the United States Department of Agriculture (USDA) approved a genetically modified potato developed by Simplot, which contains genetic modifications that prevent bruising and produce less acrylamide when fried than conventional potatoes; the modifications do not cause new proteins to be made, but rather prevent proteins from being made via RNA interference.

Genetically modified varieties have met public resistance in the U.S. and in the European Union.

Production

In 2021, world production of potatoes was 376 million tonnes (370,000,000 long tons; 414,000,000 short tons), led by China with 25% of the total (table). Other major producers were India and Ukraine .

Growth

Planting

Fort Fairfield, Maine

Seed potatoes

Potatoes are generally grown from "seed potatoes", tubers specifically grown to be free from disease and to provide consistent and healthy plants. To be disease free, the areas where seed potatoes are grown are selected with care. In the US, this restricts production of seed potatoes to only 15 states out of all 50 states where potatoes are grown. These locations are selected for their cold, hard winters that kill pests and summers with long sunshine hours for optimum growth. In the UK, most seed potatoes originate in Scotland, in areas where westerly winds reduce aphid attack and the spread of potato virus pathogens.

Specially genetically modified potatoes can also be grown from true seeds. This is rarely used in breeding experimentation.

Phases of growth

Potato growth can be divided into five phases. During the first phase, sprouts emerge from the seed potatoes and root growth begins. During the second, photosynthesis begins as the plant develops leaves and branches above-ground and stolons develop from lower leaf axils on the below-ground stem. In the third phase the tips of the stolons swell forming new tubers and the shoots continue to grow and flowers typically develop soon after. Tuber bulking occurs during the fourth phase, when the plant begins investing the majority of its resources in its newly formed tubers. At this phase, several factors are critical to a good yield: optimal soil moisture and temperature, soil nutrient availability and balance, and resistance to pest attacks. The fifth phase is the maturation of the tubers: the leaves and stems senesce and the tuber skins harden.

Challenges

Potatoes grown in a tall bag are common in gardens as they minimize the amount of digging required at harvest.

Potatoes are renowned for their ease of cultivation compared to other staple crops; however, maximizing yields and preventing disease and undesirable characteristics requires intensive management.

New tubers may start growing at the surface of the soil. Since exposure to light leads to an undesirable greening of the skins and the development of solanine as a protection from the sun's rays, growers cover surface tubers. Commercial growers cover them by piling additional soil around the base of the plant as it grows (called "hilling" up, or in British English "earthing up"). An alternative method, used by home gardeners and smaller-scale growers, involves covering the growing area with mulches such as straw or plastic sheets.

Correct potato husbandry can be an arduous task in some circumstances. Good ground preparation, harrowing, plowing, and rolling are always needed, along with a little grace from the weather and a good source of water. Three successive plowings, with associated harrowing and rolling, are desirable before planting. Eliminating all root-weeds is desirable in potato cultivation. In general, the potatoes themselves are 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. Seed potato crops are rogued in some countries to eliminate diseased plants or those of a different variety from the seed crop.

Potatoes are sensitive to heavy frosts, which damage them in the ground. Even cold weather makes potatoes more susceptible to bruising and possibly later rotting, which can quickly ruin a large stored crop.

Pests and disease

The historically significant Phytophthora infestans (cause of late blight) remains an ongoing problem in Europe and the United States. Other potato diseases include Rhizoctonia, Sclerotinia, Pectobacterium carotovorum (black leg), powdery mildew, powdery scab and leafroll virus.

Late blight

Insects that commonly transmit potato diseases or damage the plants include the Colorado potato beetle, the potato tuber moth, the green peach aphid (Myzus persicae), the potato aphid, Tuta absoluta, beet leafhoppers, thrips, and mites. The potato cyst nematode is a microscopic worm that feeds 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. According to an Environmental Working Group analysis of USDA and FDA pesticide residue tests performed from 2000 through 2008, 84% of the 2,216 tested potato samples contained detectable traces of at least one pesticide. A total of 36 unique pesticides were detected on potatoes over the 2,216 samples, though no individual sample contained more than 6 unique pesticide traces, and the average was 1.29 detectable unique pesticide traces per sample. The average quantity of all pesticide traces found in the 2,216 samples was 1.602 ppm. While this was a very low value of pesticide residue, it was the highest amongst the 50 vegetables analyzed.

Rpi-blb1 is a nucleotide-binding leucine-rich repeat (NB-LRR/NLR), an R-gene-produced immunoreceptor. It has been introgressed from wild relatives (various Solanum spp.) into the common potato. Rpi-blb1 conveys resistance to Late Blight (P. infestans).

Harvest

Modern harvester

At harvest time, gardeners usually dig up potatoes with a long-handled, three-prong "grape" (or graip), i.e., a spading fork, or a potato hook, which is similar to the graip but with tines at a 90° angle to the handle. In larger plots, the plow is the fastest implement for unearthing potatoes. Commercial harvesting is typically done with large potato harvesters, which scoop up the plant and surrounding earth. This is transported up an apron chain consisting of steel links several feet wide, which separates some of the dirt. The chain deposits into an area where further separation occurs. Different designs use different systems at this point. The most complex designs use vine choppers and shakers, along with a blower system 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.

Potatoes are usually cured after harvest to improve skin-set. Skin-set is the process by which the skin of the potato becomes resistant to skinning damage. Potato tubers may be susceptible to skinning at harvest and suffer skinning damage during harvest and handling operations. Curing allows the skin to fully set and any wounds to heal. Wound-healing prevents infection and water-loss from the tubers during storage. Curing is normally done at relatively warm temperatures (10 to 16 °C or 50 to 60 °F) with high humidity and good gas-exchange if at all possible.

Storage

Transporting to cold storage in India

Storage facilities need to be carefully designed to keep the potatoes alive and slow the natural process of sprouting which involves the breakdown of starch. It is crucial that the storage area be dark, ventilated well, and, for long-term storage, maintained at temperatures near 4 °C (39 °F). For short-term storage, temperatures of about 7 to 10 °C (45 to 50 °F) are preferred.

Temperatures below 4 °C (39 °F) convert the starch in potatoes into sugar, which alters their taste and cooking qualities and leads to higher acrylamide levels in the cooked product, especially in deep-fried dishes. The discovery of acrylamides in starchy foods in 2002 has led to international health concerns. It is not likely that the acrylamides in burnt or well-cooked food causes cancer in humans. Chemicals are used to suppress sprouting of tubers during storage. Chlorpropham is the main chemical used, but toxicity concerns have led to it being banned in the EU. Alternatives are applying maleic hydrazide to the crop whilst it is still growing or the use of ethylene, spearmint and orange oils and 1,4-dimethylnaphthalene.

Under optimum conditions in commercial warehouses, potatoes can be stored for up to 10–12 months. The commercial storage and retrieval of potatoes involves several phases: first drying surface moisture; wound healing at 85% to 95% relative humidity and temperatures below 25 °C (77 °F); a staged cooling phase; a holding phase; and a reconditioning phase, during which the tubers are slowly warmed. Mechanical ventilation is used at various points during the process to prevent condensation and the accumulation of carbon dioxide.

Yield

Potatoes are one of the most widely produced primary crops in the world.

The world dedicated 18.6 million hectares (46 million acres) to potato cultivation in 2010; the world average yield was 17.4 tonnes per hectare (7.8 short tons per acre). The United States was the most productive country, with a nationwide average yield of 44.3 tonnes per hectare (19.8 short tons per acre). United Kingdom was a close second.

New Zealand farmers have demonstrated some of the best commercial yields in the world, ranging between 60 and 80 tonnes per hectare, some reporting yields of 88 tonnes of potatoes per hectare.

There is a big gap among various countries between high and low yields, even with the same variety of potato. Average potato yields in developed economies ranges between 38 and 44 metric tons per hectare (15 and 18 long ton/acre; 17 and 20 short ton/acre). China and India accounted for over a third of world's production in 2010, and had yields of 14.7 and 19.9 metric tons per hectare (5.9 and 7.9 long ton/acre; 6.6 and 8.9 short ton/acre) respectively. The yield gap between farms in developing economies and developed economies represents an opportunity loss of over 400 million metric tons (440 million short tons; 390 million long tons) of potato, or an amount greater than 2010 world potato production. Potato crop yields are determined by factors such as the crop breed, seed age and quality, crop management practices and the plant environment. Improvements in one or more of these yield determinants, and a closure of the yield gap, can be a major boost to food supply and farmer incomes in the developing world. The food energy yield of potatoes—about 95 gigajoules per hectare (9.2 million kilocalories per acre)—is higher than that of maize (78 GJ/ha or 7.5 million kcal/acre), rice (77 GJ/ha or 7.4 million kcal/acre), wheat (31 GJ/ha or 3 million kcal/acre), or soybeans (29 GJ/ha or 2.8 million kcal/acre).

Climate change

Climate change is predicted to have significant effects on global potato production. Like many crops, potatoes are likely to be affected by changes in atmospheric carbon dioxide, temperature and precipitation, as well as interactions between these factors. As well as affecting potatoes directly, climate change will also affect the distributions and populations of many potato diseases and pests. While potato is less important than maize, rice, wheat and soybeans, which are collectively responsible for around two-thirds of all calories consumed by humans (both directly and indirectly as animal feed), it still is one of the world's most important food crops. Altogether, one 2003 estimate suggests that future (2040–2069) worldwide potato yield would be 18-32% lower than it was at the time, driven by declines in hotter areas like Sub-Saharan Africa, unless farmers and potato cultivars can adapt to the new environment.

As with the other plants, potato plants and crop yields are predicted to benefit from the CO2 fertilization effect, which would increase photosynthetic rates and therefore growth, reduce water consumption through lower transpiration from stomata and increase starch content in the edible tubers. However, potatoes are more sensitive to soil water deficits than some other staple crops like wheat, so in countries like Bolivia, where the rainy season has shortened in recent decades, the potato growing season has shortened as well. This can get worse in the future: for instance, the amount of arable land suitable for rainfed potato production in the UK may decrease by at least 75%. These changes are likely to lead to increased demand for irrigation water, particularly during the potato growing season.

Potatoes also grow best under temperate conditions. Tuber growth and yield can be severely reduced by temperature fluctuations outside 5–30 °C (41–86 °F). Temperatures above 30 °C (86 °F) can have a range of negative effects on potato, from physiological damage such as brown spots on tubers, to slower growth, premature sprouting and lower starch content. These effects can reduce crop yield and the number and weight of tubers. As a result, areas where current temperatures are near the limits of potatoes' temperature range (e.g. much of sub-Saharan Africa) will likely suffer large reductions in potato crop yields in the future. On the other hand, low temperatures reduce potato growth and present risk of frost damage. At high altitudes and in high latitude countries such as Canada and Russia , potato growth is currently limited or impossible due to risks of frost damage, and rising temperatures will likely extend potentially suitable land and/or growing season.

Changes in pests and diseases for potato crops

Climate change is predicted to affect many potato pests and diseases. These include:

• Insect pests such as the potato tuber moth and Colorado potato beetle, which are predicted to spread into areas currently too cold for them.
• Aphids which act as vectors for many potato viruses and will also be able to spread under increased temperatures.
• Several pathogens causing potato blackleg disease (e.g. Dickeya) can grow and reproduce faster at higher temperatures and so will likely become more of a problem.
• Bacterial infections such as Ralstonia solanacearum are predicted to benefit from higher temperatures and be able to spread more easily through flash flooding.
• Late blight benefits from higher temperatures and wetter conditions. Late blight is predicted to become a greater threat in some areas (e.g. in Finland) and become a lesser threat in others (e.g. in the United Kingdom).

Adaptation strategies

Shifting potato production from areas where yields will decline due to hotter temperatures and decreased water availability to places which will become suitable can help to mitigate much of the projected decline in yield: however, this can also trigger competition for land between potato crops and other crops or other land uses.), mostly due to changes in water and temperature regimes. At the same time potato production is predicted to become possible in high altitude and latitude areas where it would previously have been limited by frost damage. These changes in crop yields are predicted to cause shifts in the areas in which potato crops can be viably produced.

The other approach is through the development of varieties or cultivars which would be more adapted to altered conditions. This can be done through 'traditional' plant breeding techniques and genetic modification. These techniques allow for the selection of specific traits as a new cultivar is developed. Certain traits, such as heat stress tolerance, drought tolerance, fast growth/early maturation and disease resistance, may play an important role in creating new cultivars able to maintain yields under stressors induced by climate change.

For instance, developing cultivars with greater heat stress tolerance would be critical for maintaining yields in countries with potato production areas near current cultivars' maximum temperature limits (e.g. Sub-Saharan Africa, India ). Superior drought resistance can be achieved through improved water use efficiency (amount of food produced per amount of water used) or the ability to recover from short drought periods and still produce acceptable yields. Further, selecting for deeper root systems may reduce the need for irrigation. Finally, potatoes that grow faster could help adjust to shorter growing seasons in some areas, and also reduce the number of life cycles pests such as potato tuber moth can complete in a single growing season.

Toxicity

Potato fruit, which is not edible

Raw potatoes contain toxic compounds known as glycoalkaloids, of which the most prevalent are solanine and chaconine. Solanine is found in other plants in the same family, Solanaceae, which includes such plants as deadly nightshade (Atropa belladonna), henbane (Hyoscyamus niger) and tobacco (Nicotiana spp.), as well as the food plants eggplant and tomato. These compounds, which protect the potato plant from its predators, are generally concentrated in its leaves, flowers, sprouts, and fruits (in contrast to the tubers). In a summary of several studies, the glycoalkaloid content was in order from highest to lowest: flowers, sprouts, leaves, tuber skin, roots, berries, peel [skin plus outer cortex of tuber flesh], stems, and tuber flesh).

Exposure to light, physical damage, and age increase glycoalkaloid content within the tuber. Cooking at high temperatures—over 170 °C (338 °F)—partly destroys these compounds. The concentration of glycoalkaloids in S. jamesii (a wild potato) is sufficient to produce toxic effects in humans. Glycoalkaloid poisoning may cause headaches, diarrhea, cramps, and, in severe cases, coma and death. However, poisoning from cultivated potato varieties is very rare. Light exposure causes greening from chlorophyll synthesis, giving a visual clue as to which areas of the tuber may have become more toxic.

Different potato varieties contain different levels of glycoalkaloids. The 'Lenape' variety was released in 1967, but was withdrawn in 1970, as it contained high levels of glycoalkaloids. Since then, breeders developing new varieties test for this, and sometimes have to discard an otherwise promising cultivar. Breeders try to keep glycoalkaloid levels below 200 mg/kg (0.0032 oz/lb) (200 ppmw). However, when these commercial varieties turn green, they can still approach solanine concentrations of 1,000 mg/kg (0.016 oz/lb) (1000 ppmw). In normal potatoes, analysis has shown solanine levels may be as little as 3.5% of the breeders' maximum, with 7–187 mg/kg (0.00011–0.00299 oz/lb) being found. While a normal potato tuber has 12–20 mg/kg (0.00019–0.00032 oz/lb) of glycoalkaloid content, a green potato tuber contains 250–280 mg/kg (0.0040–0.0045 oz/lb) and its skin has 1,500–2,200 mg/kg (0.024–0.035 oz/lb).

Uses

Nutrition

Potatoes, boiled, cooked in skin, flesh, without salt

Nutritional value per 100 g (3.5 oz)
Energy	364 kJ (87 kcal)
Carbohydrates	20.1 g
Sugars	0.9 g
Dietary fiber	1.8 g
Fat	0.1 g
Protein	1.9 g
Vitamins	Quantity %DV†
Thiamine (B1)	10% 0.11 mg
Riboflavin (B2)	2% 0.02 mg
Niacin (B3)	10% 1.44 mg
Pantothenic acid (B5)	10% 0.52 mg
Vitamin B6	23% 0.3 mg
Folate (B9)	3% 10 μg
Vitamin C	16% 13 mg
Minerals	Quantity %DV†
Calcium	1% 5 mg
Iron	2% 0.31 mg
Magnesium	6% 22 mg
Manganese	7% 0.14 mg
Phosphorus	6% 44 mg
Potassium	8% 379 mg
Sodium	0% 4 mg
Zinc	3% 0.3 mg
Other constituents	Quantity
Water	77 g
Link to USDA Database entry
Units μg = micrograms • mg = milligrams IU = International units
†Percentages are roughly approximated using US recommendations for adults.

In a reference amount of 100 grams (3.5 oz), a boiled potato with skin supplies 87 calories and is 77% water, 20% carbohydrates (including 2% dietary fiber in the skin and flesh), 2% protein, and contains negligible fat (table). The protein content is comparable to other starchy vegetable staples, as well as grains.

Boiled potatoes are a rich source (20% or more of the Daily Value, DV) of vitamin B6 (23% DV), and contain a moderate amount of vitamin C (16% DV) and B vitamins, such as thiamine, niacin, and pantothenic acid (10% DV each). Boiled potatoes do not supply significant amounts of dietary minerals (table).

The potato is rarely eaten raw because raw potato starch is poorly digested by humans. Depending on the cultivar and preparation method, potatoes can have a high glycemic index (GI) and so are often excluded from the diets of individuals trying to follow a low-GI diet. There is a lack of evidence regarding the effect of potato consumption on obesity and diabetes.

In the UK, potatoes are not considered by the National Health Service as counting or contributing towards the recommended daily five portions of fruit and vegetables, the 5-A-Day program.

Culinary

Various, typically American potato preparations: (clockwise from top left) potato chips, hash browns, tater tots, mashed potato, and a baked potato

Potatoes are prepared in many ways: skin-on or peeled, whole or cut up, with seasonings or without. The only requirement involves cooking to swell the starch granules. 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 first boiled (usually peeled), and then mashed with milk or yogurt 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 can also be cooked in a microwave oven to produce a meal very similar to a steamed potato, while retaining the appearance of a conventionally baked potato. Potato chunks also commonly appear as a stew ingredient. Potatoes are boiled between 10 and 25 minutes, depending on size and type, to become soft.

Latin America

Papa rellena

Peruvian cuisine naturally contains the potato as a primary ingredient in many dishes, as around 3,000 varieties of this tuber are grown there. Some of the more notable dishes include boiled potato as a base for several dishes or with ají-based sauces like in papa a la Huancaína or ocopa, diced potato for its use in soups like in cau cau, or in carapulca with dried potato (papa seca). Smashed condimented potato is used in causa Limeña and papa rellena. French-fried potatoes are a typical ingredient in Peruvian stir-fries, including the classic dish lomo saltado.

Chuño is a freeze-dried potato product traditionally made by Quechua and Aymara communities of Peru and Bolivia, and is known in various countries of South America, including Peru, Bolivia, Argentina , and Chile. In Chile's Chiloé Archipelago, potatoes are the main ingredient of many dishes, including milcaos, chapaleles, curanto and chochoca. In Ecuador, the potato, as well as being a staple with most dishes, is featured in the hearty locro de papas, a thick soup of potato, squash, and cheese.

Europe

Baked potato with sour cream and chives

In the UK, potatoes form part of the traditional staple, fish and chips. Roast potatoes are commonly served as part of a Sunday roast dinner and mashed potatoes form a major component of several other traditional dishes, such as shepherd's pie, bubble and squeak, and bangers and mash. New potatoes may be cooked with mint and are often served with butter.

The tattie scone is a popular Scottish dish containing potatoes. Colcannon is a traditional Irish food made with mashed potato, shredded kale or cabbage, and onion; champ is a similar dish. Boxty pancakes are eaten throughout Ireland, although associated especially with the North, and in Irish diaspora communities; they are traditionally made with grated potatoes, soaked to loosen the starch and mixed with flour, buttermilk and baking powder. A variant eaten and sold in Lancashire, especially Liverpool, is made with cooked and mashed potatoes.

In the UK, game chips are a traditional accompaniment to roast gamebirds such as pheasant, grouse, partridge and quail.

Powdered cooked potato has been sold in the UK since the 1960s as Smash and is used as a food for camping and domestically.

Halušky are the national dish of many Slavic nations. Halušky dumplings are made from a batter consisting of flour and grated potatoes. Bryndzové halušky are associated to Slovak cuisine in particular.

German Bauernfrühstück ("farmer's breakfast")

In Germany, Northern (Finland, Latvia and especially Scandinavian countries), Eastern Europe (Russia, Belarus and Ukraine ) and Poland, newly harvested, early ripening varieties are considered a special delicacy. Boiled whole and served un-peeled with dill, these "new potatoes" are traditionally consumed with Baltic herring. Puddings made from grated potatoes (kugel, kugelis, and potato babka) are popular items of Ashkenazi, Lithuanian, and Belarusian cuisine. German fried potatoes and various versions of Potato salad are part of German cuisine. Bauernfrühstück (literally farmer's breakfast) is a warm German dish made from fried potatoes, eggs, ham and vegetables.

Cepelinai

Cepelinai is the national dish of Lithuania. They are a type of dumpling made from grated raw potatoes boiled in water and usually stuffed with minced meat, although sometimes dry cottage cheese (curd) or mushrooms are used instead.

In Western Europe, especially in Belgium, sliced potatoes are fried to create frieten, the original French fried potatoes. Stamppot, a traditional Dutch meal, is based on mashed potatoes mixed with vegetables.

In France, the most notable potato dish is the hachis Parmentier, named after Antoine-Augustin Parmentier, a French pharmacist, nutritionist, and agronomist who, in the late 18th century, was instrumental in the acceptance of the potato as an edible crop in the country. Pâté aux pommes de terre is a regional potato dish from the central Allier and Limousin regions. Gratin dauphinois, consisting of baked thinly sliced potatoes with cream or milk, and tartiflette, with Reblochon cheese, are also widespread.

In the north of Italy, in particular, in the Friuli region of the northeast, potatoes serve to make a type of pasta called gnocchi. Similarly, cooked and mashed potatoes or potato flour can be used in the Knödel or dumpling eaten with or added to meat dishes all over central and Eastern Europe, but especially in Bavaria and Luxembourg. Potatoes form one of the main ingredients in many soups such as the vichyssoise and Albanian potato and cabbage soup. In western Norway, komle is popular.

Potato pancakes are popular all over Central Europe, and are also known in Scandinavia, and in Jewish cuisine.

A traditional Canary Islands dish is Canarian wrinkly potatoes or papas arrugadas. Tortilla de patatas (potato omelette) and patatas bravas (a dish of fried potatoes in a spicy tomato sauce) are near-universal constituents of Spanish tapas.

North America

In the US, potatoes have become one of the most widely consumed crops and thus have a variety of preparation methods and condiments. French fries and often hash browns are commonly found in typical American fast-food burger "joints" and cafeterias. One popular favourite 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 a great popularity. Potato flakes are popular as an instant variety of mashed potatoes, which reconstitute into mashed potatoes by adding water, with butter or oil and salt to taste. A regional dish of Central New York, salt potatoes are bite-size new potatoes boiled in water saturated with salt then served with melted butter. At more formal dinners, a common practice includes taking small red potatoes, slicing them, and roasting them in an iron skillet. Among American Jews, the practice of eating latkes (fried potato pancakes) is common during the festival of Hanukkah.

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. Poutine, by contrast, is a hearty serving of French fries, fresh cheese curds and hot gravy. Tracing its origins to Quebec in the 1950s, it has become a widespread and popular dish throughout Canada.

Potato grading for Idaho potatoes is performed in which No. 1 potatoes are the highest quality and No. 2 are rated as lower in quality due to their appearance (e.g. blemishes or bruises, pointy ends). Potato density assessment can be performed by floating them in brines. High-density potatoes are desirable in the production of dehydrated mashed potatoes, potato crisps and french fries.

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  French fries served with a hamburger

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  Poutine, a Canadian dish of fried potatoes, cheese curds, and gravy

South Asia

In South Asia, the potato is a very popular traditional staple. In India, the most popular potato dishes are aloo ki sabzi, batata vada, and samosa, which is spicy mashed potato mixed with a small amount of vegetable stuffed in conical dough, and deep-fried. Potatoes are also a major ingredient as fast-food items, such as aloo chaat, where they are deep-fried and served with chutney. In Northern India, alu dum and alu paratha are a favourite part of the diet; the first is a spicy curry of boiled potato, the second is a type of stuffed chapati.

A dish called masala dosa from South India is notable all over India. It is a thin pancake of rice and pulse batter rolled over spicy smashed potato and eaten with sambhar and chutney. Poori in south India, in particular in Tamil Nadu, is almost always taken with smashed potato masal. Other favourite dishes are alu tikki and pakoda items.

Vada pav is a popular vegetarian fast-food dish in Mumbai and other regions in Maharashtra in India.

Aloo posto (a curry with potatoes and poppy seeds) is popular in East India, especially Bengal. Although potatoes are not native to India, it has become a vital part of food all over the country especially North Indian food preparations. In Tamil Nadu this tuber acquired a name based on its appearance, 'urulai-k-kizhangu' (உருளைக் கிழங்கு), meaning cylindrical tuber.

Aloo gosht, potato and meat curry, is one of the popular dishes in South Asia, especially in Pakistan .

East Asia

In East Asia, particularly Southeast Asia, rice is by far the predominant starch crop, with potatoes a secondary crop, especially in China and Japan. However, it is used in northern China where rice is not easily grown, with a popular dish being 青椒土豆丝 (qīng jiāo tǔ dòu sī), made with green pepper, vinegar and thin slices of potato. In the winter, roadside sellers in northern China will also sell roasted potatoes. It is also occasionally seen in Korean and Thai cuisines.

Other uses

Potatoes are also used for purposes other than eating by humans, for example:

• Potatoes are used to brew alcoholic beverages such as vodka, poitín, or akvavit.
• They are also used as fodder for livestock. Livestock-grade potatoes, considered too small or blemished to sell or market for human use but suitable for fodder use, have been called chats in some dialects. They may be stored in bins until use; they are sometimes ensiled. Some farmers prefer to steam them rather than feed them raw and are equipped to do so efficiently.
• Potato starch is used in the food industry as a thickener and binder for soups and sauces, in the textile industry as an adhesive, and for the manufacturing of papers and boards.
• Potatoes are commonly used in plant research. The consistent parenchyma tissue, the clonal nature of the plant and the low metabolic activity make it an ideal model tissue for experiments on wound-response studies and electron transport.
• Potatoes have been delivered with personalized messages as a novelty. Potato delivery services include Potato Parcel and Mail A Spud.

Cultural significance

In art

The potato has been an essential crop in the Andes since the pre-Columbian era. The Moche culture from Northern Peru made ceramics from the earth, water, and fire. This pottery was a sacred substance, formed in significant shapes and used to represent important themes. Potatoes are represented anthropomorphically as well as naturally.

During the late 19th century, numerous images of potato harvesting appeared in European art, including the works of Willem Witsen and Anton Mauve.

Van Gogh's 1885 painting The Potato Eaters portrays a family eating potatoes. Van Gogh said he wanted to depict peasants as they really were. He deliberately chose coarse and ugly models, thinking that they would be natural and unspoiled in his finished work.

Jean-François Millet's The Potato Harvest depicts peasants working in the plains between Barbizon and Chailly. It presents a theme representative of the peasants' struggle for survival. Millet's technique for this work incorporated paste-like pigments thickly applied over a coarsely textured canvas.

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  The Potato Eaters by Van Gogh, 1885 (Van Gogh Museum)

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  The Potato Harvest by Jean-François Millet, 1855 (Walters Art Museum)

In popular culture

Invented in 1949, and marketed and sold commercially by Hasbro in 1952, Mr. Potato Head is an American toy that consists of a plastic potato and attachable plastic parts, such as ears and eyes, to make a face. It was the first toy ever advertised on television.

In June 1992 at the Muñoz Rivera Elementary School spelling bee in Trenton, New Jersey, U.S. Vice President Dan Quayle was handed a flash card that incorrectly spelled "potato" as "potatoe" and then prompted a 12-year-old student to change his correct spelling. This incident was the subject of widespread ridicule.

See also

• Climate change and potatoes
• Irish potato candy
• List of potato cultivars
• List of potato dishes
• List of potato museums
• Loy (spade), a form of early spade used in Ireland for the cultivation of potatoes
• New World crops
• Potato battery
• International Year of the Potato

References

General and cited sources

• Economist. "Llamas and mash", The Economist 28 February 2008 online
• Economist. "The potato: Spud we like", (leader) The Economist 28 February 2008 online
• Boomgaard, Peter (2003). "In the Shadow of Rice: Roots and Tubers in Indonesian History, 1500–1950". Agricultural History 77 (4): 582–610. doi:10.1525/ah.2003.77.4.582. 
• Hawkes, J.G. (1990). The Potato: Evolution, Biodiversity & Genetic Resources, Smithsonian Institution Press, Washington, DC
• Lang, James (1975). Notes of a Potato Watcher. Texas A&M University Agriculture series. ISBN 978-1-58544-138-9. https://archive.org/details/notesofpotatowat0000lang. 
• Langer, William L (1975). "American Foods and Europe's Population Growth 1750–1850". Journal of Social History 8 (2): 51–66. doi:10.1353/jsh/8.2.51. 
• McNeill, William H. "How the Potato Changed the World's History." Social Research (1999) 66#1 pp. 67–83. ISSN 0037-783X Fulltext: Ebsco, by a leading historian
• McNeill William H (1948). "The Introduction of the Potato into Ireland". Journal of Modern History 21 (3): 218–21. doi:10.1086/237272. 
• Ó Gráda, Cormac. Black '47 and Beyond: The Great Irish Famine in History, Economy, and Memory. (1999). 272 pp.
• Ó Gráda, Cormac, Richard Paping, and Eric Vanhaute, eds. When the Potato Failed: Causes and Effects of the Last European Subsistence Crisis, 1845–1850. (2007). 342 pp.  ISBN:978-2-503-51985-2. 15 essays by scholars looking at Ireland and all of Europe
• Reader, John. Propitious Esculent: The Potato in World History (2008), 315pp a standard scholarly history
• Salaman, Redcliffe N. (1989). The History and Social Influence of the Potato, Cambridge University Press (originally published in 1949; reprinted 1985 with new introduction and corrections by J.G. Hawkes).
• Stevenson, W.R., Loria, R., Franc, G.D., and Weingartner, D.P. (2001) Compendium of Potato Diseases, 2nd ed, Amer. Phytopathological Society, St. Paul, MN.
• Zuckerman, Larry. The Potato: How the Humble Spud Rescued the Western World. (1998). 304 pp. Douglas & McIntyre. ISBN:0-86547-578-4.

Further reading

• Bohl, William H., ed (2010). Commercial Potato Production in North America: The Potato Association of America Handbook. Second Revision of American Potato Journal Supplement Volume 57 and USDA Handbook 267. The Potato Association of America. http://potatoassociation.org/documents/A_ProductionHandbook_Final_000.pdf. 
• "'Humble' Potato Emerging as World's Next Food Source". column. Reuters (Japan): p. 20. 11 May 2008. 
• Spooner, David M.; McLean, Karen; Ramsay, Gavin; Waugh, Robbie; Bryan, Glenn J. (October 2005). "A single domestication for potato based on multilocus amplified fragment length polymorphism genotyping". Proceedings of the National Academy of Sciences of the United States of America (National Academy of Sciences of the United States of America) 102 (41): 14694–14699. doi:10.1073/pnas.0507400102. PMID 16203994. Bibcode: 2005PNAS..10214694S. 
• The World Potato Atlas, released by the International Potato Center in 2006 and regularly updated. Includes current chapters of 15 countries:
  • South America: (English and Spanish): Bolivia, Colombia, Ecuador, Peru
  • Africa: Cameroon, Ethiopia, Kenya
  • Eurasia: Armenia, Bangladesh, China, India, Myanmar, Nepal, Pakistan, Tajikistan
  • 38 others as brief "archive" chapters
  • Further information links at Other Materials
• World Geography of the Potato at UGA.edu, released in 1993.
• Atlas of Wild Potatoes (2002), Systematic and Ecogeographic Studies on Crop Genepools 10, International Plant Genetic Resources Institute (IPGRI), ISBN:9789290435181
• Gauldie, Enid (1981). The Scottish Miller 1700–1900. Pub. John Donald. ISBN:0-85976-067-7.

External links

• Solanum tuberosum (potato, papas): life cycle, tuber anatomy at GeoChemBio. .

Wikidata ☰ Q10998 entry