Citrus

Citrus
OrangeBloss wb.jpg
Sweet orange (Citrus × sinensis cultivar)
Scientific classification e
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

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 of the genus 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.

History[edit]

Citrus plants are native to subtropical and tropical regions of Asia, Island Southeast Asia, and Near Oceania, and they were first domesticated in these areas.[1] A genomic, phylogenic, and biogeographical analysis by Wu et al. (2018) have shown that the center of origin of the genus Citrus is likely the southeast foothills of the Himalayas, in a region stretching from eastern Assam, northern Myanmar, to western Yunnan. It diverged from a common ancestor with Poncirus trifoliata. A change in climate conditions during the Late Miocene (11.63 to 5.33 mya) resulted in a sudden speciation event. The species resulting from this event include the citrons (Citrus medica) of South Asia; the pomelos (C. maxima) of Mainland Southeast Asia; the mandarins (C. reticulata), kumquats (C. japonica), mangshanyegan (C. mangshanensis), and ichang papedas (C. ichangensis) of southeastern China; the kaffir limes (C. hystrix) of Island Southeast Asia; and the biasong and samuyao (C. micrantha) of the Philippines.[1][5]

Map of inferred original wild ranges of the main Citrus cultivars, and selected relevant wild taxa[5]

This was later followed by the spread of citrus species into Taiwan and Japan in the Early Pliocene (5.33 to 3.6 mya), resulting in the tachibana orange (C. tachibana); and beyond the Wallace Line into Papua New Guinea and Australia during the Pleistocene (2.5 million to 11,000 years ago), where further speciation events occurred resulting in the Australian limes.[1][5]

The earliest introductions of citrus species by human migrations was during the Austronesian expansion (c. 3000-1500 BCE), where Citrus hystrix, Citrus macroptera, and Citrus maxima were among the canoe plants carried by Austronesian voyagers eastwards into Micronesia and Polynesia.[6]

The citron (Citrus medica) was also introduced early into the Mediterranean basin from India and Southeast Asia. It was introduced via two ancient trade routes: an overland route through Persia, the Levant and the Mediterranean islands; and a maritime route through the Arabian Peninsula and Ptolemaic Egypt into North Africa. Although the exact date of the original introduction is unknown due to the sparseness of archaeobotanical remains, the earliest evidence are seeds recovered from the Hala Sultan Tekke site of Cyprus, dated to around 1200 BCE. Other archaeobotanical evidence include pollen from Carthage dating back to the 4th century BCE; and carbonized seeds from Pompeii dated to around the 3rd to 2nd century BCE. The earliest complete description of the citron was first attested from Theophrastus, c. 310 BCE.[7][8][9]

Lemons, pomelos, and sour oranges are believed to have been introduced to the Mediterranean later by Arab traders at around the 10th century; and sweet oranges by the Genoese and Portuguese from Asia during the 15th to 16th century. Mandarins were not introduced until the 19th century.[7][8][9][10] 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.[10]

The "native" oranges of Florida actually originated with the Spanish conquistadores.[11][12] The agronomists of classical Rome already made many references to the cultivation of citrus fruits within the limits of their empire.[10] King Louis XIV of France housed citrus in orangeries, to protect the tropical fruit to be grown in the 1600s France.[13]

Name[edit]

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.[14] Collectively, Citrus fruits and plants are also known by the Romance loanword agrumes (literally "sour fruits").

Evolution[edit]

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 trifoliata), 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.[15] 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.[16]

The three ancestral (sometimes characterized as "original" or "fundamental") species in the genus Citrus associated with modern Citrus cultivars are the mandarin orange, pomelo, and citron. Almost all of the common commercially important citrus fruits (sweet oranges, lemons, grapefruit, limes, and so on) are hybrids involving these three species with each other, their main progenies, and other wild Citrus species within the last few thousand years.[1][17][18]

Fossil record[edit]

A fossil leaf from the Pliocene of Valdarno (Italy) is described as †Citrus meletensis[19] 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.[20]

Taxonomy[edit]

Citrus fruits clustered by genetic similarity, ternary diagram based on data from Curk, et al. (2016)[21]
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).[22]

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).[23] 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.[24] 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.[25]

Description[edit]

Slices of various citrus fruits

Tree[edit]

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.[26] 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[edit]

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.[27][28]

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.[29] The flavonoids include various flavanones and flavones.[30]

Acidity indicators[edit]

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.[31] 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[edit]

Lemons are a citrus fruit native to Asia, but now common worldwide.
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.[32] In tropical regions with no winter at all, citrus fruits remain green until maturity, hence the tropical "green oranges".[33] 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.[citation needed] 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.[34]

Citrus fruits are nonclimacteric and respiration slowly declines and the production and release of ethylene is gradual.[35] 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.

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).

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[edit]

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[edit]

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.[13]

Pests and diseases[edit]

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.[36]

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.[37]

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.[36]

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,[38] 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[edit]

Citrus plants can also develop a deficiency condition called chlorosis, characterized by yellowing leaves[39] 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.[40]

Uses[edit]

Culinary[edit]

Wedges of pink grapefruit, lime, and lemon, and a half orange (clockwise from top)
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.[41] 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[edit]

Citrus fruits have well-documented nutritional and health benefits.[10] They can actually help prevent and cure some diseases.[10]

Citrus fruit intake has been associated with a 10% reduction in odds of developing breast cancer.[42]

Oranges were historically used for their high content of vitamin C,[29] 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.[43]

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.[44] 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.[45]

Health effects[edit]

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,[46] 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,[47] a linear furanocoumarin derived from psoralen. This claim has been confirmed for lime[48][49] and bergamot. In particular, bergamot essential oil has a higher concentration of bergapten (3000–3600 mg/kg) than any other Citrus-based essential oil.[50]

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.[47] 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,[47] 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.[48][49][47] 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[edit]

Citrons (Citrus medica) for sale in Germany
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[edit]

Sweetie or Oroblanco is a pomelo-grapefruit hybrid.
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).
Clementines (Citrus ×clementina) have thinner skins than oranges.
Mikan (Citrus ×unshiu), also known as satsumas
Sweet oranges (Citrus ×sinensis) are used in many foods. Their ancestors were pomelos and mandarin oranges.
Cross-section of Odichukuthi lime
Odichukuthi fruit
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

Citrus reticulata–based

Other/Unresolved

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

See also[edit]

References[edit]

  1. ^ a b c d e Wu GA, Terol J, Ibanez V, López-García A, Pérez-Román E, Borredá C, Domingo C, Tadeo FR, Carbonell-Caballero J, Alonso R, Curk F, Du D, Ollitrault P, Roose ML, Dopazo J, Gmitter FG, Rokhsar DS, Talon M (February 2018). "Genomics of the origin and evolution of Citrus". Nature. 554 (7692): 311–316. Bibcode:2018Natur.554..311W. doi:10.1038/nature25447. PMID 29414943.
  2. ^ Gmitter, Frederick; Hu, Xulan (1990). "The possible role of Yunnan, China, in the origin of contemporary Citrus species (Rutaceae)". Economic Botany. 44 (2): 267–277. doi:10.1007/bf02860491.
  3. ^ United Nations Conference on Trade and Development. Market Information in the Commodities Area: Citrus fruits "CHARACTERISTICS". Archived from the original on 2010-10-05. Retrieved 2010-09-24.
  4. ^ Scora, Rainer W. (1975). "On the history and origin of citrus". Bulletin of the Torrey Botanical Club. 102 (6): 369–375. doi:10.2307/2484763. JSTOR 2484763.
  5. ^ a b c Fuller, Dorian Q.; Castillo, Cristina; Kingwell-Banham, Eleanor; Qin, Ling; Weisskopf, Alison (2017). "Charred pomelo peel, historical linguistics and other tree crops: approaches to framing the historical context of early Citrus cultivation in East, South and Southeast Asia". In Zech-Matterne, Véronique; Fiorentino, Girolamo (eds.). AGRUMED: Archaeology and history of citrus fruit in the Mediterranean. Publications du Centre Jean Bérard. pp. 29–48. doi:10.4000/books.pcjb.2107. ISBN 9782918887775.
  6. ^ Blench, R.M. (2005). "Fruits and arboriculture in the Indo Pacific region". Bulletin of the Indo-Pacific Prehistory Association. 24: 31–50.
  7. ^ a b Zech-Matterne, Véronique; Fiorentino, Girolamo; Coubray, Sylvie; Luro, François (2017). "Introduction". In Zech-Matterne, Véronique; Fiorentino, Girolamo (eds.). AGRUMED: Archaeology and history of citrus fruit in the Mediterranean: Acclimatization, diversification, uses. Publications du Centre Jean Bérard. ISBN 9782918887775.
  8. ^ a b Langgut, Dafna (June 2017). "The Citrus Route Revealed: From Southeast Asia into the Mediterranean". HortScience. 52 (6): 814–822. doi:10.21273/HORTSCI11023-16.
  9. ^ a b Langgut, Dafna (2017). "The history of Citrus medica (citron) in the Near East: Botanical remains and ancient art and texts". In Zech-Matterne, Véronique; Fiorentino, Girolamo (eds.). AGRUMED: Archaeology and history of citrus fruit in the Mediterranean. Publications du Centre Jean Bérard. ISBN 9782918887775.
  10. ^ a b c d e Duarte, A.; Fernandes, J.; Bernardes, J.; Miguel, G. (2016). "Citrus as a Component of the Mediterranean Diet". Journal of Spatial and Organizational Dynamics. 4: 289–304.
  11. ^ University of South Florida: Fruit
    Contrary to general belief, the orange tree is not indigenous to Florida but was introduced into the state from Valencia by the Spanish colonists.
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Further reading[edit]

  • 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[permanent dead link]
  • 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[edit]