POTATO

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.[2] Potatoes are tubers of the plant Solanum tuberosum, a perennial in the nightshade family Solanaceae.[3]
Wild potato species can be found from the southern United States to southern Chile.[4] The potato was originally believed to have been domesticated by Native Americans independently in multiple locations,[5] 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.[6][7][8] 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.[7] Over 99% of potatoes presently cultivated worldwide descend from varieties that originated in the lowlands of south-central Chile.[9] 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.[10]

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).[11][12] 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.[13] In many of the chronicles detailing agriculture and plants no distinction is made between the two.[14] Potatoes are occasionally referred to as "Irish potatoes" or "white potatoes" in the United States to distinguish them from sweet potatoes.[13]
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.[15] 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.[16][12]
At least six languages—Afrikaans, Dutch, French, (West) Frisian, Hebrew, Persian[17] 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".[18][19]

Plant description

Diagram depicting the morphology of the potato plant. Note the formation of tubers from stolons.
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. The alternately arranged leaves have a petiole with six to eight symetrical leaflets and one top, unpaired leaflet, which is 10 cm (3.9 in) to 30 cm (12 in) long and 5 cm (2.0 in) to 15 cm (5.9 in) wide. They present hairs or trichomes on their surface, to varying degrees depending on the cultivar.
Potato plants 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.
The plant develops tubers as a nutrient storage organ. Traditionally, it was thought that the tubers are roots because they are developed underground. In fact, they are stems that form from thickened rhizomes) at the tips of stolons. These stolons arise as branches from underground nodes. [20] On the surface of the tubers there are "eyes," which act as sinks to protect the vegetative buds from which the stems originate. The "eyes" are arranged in helical form. In addition, the tubers have small holes that allow breathing, called lenticels. The lenticels are circular and their number varies depending of the size of the tuber and environmental conditions. Tubers form in response to decreasing day length, although this tendency has been minimized in commercial varieties.[21]
After flowering, potato plants produce small green fruits that resemble green cherry tomatoes, each containing about 300 very small seeds.[22] 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.[23] 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.[23] Plants having a 'Sli' gene produce pollen which is compatible to its own parent and plants with similar S genes.[24] This gene was recently cloned by Wageningen University and Solynta in 2021, which would allow for faster and more focused breeding.[23][25]
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.[26] Wild potato species useful for breeding may include Solanum desmissum and S. stoloniferum, among others.[27]

Biosynthesis of starch
Sucrose is a product of photosynthesis.[28] Ferreira et al. (2010) found that the genes for starch biosynthesis start to be transcribed at the same time as sucrose synthase activity begins.[28] This transcription – including starch synthase – also shows a diurnal rhythm, correlating with the sucrose supply arriving from the leaves.[28]