Citrus

Citrus is a genus of flowering trees and shrubs in the rue family, Rutaceae. Plants in the genus produce citrus fruits, including important crops such as oranges, lemons, grapefruits, pomelos, and limes.

The most recent research indicates an origin in the Himalayas.[1] Previous research indicated an origin in the part of Southeast Asia bordered by Northeast India, Burma (Myanmar), and the Yunnan province of China,[2][3][4] and it is in this region that some commercial species such as oranges, mandarins, and lemons originated. Citrus fruit has been cultivated in an ever-widening area since ancient times.

Citrus
OrangeBloss wb
Sweet orange (Citrus × sinensis cultivar)
Scientific classification
Kingdom: Plantae
Clade: Angiosperms
Clade: Eudicots
Clade: Rosids
Order: Sapindales
Family: Rutaceae
Subfamily: Aurantioideae
Tribe: Citreae
Subtribe: Citrinae
Genus: Citrus
L.
Species and hybrids

Ancestral species:
Citrus maximaPomelo
Citrus medicaCitron
Citrus reticulataMandarin orange
Citrus micrantha – a papeda
Citrus hystrixKaffir lime
Citrus cavaleriei - Ichang papeda Citrus japonica - Kumquat


Important hybrids:
Citrus × aurantiifoliaKey lime
Citrus × aurantiumBitter orange
Citrus × latifoliaPersian lime
Citrus × limonLemon
Citrus × limoniaRangpur
Citrus × paradisiGrapefruit
Citrus × sinensisSweet orange
Citrus × tangerinaTangerine
See also below for other species and hybrids.

Synonyms

Eremocitrus
Microcitrus
and see text

History

Citrus plants are native to subtropical and tropical regions of Asia and the Malay Archipelago, and they were first domesticated in these areas. Some citrus species have been present in the Mediterranean basin for centuries.[5] This group of species has reached great importance in some of the Mediterranean countries, and in the case of orange, mandarin, and lemon trees, they found here soil and climatic conditions which allow them to achieve a high level of fruit quality, even better than in the regions from where they came.[5]

The "native" oranges of Florida actually originated with the Spanish conquistadores.[6][7] The agronomists of classical Rome already made many references to the cultivation of citrus fruits within the limits of their empire.[5] King Louis XIV of France housed citrus in orangeries, to protect the tropical fruit to be grown in the 1600s France.[8]

Name

The generic name originated from Latin, where it referred to either the plant now known as citron (C. medica) or a conifer tree (Thuja). It is somehow related to the ancient Greek word for cedar, κέδρος (kédros). This may be due to perceived similarities in the smell of citrus leaves and fruit with that of cedar.[9] Collectively, Citrus fruits and plants are also known by the Romance loanword agrumes (literally "sour fruits").

Evolution

The large citrus fruit of today evolved originally from small, edible berries over millions of years. Citrus plants diverged from a common ancestor about 15 million years ago, which was about when it diverged from the closely related severinia, for example the Chinese box orange. About 7 million years ago, citrus plants diverged into two groups, the main citrus genus and the ancestors of the trifoliate orange (poncirus), which is closely enough related that it can still be hybridized with all other citrus. These estimates are made using genetic mapping of plant chloroplasts.[10] A DNA study published in Nature in 2018 concludes that citrus trees originated in the foothills of the Himalayas, in the area of Assam (India), western Yunnan (China), and northern Myanmar.[11]

The three original species in the genus Citrus that have been hybridized into most modern commercial citrus fruit are the mandarin orange, pomelo, and citron.[12] Within the last few thousand years, all common citrus fruits (sweet oranges, lemons, grapefruit, limes, and so on) were created by crossing those original species.

Fossil record

A fossil leaf from the Pliocene of Valdarno (Italy) is described as †Citrus meletensis[13] In China, fossil leaf specimens of †Citrus linczangensis have been collected from coal-bearing strata of the Bangmai Formation in the Bangmai village, about 10 km northwest of Lincang City, Yunnan. The Bangmai Formation contains abundant fossil plants and is considered to be of late Miocene age. Citrus linczangensis and C. meletensis share some important characters, such as an intramarginal vein, an entire margin, and an articulated and distinctly winged petiole.[14]

Taxonomy

Citrus tern cb simplified 1
Citrus fruits clustered by genetic similarity, ternary diagram based on data from Curk, et al. (2016)[15]
S12863-014-0152-1-3
Three-dimensional projection of a principal component analysis of citrus hybrids, with citron (yellow), pomelo (blue), mandarin (red), and micrantha (green) defining the axes. Hybrids are expected to plot between their parents. ML: ‘Mexican’ lime; A: ‘Alemow’; V: ‘Volkamer’ lemon; M: ‘Meyer’ lemon; L: Regular and ‘Sweet’ lemons; B: Bergamot orange; H: Haploid clementine; C: Clementines; S: Sour oranges; O: Sweet oranges; G: Grapefruits. Figure from Curk, et al. (2014).[16]

The taxonomy and systematics of the genus are complex and the precise number of natural species is unclear, as many of the named species are hybrids clonally propagated through seeds (by apomixis), and genetic evidence indicates that even some wild, true-breeding species are of hybrid origin.

Most cultivated Citrus spp. seem to be natural or artificial hybrids of a small number of core ancestral species, including the citron, pomelo, mandarin, and papeda (see image).[17] Natural and cultivated citrus hybrids include commercially important fruit such as oranges, grapefruit, lemons, limes, and some tangerines.

Apart from these core citrus species, Australian limes and the recently discovered mangshanyegan are grown. Kumquats and Clymenia spp. are now generally considered to belong within the genus Citrus.[18] Trifoliate orange, which is often used as commercial rootstock, is an outgroup and may or may not be categorized as a citrus.

Phylogenetic analysis suggests the species of Oxanthera from New Caledonia should be transferred to the genus Citrus.[19]

Description

Citrus fruits
Slices of various citrus fruits

Tree

These plants are large shrubs or small to moderate-sized trees, reaching 5–15 m (16–49 ft) tall, with spiny shoots and alternately arranged evergreen leaves with an entire margin.[20] The flowers are solitary or in small corymbs, each flower 2–4 cm (0.79–1.57 in) diameter, with five (rarely four) white petals and numerous stamens; they are often very strongly scented.

Fruit

The fruit is a hesperidium, a specialised berry, globose to elongated, 4–30 cm (1.6–11.8 in) long and 4–20 cm (1.6–7.9 in) diameter, with a leathery rind or "peel" called a pericarp. The outermost layer of the pericarp is an "exocarp" called the flavedo, commonly referred to as the zest. The middle layer of the pericarp is the mesocarp, which in citrus fruits consists of the white, spongy "albedo", or "pith". The innermost layer of the pericarp is the endocarp. The space inside each segment is a locule filled with juice vesicles, or "pulp". From the endocarp, string-like "hairs" extend into the locules, which provide nourishment to the fruit as it develops.[21][22]

Citrus fruits are notable for their fragrance, partly due to flavonoids and limonoids (which in turn are terpenes) contained in the rind, and most are juice-laden. The juice contains a high quantity of citric acid giving them their characteristic sharp flavour. The genus is commercially important as many species are cultivated for their fruit, which is eaten fresh, pressed for juice, or preserved in marmalades and pickles.

They are also good sources of vitamin C and flavonoids. The content of vitamin C in the fruit depends on the species, variety, and mode of cultivation. Fruits produced with organic agriculture have been shown to contain more vitamin C than those produced with conventional agriculture in the Algarve, but results depended on the species and cultivar.[23] The flavonoids include various flavanones and flavones.[24]

Acidity indicators

The Moroccan professor Henri Chapot discovered that the acidity in the more common citrons or lemons is indicated by red on the inner coat of seeds specifically on the chalazal spot, violet pigmentation on the outer side of the flower blossom, and by the new buds that are reddish-purplish. The acid-free varieties of citrus are completely lacking the red color in all the mentioned spots.[25] This designation was cited by Herbert John Webber and Leon Dexter Batchelor, the editors of the fundamental treatise on citrus, namely The Citrus Industry, which was published by the University of California, Riverside in 1967.

Cultivation

Lemon on a Wood Table
Lemons are a citrus fruit native to Asia, but now common worldwide.
Limes
Limes in a grocery store

Citrus trees hybridise very readily – depending on the pollen source, plants grown from a Persian lime's seeds can produce fruit similar to grapefruit. Thus, all commercial citrus cultivation uses trees produced by grafting the desired fruiting cultivars onto rootstocks selected for disease resistance and hardiness.

The colour of citrus fruits only develops in climates with a (diurnal) cool winter.[26] In tropical regions with no winter at all, citrus fruits remain green until maturity, hence the tropical "green oranges".[27] The Persian lime in particular is extremely sensitive to cool conditions, thus it is not usually exposed to cool enough conditions to develop a mature colour. If they are left in a cool place over winter, the fruits will change colour to yellow.

The terms "ripe" and "mature" are usually used synonymously, but they mean different things. A mature fruit is one that has completed its growth phase. Ripening is the changes that occur within the fruit after it is mature to the beginning of decay. These changes usually involve starches converting to sugars, a decrease in acids, and a softening and change in the fruit's colour.[28]

Citrus fruits are nonclimacteric and respiration slowly declines and the production and release of ethylene is gradual.[29] The fruits do not go through a ripening process in the sense that they become "tree ripe". Some fruits, for example cherries, physically mature and then continue to ripen on the tree. Other fruits, such as pears, are picked when mature, but before they ripen, then continue to ripen off the tree. Citrus fruits pass from immaturity to maturity to overmaturity while still on the tree. Once they are separated from the tree, they do not increase in sweetness or continue to ripen. The only way change may happen after being picked is that they eventually start to decay.

With oranges, colour cannot be used as an indicator of ripeness because sometimes the rinds turn orange long before the oranges are ready to eat. Tasting them is the only way to know whether or not they are ready to eat.

Mandariner Citrus deliciosa
Mediterranean Mandarin (Citrus ×deliciosa plantation, Son Carrió (Mallorca)

Citrus trees are not generally frost hardy. Mandarin oranges (C. reticulata) tend to be the hardiest of the common Citrus species and can withstand short periods down to as cold as −10 °C (14 °F), but realistically temperatures not falling below −2 °C (28 °F) are required for successful cultivation. Tangerines, tangors and yuzu can be grown outside even in regions with more marked subfreezing temperatures in winter, although this may affect fruit quality. A few hardy hybrids can withstand temperatures well below freezing, but do not produce quality fruit. Lemons can be commercially grown in cooler-summer/moderate-winter, coastal Southern California, because sweetness is neither attained nor expected in retail lemon fruit. The related trifoliate orange (C. trifoliata) can survive below −20 °C (−4 °F); its fruit are astringent and inedible unless cooked, but a few better-tasting cultivars and hybrids have been developed (see citranges).

Citrus leaf
Leaf of Citrus tree

The trees thrive in a consistently sunny, humid environment with fertile soil and adequate rainfall or irrigation. Abandoned trees in valleys may suffer, yet survive, the dry summer of Central California's Inner Coast Ranges. At any age, citrus grows well enough with infrequent irrigation in partial shade, but the fruit crop is smaller. Being of tropical and subtropical origin, oranges, like all citrus, are broadleaved and evergreen. They do not drop leaves except when stressed. The stems of many varieties have large sharp thorns. The trees flower in the spring, and fruit is set shortly afterward. Fruit begins to ripen in fall or early winter, depending on cultivar, and develops increasing sweetness afterward. Some cultivars of tangerines ripen by winter. Some, such as the grapefruit, may take up to 18 months to ripen.

Production

Hauptanbaugebiete-Zitrusfrüchte
Major producer regions

According to UN 2007 data, Brazil, China, the United States, Mexico, India, and Spain are the world's largest citrus-producing countries.

Major commercial citrus-growing areas include southern China, the Mediterranean Basin (including southern Spain), South Africa, Australia, the southern United States, Mexico, and parts of South America. In the United States, Florida, California, Arizona, and Texas are major producers, while smaller plantings are present in other Sun Belt states and in Hawaii.

As ornamental plants

Citrus trees grown in tubs and wintered under cover were a feature of Renaissance gardens, once glass-making technology enabled sufficient expanses of clear glass to be produced. An orangery was a feature of royal and aristocratic residences through the 17th and 18th centuries. The Orangerie at the Palace of the Louvre, 1617, inspired imitations that were not eclipsed until the development of the modern greenhouse in the 1840s. In the United States, the earliest surviving orangery is at the Tayloe House, Mount Airy, Virginia. George Washington had an orangery at Mount Vernon.

Some modern hobbyists still grow dwarf citrus in containers or greenhouses in areas where the weather is too cold to grow it outdoors. Consistent climate, sufficient sunlight, and proper watering are crucial if the trees are to thrive and produce fruit. Compared to many of the usual "green shrubs", citrus trees better tolerate poor container care. For cooler winter areas, limes and lemons should not be grown, since they are more sensitive to winter cold than other citrus fruits. Hybrids with kumquats (× Citrofortunella) have good cold resistance. A citrus tree in a container may have to be repotted every 5 years or so, since the roots may form a thick "root-ball" on the bottom of the pot.[8]

Pests and diseases

Citrus canker on fruit
Citrus canker is caused by the gammaproteobacterium Xanthomonas axonopodis

Citrus plants are very liable to infestation by aphids, whitefly, and scale insects (e.g. California red scale). Also rather important are the viral infections to which some of these ectoparasites serve as vectors such as the aphid-transmitted Citrus tristeza virus, which when unchecked by proper methods of control is devastating to citrine plantations. The newest threat to citrus groves in the United States is the Asian citrus psyllid.

The Asian citrus psyllid is an aphid-like insect that feeds on the leaves and stems of citrus trees and other citrus-like plants. The real danger lies that the psyllid can carry a deadly, bacterial tree disease called Huanglongbing (HLB), also known as citrus greening disease.[30]

In August 2005, citrus greening disease was discovered in the south Florida region around Homestead and Florida City. The disease has since spread to every commercial citrus grove in Florida. In 2004–2005, USDA statistics reported the total Florida citrus production to be 169.1 million boxes of fruit. The estimate for all Florida citrus production in the 2015–2016 season is 94.2 million boxes, a 44.3% drop.[31]

In June 2008, the psyllid was spotted dangerously close to California – right across the international border in Tijuana, Mexico. Only a few months later, it was detected in San Diego and Imperial Counties, and has since spread to Riverside, San Bernardino, Orange, Los Angeles and Ventura Counties, sparking quarantines in those areas. The Asian citrus psyllid has also been intercepted coming into California in packages of fruit and plants, including citrus, ornamentals, herbs and bouquets of cut flowers, shipped from other states and countries.[30]

The foliage is also used as a food plant by the larvae of Lepidoptera (butterfly and moth) species such as the Geometridae common emerald (Hemithea aestivaria) and double-striped pug (Gymnoscelis rufifasciata), the Arctiidae giant leopard moth (Hypercompe scribonia), H. eridanus, H. icasia and H. indecisa, many species in the family Papilionidae (swallowtail butterflies), and the black-lyre leafroller moth ("Cnephasia" jactatana), a tortrix moth.

Since 2000, the citrus leafminer (Phyllocnistis citrella) has been a pest in California,[32] boring meandering patterns through leaves.

In eastern Australia, the bronze-orange bug (Musgraveia sulciventris) can be a major pest of citrus trees, particularly grapefruit. In heavy infestations it can cause flower and fruit drop and general tree stress.

European brown snails (Cornu aspersum) can be a problem in California, though laying female Khaki Campbell and other mallard-related ducks can be used for control.

Deficiency diseases

Citrus plants can also develop a deficiency condition called chlorosis, characterized by yellowing leaves[33] highlighted by contrasting leaf veins. The shriveling leaves eventually fall, and if the plant loses too many, it will slowly die. This condition is often caused by an excessively high pH (alkaline soil), which prevents the plant from absorbing iron, magnesium, zinc, or other nutrients it needs to produce chlorophyll. This condition can be cured by adding an appropriate acidic fertilizer formulated for citrus, which can sometimes revive a plant to produce new leaves and even flower buds within a few weeks under optimum conditions. A soil which is too acidic can also cause problems; citrus prefers neutral soil (pH between 6 and 8). Citrus plants are also sensitive to excessive salt in the soil. Soil testing may be necessary to properly diagnose nutrient-deficiency diseases.[34]

Uses

Culinary

NIH citrus
Wedges of pink grapefruit, lime, and lemon, and a half orange (clockwise from top)
Pomeranzen
Ripe Bitter oranges (Citrus × aurantium) from Asprovalta

Many citrus fruits, such as oranges, tangerines, grapefruits, and clementines, are generally eaten fresh. They are typically peeled and can be easily split into segments. Grapefruit is more commonly halved and eaten out of the skin with a spoon.[35] Special spoons (grapefruit spoons) with serrated tips are designed for this purpose. Orange and grapefruit juices are also popular breakfast beverages. More acidic citrus, such as lemons and limes, are generally not eaten on their own. Meyer lemons can be eaten out of hand with the fragrant skin; they are both sweet and sour. Lemonade or limeade are popular beverages prepared by diluting the juices of these fruits and adding sugar. Lemons and limes are also used as garnishes or in cooked dishes. Their juice is used as an ingredient in a variety of dishes; it can commonly be found in salad dressings and squeezed over cooked fish, meat, or vegetables.

A variety of flavours can be derived from different parts and treatments of citrus fruits. The rind and oil of the fruit is generally very bitter, especially when cooked, so is often combined with sugar. The fruit pulp can vary from sweet to extremely sour. Marmalade, a condiment derived from cooked orange and lemon, can be especially bitter, but is usually sweetened to cut the bitterness and produce a jam-like result. Lemon or lime is commonly used as a garnish for water, soft drinks, or cocktails. Citrus juices, rinds, or slices are used in a variety of mixed drinks. The colourful outer skin of some citrus fruits, known as zest, is used as a flavouring in cooking; the white inner portion of the peel, the pith, is usually avoided due to its bitterness. The zest of a citrus fruit, typically lemon or an orange, can also be soaked in water in a coffee filter, and drunk.

Medical

Citrus fruits have well-documented nutritional and health benefits.[5] They can actually help prevent and cure some diseases.[5]

Citrus fruit intake has been associated with a 10% reduction in odds of developing breast cancer.[36]

Oranges were historically used for their high content of vitamin C,[23] which prevents scurvy. Scurvy is caused by vitamin C deficiency, and can be prevented by having 10 mg of vitamin C a day. An early sign of scurvy is fatigue. If ignored, later symptoms are bleeding and bruising easily. British sailors were given a ration of citrus fruits on long voyages to prevent the onset of scurvy, hence the British nickname of Limey.

Pectin is a structural heteropolysaccharide contained in the primary cell walls of plants. Limes and lemons, as well as oranges and grapefruits, are among the highest in this level.[37]

After consumption, the peel is sometimes used as a facial cleanser.

Before the development of fermentation-based processes, lemons were the primary commercial source of citric acid.

Citrus fruit intake is associated with a reduced risk of stomach cancer.[38] Also, citrus fruit juices, such as orange, lime, and lemon, may be useful for lowering the risk of specific types of kidney stones. Grapefruit is another fruit juice that can be used to lower blood pressure because it interferes with the metabolism of calcium channel blockers.[39] Lemons have the highest concentration of citrate of any citrus fruit, and daily consumption of lemonade has been shown to decrease the rate of kidney stone formation.[40]

Health effects

Some Citrus species contain significant amounts of furanocoumarins, a diverse family of naturally occurring organic chemical compounds. In humans, some (not all) of these chemical compounds act as strong photosensitizers when applied topically to the skin, while other furanocoumarins interact with medications when taken orally. The latter is called the “grapefruit juice effect”, a common name for a related group of grapefruit-drug interactions.

Due to the photosensitizing effects of certain furanocoumarins, some Citrus species are known to cause phytophotodermatitis,[41] a potentially severe skin inflammation resulting from contact with a light-sensitizing botanical agent followed by exposure to ultraviolet light. In Citrus species, the primary photosensitizing agent appears to be bergapten,[42] a linear furanocoumarin derived from psoralen. This claim has been confirmed for lime[43][44] and bergamot. In particular, bergamot essential oil has a higher concentration of bergapten (3000–3600 mg/kg) than any other Citrus-based essential oil.[45]

In general, three Citrus ancestral species (pomelos, citrons, and papedas) synthesize relatively high quantities of furanocoumarins, whereas a fourth ancestral species (mandarins) is practically devoid of these compounds.[42] Since the production of furanocoumarins in plants is believed to be heritable, the descendants of mandarins (such as sweet oranges, tangerines, and other small mandarin hybrids) are expected to have low quantities of furanocoumarins, whereas other hybrids (such as limes, grapefruit, and sour oranges) are expected to have relatively high quantities of these compounds.

In one comprehensive study of 61 Citrus varieties,[42] two papedas (Citrus micrantha and Citrus hystrix) had the highest concentrations of furanocoumarins of any Citrus species (even more than the bergamot), in both the peel and the pulp. The study also found high furanocoumarin content in the peel of lime and bergamot, and in the pulp of pomelo, grapefruit, and sour orange. These results are consistent with what is already known, that is, lime and bergamot lead to phytophotodermatitis, while pomelo and grapefruit are involved in grapefruit-drug interactions.

In most Citrus species, the peel contains a greater diversity and a higher concentration of furanocoumarins than the pulp of the same fruit.[43][44][42] An exception is bergamottin, a furanocoumarin implicated in grapefruit-drug interactions, which is more concentrated in the pulp of certain varieties of pomelo, grapefruit, and sour orange.

List of citrus fruits

Cedri BMK
Citrons (Citrus medica) for sale in Germany
Citrus australasica red whole
Red Finger Lime (Citrus australasica), a rare delicacy from Australia

The genus Citrus has been suggested to originate in the eastern Himalayan foothills. Prior to human cultivation, it consisted of just a few species, though the status of some as distinct species has yet to be confirmed:

Hybrids and cultivars

Sweetie (Citrus)
Sweetie or Oroblanco is a pomelo-grapefruit hybrid.
Yemenite
The etrog, or citron, is central to the ritual of the Jewish Sukkot festival. Many varieties are used for this purpose (including the Yemenite variety pictured).
Clementinepeeled
Clementines (Citrus ×clementina) have thinner skins than oranges.
Citrus unshiu-unshu mikan-2
Mikan (Citrus ×unshiu), also known as satsumas
Ambersweet oranges
Sweet oranges (Citrus ×sinensis) are used in many foods. Their ancestors were pomelos and mandarin oranges.
Odichukuthi lime crossection
Cross-section of Odichukuthi lime
Odichukuthi naranga
Odichukuthi fruit
Frutto pompia
A pompia fruit

Sorted by parentage. As each hybrid is the product of (at least) two parent species, they are listed multiple times.

Citrus maxima-based

  • Amanatsu, natsumikan – Citrus ×natsudaidai (C. maxima × unknown)
  • Cam sành – (C. reticulata × C. ×sinensis)
  • Dangyuja – (Citrus grandis Osbeck)
  • GrapefruitCitrus ×paradisi (C. maxima × C. ×sinensis)
  • Imperial lemon – (C. ×limon × C. ×paradisi)
  • Kinnow – (C. ×nobilis × C. ×deliciosa)
  • Kiyomi – (C. ×sinensis × C. ×unshiu)
  • Minneola tangelo – (C. reticulata × C. ×paradisi)
  • Orangelo, Chironja – (C. ×paradisi × C. ×sinensis)
  • Oroblanco, Sweetie – (C. maxima × C. ×paradisi)
  • Sweet orangeCitrus ×sinensis (probably C. maxima × C. reticulata)
  • TangeloCitrus ×tangelo (C. reticulata × C. maxima or C. ×paradisi)
  • TangorCitrus ×nobilis (C. reticulata × C. ×sinensis)
  • Ugli – (C. reticulata × C. maxima or C. ×paradisi)

Citrus medica-based

  • Alemow, Colo – Citrus ×macrophylla (C. medica × C. micrantha)
  • Buddha's handCitrus medica var. sarcodactylus, a fingered citron.
  • Citron varieties with sour pulpDiamante citron, Florentine citron, Greek citron and Balady citron
  • Citron varieties with sweet pulp – Corsican citron and Moroccan citron.
  • Etrog, a group of citron cultivars that are traditionally used for a Jewish ritual. Etrog is Hebrew for citron in general.
  • Fernandina – Citrus ×limonimedica (probably (C. medica × C. maxima) × C. medica)
  • Ponderosa lemon – (probably (C. medica × C. maxima) × C. medica)
  • LemonCitrus ×limon (C. medica × C. ×aurantium)
  • Key lime, Mexican lime, Omani lime – Citrus ×aurantiifolia (C. medica × C. micrantha)
  • Limetta, Sweet Lemon, Sweet Lime, mosambi – Citrus ×limetta (C. medica × C. ×aurantium)
  • Lumia – a pear shaped lemon hybrid, (several distinct hybrids)
  • Persian lime, Tahiti lime – C. xlatifolia (C. xaurantiifolia x C. xlimon)
  • Rhobs el Arsa – bread of the garden, a Moroccan citron x lemon hybrid.
  • Yemenite citron – a pulpless true citron.

Citrus reticulata–based

  • Bergamot orangeCitrus ×bergamia (C. ×limon × C. ×aurantium)
  • Bitter orange, Seville Orange – Citrus ×aurantium (C. maxima × C. reticulata)
  • Blood orangeCitrus ×sinensis cultivars
  • Calamondin, Calamansi – (Citrus reticulata × Citrus japonica)
  • Cam sành – (C. reticulata × C. ×sinensis)
  • ChinottoCitrus ×aurantium var. myrtifolia or Citrus ×myrtifolia
  • ChungGyun – Citrus reticulata cultivar
  • ClementineCitrus ×clementina
  • Cleopatra MandarinCitrus ×reshni
  • Siranui – Citrus reticulata cv. 'Dekopon' (ChungGyun × Ponkan)
  • DaidaiCitrus ×aurantium var. daidai or Citrus ×daidai
  • GrapefruitCitrus ×paradisi (C. maxima × C. ×sinensis)
  • Hermandina – Citrus reticulata cv. 'Hermandina'
  • Imperial lemon – ((C. maxima × C. medica) × C. ×paradisi)
  • Kinnow, Wilking – (C. ×nobilis × C. ×deliciosa)
  • Kiyomi – (C. sinensis × C. ×unshiu)
  • Laraha – ''C. ×aurantium ssp. currassuviencis
  • Mediterranean mandarin, Willow Leaf – Citrus ×deliciosa
  • Meyer lemon, Valley Lemon – Citrus ×meyeri (C. medica × C. ×sinensis)
  • Michal mandarin – Citrus reticulata cv. 'Michal'
  • Mikan, Satsuma – Citrus ×unshiu
  • Naartjie – (C. reticulata × C. nobilis)
  • Nova mandarin, Clemenvilla
  • Orangelo, Chironja – (C. ×paradisi × C. ×sinensis)
  • Oroblanco, Sweetie – (C. maxima × C. ×paradisi)
  • Palestine sweet limeCitrus ×limettioides Tanaka (C. medica × C. ×sinensis)
  • PonkanCitrus reticulata cv. 'Ponkan'
  • Rangpur, Lemanderin, Mandarin Lime – Citrus ×limonia (C. reticulata × C. medica)
  • Rough lemonCitrus ×jambhiri Lush. (C. reticulata × C. medica)
  • Shekwasha, Hirami Lemon, Taiwan Tangerine – Citrus ×depressa
  • Sunki, Suenkat – Citrus sunki or C. reticulata var. sunki
  • Sweet orangeCitrus ×sinensis (C. maxima × C. reticulata)
  • Tachibana orangeCitrus tachibana (Mak.) Tanaka or C. reticulata var. tachibana
  • TangeloCitrus ×tangelo (C. reticulata × C. maxima or C. ×paradisi)
  • TangerineCitrus ×tangerina
  • TangorCitrus ×nobilis (C. reticulata × C. ×sinensis)
  • Ugli – (C. reticulata × C. maxima or C. ×paradisi)
  • Volkamer lemon – Citrus ×volkameriana (C. reticulata × C. medica)
  • YuzuCitrus ×junos (C. reticulata × C. ×ichangensis)

Other/Unresolved

  • Djeruk limau – Citrus ×amblycarpa
  • Gajanimma, Carabao Lime – Citrus ×pennivesiculata
  • Hyuganatsu, Hyuganatsu pumelo – Citrus tamurana
  • Ichang lemon – (C. ichangensis × C. maxima)
  • Imperial lemon, Shangjuan – (C. ×limon × C. ×paradisi)
  • Iyokan, anadomikanCitrus ×iyo
  • KabosuCitrus ×sphaerocarpa
  • Odichukuthi – Citrus Odichukuthi from Malayalam
  • Ougonkan – Citrus flaviculpus hort ex.Tanaka
  • Pompia – Citrus limon var. pompia Camarda, 2015, formerly Citrus monstruosa, a nomen nudum[48]
  • Sakurajima komikan orange
  • Shonan gold – (Ougonkan) Citrus flaviculpus hort ex. Tanaka × (Imamura unshiu), Citrus unshiu Marc
  • SudachiCitrus ×sudachi

For hybrids with kumquats, see citrofortunella. For hybrids with the trifoliate orange, see citrange.

See also

References

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  15. ^ Curk, Franck; Ollitrault, Frédérique; Garcia-Lor, Andres; Luro, François; Navarro, Luis; Ollitrault, Patrick (2016). "Phylogenetic origin of limes and lemons revealed by cytoplasmic and nuclear markers". Annals of Botany. 11 (4): 565–583. doi:10.1093/aob/mcw005. PMC 4817432. PMID 26944784.
  16. ^ Curk, Franck; Ancillo, Gema; Garcia-Lor, Andres; Luro, François; Perrier, Xavier; Jacquemoud-Collet, Jean-Pierre; Navarro, Luis; Ollitrault, Patrick (December 2014). "Next generation haplotyping to decipher nuclear genomic interspecific admixture in Citrusspecies: analysis of chromosome 2". BMC Genetics. 15 (1): 152. doi:10.1186/s12863-014-0152-1. ISSN 1471-2156. PMC 4302129. PMID 25544367.
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  42. ^ a b c d Dugrand-Judek, Audray; Olry, Alexandre; Hehn, Alain; Costantino, Gilles; Ollitrault, Patrick; Froelicher, Yann; Bourgaud, Frédéric (November 2015). "The Distribution of Coumarins and Furanocoumarins in Citrus Species Closely Matches Citrus Phylogeny and Reflects the Organization of Biosynthetic Pathways". PLoS One. 10 (11): e0142757. doi:10.1371/journal.pone.0142757. PMC 4641707. PMID 26558757.
  43. ^ a b Nigg, H. N.; Nordby, H. E.; Beier, R. C.; Dillman, A.; Macias, C.; Hansen, R. C. (1993). "Phototoxic coumarins in limes" (PDF). Food Chem Toxicol. 31 (5): 331–35. doi:10.1016/0278-6915(93)90187-4. PMID 8505017.
  44. ^ a b Wagner, A. M.; Wu, J. J.; Hansen, R. C.; Nigg, H. N.; Beiere, R. C. (2002). "Bullous phytophotodermatitis associated with high natural concentrations of furanocoumarins in limes". Am J Contact Dermat. 13 (1): 10–14. doi:10.1053/ajcd.2002.29948. ISSN 0891-5849. PMID 11887098.
  45. ^ "Toxicological Assessment of Furocoumarins in Foodstuffs" (PDF). The German Research Foundation (DFG). DFG Senate Commission on Food Safety (SKLM). 2004. Retrieved November 1, 2018.
  46. ^ a b c GRIN. "Species list in GRIN for genus Citrus". Taxonomy for Plants. National Germplasm Resources Laboratory, Beltsville, Maryland: USDA, ARS, National Genetic Resources Program. Archived from the original on 20 January 2009. Retrieved 6 January 2011.
  47. ^ P. J. Wester (1915), "Citrus Fruits In The Philippines", Philippine Agricultural Review, 8
  48. ^ Pompia Citron oscartintori.it, accessed 2 October 2018

Further reading

  • Andrews, A.C. (1961). "Acclimatization of citrus fruits in the Mediterranean region". Agricultural History. 35 (1): 35–46.
  • Araújo, De; Freitas, E.; de Queiroz, L. Paganucci; Machado, M.A. (2003). "What is Citrus? Taxonomic implications from a study of cp-DNA evolution in the tribe Citreae (Rutaceae subfamily Aurantioideae)". Organisms Diversity & Evolution. 3 (1): 55–62. doi:10.1078/1439-6092-00058.
  • Duarte, A.; Fernandes, J.; Bernardes, J.; Miguel, G. 2016. Citrus as a Component of the Mediterranean Diet. Journal of Spatial and Organizational Dynamics – JSOD, IV(4): 289–304.
  • Nicolosi, E.; Deng, Z.N.; Gentile, A.; La Malfa, S.; Continella, G.; Tribulato, E. (2000). "Citrus phylogeny and genetic origin of important species as investigated by molecular markers". Theoretical and Applied Genetics. 100 (8): 1155–1166. doi:10.1007/s001220051419.
  • Calabrese, Francesco (2002): Origin and history. In: Dugo, Giovanni & Di Giacomo, Angelo (eds.) (2002): Citrus. Taylor & Francis. ISBN 0-415-28491-0
  • Ellis, R.H.; Hong, T.D. & Roberts, E.H. (1985): Chapter 64. Rutaceae. In: Handbook of Seed Technology for Genebanks (Volume II: Compendium of Specific Germination Information and Test Recommendations). International Board for Plant Genetic Resources, Rome, Italy. HTML fulltext
  • Frison, E.A. & Taher, M.M. (eds.) (1991): FAO/IBPGR Technical Guidelines for the Safe Movement of Citrus Germplasm. FAO, IOCV, IPGRI. PDF fulltext
  • International Plant Genetic Resources Institute (IPGRI) (1999): Descriptors for Citrus (Citrus spp.). PDF fulltext
  • Janick, Jules (2005): Purdue University Tropical Horticulture Lecture 32: Citrus
  • Luro, F.; Laigret, F.; Bové, J.M. & Ollitrault, P. (1995): RFLP analysis of cytoplasmic and nuclear genomes used for citrus taxonomy. In: Mandarines – développements scientifiques récents, résumés oraux et posters: 12–13. CIRAD-FLHOR, San Nicolao, France. HTML abstract
  • Molina, A.B.; Roa, V.N.; Bay-Petersen, J.; Carpio, A.T. & Joven, J.E.A. (eds.) (2000): Citrus, Proceedings of a regional workshop on disease management of banana and citrus through the use of disease-free planting materials held in Davao City, Philippines, 14–16 October 1998. INIBAP. PDF fulltext
  • Sackman. Douglas Cazaux (2005): Orange Empire: California and the Fruits of Eden.
  • University of California Division of Agricultural Sciences (UC-DAS) (1967–1989): The Citrus Industry. HTML fulltext of Vol. 1, 2, & Vol. 5, Chapter 5

External links

Bergamot orange

Citrus bergamia, the bergamot orange (pronounced ), is a fragrant citrus fruit the size of an orange, with a yellow or green color similar to a lime, depending on ripeness.

Genetic research into the ancestral origins of extant citrus cultivars found bergamot orange to be a probable hybrid of lemon and bitter orange. Extracts have been used to scent food, perfumes, and cosmetics. Use on the skin can increase photosensitivity, resulting in greater damage from sun exposure.

Bitter orange

Bitter orange, Seville orange, sour orange, bigarade orange, or marmalade orange refers to a citrus tree (Citrus × aurantium) and its fruit. It is native to southeast Asia, and has been spread by humans to many parts of the world. Wild trees are found near small streams in generally secluded and wooded parts of Florida and The Bahamas after it was introduced to the area from Spain, where it had been introduced and cultivated heavily beginning in the 10th century by the Moors. The bitter orange is believed to be a cross between Citrus maxima × Citrus reticulata

Calamondin

Calamondin (Citrus microcarpa, × Citrofortunella microcarpa or × Citrofortunella mitis), also known as calamansi, is an economically-important citrus hybrid predominantly cultivated in the Philippines. It is native to the Philippines and surrounding areas in southern China, Taiwan, Borneo, and Sulawesi. Calamondin is ubiquitous in traditional Filipino cuisine. It is used in various condiments, beverages, dishes, marinades, and preserves. Calamondin is also used as ingredients in the cuisines of Malaysia and Indonesia.

Calamondin is a citrofortunella, an intergeneric hybrid between a member of the genus Citrus (in this case probably the mandarin orange) and the kumquat. it was formerly considered as belonging to a separate genus Fortunella.

Camping World Stadium

Camping World Stadium is a stadium in Orlando, Florida, located in the West Lakes neighborhood of Downtown Orlando, west of new sports and entertainment facilities including the Amway Center, the Dr. Phillips Center for the Performing Arts and Orlando City Stadium. It opened in 1936 as Orlando Stadium and has also been known as the Tangerine Bowl and Florida Citrus Bowl. The City of Orlando owns and operates the stadium.Camping World Stadium is the current home venue of the Cure Bowl, the Citrus Bowl and the Camping World Bowl. It is also the regular host of other college football games including the Florida Classic between Florida A&M and Bethune-Cookman, the MEAC/SWAC Challenge, and the Camping World Kickoff. The stadium was built for football and in the past, it has served as home of several alternate-league American football teams. From 2011 to 2013, it was the home of the Orlando City SC, a soccer team in USL Pro. From 1979 to 2006, it served as the home of the UCF Knights football team (since 2007, the team has played at campus-owned and based Spectrum Stadium). It was also one of the nine venues used for the 1994 FIFA World Cup.

Citron

The citron (Citrus medica) is a large fragrant citrus fruit with a thick rind. It is one of the original citrus fruits from which all other citrus types developed through natural hybrid speciation or artificial hybridization. Though citron cultivars take on a wide variety of physical forms, they are all closely related genetically. It is used widely in Asian cuisine, and also in traditional medicines, perfume, and for religious rituals and offerings. Hybrids of citrons with other citrus are commercially prominent, notably lemons and many limes.

Citrus Bowl

The Citrus Bowl is an annual college football bowl game played at Camping World Stadium in Orlando, Florida. The bowl is operated by Florida Citrus Sports, a non-profit group that also organizes the Camping World Bowl and Florida Classic.

The game was first played as the Tangerine Bowl in 1947 before being renamed as the Florida Citrus Bowl in 1983. When Capital One was the game's title sponsor between 2001 to 2014, the game was referred to simply as the Capital One Bowl from 2003 to 2014. Other previous sponsors include CompUSA (1994–1999), Ourhouse.com (2000), and Buffalo Wild Wings (2015–2017) and Overton's (2018). Presently, it is being sponsored by VRBO, a vacation rental marketplace, and is known as the VRBO Citrus Bowl.

Since becoming one of the premier bowls, the Citrus Bowl is typically played at 1 p.m. EST on New Year's Day, immediately before the Rose Bowl, both of which have been televised on ESPN since 2011. When January 1 is a Sunday, the game has been played on January 2 or December 31, to avoid conflicting with the National Football League schedule. As of 2015, at $4.25 million per team, it has the largest payout of all the non-College Football Playoff (CFP) bowls. In nearly every year since 1985, the game has featured two teams ranked in the Top 25.

Citrus County, Florida

Citrus County is a county located in the U.S. state of Florida. As of the 2010 census, the population was 141,236. Its county seat is Inverness, and its largest community is Homosassa Springs.

Citrus County comprises the Homosassa Springs, Fla. Metropolitan Statistical Area.

Clementine

A clementine (Citrus × clementina) is a tangor, a hybrid between a willowleaf mandarin orange (C. × deliciosa) and a sweet orange (C. × sinensis), so named in 1902. The exterior is a deep orange colour with a smooth, glossy appearance. Clementines can be separated into 7 to 14 segments. Similar to tangerines, they tend to be easy to peel. They are typically juicy and sweet, with less acid than oranges. Their oils, like other citrus fruits, contain mostly limonene as well as myrcene, linalool, α-pinene and many complex aromatics.

Grapefruit

The grapefruit (Citrus × paradisi) is a subtropical citrus tree known for its relatively large sour to semi-sweet, somewhat bitter fruit. Grapefruit is a citrus hybrid originating in Barbados as an accidental cross between two introduced species – sweet orange (C. sinensis), and pomelo (or shaddock) (C. maxima) – both of which were introduced from Asia in the seventeenth century. When found, it was nicknamed the "forbidden fruit". Frequently, it is misidentified as the very similar parent species, pomelo.The grape part of the name alludes to clusters of fruit on the tree that often appear similar to grape clusters. The interior flesh is segmented and varies in color from white to yellow to red to pink.

Kaffir lime

Citrus hystrix, called the kaffir lime, makrut lime (US: , UK: ) or Mauritius papeda, is a citrus fruit native to tropical Southeast Asia and southern China.Its fruit and leaves are used in Southeast Asian cuisine and its essential oil is used in perfumery. Its rind and crushed leaves emit an intense citrus fragrance.

Key lime

The Key lime (Citrus × aurantiifolia) is a citrus hybrid (C. micrantha x C. medica) with a spherical fruit, 2.5–5 cm (1–2 in) in diameter. The Key lime is usually picked while it is still green but it becomes yellow when ripe.

It is smaller and seedier, with a higher acidity, a stronger aroma, and a thinner rind, than that of the Persian lime (Citrus × latifolia). The Key lime is valued for its unique flavor compared with other limes. The name is derived from its association with the Florida Keys, where it is best known as the flavoring ingredient in Key lime pie. It is also known as West Indian lime, bartender’s lime, Omani lime, or Mexican lime, the last classified as a distinct race with a thicker skin and darker green color. Philippine varieties have various names, including dayap and bilolo.

Kumquat

Kumquats (or cumquats in Australian English, ; Citrus japonica) are a group of small fruit-bearing trees in the flowering plant family Rutaceae. They were previously classified as forming the now historical genus Fortunella, or placed within Citrus sensu lato.

The edible fruit closely resembles the orange (Citrus sinensis) in color and shape but is much smaller, being approximately the size of a large olive. Kumquat is a fairly cold-hardy citrus.

Lemon

The lemon, Citrus limon (L.) Osbeck, is a species of small evergreen tree in the flowering plant family Rutaceae, native to South Asia, primarily North eastern India.

The tree's ellipsoidal yellow fruit is used for culinary and non-culinary purposes throughout the world, primarily for its juice, which has both culinary and cleaning uses. The pulp and rind (zest) are also used in cooking and baking. The juice of the lemon is about 5% to 6% citric acid, with a pH of around 2.2, giving it a sour taste. The distinctive sour taste of lemon juice makes it a key ingredient in drinks and foods such as lemonade and lemon meringue pie.

Lime (fruit)

A lime (from French lime, from Arabic līma, from Persian līmū, "lemon") is a hybrid citrus fruit, which is typically round, green in color, 3–6 centimetres (1.2–2.4 in) in diameter, and contains acidic juice vesicles.There are several species of citrus trees whose fruits are called limes, including the Key lime (Citrus aurantifolia), Persian lime, kaffir lime, and desert lime. Limes are a rich source of vitamin C, sour and are often used to accent the flavours of foods and beverages. They are grown year-round. Plants with fruit called "limes" have diverse genetic origins; limes do not form a monophyletic group.

Mandarin orange

The mandarin orange (Citrus reticulata), also known as the mandarin or mandarine, is a small citrus tree with fruit resembling other oranges, usually eaten plain or in fruit salads. Reddish-orange mandarin cultivars can be marketed as tangerines, but this is not a botanical classification.

Mandarins are smaller and oblate, rather than spherical, like the common oranges (which are a mandarin hybrid). The taste is considered less sour, as well as sweeter and stronger. A ripe mandarin is firm to slightly soft, heavy for its size, and pebbly-skinned. The peel is thin, with little white mesocarp, so they are usually easier to peel and to split into segments. Hybrids generally have these traits to a lesser degree.

The mandarin orange tree is more drought-tolerant than the fruit. The mandarin is tender and is damaged easily by cold. It can be grown in tropical and subtropical areas.According to molecular studies, the mandarin, the citron, the pomelo, and to a lesser extent the papedas and kumquat, were the ancestors of most other commercial citrus varieties, through breeding or natural hybridization; mandarins are therefore important as the only sweet fruit among the parental species. Though some mandarin cultivars remain pure, most have some degree of pomelo hybridization, while in some cases the amount of pomelo is substantial.

Orange (fruit)

The orange is the fruit of the citrus species Citrus × sinensis in the family Rutaceae. It is also called sweet orange, to distinguish it from the related Citrus × aurantium, referred to as bitter orange. The sweet orange reproduces asexually (apomixis through nucellar embryony); varieties of sweet orange arise through mutations.The orange is a hybrid between pomelo (Citrus maxima) and mandarin (Citrus reticulata). The chloroplast genome, and therefore the maternal line, is that of pomelo. The sweet orange has had its full genome sequenced.Sweet orange originated in ancient China and the earliest mention of the sweet orange was in Chinese literature in 314 BC. As of 1987, orange trees were found to be the most cultivated fruit tree in the world. Orange trees are widely grown in tropical and subtropical climates for their sweet fruit. The fruit of the orange tree can be eaten fresh, or processed for its juice or fragrant peel. As of 2012, sweet oranges accounted for approximately 70% of citrus production.In 2014, 70.9 million tonnes of oranges were grown worldwide, with Brazil producing 24% of the world total followed by China and India.

Pomelo

The pomelo, Citrus maxima or Citrus grandis, is the largest citrus fruit from the Rutaceae family. It is a natural (non-hybrid) citrus fruit, similar in appearance to a large grapefruit, native to South and Southeast Asia. The pomelo is one of the original citrus species from which the rest of cultivated citrus have been hybridized. The popular fruit is used in many Chinese festive celebrations throughout Southeast Asia.

Tangerine

The tangerine (Citrus tangerina) is a group of orange-colored citrus fruit consisting of hybrids of mandarin orange (Citrus reticulata).

The name was first used for fruit coming from Tangier, Morocco, described as a mandarin variety. Under the Tanaka classification system, Citrus tangerina is considered a separate species. Under the Swingle system, tangerines are considered to be a group of mandarin (C. reticulata) varieties. Genetic study has shown tangerines to be mandarin orange hybrids containing some pomelo DNA. Some differ only in disease resistance. The term is currently applied to any reddish-orange mandarin (and, in some jurisdictions, mandarin-like hybrids, including some tangors).Tangerines are smaller and less rounded than common oranges. The taste is considered less sour, as well as sweeter and stronger, than that of an orange. A ripe tangerine is firm to slightly soft, heavy for its size, and pebbly-skinned with no deep grooves, as well as orange in color. The peel is very thin, with very little bitter white mesocarp, which makes them usually easier to peel and to split into segments. All of these traits are shared by mandarins generally.

Peak tangerine season lasts from autumn to spring. Tangerines are most commonly peeled and eaten out of hand. The fresh fruit is also used in salads, desserts and main dishes. The peel is used fresh or dried as a spice or zest for baking and drinks, and eaten coated in chocolate. Fresh tangerine juice and frozen juice concentrate are commonly available in the United States.

Yuzu

Yuzu (Citrus junos, from Japanese ユズ or 柚子) is a citrus fruit and plant in the family Rutaceae. It is called yuja (from Korean 유자) in Korean cuisine. Both Japanese yuzu and Korean yuja are cognates of the Chinese yòuzi (柚子), but the Chinese word refers to the pomelo. Yuzu is called xiāngchéng (香橙) in Chinese.

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