Citrus taxonomy is the botanical classification of the species , varieties , cultivars , and graft hybrids within the genus Citrus and related genera, found in cultivation and in the wild.
117-427: The Key lime or acid lime ( Citrus × aurantiifolia or C. aurantifolia ) is a citrus hybrid ( C. hystrix × C. medica ) native to tropical Southeast Asia . It has a spherical fruit, 2.5–5 centimetres (1–2 inches) in diameter. The Key lime is usually picked while it is still green, but it becomes yellow when ripe. The Key lime has thinner rind and is smaller, seedier, more acidic and more aromatic than
234-429: A finger lime and calamansi cross). Initially, many citrus types were identified and named by individual taxonomists, resulting in a large number of identified species: 870 by a 1969 count. Some order was brought to citrus taxonomy by two unified classification schemes, those of Chōzaburō Tanaka and Walter Tennyson Swingle , that can be viewed as extreme alternative visions of the genus. Swingle's system divided
351-557: A species by themselves, especially in folk taxonomy , are: All of these hybrids have in turn been bred back with their parent stocks or with other pure or hybrid citrus to form a broad array of fruits. Naming of these is inconsistent, with some bearing a variant of the name of one of the parents or simply another citrus with superficially-similar fruit, a distinct name, or a portmanteau of ancestral species. The Ponderosa lemon ( Citrus limon × medica ) and Florentine citron ( Citrus × limonimedica ) are both true lemon/citron hybrids,
468-419: A stable lineage only through vegetative propagation . Some hybrids do reproduce true to type via nucellar seeds in a process called apomixis . As such, many hybrid species represent the clonal progeny of a single original F1 cross, though others combine fruit with similar characteristics that have arisen from distinct crosses. All of the wild 'pure' citrus species trace to a common ancestor that lived in
585-430: A tetraploid . Historically, hybrids with similar characteristics have been placed together in a number of hybrid species, yet relatively recent genomic analysis has revealed some hybrids assigned to the same species to be of quite distinct ancestry. No alternative system of grouping fruit in hybrid species has been adopted. While most citrus hybrids derive from the three core species, hybrids have also been derived from
702-491: A binomial name, while a unique species name is reserved for each combination of ancestral species, independent of the specific order of crossing or proportional representation of the ancestral species in a given hybrid. Individual hybrids of each type are then distinguished by a variety name. Thus hybrids that are crosses between mandarin ( C. reticulata ) and pomelo ( C. maxima ) would all be C. × aurantium , with specific crosses including: C. × aurantium var. sinensis for
819-568: A characteristic passed down to the subspecies' hybrid descendants such as hybrid mandarins, oranges, lemons and grapefruit. A distinct class of mandarins are native to the Japanese and neighboring islands. Initial characterization of one of these, the Tachibana orange (Tanaka's Citrus tachibana ), native to Taiwan, the Ryukyu Islands and southern Japan, classified it as a subspecies nesting within
936-462: A citrus hybrid. His Citrus he likewise subdivided into two subgenera: citrons, pomelos, mandarins, oranges, grapefruits and lemons were placed in subgenus Eucitrus (later called simply subgenus Citrus ), while the hardy but slow-growing trees with relatively unpalatable fruit he placed in subgenus Papeda . His genus Citrus consisted of just 16 species , dividing them further into varieties , and lastly cultivars or hybrids. The Swingle system
1053-405: A combination of the characteristics of the two contributing species due to the presence of cells from both in that fruit. In an extreme example, on separate branches Bizzarria produces fruit identical to each of the two contributing species, but also fruit that appears to be half one species and half the other, unmixed. In taxonomy, graft hybrids are distinguished from genetic hybrids by designating
1170-412: A degree of acceptance, two modern phylogenetic studies obtained results in conflict with Mabberley's, and retained Feronioella as a distinct genus closely related to Luminia , with which Swingle had placed Feroniella in a grouping referred to as 'wood apples'. The pomelo ( Citrus maxima ), a second of the core species from which most citrus hybrids have derived, is native to southeast Asia. Among
1287-421: A different branch of the tribe Citreae and given a new genus by Swingle) and more controversially Poncirus , which is the earliest branching of Swingle's genera, and a genus not previously recognized as a close citrus relative, Feroniella . There remains a lack of consensus as to which wild plants and hybrids merit distinct species status, a phenomenon exacerbated by the prior failure to correctly identify
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#17330845351751404-444: A hybrid and one of the hybrid's parent species. Citrus plants hybridize easily between species with completely different morphologies, and similar-looking citrus fruits may have quite different ancestries. Some differ only in disease resistance. Conversely, different-looking varieties may be nearly genetically identical, and differ only by a bud mutation . Genomic analysis of wild and domesticated citrus cultivars has suggested that
1521-478: A hybrid as such a cross between two species can present challenges. In some cases the parental species that gave rise to a hybrid have yet to be determined, while genotyping reveals some hybrids to descend from three or more ancestral species. In the Ollitrault system, a hybrid will be given a species name corresponding to the ancestral species contributions to it, as well as a distinctive variety name. Hybrid taxonomy
1638-681: A lack of popular support; consequently, it was dissolved by the British in 1963, with nine provinces eventually becoming independent sovereign states and four becoming current British Overseas Territories . "West Indies" or "West India" was a part of the names of several companies of the 17th and 18th centuries, including the Danish West India Company , the Dutch West India Company , the French West India Company , and
1755-413: A large range of hybrids. Swingle saw three species of mandarin, while Tanaka identified five groups with a total of 36 species. Webber (1948) divided them into four groups, king, satsuma, mandarin, and tangerine, and Hodgson (1967) saw in them four species. Genomic analysis suggests just one mainland-Asian species, Citrus reticulata . In an observation originally made in a study of their hybrid progeny,
1872-1243: A mandarin native to the Ryukyu Islands designated C. ryukyuensis , and a rare wild species from Southeast Asia, the mountain citron . A number of further species originally placed in other genera have recently been subsumed into Citrus as a result of phylogenetic analysis, but these have yet to be characterized on a phylogenomic level to confirm their status as unique pure species. Artificial interbreeding seems possible among all citrus plants, though there are certain limitations to natural interbreeding due to plant physiology and differences in natural breeding seasons. This ability to cross-pollinate extends to some related species that some classifications place in distinct genera. The ability of citrus hybrids to self-pollinate and to reproduce sexually also helps create new varieties, as does spontaneous mutation and genome duplication. The three most predominant ancestral citrus taxa are citron ( C. medica ), pomelo ( C. maxima ), and mandarin ( C. reticulata ). These taxa interbreed freely, despite being quite genetically distinct, having arisen through allopatric speciation , with citrons evolving in northern Indochina , pomelos in
1989-465: A mature tree to sever roots, will encourage new sprouts that can be transplanted to another location. Clones are often bud grafted into rough lemon or bitter orange to obtain strong root stocks. It is often advisable to graft the plants onto rootstocks with low susceptibility to gummosis because seedlings generally are highly vulnerable to the disease. Useful rootstocks include wild grapefruit, cleopatra mandarin and tahiti limes . C. macrophylla
2106-593: A pomelo/citron hybrid, though another lumia variety, the Pomme d'Adam , is a micrantha/citron cross, like the Key lime. The most common and commercially popular 'limes', the Persian limes , are Key lime/lemon hybrids that combine the genetic lineages of four ancestral citrus species: mandarin, pomelo, citron and micrantha. While most other citrus are diploid , many of the Key lime hybrid progeny have unusual chromosome numbers. For example,
2223-442: A replacement species name for this Yunnan trifoliate orange. Citrus hybrids include many varieties and species that have been selected by plant breeders . This is done not only for the useful characteristics of the fruit, but also for plant size and growth characteristics such as cold-tolerance. Some citrus hybrids occurred naturally, and others have been deliberately created, either by cross pollination and selection among
2340-469: A second type are the result of hybridization with pomelos followed by subsequent backcrossing with mandarins to retain only a few pomelo traits. The third type arose more recently from the crossing of these hybrids again with pomelos or sweet oranges (which are themselves crosses of hybrid mandarins and pomelos). This produces mandarins with more, longer stretches of pomelo DNA. Some commercial mandarins are hybrids with lemons, while several were found to have
2457-556: A separate genus, Fortunella , named in honor of Robert Fortune . He divided the kumquats into two subgenera, the Protocitrus , containing the primitive Hong Kong kumquat ( F. hindsii ), and Eufortunella , comprising the round ( F. japonica ), oval kumquat ( F. margarita ) and Meiwa kumquats ( F. crassifolia ), to which Tanaka added two others, the Malayan kumquat (which he christened F. swinglei but more commonly called F. polyandra ) and
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#17330845351752574-456: A significant contribution (35–65%) from papedas. 'Mangshan wild mandarin' is a name used for all of the similar-looking wild mandarin-like fruit of the Mangshan area, but has been found to include two genetically-distinct groups, one representing pure, wild "true" mandarins (the mangshanyeju subspecies of C. reticulata ), and the other the genetically-distinct and only distantly-related species,
2691-414: A single hybrid ancestor. Novel varieties, and in particular seedless or reduced-seed varieties, have also been generated from these unique hybrid ancestral lines using gamma irradiation of budwood to induce mutations. Mandarin oranges (tangerines, satsumas – Citrus reticulata ) are one of the basic species, but the name mandarin is also used more generally for all small, easily peeled citrus, including
2808-490: A subspecies-level division has been characterized in this mainland-Asian species. Wang, et al. , found that domesticated mandarins fell into two genetic clusters that linked to different branches of the tree of wild mandarins, had different deduced population histories and had distinct patterns of pomelo introgression, suggesting that they derive from separate domestication events. Wu, et al. , would later extend this observation, similarly detecting two divergent subspecies within
2925-458: A thicker skin and darker green colour. Philippine varieties have various names, including dayap and bilolo . The English word lime was derived, via Spanish then French , from the Arabic word ليمة līma , which is, in turn, a derivation of the Persian word limu لیمو . Key is from Florida Keys , where the fruit was naturalised. The earliest known use of the name is from 1905, where
3042-455: Is "× Citroncirus ". The group includes the citrange , a hybrid between the trifoliate and sweet oranges , and the citrumelo , a hybrid of trifoliate orange and 'Duncan' grapefruit . As with Citrofortunella, were Poncirus subsumed into Citrus , these hybrids would no longer be intergeneric, and would likewise fall within Citrus , rendering Citroncirus invalid. Due to the sterility of many of
3159-404: Is a cold-hardy plant distinguishable by its compound leaves with three leaflets and its deciduous nature, but is close enough to the genus Citrus to be used as a rootstock. Swingle moved the trifoliate orange from Citrus to its own genus , Poncirus , but Mabberley and Zhang reunited the genera Swingle had separated back into Citrus . Early phylogenetic analysis nested Poncirus within
3276-791: Is a coating of coconut oil that improves shelf life, thereby achieving a constant market supply of Key limes. Key limes are made into black lime by boiling them in brine and drying them. Black lime is a condiment commonly used in the Middle East. The yield varies depending on the age of the trees. Five- to seven-year-old orchards may yield about 6 t/ha (2.7 tons/acre), with harvests increasing progressively until they stabilise at about 12–18 t/ha (5.4–8 tons/acre). Seedling trees take longer to attain their maximal harvest, but eventually out-yield grafted trees. The annual Key Lime Festival in Key West, Florida , has been held every year since 2002 over
3393-825: Is a volcanic island arc rising along the leading edge of the Caribbean Plate due to the subduction of the Atlantic seafloor of the North American and South American plates . Major islands of the Lesser Antilles likely emerged less than 20 Ma, during the Miocene . The volcanic activity that formed these islands began in the Paleogene, after a period of volcanism in the Greater Antilles ended, and continues today. The main arc of
3510-511: Is also sometimes used as a rootstock in Florida to add vigor. Climatic conditions and fruit maturation are crucial in cultivation of the lime tree. Under consistently warm conditions potted trees can be planted at any season, whereas in cooler temperate regions it is best to wait for the late winter or early spring. The Key lime tree does best in sunny sites, well-drained soils, good air circulation, and protection from cold wind. Because its root system
3627-693: Is estimated that nearly 70% of Cuba consists of karst limestone . The Blue Mountains of Jamaica are a granite outcrop rising over 2,000 meters (6000'), while the rest of the island to the west consists mainly of karst limestone. Much of Hispaniola, Puerto Rico, and the Virgin Islands were formed by the collision of the Caribbean Plate with the North American Plate and consist of 12 island arc terranes . These terranes consist of oceanic crust , volcanic and plutonic rock . The Lesser Antilles
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3744-515: Is generally followed globally today with much modification; there are still large differences in nomenclature between countries and individual scientists. The 'Tanaka system' (1954) instead provides a separate species name for each cultivar, regardless of whether it is pure or a hybrid of two or more species or varieties, and resulted in 159 identified species. It thus represents an example of taxonomic " splitting ", and in assigning separate species names to horticultural variants does not conform to
3861-680: Is geologically the oldest of the three archipelagos and includes both the largest islands ( Cuba , Jamaica , Hispaniola , and Puerto Rico ) and the tallest mountains ( Pico Duarte , Blue Mountain , Pic la Selle , Pico Turquino ) in the Caribbean. The islands of the Greater Antilles are composed of strata of different geological ages including Precambrian fragmented remains of the North American Plate (older than 539 million years), Jurassic aged limestone (201.3-145 million years ago), as well as island arc deposits and oceanic crust from
3978-443: Is inconsistent. There is disagreement over whether to assign species names to hybrids, and even modern hybrids of known parentage are sold under general common names that give little information about their ancestry, or even imply technically incorrect identity. This can be a problem for those who cannot eat some citrus varieties. Drug interactions with chemicals found in some citrus, including grapefruit and Seville oranges , make
4095-622: Is native to Southeast Asia . Its apparent path of introduction was through the Middle East to North Africa , then to Sicily and Andalucia and then, via Spanish explorers, to the West Indies , including the Florida Keys . Henry Perrine is credited with introducing the Key lime to Florida. From the Caribbean, lime cultivation spread to tropical and subtropical North America, including Mexico , Florida , and later California . In California in
4212-553: Is nested within the citrus phylogenetic tree, most closely related to kumquats, suggesting that all these species should be included in the genus Citrus . Wu, et al. , found that several of the finger lime cultivars were actually hybrids with round lime, and concluded there were just three species among those tested, desert lime ( C. glauca ), round lime ( C. australis ) and the finger lime ( C. australasica ), though their analysis did not include other types previously identified as distinct species. In more limited genomic analysis,
4329-438: Is shallow, the Key lime is planted in trenches or into prepared and broken rocky soil to give the roots a better anchorage and improve the trees' wind resistance. Pruning and topping should be planned to maximise the circulation of air and provide plenty of sunlight. This keeps the crown healthily dry, improves accessibility for harvesting, and discourages the organisms that cause gummosis. The method of cultivation greatly affects
4446-532: The Citrus subgenus Papeda to separate its members from the more edible citrus that also differ from other citrus in having stamens that grow separately, not united at their base. He included in this group the kaffir lime ( Citrus hystrix ), as well as its likely taxonomic synonym the micrantha ( Citrus micrantha ), and the Ichang papeda ( Citrus cavaleriei ). Since the latter two species locate to different branches of
4563-452: The mangshanyegan ( C. mangshanensis ), akin to another local fruit known as the yuanju , and found to be the most distant branch of all the citrus. In a limited genomic analysis, Feroniella was found to cluster with C. reticulata deep within Citrus , leading botanist David Mabberley to propose that the sole member of this genus, F. lucida , be moved to the genus Citrus and rechristened C. lucida . Though this has received
4680-744: The Achaemenid Empire ), and ultimately its cognate , the Sanskrit Sindhu , or "river", specifically the Indus River and its well-settled southern basin. The ancient Greeks referred to the Indians as Indoi ( Ἰνδοί ), which translates as "The people of the Indus". In 1492, Christopher Columbus and his Spanish fleet left Spain seeking a western sea passage to the Eastern world , hoping to profit from
4797-1039: The Americas . The Indies from both regions were further distinguished depending on the European world power to which they belong. In the East Indies , there were the Spanish East Indies and the Dutch East Indies . In the West Indies, the Spanish West Indies , the Dutch West Indies , the French West Indies , the British West Indies , and the Danish West Indies . The term was used to name
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4914-635: The Atlantic island nation of Bermuda , all of which are geographically distinct from the three main island groups, but culturally related. The English term Indie is derived from the Classical Latin India , a reference to the territories in South Asia adjacent and east to the Indus River . India itself derived successively from Hellenistic Greek India ( Ἰνδία ), ancient Greek Indos ( Ἰνδός ), Old Persian Hindush (an eastern province of
5031-502: The Bergamot orange is a sweet orange/lemon hybrid and the Oroblanco is a grapefruit/pomelo mix, while tangelos are tangerine (mandarin)/pomelo or mandarin/grapefruit hybrids, orangelos result from grapefruit backcrossed with sweet orange, and a sweet orange backcrossed with a tangerine gives the tangor . One lumia , a member of the sweet lemons , is the product of crossing a lemon with
5148-619: The Caribbean Sea , attacking Spanish and Portuguese shipping and coastal areas. They often took refuge and refitted their ships in the areas the Spanish could not conquer, including the islands of the Lesser Antilles, the northern coast of South America, including the mouth of the Orinoco , and the Atlantic Coast of Central America. In the Lesser Antilles, they managed to establish a foothold following
5265-709: The Cretaceous (145-66 million years ago). The Greater Antilles originated near the Isthmian region of present-day Central America in the Late Cretaceous (commonly referred to as the Proto-Antilles), then drifted eastward arriving in their current location when colliding with the Bahama Platform of the North American Plate ca. 56 million years ago in the late Paleocene . This collision caused subduction and volcanism in
5382-448: The Florida peninsula of North America south-southeast to the northern coast of Venezuela . These islands include active volcanoes , low-lying atolls , raised limestone islands, and large fragments of continental crust containing tall mountains and insular rivers. Each of the three archipelagos of the West Indies has a unique origin and geologic composition. The Greater Antilles
5499-645: The Ichang papeda ( C. cavaleriei ), the mangshanyegan ( C. mangshanensis ), and the oval (Nagami) kumquat ( Fortunella margarita or C. japonica var. margarita ). Three from Australia were identified: the desert lime ( C. glauca ), round lime ( C. australis ) and the finger lime ( C. australasica ). Many other cultivars previously identified as species were found to be closely related variants ( subspecies or varieties ) or hybrids of these species, though not all cultivars were evaluated. Subsequent studies have added two additional species to this list of pure species:
5616-508: The Independence Day weekend and is a celebration of Key limes in food, drinks, and culture, with a significant emphasis on Key lime pie . Citrus hybrid Citrus taxonomy is complex and controversial. Cultivated citrus are derived from various citrus species found in the wild. Some are only selections of the original wild types, many others are hybrids between two or more original species, and some are backcrossed hybrids between
5733-461: The Indian wild orange , once suggested as a possible ancestor of today's cultivated citrus fruits, yielded conflicting phylogenetic placements in more limited genetic analysis, but study of nuclear markers and chloroplast DNA showed it to be of maternal citron lineage, with further genetic contributions from mandarin and papeda. A large group of commercial hybrids involve the kumquat , Fortunella in
5850-701: The Lucayan Archipelago . The subregion includes all the islands in the Antilles , in addition to The Bahamas and the Turks and Caicos Islands , which are in the North Atlantic Ocean . The term is often interchangeable with "Caribbean", although the latter may also include coastal regions of Central and South American mainland nations, including Mexico , Belize , Honduras , Panama , Colombia , Venezuela , French Guiana , Guyana , and Suriname , as well as
5967-620: The Malay Archipelago , and mandarins in Vietnam , southern China , and Japan . The hybrids of these taxa include familiar citrus fruits like oranges , grapefruit , lemons , and some limes and tangerines . These three have also been hybridized with other citrus taxa, for example, the Key lime arose from a citron crossing with a micrantha. In many cases, the varieties are propagated asexually , and lose their characteristic traits if bred. Some of
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#17330845351756084-529: The New Guinea wild lime , Clymenia and Oxanthera (false orange) all cluster with the Australian limes as members of Citrus . The outback lime is a desert lime agriculturally selected for more commercial traits, while some commercial varieties of the Australian lime are hybrids with mandarins, lemons, and/or sweet oranges. Clymenia , will hybridize with kumquats and some limes . The trifoliate orange
6201-404: The Persian lime ( Citrus × latifolia ). It is valued for its characteristic flavor. The name comes from its association with the Florida Keys , where it is best known as the flavoring ingredient in Key lime pie . Not to be confused with West Indian lime , bartender's lime , Omani lime , or Mexican lime which are similar, but slightly different. The last classified as a distinct race with
6318-788: The Spanish Council of the Indies , the British East India Company , the Dutch East India and West India companies, the French East India Company , and the Danish East India Company . Many cultures were indigenous to these islands, with evidence dating some of them back to the mid-6th millennium BCE. In the late 16th century, French, English and Dutch merchants and privateers began operations in
6435-542: The Swedish West India Company . West Indian is the official term used by the U.S. government to refer to people of the West Indies. The term survives today mainly through the West Indies cricket team , representing all of the nations in the West Indian islands. The West Indies are a geologically complex island system consisting of 7,000 islands and islets stretching over 3,000 km (2000 miles) from
6552-948: The Treaty of the Danish West Indies . The Danish West Indies became an insular area of the U.S., called the United States Virgin Islands . Between 1958 and 1962, the United Kingdom re-organised all their West Indies island territories (except the British Virgin Islands and the Bahamas ) into the West Indies Federation . They hoped that the Federation would coalesce into a single, independent nation. The Federation had limited powers, numerous practical problems, and
6669-681: The Western Caribbean Zone in place in the early-18th century. In the Miskito Kingdom, the rise to power of the Miskito-Zambos , who originated in the survivors of a rebellion aboard a slave ship in the 1640s and the introduction of enslaved Africans by British settlers within the Miskito area and in Belize, also transformed this area into one with a high percentage of persons of African descent as
6786-407: The florentine citron is probably of hybrid origin. Genetic analysis of citrons has shown that they divide into three groups. One cluster consists of wild citrons that originated in China and produce non-fingered fruit with pulp and seeds. A second cluster, also native to China, consist of the fingered citrons, most of which are seedless and must be propagated artificially. The third cluster represents
6903-413: The trifoliate orange does not naturally interbreed with core taxa due to different flowering times, but hybrids have been produced artificially between Poncirus and members of the genus Citrus . Genomic analysis of several such hybrids showed all to have involved P. trifoliata and not P. polyandra . In the Swingle system the name coined for these intra-generic crosses, represented as a hybrid genus,
7020-938: The 'core species', citrons , mandarins , and pomelos , which share in common a complex floral anatomy that gives rise to more complex fruit. These core species, and to a lesser extent other citrus, have given rise to a wide variety of hybrids for which the naming is inconsistent. The same common names may be given to different species, citrus hybrids or mutations. For example, citrus with green fruit tend to be called 'limes' independent of their origin: Australian limes, musk limes , Key limes , kaffir limes , Rangpur limes , sweet limes and wild limes are all genetically distinct. Fruit with similar ancestry may be quite different in name and traits (e.g. grapefruit, common oranges, and ponkans are all mandarin–pomelo hybrids). Many traditional citrus groups, such as true sweet oranges and lemons, seem to be bud sports , clonal families of cultivars that have arisen from distinct spontaneous mutations of
7137-535: The Australian species. Most modern cultivars are actually hybrids derived from a small number of 'pure' original species. Though hundreds of species names have been assigned, a recent genomic study by Wu, et al. identified just ten ancestral species of citrus among more than a hundred cultivars studied. Of these ten, seven were native to Asia: pomelo ( Citrus maxima ), the 'pure' mandarins ( C. reticulata – most mandarin cultivars were hybrids of this species with pomelo), citrons ( C. medica ), micranthas ( C. micrantha ),
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#17330845351757254-489: The Citrinae subtribe into three groups, the 'primitive citrus' distant relatives, the closer 'near citrus' including citrus-related genera like Atalantia , and the "true citrus", for the species that had historically been placed in Citrus but many of which he elevated to separate genera: Poncirus (trifoliate orange), Fortunella (kumquat), Eremocitrus (desert limes), Microcitrus (finger and round limes), as well as an additional genus, Clymenia , formerly thought to be
7371-427: The Himalayan foothills, where a late- Miocene citrus fossil, Citrus linczangensis , has been found. At that time, a lessening of the monsoons and resultant drier climate in the region allowed the citrus ancestor to expand across south and east Asia in a rapid genetic radiation. After the plant crossed the Wallace line a second radiation took place in the early Pliocene (about 4 million years ago) to give rise to
7488-452: The Jiangsu kumquat ( F. obovata ), and Huang added another, F. bawangica . Since the kumquat is a cold-hardy species , there are many hybrids between common citrus members and the kumquat. Swingle coined a separate hybrid genus for these, which he called × Citrofortunella . Subsequent study of the many commercial citrus lineages revealed such complexity that the genera could not be separated, and genomic analysis rooted Fortunella within
7605-431: The Kirk lime. The New Caledonia and Kaghzi limes appear to have resulted from an F2 Key lime self-pollination, while a spontaneous genomic duplication gave us the tetraploid Giant Key lime. The potential to produce a wider variety of lime hybrids from the Key lime due to its tendency to form diploid gametes may reduce the disease risk presented by the limited diversity of the current commercial limes. C. aurantiifolia
7722-412: The Lesser Antilles runs north from the coast of Venezuela to the Anegada Passage , a strait separating them from the Greater Antilles, and includes 19 active volcanoes. The Lucayan Archipelago includes The Bahamas and the Turks and Caicos Islands , a chain of barrier reefs and low islands atop the Bahama Platform. The Bahama Platform is a carbonate block formed of marine sediments and fixed to
7839-431: The Mediterranean citrons, thought to have originally been introduced there from India. Some fingered citron varieties are used in buddhist offerings , and some more common varieties are used as the etrog in the Jewish harvest festival of Sukkot . There is also a specific variety of citron called etrog . The Mountain citron is a complex citrus hybrid that only includes trace amounts of true citron. Swingle coined
7956-454: The North American Plate. The emergent islands of the Bahamas and Turks and Caicos likely formed from accumulated deposits of wind-blown sediments during Pleistocene glacial periods of lower sea level. N.B.: Territories in italics are parts of transregional sovereign states or non-sovereign dependencies. These three Dutch Caribbean territories form the BES islands . Physiographically , these are continental islands not part of
8073-441: The Northern Hemisphere. Skin contact can sometimes cause phytophotodermatitis , which makes the skin especially sensitive to ultraviolet light. The Key lime cultivar is a citrus hybrid , Citrus micrantha × Citrus medica (a papeda - citron cross). The Key lime has given rise to several other lime varieties. The best known, the triploid progeny of a Key lime-lemon cross, is the Persian lime ( Citrus × latifolia ),
8190-435: The Persian lime is triploid , deriving from a diploid Key lime gamete and a haploid lemon ovule . A second group of Key lime hybrids, including the Tanepao lime and Madagascar lemon, are also triploid but instead seem to have arisen from a backcross of a diploid Key lime ovule with a citron haploid gamete. The "Giant Key lime" owes its increased size to a spontaneous duplication of the entire diploid Key lime genome to produce
8307-556: The Proto-Antillean area and likely resulted in continental uplift of the Bahama Platform and changes in sea level. The Greater Antilles have continuously been exposed since the start of the Paleocene or at least since the Middle Eocene (66-40 million years ago), but which areas were above sea level throughout the history of the islands remains unresolved. The oldest rocks in the Greater Antilles are located in Cuba. They consist of metamorphosed graywacke , argillite , tuff , mafic igneous extrusive flows, and carbonate rock . It
8424-503: The Swingle system. Citrofortunella was coined as a genus containing intergeneric hybrids between members of the Citrus and the Fortunella , and is named after its parent genera. Such hybrids often combine the cold hardiness of the kumquat with some edibility properties of the other Citrus species. As members of a hybrid genus, these crosses were marked with the multiplication sign before
8541-536: The Tachibana, proved to be either natural F1 hybrids between this native Ryukyu mandarin and mainland mandarin species that had recolonized the islands after a period of isolation, or else later agricultural hybrids with introduced Asian cultivars. All characterized commercial varieties called mandarins are actually inter-species hybrids . Wu, et al. , divided mandarins into three types, based on their degree of hybridization. In addition to genetically pure mandarins,
8658-462: The ancestry of citrus fruit of interest: many commonly sold citrus varieties are grapefruit hybrids or pomelo -descended grapefruit relatives . One medical review has advised patients on medication to avoid all citrus juice, although some citrus fruits contain none of the problematic furanocoumarins . Citrus allergies can also be specific to only some fruit or some parts of some fruit. The most common citrus hybrids that are sometimes treated as
8775-461: The cells of the two intermix at the graft site, and can produce shoots from the same tree that bear different fruit. For example, the 'Faris' lemon, has some branches with purple immature leaves and flowers with a purple blush that give rise to sour fruit, while other branches produce genetically distinct sweet lemons coming from white flowers, with leaves that are never purple. Graft hybrids can also give rise to an intermixed shoot that bears fruit with
8892-523: The citrus phylogenetic tree, the group would be polyphyletic and not a valid division. Both the micrantha and the Ichang papeda have also given rise to hybrids with other citrus. Sometimes included among the papedas was the mountain citron, not affiliated with the true citrons, and subsequently found to be a pure species most closely related to kumquats. Kumquats were originally classified by Carl Peter Thunberg as Citrus japonica in his 1784 book Flora Japonica . In 1915, Swingle reclassified them in
9009-433: The citrus, consistent with a single genus, but the genomic sequencing of Wu, et al. , placed it outside the cluster representing Citrus , and the authors retained a separate genus Poncirus . Ollitrault, Curk and Krueger indicate that the majority of data are consistent with the enlarged Citrus that includes the trifoliate orange, though they recognize that many botanists still follow Swingle. A further complication to
9126-532: The colonisation of Saint Kitts in 1624 and Barbados in 1626, and when the Sugar Revolution took off in the mid-17th century, they brought in thousands of enslaved Africans to work the fields and mills as labourers. These enslaved Africans wrought a demographic revolution, replacing or joining with either the indigenous Caribs or the European settlers who were there as indentured servants . The struggle between
9243-479: The four species ancestral to most commercial hybrids, and did not include similar species designations for more exotic hybrids involving other citrus species, such as the Ichang papeda, kumquat, or trifoliate orange. Likewise, Ollitrault, Curk and Krueger accepted that the whole-genome characterization necessary to unambiguously assign a hybrid species name under their system is not available for many varieties. Most commercial varieties are descended from one or more of
9360-399: The fruit was described as "the finest on the market. It is aromatic, juicy, and highly superior to the lemon." C. aurantiifolia is a shrubby tree, growing to 5 metres (16 feet), with many thorns . Dwarf varieties exist that can be grown indoors during winter months and in colder climates. Its trunk, which rarely grows straight, has many branches, and they often originate quite far down on
9477-431: The genetic hybrids as well as disease- or temperature-sensitivity of some Citrus trees, domesticated citrus cultivars are usually propagated via grafting to the rootstock of other, often hardier though less palatable citrus or close relatives. As a result, graft hybrids, also called graft-chimaeras , can occur in Citrus . After grafting , the cells from the scion and rootstock are not somatically fused , but rather
9594-449: The genetically pure citrus strains and distinguish them from hybrids. In 2020, a new taxonomic system was proposed by Ollitrault, Curk and Krueger, with the goal of harmonizing traditional naming systems with the new genomic data that have both allowed the pure ancestral species to be distinguished from hybrids, and enabled the ancestry of those hybrids to be identified among the ancestral species. In their system, each ancestral species has
9711-530: The genus name, for example × Citrofortunella microcarpa . With the return of kumquats to within Citrus , Citrofortunella are no longer viewed as being intergeneric hybrids and thus likewise belong in Citrus , while Citrofortunella as a distinct genus name would no longer be valid . Examples of the Citrofortunella include the calamansi , limequat , and yuzuquat , crossing kumquat with tangerine , Key lime , and yuzu respectively. As with kumquats,
9828-639: The hardier, thornless Persian limes. Since the North American Free Trade Agreement came into effect, most Key limes on the United States market have been grown in Mexico, Central America and South America . They are also grown in Texas , Florida, and California. There are various approaches to the cultivation of Key limes. This variety of citrus can be propagated from seed and will grow true to
9945-473: The highest market value, it is important not to pick the fruit too early in the morning; the turgor is high then, and handling turgid fruit releases the peel oils and may cause spoilage. Shelf life of Key limes is an important consideration in marketing. The lime still ripens for a considerable time after harvesting, and it is usually stored between 12.5 and 15.5 °C (55–60 °F) at a relative humidity of 75–85%. Special procedures are employed to control
10062-458: The hybrids deriving from mandarin/pomelo crosses, there is a direct correlation between the proportion of pomelo DNA in the hybrid and fruit size, while the more palatable mandarins are those that have received specific genes from pomelos that alter their acidity. Some of the more common pomelos are genetically pure, while a number have a single small region of introgressed mandarin DNA on one chromosome,
10179-728: The hybrids have in turn interbred with one another hybrid or with the original taxa, making the citrus family tree a complicated network. Kumquats do not naturally interbreed with core taxa due to different flowering times, but hybrids (such as the calamansi ) exist. Australian limes are native to Australia and Papua New Guinea , so they did not naturally interbreed with the core taxa, but they have been crossbred with mandarins and calamansis by modern breeders. Humans have deliberately bred new citrus fruits by propagating seedlings of spontaneous crosses (e.g. clementines ), creating or selecting mutations of hybrids, (e.g. Meyer lemon ), and crossing different varieties (e.g. 'Australian Sunrise',
10296-517: The late 19th century, "Mexican" limes were more highly valued than lemons; however, in Florida, they were generally considered weeds. Then, in 1894–95, the Great Freeze destroyed the Florida lemon groves, and farmers replanted Mexican limes instead; they soon became known as the Florida Key Lime, a "beloved regional crop". But when the 1926 Miami hurricane ripped them up, they were replanted with
10413-618: The lucrative spice trade emanating from Hindustan , Indochina , and Insulindia , the regions currently found within the Indian Subcontinent and Southeast Asia , which were first simply referred to by Spanish and Portuguese explorers as the Indias (Indies) . Thinking he had landed on the easternmost part of the Indies in the Eastern world when he came upon the New World , Columbus used
10530-520: The micrantha, Ichang papeda, kumquat , Australian limes, and trifoliate orange. The best known hybrid from micrantha is the Key lime (or Mexican lime), derived from the breeding of a male citron and a female micrantha. Several citrus varieties are Ichang papeda/mandarin crosses (for which Swingle coined the term ichandarin ), including Sudachi and Yuzu (which also includes smaller contributions from pomelo and kumquat). Other more exotic citrus have likewise proved hybrids that include papeda. For example,
10647-476: The most widely produced lime, globally. Others are, like their parent, classed within C. aurantiifolia . Backcrossing with citron has produced a distinct group of triploid limes that are also of commercial value to a limited degree, the seedy Tanepeo, Coppenrath, Ambilobe and Mohtasseb lime varieties as well as the Madagascar lemon. Hybridization with a mandarin - pomelo cross similar to the oranges has produced
10764-460: The new plants have been viewed as different species from any of their parents. In older taxonomic systems, citrus hybrids have often been given unique hybrid names , marked with a multiplication sign after the word Citrus (or abbreviation C. ); for example, the Key lime is Citrus × aurantifolia , and also are referred to by joining the names of the crossed species or hybrids that produced them, as with sunquat – C. limon × japonica . Styling
10881-558: The northern Europeans and the Spanish spread southward in the mid to late seventeenth century, as English, Dutch, French and Spanish colonists, and in many cases, enslaved Africans first entered and then occupied the coast of The Guianas (which fell to the French, English and Dutch) and the Orinoco valley, which fell to the Spanish. The Dutch, allied with the Caribs of the Orinoco, would eventually carry
10998-426: The parent. The seeds must be kept moist until they can be planted, as they will not germinate if allowed to dry out. If the plants are propagated from seed, the seeds should be stored at least 5–6 months before planting. Alternatively, vegetative propagation from cuttings or by air layering may permit fruit production within one year, and from genetically more predictable lines of plants. Another method, digging around
11115-462: The phylogenetic tree of Citrus . Since their placement in distinct genera would make Citrus a paraphyletic grouping, it has been suggested that all of these are correctly members of the genus Citrus . Similarly, genomic analysis has suggested that other genera previously split off from Citrus likewise belong within this expanded phylogenetic concept of the genus Citrus , including Clymenia , Oxanthera (false oranges, moved out of Citrus to
11232-536: The placement of Poncirus is the conflicting phylogenetic data: its nuclear genome places Poncirus as an outgroup to other citrus, while its chloroplast DNA (cpDNA) nests within a Citrus subclade. This led Talon, et al. to conclude that the trifoliate orange likely is either the progeny of an ancient hybridization between a core citrus and an unidentified more distant relative, or at some time in its history acquired an introgressed cpDNA genome from another species. A second trifoliate orange, Poncirus polyandra ,
11349-457: The polyphyletic tree of Citrus . As a result there is growing acceptance for the restoration of kumquats to Citrus , though the assignment of individual species among the kumquats remains controversial due in part to insufficient genomic data on the variants. The Flora of China unites all kumquats as the single species, Citrus japonica . Based on chromosomal analysis, Yasuda, et al., identified Jiangsu and Malayan kumquats as hybrids and see
11466-517: The product of hybridization among these wild species, with most coming from crosses involving citrons , mandarins and pomelos . Many different phylogenies for the non-hybrid citrus have been proposed, and the phylogeny based on their nuclear genome does not match that derived from their chloroplast DNA, probably a consequence of the rapid initial divergence. Taxonomic terminology is not yet settled. Most hybrids express different ancestral traits when planted from seeds ( F2 hybrids ) and can continue
11583-554: The progenitor of modern citrus species expanded out of the Himalayan foothills in a rapid radiation that has produced at least 11 wild species in South and East Asia and Australia, with more than a half-dozen additional candidates for which either insufficient characterization prevents definitive species designation, or there is a lack of consensus for their placement within the Citrus genus rather than sister genera. Most commercial cultivars are
11700-402: The progeny, or (rarely, and only recently) as somatic hybrids . The aim of plant breeding of hybrids is to use two or more different citrus varieties or species, in order to get traits intermediate between those of the parents, or to transfer individual desirable traits of one parent into the other. In some cases, particularly with the natural hybrids, it has been viewed as hybrid speciation and
11817-591: The remainder of the Eufortunella subgenus as a single species, while retaining a distinct species designation for the Hong Kong kumquat. Australian and New Guinean citrus species had been viewed as belonging to separate genera by Swingle, who placed in Microcitrus all but the desert lime, which he assigned to Eremocitrus . However, genomic analysis shows that though they form a distinct clade from other citrus, this
11934-553: The result of a cross followed by extensive backcrossing with pomelo. Varieties of true (non-hybrid) citron ( Citrus medica ) have distinctly different forms. The citron usually propagates by cleistogamy , a self-pollination within an unopened flower, and this results in the lowest levels of heterozygosity among the citrus species. Because of this, it will generally serve as the male parent of any hybrid progeny. Many citron varieties were proven to be non-hybrids despite their rather dramatic morphological differences; however,
12051-522: The shelf life; for example, applications of growth regulators , fruit wax , fungicides , precise cooling, calcium compounds, silver nitrate , and special packing material. The preferred storage conditions are temperatures of 9–10 °C (48–50 °F) and a humidity over 85%, but even in ideal conditions post-harvesting losses are high. In India most Key lime producers are small-scale farmers without access to such post-harvesting facilities, but makeshift expedients can be of value. One successful procedure
12168-507: The size and quality of the harvest. Trees cultivated from seedlings take 4–8 years before producing a harvest. They attain their maximal yield at about 10 years of age. Trees produced from cuttings and air layering bear fruit much sooner, sometimes producing fruit (though not a serious harvest) a year after planting. It takes approximately 9 months from the blossom to the fruit. When the fruit have grown to harvesting size and begin to turn yellow they are picked and not clipped. To achieve produce of
12285-463: The standard species concept. Tanaka also divided into subgenera, but different than in Swingle's system, introducing Archicitrus (which he subdivided into five sections, Papeda, Limonellus, Aruntium, Citrophorum and Cephalocitrus) and Metacitrus (divided into Osmocitrus, Acrumen and Pseudofortunella). This system is commonly used in Tanaka's native Japan. A 1969 analysis by Hodgson intended to harmonize
12402-587: The struggles deep into South America, first along the Orinoco and then along the northern reaches of the Amazon . Since no European country had occupied much of Central America, gradually, the English of Jamaica established alliances with the Miskito Kingdom of modern-day Nicaragua and Honduras and then began logging on the coast of modern-day Belize . These interconnected commercial and diplomatic relations comprised
12519-476: The subgenera suggested by Tanaka proved similar to the phylogenetic divisions of pure founder species, Swingle's subgenera were polyphyletic , and hence do not represent valid taxonomy. His novel genera also fail to withstand phylogenetic analysis. Swingle had elevated kumquats into a separate genus Fortunella , while two genera were suggested by him for the Australian limes, Microcitrus and Eremocitrus . However, genomic analysis shows these groups nested within
12636-495: The sweet orange, C. × aurantium var. paradisi for grapefruit, and C. × aurantium var. clementina for the clementine. Likewise, hybrids combining mandarins and citrons would all be varieties of C. × limonia , those of pomelo and citron, C. x lumia , while tri-species hybrids of citrons, pomelos and mandarins would be C. × limon , and a tetra-species cross involving these three species along with C. micrantha would be C. × latifolia . This naming system focused on
12753-737: The term Indias to refer to the Americas , calling its native people Indios (Indians) . To avoid confusion between the known Indies of the Eastern Hemisphere and the newly discovered Indies of the Western Hemisphere , the Spanish named the territories in the East Indias Orientales (East Indies) and the territories in the West Indias Occidentales (West Indies) . Originally, the term West Indies applied to all of
12870-434: The trunk. The leaves are ovate, 2.5–9 centimetres (1– 3 + 1 ⁄ 2 inches) long, resembling orange leaves (the scientific name aurantiifolia referring to this resemblance to the leaves of Citrus aurantium ). The flowers are 2.5 cm (1 in) in diameter, are yellowish white with a light purple tinge on the margins. Flowers and fruit appear throughout the year, but are most abundant from May to September in
12987-517: The two contributing species with a plus sign between the individual names ( Citrus medica + C. aurantium ). West Indies The West Indies is a subregion of North America , surrounded by the North Atlantic Ocean and the Caribbean Sea , which comprises 13 independent island countries and 19 dependencies in three archipelagos : the Greater Antilles , the Lesser Antilles , and
13104-401: The two schemes accepted 36 species. These initial attempts at Citrus systematization all predated the recognition, which began to gain traction in the mid-1970s, that the majority of cultivars represent hybrids of just three species, citron, mandarin and pomelo. Phylogenetic analysis confirms this hybrid origin of most citrus cultivars, indicating a small number of founder species. While
13221-765: The volcanic Windward Islands arc. Based on proximity, these islands are sometimes grouped with the Windward Islands culturally and politically. Disputed territories administered by Colombia . The United Nations geoscheme includes Mexico in Central America . These three form the SSS islands that with the ABC islands comprise the Dutch Caribbean , of which the BES islands are not direct Kingdom constituents but subsumed with
13338-521: The wild mandarins of the East-Asian mainland. However, a directed study of these island cultivars revealed the existence of a second mandarin true-species that diverged from the mainland species between 2.2 and 2.8 million years ago, following the geographical isolation of the islands through rising sea levels. Unlike the mainland species, this Ryukyu mandarin, named C. ryukyuensis , reproduces sexually. The previously-characterized island cultivars, including
13455-451: The wild populations that gave rise to Wang's northern and southern domesticate classes, which they described as 'common mandarins' and mangshanyeju ( Mangshan wild mandarins). It was specifically in the latter that a genetic mutation caused by the insertion of a transposable element adjacent to the CitRKD1 gene led to the ability of these mandarins to reproduce asexually through apomixis ,
13572-467: Was discovered in Yunnan ( China ) in the 1980s. Zhang and Mabberley later concluded this was likely a hybrid between the trifoliate orange and some other Citrus . However, recent genomic analysis of P. polyandra showed low heterozygosity, the opposite of what one would expect for a hybrid. Were Poncirus subsumed into Citrus , C. polyandra would be unavailable, so C. polytrifolia has been suggested as
13689-465: Was found in most of the rest of the Caribbean. From the 17th through the 19th century, the European colonial territories of the West Indies were the French West Indies , British West Indies , the Danish West Indies , the Netherlands Antilles (Dutch West Indies), and the Spanish West Indies . In 1916, Denmark sold the Danish West Indies to the United States for US$ 25 million in gold, per
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