Trifoliate orange | |
---|---|
A fruiting tree in Jardin des Plantes, Paris | |
Scientific classification | |
Kingdom: | Plantae |
Clade: | Tracheophytes |
Clade: | Angiosperms |
Clade: | Eudicots |
Clade: | Rosids |
Order: | Sapindales |
Family: | Rutaceae |
Genus: | Citrus |
Species: | C. trifoliata |
Binomial name | |
Citrus trifoliata | |
Synonyms [1] | |
|
The trifoliate orange, Citrus trifoliata (syn. Poncirus trifoliata), is a member of the family Rutaceae. Whether the trifoliate oranges should be considered to belong to their own genus, Poncirus, or be included in the genus Citrus is debated. The species is unusual among citrus for having deciduous, compound leaves and pubescent (downy) fruit. [2] [3]
It is native to northern China and Korea, and is also known as the Japanese bitter-orange (karatachi), [4] hardy orange [5] or Chinese bitter orange.
The plant is a fairly cold-hardy citrus (USDA zone 6) and will tolerate moderate frost and snow, making a large shrub or small tree 4–8 m (13–26 ft) tall. Because of its relative hardiness, citrus grafted onto Citrus trifoliata are usually hardier than when grown on their own roots. [6]
The trifoliate orange is recognizable by the large 3–5 cm (1.2–2.0 in) thorns on the shoots, and its deciduous leaves with three (or rarely, five) leaflets, typically with the middle leaflet 3–5 cm (1.2–2.0 in) long, and the two side leaflets 2–3 cm (0.79–1.18 in) long. The flowers are white, with pink stamens, 3–5 cm (1.2–2.0 in) in diameter, larger than those of true citrus but otherwise closely resembling them, except that the scent is much less pronounced than with true citrus. As with true citrus, the leaves give off a spicy smell when crushed.
The fruits are green, ripening to yellow, and 3–4 cm (1.2–1.6 in) in diameter similar in size to a lime and resembling a small orange, but with a finely downy surface and having a fuzzy texture similar to a peach. The fruits also have distinctive smell from other citrus varieties and often contain a high concentration of seeds.
The cultivar 'Flying Dragon' is dwarfed in size, has highly twisted, contorted stems, and has even stronger thorns than the type. It makes an excellent barrier hedge due to its density and strong curved thorns. Such hedges have been grown for over 50 years at Oklahoma State University in Stillwater, and are highly student-proof. [7] The plant is also highly deer-resistant. [8] In central London, mature specimens of the trifoliate orange can be seen in the gardens of St Paul's Cathedral.[ citation needed ]
Trifoliate orange and various hybrids of this plant are widely used as citrus rootstock, and valued for their resistance to cold, the tristeza virus, and the oomycete Phytophthora parasitica (root rot). [9]
Recent studies have revealed that the trifoliate orange contains auraptene at a high concentration, which is one of the functional components having immunity against citrus tristeza virus (CTV). [10]
The fruits are very bitter, due in part to their poncirin content. Most people consider them inedible fresh, but they can be made into marmalade. [8] When dried and powdered, they can be used as a condiment. [11]
The fruits of the trifoliate orange are widely used in medical traditions of East Asia as a treatment for allergic inflammation. [12]
The trifoliate orange was historically considered a member of the genus Citrus until Walter Swingle (1871 – 1952) moved it in 1943 to its own novel genus, Poncirus, based on its deciduous trifoliate leaves differing from other Citrus, as part of a larger reclassification that split the historical Citrus into seven genera. However, David Mabberley and Dianxiang Zhang reunited all of Swingle's novel genera back into Citrus in 2008. [13] Early phylogenetic analysis of trifoliate orange plastids nested Poncirus within the citrus, consistent with a single genus, [14] [15] [16] [17] but the sequencing of the nuclear genome by Wu, et al. showed its genome to be most divergent, different enough to justify retention of Poncirus as a separate genus. [18] To explain the conflict between the plastid and nuclear genomic analysis, it was speculated that the trifoliate orange is likely either the progeny of an ancient hybridization between a core citrus and an unidentified more distant relative, or at some time in its history it acquired an introgressed cpDNA genome from another species. [19] 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. [13]
A second species of trifoliate orange native to Yunnan (China) has been reported and named Poncirus polyandra. [20] Were Poncirus to be subsumed into Citrus, where C. polyandra is unavailable, the name Citrus polytrifolia has been suggested. [21] Zhang and Mabberley concluded this Yunnan cultivar is likely a hybrid between the trifoliate orange and another Citrus, [2] but recent genomic analysis of P. polyandra showed low levels of heterozygosity, [22] the opposite of what one would expect for a hybrid. This analysis dated its divergence from P. trifoliata about 2.82 million years ago. [22]
The trifoliate orange does not naturally interbreed with core Citrus taxa due to different flowering times, [23] but hybrids have been produced artificially between the trifoliate orange and other citrus. In the Swingle system, where the trifoliate orange is placed in Poncirus, a hybrid genus name has been coined for these intra-generic crosses, "× Citroncirus". The most notable of these are the citrange, a cross between the trifoliate and sweet oranges, and the citrumelo, a hybrid of trifoliate orange and 'Duncan' grapefruit. Placing the trifoliate orange in Citrus would mean these hybrids would no longer be intergeneric, but instead hybrids within Citrus. Genomic analysis of a number of these hybrids showed them all to derive from P. trifoliata and not P. polyandra. [22]
Kumquats, or cumquats in Australian English, are a group of small, angiosperm, fruit-bearing trees in the family Rutaceae. Their taxonomy is disputed. They were previously classified as forming the now-historical genus Fortunella or placed within Citrus, sensu lato. Different classifications have alternatively assigned them to anywhere from a single species, Citrus japonica, to numerous species representing each cultivar. Recent genomic analysis defines three pure species, Citrus hindsii, C. margarita and C. crassifolia, with C. × japonica being a hybrid of the last two.
Citrus is a genus of flowering trees and shrubs in the family Rutaceae. Plants in the genus produce citrus fruits, including important crops such as oranges, mandarins, lemons, grapefruits, pomelos, and limes.
A mandarin orange, also known as mandarin or mandarine, is a small, rounded citrus tree fruit. Treated as a distinct species of orange, it is usually eaten plain or in fruit salads. Tangerines are a group of orange-colored citrus fruit consisting of hybrids of mandarin orange with some pomelo contribution.
The tangerine is a type of citrus fruit that is orange in color, that is considered either a variety of Citrus reticulata, the mandarin orange, or a closely related species, under the name Citrus tangerina, or yet as a hybrid of mandarin orange varieties, with some pomelo contribution.
Citrus unshiu is a semi-seedless and easy-peeling citrus species, also known as the satsuma mandarin or Japanese mandarin. During the Edo period of Japan, kishu mikans were more popular because there was a popular superstition that eating Citrus unshiu without seeds made people prone to infertility. Citrus unshiu became popular in Japan after modernization started in the Meiji period. It was introduced to the West from the Satsuma region of Japan in 1878.
Persian lime, also known by other common names such as seedless lime, Bearss lime and Tahiti lime, is a citrus fruit species of hybrid origin, known only in cultivation. The Persian lime is a triploid cross between Key lime and lemon.
Rangpur, Citrus × limonia or Citrus reticulata × medica, sometimes called the rangpur lime, mandarin lime or lemandarin, is a hybrid between the mandarin orange and the citron. It is a citrus fruit with a very acidic taste and an orange peel and flesh.
Sweet lemon and sweet lime refer to groups of citrus hybrids that contain low acid pulp and juice. They are hybrids often similar to non-sweet lemons or limes, but with less citron parentage. Sweet limes and lemons are not sharply separated:
The sweet lime, Citrus limettioides Tan., is often confused with the sweet lemon, C. limetta Tan., which, in certain areas, is referred to as "sweet lime". In some of the literature, it is impossible to tell which fruit is under discussion.
Citreae is one of the two tribes of the flowering plant family Rutaceae, subfamily Aurantioideae, the other being Clauseneae.
The kishu mikan is a hybrid variety of mikan, or mandarin orange, found in Southern China and also grown in Japan.
Clymenia is a small genus of flowering plants in the family Rutaceae with two species. The genus is often included in Citrus.
The micrantha is a wild citrus from the papeda group, native to southern Philippines, particularly islands of Cebu and Bohol. Two varieties are recognized: small-flowered papeda, locally known as biasong, and small-fruited papeda or samuyao.
The lumia is also called the pear lemon, since its shape resembles a pear. It is also called French lime and sometimes sweet lemon, even though it is not necessarily sweet.
Rhobs al-Arsa is a very popular citrus fruit in Morocco.
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.
Citrus rootstock are plants used as rootstock for citrus plants. A rootstock plant must be compatible for scion grafting, and resistant to common threats, such as drought, frost, and common citrus diseases.
Citrumelo is also called Swingle citrumelo trifoliate hybrid, because it is cold hardy and is a hybrid between a 'Duncan' grapefruit and a trifoliate orange, developed by Walter Tennyson Swingle.
Citrus mangshanensis, the mangshanyegan, is a wild citrus fruit species.
Citrus × deliciosa is a citrus hybrid mandarin orange with just under 6 % pomelo ancestry. It is related to the ponkan.
The tachibana orange is a variety of mandarin orange, a citrus fruit. They grow wild in the forests of Japan and are referred to in the poetry of the early Japanese and Ryukyu Islands kingdoms. The Tanaka System assigns them their own species, while the Swingle System places them in the same species with other mandarin oranges.