Mandarin orange
The mandarin orange ("Citrus reticulata"), also known as the mandarin or mandarine, is a small citrus tree fruit. Treated as a distinct species of orange, it is usually eaten plain or in fruit salads. Tangerines are a group of orange-coloured citrus fruit consisting of hybrids of mandarin orange with some pomelo contribution. Mandarins are smaller and oblate, unlike the spherical common oranges (which are a mandarin–pomelo hybrid). The taste is considered sweeter and stronger than the common orange. A ripe mandarin is firm to slightly soft, heavy for its size, and pebbly-skinned. The peel is  thin, loose, with little white mesocarp, so they are usually easier to peel and to split into segments. Hybrids usually have these traits to a lesser degree. The mandarin is tender and is damaged easily by cold. It can be grown in tropical and subtropical areas. According to genetic studies, the mandarin was one of the original citrus species; through breeding or natural hybridization, it is the ancestor of many hybrid citrus cultivars. With the citron and pomelo, it is the ancestor of the most commercially important hybrids (such as sweet and sour oranges, grapefruit, and many lemons and limes ). The mandarin has also been hybridized with other citrus species, such as the desert lime and the kumquat. Though the ancestral mandarin was bitter, most commercial mandarin strains derive from hybridization with pomelo, which give them a sweet fruit. Etymology. "Citrus reticulata" is from Latin, where reticulata means "netted". The name "mandarin orange" is a calque of Swedish "mandarin apelsin" ["apelsin" from German "Apfelsine" ("Apfel" + "Sina"), meaning "Chinese apple"], first attested in the 18th century. The form "mandarine" derives from the French name for this fruit. The reason for the epithet "mandarin" is not clear; it may relate to  the yellow colour of some robes worn by mandarin dignitaries. Botany. "Citrus reticulata" is a moderate-sized tree some in height. The tree trunk and major branches have thorns. The leaves are shiny, green, and rather small. The petioles are short, almost wingless or slightly winged. The flowers are borne singly or in small groups in the leaf-axils. Citrus are usually self-fertile (needing only a bee to move pollen within the same flower) or parthenocarpic (not needing pollination and therefore seedless, such as the satsuma). A mature mandarin tree can yield up to of fruit. Fruit. Mandarin orange  fruits are small . Their colour is orange, yellow-orange, or red-orange. The skin is thin and peels off easily. Their easiness to peel is an important advantage of mandarin oranges over other citrus fruits. Just like with other citrus fruits, the endocarp (inner flesh) is separated into segments, which in their turn consist of a large number of elongated cells. The fruits may be seedless or contain a small number of seeds. Mandarin orange fruits are sweet to taste, and can be eaten as whole or squeezed to make juice. Production. In 2019, world production of mandarin oranges (combined  with tangerines, clementines, and satsumas in reporting to FAOSTAT) was 35.4 million tonnes, led by China with 56% of the global total (table). Producing more than one million tonnes each in 2019 were Spain, Turkey, Morocco, and Egypt. Uses. Fresh. Mandarins are generally peeled and eaten fresh or used in salads, desserts and main dishes. Fresh mandarin juice and frozen juice concentrate are commonly available in the United States. The number of seeds in each segment (carpel) varies greatly. Peel. The peel is used fresh, whole or zested, or dried as chenpi. It can be used as a spice for  cooking, baking, drinks, or candy. Essential oil from the fresh peel may be used as a flavouring for candy, in gelatins, ice cream, chewing gum, and baked goods. It is also used as a flavouring in liqueurs. In Chinese cuisine, the peel of the mandarin orange, called chenpi, is used to flavor sweet dishes and sauces. Canning. Canned mandarin segments are peeled to remove the white pith prior to canning; otherwise, they turn bitter. Segments are peeled using a chemical process. First, the segments are scalded in hot water to loosen the skin; then they are bathed in a lye  solution, which digests the albedo and membranes. Finally, the segments are rinsed several times in plain water. Once orange segments are properly prepared, mandarin oranges undergo heat processing to remove bacteria that can cause spoilage. The oranges are then packed in airtight sealed containers. Ascorbic acid may also be added. Traditional medicine. In traditional Chinese medicine, the dried peel of the fruit is used in regulation of ch'i and to enhance digestion. Nutrition. A mandarin orange contains 85% water, 13% carbohydrates, and negligible amounts of fat and protein (table). Among micronutrients, only vitamin C is in significant content (32% of  the Daily Value) in a 100-gram reference serving, with all other nutrients in low amounts. Cultural significance. During Chinese New Year, mandarin oranges/tangerine/satsumas are considered traditional symbols of abundance and good fortune. During the two-week celebration, they are frequently displayed as decoration and presented as gifts to friends, relatives, and business associates. Mandarin oranges, particularly from Japan, are a Christmas tradition in Canada, the United States, the United Kingdom and Russia. In Canada and the United States, they are commonly purchased in 5- or 10-pound boxes, individually wrapped in soft green paper, and given in  Christmas stockings. This custom goes back to the 1880s, when Japanese immigrants in Canada and the United States began receiving Japanese mandarin oranges from their families back home as gifts for the New Year. The tradition quickly spread among the non-Japanese population, and eastwards across the country: each November harvest, "The oranges were quickly unloaded and then shipped east by rail. 'Orange Trains' – trains with boxcars painted orange – alerted everyone along the way that the irresistible oranges from Japan were back again for the holidays. For many, the arrival of Japanese mandarin oranges signaled the real beginning of the  holiday season." This Japanese tradition merged with European traditions related to the Christmas stocking. Saint Nicholas is said to have put gold coins into the stockings of three poor girls so that they would be able to afford to get married. Sometimes the story is told with gold balls instead of bags of gold, and oranges became a symbolic stand-in for these gold balls, and are put in Christmas stockings in Canada along with chocolate coins wrapped in gold foil. Satsumas were also grown in the United States from the early 1900s, but Japan remained a major supplier. U.S.  imports of these Japanese oranges was suspended due to hostilities with Japan during World War II. While they were one of the first Japanese goods allowed for export after the end of the war, residual hostility led to the rebranding of these oranges as "mandarin" oranges. The delivery of the first batch of mandarin oranges from Japan in the port of Vancouver, British Columbia (Canada), is greeted with a festival that combines Santa Claus and Japanese dancers—young girls dressed in traditional kimono. Historically, the Christmas fruit sold in North America was mostly Dancys, but now it is more often  a hybrid. Literature. In Canadian literature, particularly in Gabrielle Roy's novel about Montreal, "The Tin Flute", a mandarin orange figures as a touch of luxury for the dying son of the poor Lacasse family, around which the novel is woven. Mandarin oranges are mentioned in Sinclair Ross' 1942 novel, "As for Me and My House", and his 1939 short story, "Cornet at Night". Genetics and origin. Mandarins are one of the core ancestral citrus taxa, and are thought to have evolved in regions including South China and Japan in East Asia, and Vietnam in Southeast Asia. Mandarins appear to  have been domesticated at least twice, in the north and south Nanling Mountains, derived from separate wild subspecies. Wild mandarins are still found there, including Daoxian mandarines (sometimes given the species name "Citrus daoxianensis") as well as some members of the group traditionally called 'Mangshan wild mandarins', a generic grouping for the wild mandarin-like fruit of the Mangshan area that includes both true mandarins ("mangshanyeju", the southern subspecies) and the genetically-distinct and only distantly-related Mangshanyegan. The wild mandarins were found to be free of the introgressed pomelo ("C. maxima") DNA found in domestic mandarins but they did  appear to have small amounts (~1.8%) of introgression from the ichang papeda, which grows wild in the same region. The Nanling Mountains are also home to northern and southern genetic clusters of domestic mandarins that have similar levels of sugars in the fruit compared to their wild relatives, but appreciably (in some almost 90-fold) lower levels of citric acid. The clusters display different patterns of pomelo introgression, have different deduced historical population histories, and are most closely related to distinct wild mandarins, suggesting two independent domestications in the north and south. All tested domesticated cultivars were found to belong  to one of these two genetic clusters, with varieties such as Nanfengmiju, Kishu and Satsuma deriving from the northern domestication event producing larger, redder fruit, while Willowleaf, Dancy, Sunki, Cleopatra, King, Ponkan, and others derived from the smaller, yellower-fruited southern cluster. The Tanaka classification system divided domestic mandarins and similar fruit into numerous species, giving distinct names to cultivars such as willowleaf mandarins ("C. deliciosa"), satsumas ("C. unshiu"), tangerines ("C. tangerina"). Under the Swingle system, all these are considered to be varieties of a single species, "Citrus reticulata". Hodgson represented them as several subgroups: common ("C. reticulata"), Satsuma, King  ("C. nobilis"), Mediterranean (willowleaf), small-fruited ("C. indica", "C. tachibana" and "C. reshni"), and mandarin hybrids. In the genomic-based species taxonomy of Ollitrault et al., only pure mandarins would fall under "C. reticulata", while the pomelo admixture found in the majority of mandarins would cause them to be classified as varieties of "C. aurantium". Genetic analysis is consistent with continental mandarins representing a single species, with much of the variation within mandarins being due to hybridization. A separate species, "Citrus ryukyuensis" that diverged from the mainland species between 2 and 3 million years ago when cut off by rising  sea levals was found growing on the island of Okinawa, and its natural and agricultural hybridization with the mainland mandarin species has produced some of the unique island mandarin cultivars of Japan and Taiwan, such as the Tachibana orange, previously classified as a subspecies of pure mandarin before its parent was identified, and the Shekwasha. Some of the small number of cultivars were found to be pure in initial gemonic analysis, including Sun Chu Sha mandarin and Nanfengmiju, but Wang detected in them not only an apparent Ichang papeda introgression found in all examined mandarins but also the distinct pomelo  DNA of the domesticated mandarins. Following initial hybridization, natural or cultivated backcrosses of the initial mandarin-pomelo hybrids with the mandarin stock produced mandarins with limited pomelo contribution, that differed between the northern and southern domesticates. An 'acidic' group of cultivars including Sunki and Cleopatra mandarins that likewise previously were thought to be pure but since found to contain small regions of introgressed pomelo DNA are too sour to be edible, but are widely used as rootstock and grown for juice. Another group of mandarins, including some tangerines, Satsuma and King mandarins, show a greater pomelo contribution and derive from  the limited-pomelo hybrids being crossed again, with sweet orange or pomelo, and likewise backcrossing in some cases, producing cultivars with moderate to high levels of pomelo introgression. Hybrid mandarins thus fall on a continuum of increasing pomelo contribution with clementines, sweet and sour oranges, and grapefruit. Mandarins and their hybrids are sold under a variety of names. Varieties. Domesticated mandarins and hybrids. (Species names are those from the Tanaka system. Recent genomic analysis would place them all in "Citrus reticulata", except the "C. ryukyuensis" hybrids)