Sweet potato
The sweet potato or sweetpotato (Ipomoea batatas) is a dicotyledonous plant in the morning glory family, Convolvulaceae. Its sizeable, starchy, sweet-tasting tuberous roots are used as a root vegetable, which is a staple food in parts of the world. Cultivars of the sweet potato have been bred to bear tubers with flesh and skin of various colors. Moreover, the young shoots and leaves are occasionally eaten as greens. The sweet potato and the potato are only distantly related, both being in the order Solanales. Although darker sweet potatoes are often known as yams in parts of North America, they are even more distant from actual yams, which are monocots in the order Dioscoreales.
The sweet potato originates in South America in what is present-day Ecuador. The domestication of sweet potato occurred in either Central or South America. In Central America, domesticated sweet potatoes were present at least 5,000 years ago, with the origin of I. batatas possibly between the Yucatán Peninsula of Mexico and the mouth of the Orinoco River in Venezuela. The cultigen was most likely spread by local people to the Caribbean and South America by 2500 BCE.
I. trifida, a diploid, is the closest wild relative of the sweet potato, which originated with an initial cross between a tetraploid and another diploid parent, followed by a second complete genome duplication event. The oldest radiocarbon dating remains of the sweet potato known today were discovered in caves from the Chilca Canyon, in the south-central zone of Peru, and yield an age of 8080 ± 170 BC.
The genome of cultivated sweet potatoes contains sequences of DNA from Agrobacterium (sensu lato; specifically, one related to Rhizobium rhizogenes), with genes actively expressed by the plants. The T-DNA transgenes were not observed in closely related wild relatives of the sweet potato. Studies indicated that the sweet potato genome evolved over millennia, with eventual domestication of the crop taking advantage of natural genetic modifications. These observations make sweet potatoes the first known example of a naturally transgenic food crop.
Before the arrival of Europeans to the Americas, sweet potato was grown in Polynesia, generally spread by vine cuttings rather than by seeds. Sweet potato has been radiocarbon-dated in the Cook Islands to 1210, 1400 CE. A common hypothesis is that a vine cutting was brought to central Polynesia by Polynesians who had traveled to South America and back, and spread from there across Polynesia to Easter Island, Hawaii and New Zealand. Genetic similarities have been found between Polynesian peoples and indigenous Americans including the Zenú, a people inhabiting the Pacific coast of present-day Colombia, indicating that Polynesians could have visited South America and taken sweet potatoes prior to European contact.
Dutch linguists and specialists in Amerindian languages Willem Adelaar and Pieter Muysken have suggested that the word for sweet potato is shared by Polynesian languages and languages of South America: Proto-Polynesian * (compare Rapa Nui , Hawaiian , Māori ) may be connected with Quechua and Aymara ~ . Adelaar and Muysken assert that the similarity in the word for sweet potato is near proof of either incidental contact or sporadic contact between the Central Andes and Polynesia.
Some researchers, citing divergence time estimates, suggest that sweet potatoes might have been present in Polynesia thousands of years before humans arrived there. However, the present scholarly consensus favours the pre-Columbian contact model.
In 2020, global production of sweet potatoes was 89 million tonnes, led by China with 55% of the world total. Secondary producers were Malawi, Tanzania, and Nigeria. It is the fifth most important food crop in developing countries. Studies are being done to develop a salt tolerant variety to combat the effects of climate change.
The plant does not tolerate frost. It grows best at an average temperature of 24°C, with abundant sunshine and warm nights. Annual rainfalls of 750, 1000 mm are considered most suitable, with a minimum of 500 mm in the growing season. The crop is sensitive to drought at the tuber initiation stage 50, 60 days after planting, and it is not tolerant to waterlogging, which may cause tuber rots and reduce the growth of storage roots if aeration is poor.
Sweet potatoes are cultivated throughout tropical and warm temperate regions wherever there is sufficient water to support their growth. Sweet potatoes became common as a food crop in the islands of the Pacific Ocean, South India, Uganda and other African countries. A cultivar of the sweet potato called the boniato is grown in the Caribbean; its flesh is cream-colored, unlike the more common orange hue seen in other cultivars. Boniatos are not as sweet and moist as other sweet potatoes, but their consistency and delicate flavor are different from the common orange-colored sweet potato.
Cooked sweet potato (baked in skin) is 76% water, 21% carbohydrates, 2% protein, and contains negligible fat. In a 100-gram reference amount, baked sweet potato provides 86 kcal of food energy, and rich contents (20% or more of the Daily Value, DV) of vitamin A (120% DV), vitamin C (24% DV), manganese (24% DV), and vitamin B6 (20% DV). It is a moderate source (10, 19% DV) of some B vitamins and potassium.
Sweet potato cultivars with dark orange flesh have more beta-carotene (converted to a higher vitamin A content once digested) than those with light-colored flesh, and their increased cultivation is being encouraged in Africa where vitamin A deficiency is a serious health problem. Sweet potato leaves are edible and can be prepared like spinach or turnip greens.
According to a study by the United Nations Food and Agriculture Organization, sweet potatoes are the most efficient staple food to grow in terms of farmland, yielding approximately 35 MJ per hectare daily.
In East Asia, roasted sweet potatoes are popular street food. In China, sweet potatoes, typically yellow cultivars, are baked in a large iron drum and sold as street food during winter. In Korea, sweet potatoes, known as gamja, are roasted in a drum can, baked in foil or on an open fire, typically during winter. In Japan, a dish similar to the Korean preparation is called yaki-imo (roasted sweet potato), which typically uses either the yellow-fleshed Japanese sweet potato or the purple-fleshed Okinawan sweet potato, which is known as satsuma-imo.
In Kenya, Rhoda Nungo of the home economics department of the Ministry of Agriculture has written a guide to using sweet potatoes in modern recipes. This includes uses both in the mashed form and as flour from the dried tubers to replace part of the wheat flour and sugar in baked products such as cakes, chapatis, mandazis, bread, buns and cookies. A nutritious juice drink is made from the orange-fleshed cultivars, and deep-fried snacks are also included.
In the Philippines, sweet potatoes (locally known as kamote) are an important food crop in rural areas. They are often a staple among impoverished families in provinces, as they are easier to cultivate and cost less than rice. The tubers are boiled or baked in coals and may be dipped in sugar or syrup. Young leaves and shoots (locally known as kamote tops) are eaten fresh in salads with shrimp paste or fish sauce.
In South America, the juice of red sweet potatoes is combined with lime juice to make a dye for cloth. By varying the proportions of the juices, every shade from pink to black can be obtained. Purple sweet potato color is also used as a natural food coloring.
Cuttings of sweet potato vine, either edible or ornamental cultivars, will rapidly form roots in water and will grow in it, indefinitely, in good lighting with a steady supply of nutrients. For this reason, sweet potato vine is ideal for use in home aquariums, trailing out of the water with its roots submerged, as its rapid growth is fueled by toxic ammonia and nitrates, a waste product of aquatic life, which it removes from the water.
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Common questions
What is the scientific name of the sweet potato?
The scientific name of the sweet potato is Ipomoea batatas. It belongs to the morning glory family known as Convolvulaceae.
Where did the sweet potato originate and when was it domesticated?
The sweet potato originates in South America within present-day Ecuador. Domestication occurred at least 5,000 years ago between the Yucatán Peninsula of Mexico and the mouth of the Orinoco River in Venezuela.
How many tonnes of sweet potatoes were produced globally in 2020?
Global production of sweet potatoes reached 89 million tonnes in 2020. China led this total with 55% of the world output while Malawi, Tanzania, and Nigeria served as secondary producers.
Why are sweet potatoes considered naturally transgenic food crops?
Sweet potatoes contain DNA sequences from Agrobacterium specifically related to Rhizobium rhizogenes that remain actively expressed in the plant genome. This natural genetic modification makes them the first known example of a naturally transgenic food crop.
What nutrients does baked sweet potato provide per 100 grams?
A 100-gram reference amount of baked sweet potato provides 86 kcal of energy along with rich contents of vitamin A at 120% DV and vitamin C at 24% DV. It also supplies manganese at 24% DV and vitamin B6 at 20% DV.