citrus

The large citrus fruit of today evolved originally from small, edible berries over millions of years. Citrus species began to diverge from a common ancestor about 15 million years ago, at about the same time that Severinia (such as the Chinese box orange) diverged from the same ancestor. About 7 million years ago, the ancestors of Citrus split into the main genus, Citrus, and the Poncirus group (such as the trifoliate orange), which some taxonomies consider a separate genus and others include in Citrus{{cite book |chapter=Citrus taxonomy |last1=Ollitrault |first1=Patrick |last2=Curk |first2=Franck |last3=Krueger |first3=Robert |title=The Citrus Genus |editor-last1=Talon |editor-first1=Manuel |editor-last2=Caruso |editor-first2=Marco |editor-last3=Gmitter |editor-first3=Frederick G. Jr. |publisher=Elsevier |date=2020 |pages=57–81 |isbn=978-0-12-812163-4 |chapter-url= https://books.google.com/books?id=2wo4swEACAAJ&pg=PA57 |doi=10.1016/B978-0-12-812163-4.00004-8|s2cid=242819146 }} Poncirus

is closely enough related that it can still be hybridized with all other citrus and used as rootstock. These estimates are made using genetic mapping of plant chloroplasts.{{Cite web|url=http://mbe.oxfordjournals.org/content/early/2015/04/05/molbev.msv082.full.pdf+html|title=A phylogenetic analysis of 34 chloroplast genomes elucidates the relationships between wild and domestic species within the genus Citrus|date=31 January 2016|access-date=6 May 2021|archive-date=31 January 2016|archive-url=https://web.archive.org/web/20160131222305/http://mbe.oxfordjournals.org/content/early/2015/04/05/molbev.msv082.full.pdf+html|url-status=bot: unknown}} A DNA study published in Nature in 2018 concludes that the genus Citrus evolved in the foothills of the Himalayas, in the area of Assam (India), western Yunnan (China), and northern Myanmar.{{cite web |last=Briggs |first=Helen |date=8 February 2018 |title=DNA Story of when life first gave us lemons |work=BBC News |url=https://www.bbc.com/news/science-environment-42960445 |access-date=19 July 2022}}

File:Map of inferred original wild ranges of the main Citrus cultivars, and selected relevant wild taxa (Fuller et al., 2017).png

The three ancestral 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 between these three species, their main progenies, and other wild Citrus species within the last few thousand years.{{cite journal |title=A genealogy of the citrus family |first1=Riccardo |last1=Velasco |first2=Concetta |last2=Licciardello |journal=Nature Biotechnology |volume=32 |issue=7 |pages=640–642 |doi=10.1038/nbt.2954 |pmid=25004231 |year=2014 |s2cid=9357494 |doi-access=free}}{{cite book |last1=Inglese |first1=Paolo |title=Oxford Research Encyclopedia of Environmental Science |last2=Sortino |first2=Giuseppe |chapter=Citrus History, Taxonomy, Breeding, and Fruit Quality |date=2019 |doi=10.1093/acrefore/9780199389414.013.221 |isbn=9780199389414}}

Citrus plants are native to subtropical and tropical regions of Asia, Island Southeast Asia, Near Oceania, and northeastern and central Australia. Domestication of citrus species involved much hybridization and introgression, leaving much uncertainty about when and where domestication first happened.{{cite journal | last1=Wu | first1=Guohong Albert | last2=Terol | first2=Javier | last3=Ibanez | first3=Victoria | last4=López-García | first4=Antonio | last5=Pérez-Román | first5=Estela | last6=Borredá | first6=Carles | last7=Domingo | first7=Concha | last8=Tadeo | first8=Francisco R. | last9=Carbonell-Caballero | first9=Jose | last10=Alonso | first10=Roberto | last11=Curk | first11=Franck | last12=Du | first12=Dongliang | last13=Ollitrault | first13=Patrick | last14=Roose | first14=Mikeal L. | last15=Dopazo | first15=Joaquin | last16=Gmitter | first16=Frederick G. | last17=Rokhsar | first17=Daniel S. | last18=Talon | first18=Manuel |display-authors=5 | title=Genomics of the origin and evolution of Citrus | journal=Nature | volume=554 | issue=7692 | year=2018 | pages=311–316 | doi=10.1038/nature25447 | doi-access=free | pmid=29414943 | bibcode=2018Natur.554..311W | hdl=20.500.11939/5741 | hdl-access=free}} A genomic, phylogenic, and biogeographical analysis by Wu et al. (2018) has 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. cavaleriei) of southeastern China; the kaffir limes (C. hystrix) of Island Southeast Asia; and the biasong and samuyao (C. micrantha) of the Philippines.

This was 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 Early Pleistocene (2.5 million to 800,000 years ago), where further speciation events created the Australian limes.{{cite book |first1=Dorian Q. |last1=Fuller |first2=Cristina |last2=Castillo |first3=Eleanor |last3=Kingwell-Banham |first4=Ling |last4=Qin |first5=Alison |last5=Weisskopf|editor1-first=Véronique |editor1-last=Zech-Matterne |editor2-first=Girolamo|editor2-last=Fiorentino |title=AGRUMED: Archaeology and history of citrus fruit in the Mediterranean |chapter=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 |publisher=Publications du Centre Jean Bérard |year=2017 |pages=29–48 |isbn=9782918887775 |doi=10.4000/books.pcjb.2107 |url=https://hal.archives-ouvertes.fr/hal-03501166/file/2017-Ruas-etal-Citrus.pdf |chapter-url =https://books.openedition.org/pcjb/2173?lang=en}}

A fossil leaf from the Pliocene of Valdarno, Italy is described as †Citrus meletensis.Citrus meletensis (Rutaceae), a new species from the Pliocene of Valdarno (Italy). Fischer, T.C. & Butzmann, Plant Systematics and Evolution – March 1998, Volume 210, Issue 1, pp 51–55. doi:10.1007/BF00984727

In China, fossil leaf specimens of †Citrus linczangensis have been collected from late Miocene coal-bearing strata of the Bangmai Formation in Yunnan province. C. linczangensis resembles C. meletensis in having an intramarginal vein, an entire margin, and an articulated and distinctly winged petiole.{{cite journal |last1=Xie |first1=Sanping Xie |last2=Manchester |first2=Steven R. |last3=Liu |first3=Kenan |last4=Sun |first4=Bainian |title=Citrus linczangensis sp. n., a Leaf Fossil of Rutaceae from the Late Miocene of Yunnan, China |journal=International Journal of Plant Sciences |date=October 2013 |volume=174 |issue=8 |pages=1201–1207| doi=10.1086/671796 |bibcode=2013IJPlS.174.1201X }}

{{Main|Citrus taxonomy}}

Many cultivated Citrus species are natural or artificial hybrids of a small number of core ancestral species, including the citron, pomelo, and mandarin. Natural and cultivated citrus hybrids include commercially important fruit such as oranges, grapefruit, lemons, limes, and some tangerines. The multiple hybridisations have made the taxonomy of Citrus complex.{{Cite book |last1=Klein |first1=Joshua D. |volume=2 |pages=199–214 |doi=10.1007/978-94-017-9276-9_10 |series=Medicinal and Aromatic Plants of the World |year=2014 |title=Medicinal and Aromatic Plants of the Middle-East |isbn=978-94-017-9275-2 |chapter=Citron Cultivation, Production and Uses in the Mediterranean Region}}{{cite journal |last1=Wu |first1=Guohong Albert |last2=Terol |first2=Javier |last3=Ibanez |first3=Victoria |last4=López-García |first4=Antonio |last5=Pérez-Román |first5=Estela |last6=Borredá |first6=Carles |last7=Domingo |first7=Concha |last8=Tadeo |first8=Francisco R. |last9=Carbonell-Caballero |first9=Jose |last10=Alonso |first10=Roberto |last11=Curk |first11=Franck |last12=Du |first12=Dongliang |last13=Ollitrault |first13=Patrick |last14=Roose |first14=Mikeal L. Roose |last15=Dopazo |first15=Joaquin |last16=Gmitter Jr |first16=Frederick G. |last17=Rokhsar |first17=Daniel |last18=Talon |first18=Manuel |display-authors=6 |title=Genomics of the origin and evolution of Citrus |journal=Nature |year=2018 |volume=554 |issue=7692 |pages=311–316 |doi=10.1038/nature25447 |pmid=29414943 |bibcode=2018Natur.554..311W |doi-access=free |hdl=20.500.11939/5741 |hdl-access=free}} and Supplement

File:Hybrid origins of Citrus.svg of citron, mandarin and pomelo.]]

Apart from these core species, Australian limes and the recently discovered mangshanyegan are grown. Kumquats and Clymenia spp. are now generally considered to belong within the genus Citrus.{{cite thesis |last=García Lor |first=Andrés |title=Organización de la diversidad genética de los cítricos |language=Spanish |trans-title=Organisation of the genetic diversity of the citruses |year=2013 |url=https://riunet.upv.es/bitstream/handle/10251/31518/Versión3.Tesis%20Andrés%20García-Lor.pdf |page=79}} The false oranges, Oxanthera from New Caledonia, have been transferred to the Citrus genus on phylogenetic evidence.Bayer, R. J., et al. (2009). [https://web.archive.org/web/20150331210237/http://www.amjbot.org/content/96/3/668.full A molecular phylogeny of the orange subfamily (Rutaceae: Aurantioideae) using nine cpDNA sequences.] American Journal of Botany 96(3), 668–685.{{cite web |title=Oxanthera Montrouz |work=Plants of the World Online |publisher=Royal Botanic Gardens, Kew |url=https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:35867-1 |access-date=10 September 2021}} A recent taxonomy reincorporates the trifoliate orange (Poncirus) into an enlarged Citrus, but recognizes that many botanists still follow Swingle in splitting it off.

The earliest introductions of citrus species by human migrations was during the Austronesian expansion ({{circa|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.{{cite journal |last1=Blench |first1=R.M. |title=Fruits and arboriculture in the Indo Pacific region |journal=Bulletin of the Indo-Pacific Prehistory Association |date=2005 |volume=24 |pages=31–50 |url=https://www.researchgate.net/publication/255579031}}

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 includes 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 written by Theophrastus, {{circa|310 BCE}}.

Lemons, pomelos, and sour oranges were introduced to the Mediterranean by Arab traders around the 10th century CE. Sweet oranges were brought to Europe by the Genoese and Portuguese from Asia during the 15th to 16th century. Mandarins were not introduced until the 19th century.{{cite book |first2=Girolamo |last2=Fiorentino |first1=Véronique |last1=Zech-Matterne |first3=Sylvie |last3=Coubray |first4=François |last4=Luro|editor1-first=Véronique |editor1-last=Zech-Matterne|editor2-first=Girolamo|editor2-last=Fiorentino |title=AGRUMED: Archaeology and history of citrus fruit in the Mediterranean: Acclimatization, diversification, uses |chapter=Introduction |publisher=Publications du Centre Jean Bérard |year=2017 |isbn=9782918887775|chapter-url =https://books.openedition.org/pcjb/2240}}{{cite journal |last1=Langgut |first1=Dafna |title=The Citrus Route Revealed: From Southeast Asia into the Mediterranean |journal=HortScience |date=June 2017 |volume=52 |issue=6 |pages=814–822 |doi=10.21273/HORTSCI11023-16 |doi-access=free}}{{cite book |first1=Dafna |last1=Langgut |editor1-first=Véronique |editor1-last=Zech-Matterne |editor2-first=Girolamo |editor2-last=Fiorentino |title=AGRUMED: Archaeology and history of citrus fruit in the Mediterranean |chapter=The history of Citrus medica (citron) in the Near East: Botanical remains and ancient art and texts |publisher=Publications du Centre Jean Bérard |year=2017 |isbn=9782918887775 |chapter-url =https://books.openedition.org/pcjb/2184#text}} Oranges were introduced to Florida by Spanish colonists.{{Cite web |url=http://fcit.usf.edu/florida/docs/f/fruit.htm |title=Exploring Florida Documents: Fruit |website=fcit.usf.edu}}{{Cite web |url=https://www.tytyga.com/History-of-the-Citrus-and-Citrus-Tree-Growing-in-America-a/381.htm |title=History of the Citrus and Citrus Tree Growing in America |website=www.tytyga.com}} In cooler parts of Europe, citrus fruit was grown in orangeries starting in the 17th century; many were as much status symbols as functional agricultural structures.{{cite journal |last=Britz |first=Billie S. |title=Environmental Provisions for Plants in Seventeenth-Century Northern Europe |journal=The Journal of the Society of Architectural Historians |volume=33 |issue=2 |date=May 1974 |pages=133–144|doi=10.2307/988906 |jstor=988906 }}

The generic name Citrus originates from Latin, where it denoted either the citron (C. medica) or a conifer tree (Thuja). The Latin word is related to the ancient Greek word for the cedar of Lebanon, {{lang|grc|κέδρος}} ({{lang|grc-Latn|kédros}}), perhaps from a perceived similarity of the smell of citrus leaves and fruit with that of cedar.{{cite book |url=https://books.google.com/books?id=S0-h00_-3CUC |first=Pinchas |last=Spiegel-Roy |author2=Eliezer E. Goldschmidt |title=Biology of Citrus |publisher=Cambridge University Press |year=1996 |isbn=978-0-521-33321-4 |page=4 }}

Citrus plants are large shrubs or small to moderate-sized trees, reaching {{convert|5|–|15|m|abbr=on}} tall, with spiny shoots and alternately arranged evergreen leaves with an entire margin.{{Cite web |url=https://crfg.org/wp-content/uploads/CITRUS-PRUNING-Presentation.pdf |title=Citrus Pruning |last=Del Hotal |first=Tom |website=California Rare Fruit Growers}} The flowers are solitary or in small corymbs, each flower {{convert|2|–|4|cm|abbr=on}} diameter, with five (rarely four) white petals and numerous stamens; they are often very strongly scented, due to the presence of essential oil glands.{{cite book |last1=Ortiz |first1=Jesus M. |editor1-last=Di Giacomo |editor1-first=Angelo |editor2-last=Dugo |editor2-first=Giovanni |title=Citrus: The Genus Citrus |date=2002 |publisher=Taylor & Francis |isbn=978-0-2032-1661-3 |pages=16–35 |url=https://books.google.com/books?id=OLaykfpqSaYC&dq=Citrus+genus&pg=PP1 |chapter=Botany: taxonomy, morphology and physiology of fruits, leaves and flowers}}

{{main list|List of citrus fruits}}

File:Structure of an orange.svg ]]

The fruit is a hesperidium, a specialised berry with multiple carpels, globose to elongated,{{cite web |author=Janick, Jules |date=2005 |publisher=Purdue University Tropical Horticulture Lecture 32 |url=http://www.hort.purdue.edu/newcrop/tropical/lecture_32/lec_32.html |title=Citrus|access-date=28 February 2020|archive-url=https://web.archive.org/web/20050624235046/http://www.hort.purdue.edu/newcrop/tropical/lecture_32/lec_32.html|archive-date=24 June 2005}} {{convert|4|–|30|cm|abbr=on}} long and {{convert|4|–|20|cm|abbr=on}} 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. This surrounds a variable number of carpels, shaped as radial segments. The seeds, if present, develop inside the carpels. 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.{{cite web |url=http://www.botgard.ucla.edu/html/botanytextbooks/economicbotany/Citrus/b1241tx.html |title=Citrus fruit diagram |work=ucla.edu |url-status=dead |archive-url=https://web.archive.org/web/20121003070722/http://www.botgard.ucla.edu/html/botanytextbooks/economicbotany/Citrus/b1241tx.html |archive-date=3 October 2012}} The genus is commercially important with cultivars of many species grown for their fruit. Some cultivars have been developed to be easy to peel and seedless, meaning they are parthenocarpic.

The fragrance of citrus fruits is conferred by flavonoids and limonoids in the rind. The flavonoids include various flavanones and flavones.{{cite web |url=http://www.jstage.jst.go.jp/article/bbb/70/1/70_178/_article |title=Flavonoid Composition of Fruit Tissues of Citrus Species |access-date=5 July 2011 |archive-url=https://web.archive.org/web/20070528015124/http://www.jstage.jst.go.jp/article/bbb/70/1/70_178/_article |archive-date=28 May 2007 |url-status=dead}} The carpels are juicy; they contain a high quantity of citric acid, which with other organic acids including ascorbic acid (vitamin C) give them their characteristic sharp taste.{{cite book |last1=Abolore |first1=Rasaq S. |last2=Tsegaye |first2=Bahiru |last3=Jaiswal |first3=Swarna |last4=Jaiswal |first4=Amit K. |title=Value-Addition in Beverages through Enzyme Technology |chapter=An overview of industrial enzymes in beverage production and processing |publisher=Elsevier |year=2023 |isbn=978-0-323-85683-6 |doi=10.1016/b978-0-323-85683-6.00013-2 |pages=1–26 (section 1.2.3.2 Citrus juice)}} Citrus fruits are diverse in size and shape, as well as in color and flavor, reflecting their biochemistry;{{cite web |url=http://www.ars-grin.gov/cgi-bin/npgs/html/splist.pl?2640 |title=Species list in GRIN for genus Citrus |author=GRIN |work=Taxonomy for Plants |publisher=USDA, ARS, National Genetic Resources Program |location=National Germplasm Resources Laboratory, Beltsville, Maryland |access-date=6 January 2011 |author-link=Germplasm Resources Information Network |url-status=dead |archive-url=https://web.archive.org/web/20090120155922/http://www.ars-grin.gov/cgi-bin/npgs/html/splist.pl?2640 |archive-date=20 January 2009}}{{cite book |last1=Luro |first1=François |last2=Curk |first2=Franck |last3=Froelicher |first3=Yann |last4=Ollitrault |first4=Patrick |title=AGRUMED: Archaeology and history of citrus fruit in the Mediterranean |chapter=Recent insights on Citrus diversity and phylogeny |publisher=Publications du Centre Jean Bérard |date=2017 |isbn=978-2-918887-77-5 |doi=10.4000/books.pcjb.2169}} for instance, grapefruit is made bitter-tasting by a flavanone, naringin.

File:Ichangfruit.jpg|Ichang papeda

File:Quinotos.jpg|Kumquat, with a seed inside one of the carpels

File:Buddhas hand 1.jpg|Buddha's hand

File:Citrus australasica red whole.jpg|Red finger lime

File:Fortpolyandra.jpg|Clymenia

{{Further|Citrus production}}

File:Mandariner Citrus deliciosa.jpg) plantation, Mallorca ]]

Most commercial citrus cultivation uses trees produced by grafting the desired fruiting cultivars onto rootstocks selected for disease resistance and hardiness.{{cite web |title=How to grow citrus fruit |url=https://www.rhs.org.uk/fruit/citrus/grow-your-own |publisher=Royal Horticultural Society |access-date=21 October 2024}} The trees are not generally frost hardy. They thrive in a consistently sunny, humid environment with fertile soil and adequate water.

The color of citrus fruits only develops in climates with a (diurnal) cool winter. In tropical regions with no winter at all, citrus fruits remain green until maturity, hence the tropical "green oranges".{{Cite web |url=https://plantscientist.wordpress.com/2014/12/04/why-is-my-orange-green/ |title=Why is my orange green? |last=Shailes |first=Sarah |date=4 December 2014 |website=Plant Scientist}} The terms 'ripe' and 'mature' are widely used synonymously, but they mean different things. A mature fruit is one that has completed its growth phase. Ripening is the sequence of changes within the fruit from maturity to the beginning of decay. These changes involve the conversion of starches to sugars, a decrease in acids, softening, and a change in the fruit's color.{{cite book |first1=Helgi |last1=Öpik |first2=Stephen A. |last2=Rolfe |first3=Arthur John |last3=Willis |first4=Herbert Edward |last4=Street |title=The Physiology of Flowering Plants |year=2005 |publisher=Cambridge University Press |isbn=978-0-521-66251-2 |pages=309– }} Citrus fruits are non-climacteric and respiration slowly declines and the production and release of ethylene is gradual.{{cite book |first1=Pinchas |last1=Spiegel-Roy |first2=Eliezer E. |last2=Goldschmidt |title=Biology of Citrus |url=https://books.google.com/books?id=S0-h00_-3CUC&pg=PA101 |access-date=31 July 2010 |year=1996 |publisher=Cambridge University Press |isbn=978-0-521-33321-4 |pages=101– }}

{{further|Citrus production}}

File:Hauptanbaugebiete-Zitrusfrüchte.svg

According to the UN Food and Agriculture Organization, world production of all citrus fruits in 2016 was 124 million tonnes, with about half of this production as oranges.{{cite web |title=Citrus fruit, fresh and processed: Statistical Bulletin |url=http://www.fao.org/3/a-i8092e.pdf |publisher=UN Food and Agriculture Organization |access-date=28 February 2020 |date=2016}} At US $15.2 billion equivalent in 2018, citrus tradehttps://oec.world/en/profile/hs/citrus?disaggregationYearSelector=tradeYear3 OEC — The Observer of Economic Complexity, Citrus makes up nearly half of the world fruit trade, which was US$32.1 billion that year.https://oec.world/en/profile/sitc/fruit OEC — The Observer of Economic Complexity, Fruit According to the United Nations Conference on Trade and Development, citrus production grew during the early 21st century mainly by the increase in cultivation areas, improvements in transportation and packaging, rising incomes and consumer preference for healthy foods. In 2019–20, world production of oranges was estimated to be 47.5 million tonnes, led by Brazil, Mexico, the European Union, and China as the largest producers.{{cite web |title=Citrus: World Markets and Trade |url=https://apps.fas.usda.gov/psdonline/circulars/citrus.pdf |publisher=US Department of Agriculture |access-date=28 February 2020 |date=1 January 2020}}

{{main list|List of citrus diseases}}

Among the diseases of citrus plantations are citrus black spot (a fungus), citrus canker (a bacterium), citrus greening (a bacterium, spread by an insect pest), and sweet orange scab (a fungus, Elsinöe australis).{{cite web |title=Citrus diseases |url=https://www.aphis.usda.gov/plant-pests-diseases/citrus-diseases |website=U. S. Department of Agriculture Animal and Plant Health Inspection Service |access-date=20 October 2024 |date=22 August 2024}} Citrus plants are liable to infestation by ectoparasites which act as vectors to plant diseases: for example, aphids transmit the damaging citrus tristeza virus,{{cite journal |last1=Lee |first1=Richard F. |title=Chapter Five - Control of Virus Diseases of Citrus |journal=Advances in Virus Research |date=2015 |volume=92 |pages=143–173 |doi=10.1016/bs.aivir.2014.10.002 |pmid=25591879 }} while the aphid-like Asian citrus psyllid can carry the bacterium which causes the serious citrus greening disease.{{cite journal |last1=Alquézar |first1=Berta |last2=Carmona |first2=Lourdes |last3=Bennici |first3=Stefania |last4=Peña |first4=Leandro |title=Engineering of citrus to obtain huanglongbing resistance |journal=Current Opinion in Biotechnology |publisher=Elsevier |volume=70 |year=2021 |doi=10.1016/j.copbio.2021.06.003 |pages=196–203 |s2cid=235712334 |pmid=34198205|doi-access=free |hdl=10251/189663 |hdl-access=free }}{{cite web |url=http://www.californiacitrusthreat.org/asian-citrus-psyllid.php |title=About the Asian Citrus Psyllid and Huanglongbing |work=californiacitrusthreat.org |access-date=30 November 2012 |archive-date=13 December 2012 |archive-url=https://web.archive.org/web/20121213014128/http://www.californiacitrusthreat.org/asian-citrus-psyllid.php |url-status=dead}} This threatens production in Florida,{{Cite web |url=https://www.nass.usda.gov/Statistics_by_State/Florida/Publications/Citrus/Citrus_Statistics/2015-16/fcs1516.pdf |title=Florida Citrus Statistics 2015–2016 |date=3 October 2017 |website=United States Department of Agriculture – National Agricultural Statistics Service|access-date=3 October 2017 |pages=62 |quote=Abandoned groves are a threat to the citrus industry and are a haven for psyllids carrying the bacterium that causes greening disease.}}{{cite news |last=Nelson |first=Diane|title=Can Science Save Citrus? Farmers, researchers try to hold off deadly citrus greening long enough to find cure |date=27 August 2019 |url=https://www.ucdavis.edu/food/news/can-science-solve-citrus-greening-disease/ |access-date=20 September 2019}} California, and worldwide. Citrus groves are attacked by parasitic Nematodes including citrus (Tylenchulus semipenetrans) and sheath nematodes (Hemicycliophora spp.).{{Cite web |title=Nematodes / Citrus / Agriculture: Pest Management Guidelines / UC Statewide IPM Program |url=https://ipm.ucanr.edu/agriculture/citrus/nematodes/#gsc.tab=0 |access-date=2024-11-14 |website=ipm.ucanr.edu}}A Sheath Nematode, Hemicycliophora arenaria raski, Pathogenic to Citrus, by D. E. Stokes, Florida Department of Agriculture and Consumer Services, July 1977[https://ccmedia.fdacs.gov/content/download/10832/file/nem029.pdf]

File:Citrus Black Spot on Valencia orange (detail).jpg|Citrus black spot on a Valencia orange

File:CTV Leaf Chlorosis.jpg|Chlorosis caused by Citrus tristeza virus

File:Citrus canker on fruit.jpg|Citrus canker, caused by the gammaproteobacterium Xanthomonas axonopodis

File:Asian Citrus Psyllid adult (detail).jpg|Asian citrus psyllid, vector of citrus greening disease

File:Huanglongbing (cropped).jpg|Citrus greening disease on mandarin orange

File:Life stages of citrus nematode.svg|Life stages of the citrus nematode,Tylenchulus semipenetrans

Citrus plants can develop the deficiency condition chlorosis, characterized by yellowing leaves.Online at SumoGardener {{cite web |url=http://sumogardener.com/yellow-leaves-citrus-trees/ |title=How to Avoid Yellow Leaves on Citrus Trees |date=9 July 2016}} The condition is often caused by an excessively high pH (alkaline soil), which prevents the plant from absorbing nutrients such as iron, magnesium, and zinc needed to produce chlorophyll.{{cite web |last1=Mauk |first1=Peggy A. |last2=Shea |first2=Tom |title=Questions and Answers to Citrus Management (3rd ed.) |url=http://ucanr.edu/datastoreFiles/391-272.pdf |publisher=University of California Cooperative Extension |access-date=24 May 2014 |pages=7–8}}

File:Bergapten-from-xtal-3D-bs-17.png (5-methoxypsoralen) is a furanocoumarin in some citrus fruits that causes skin inflammation when followed by ultraviolet light.]]

Some Citrus species contain significant amounts of furanocoumarins.{{cite journal |last1=Chen |first1=Meng |last2=Zhou |first2=Shu-yi |last3=Fabriaga |first3=Erlinda |last4=Zhang |first4=Pian-hong |last5=Zhou |first5=Quan |title=Food-drug interactions precipitated by fruit juices other than grapefruit juice: An update review |journal=Journal of Food and Drug Analysis |volume=26 |issue=2 |year=2018 |issn=1021-9498 |pmid=29703387 |doi=10.1016/j.jfda.2018.01.009 |pages=S61–S71 |pmc=9326888 | doi-access=free}}{{cite journal |last1=Hung |first1=Wei-Lun |last2=Suh |first2=Joon Hyuk |last3=Wang |first3=Yu |title=Chemistry and health effects of furanocoumarins in grapefruit |journal=Journal of Food and Drug Analysis |volume=25 |issue=1 |year=2017 |issn=1021-9498 |doi=10.1016/j.jfda.2016.11.008 |pages=71–83 |pmid=28911545 |pmc=9333421 | doi-access=free}} In humans, some of these act as strong photosensitizers when applied topically to the skin, while others interact with medications when taken orally in the grapefruit juice effect. Due to the photosensitizing effects of certain furanocoumarins, some Citrus species cause phytophotodermatitis,{{cite journal |journal=The Electronic Textbook of Dermatology |url=http://telemedicine.org/botanica/bot1.htm |title=Botanical Dermatology |last1=McGovern |first1=Thomas W. |last2=Barkley |first2=Theodore M. |volume=37 |issue=5 |at=Section [http://telemedicine.org/botanica/bot5.htm Phytophotodermatitis] |publisher=Internet Dermatology Society |date=2000 |access-date=29 November 2018 |pmid=9620476 |doi=10.1046/j.1365-4362.1998.00385.x |s2cid=221810453|url-access=subscription }} 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,{{cite journal |last1=Dugrand-Judek |first1=Audray |last2=Olry |first2=Alexandre |last3=Hehn |first3=Alain |last4=Costantino |first4=Gilles |last5=Ollitrault |first5=Patrick |last6=Froelicher |first6=Yann |last7=Bourgaud |first7=Frédéric |title=The Distribution of Coumarins and Furanocoumarins in Citrus Species Closely Matches Citrus Phylogeny and Reflects the Organization of Biosynthetic Pathways |journal=PLOS ONE |date=November 2015 |volume=10 |issue=11 |page=e0142757 |doi=10.1371/journal.pone.0142757 |pmid=26558757 |pmc=4641707 |bibcode=2015PLoSO..1042757D |doi-access=free}} a linear furanocoumarin derived from psoralen. This claim has been confirmed for lime{{cite journal |journal=Food Chem Toxicol |year=1993 |volume=31 |issue=5 |pages=331–35 |title=Phototoxic coumarins in limes |last1=Nigg |first1=H. N. |last2=Nordby |first2=H. E. |last3=Beier |first3=R. C. |last4=Dillman |first4=A. |last5=Macias |first5=C. |last6=Hansen |first6=R. C. |pmid=8505017 |doi=10.1016/0278-6915(93)90187-4 |url=https://eurekamag.com/pdf/002/002671183.pdf}}{{cite journal |last1=Wagner |first1=A. M. |last2=Wu |first2=J. J. |last3=Hansen |first3=R. C. |last4=Nigg |first4=H. N. |last5=Beiere |first5=R. C. |title=Bullous phytophotodermatitis associated with high natural concentrations of furanocoumarins in limes |journal=Am J Contact Dermat |date=2002 |volume=13 |issue=1 |pages=10–14 |doi=10.1053/ajcd.2002.29948 |pmid=11887098 |issn=0891-5849}} and bergamot. In particular, bergamot essential oil has a higher concentration of bergapten (3–3.6 g/kg) than any other Citrus-based essential oil.{{cite web |work=The German Research Foundation (DFG) |url=https://www.dfg.de/download/pdf/dfg_im_profil/reden_stellungnahmen/2006/sklm_furocoumarine_en_2006.pdf |title=Toxicological Assessment of Furocoumarins in Foodstuffs |publisher=DFG Senate Commission on Food Safety (SKLM) |date=2004 |access-date=1 November 2018 |archive-date=24 December 2019 |archive-url=https://web.archive.org/web/20191224130338/https://www.dfg.de/download/pdf/dfg_im_profil/reden_stellungnahmen/2006/sklm_furocoumarine_en_2006.pdf |url-status=dead |pages=3, 26 }}

A systematic review indicates that citrus fruit consumption is associated with a 10% reduction of risk for developing breast cancer.{{Cite journal |last1=Song |first1=Jung-Kook |last2=Bae |first2=Jong-Myon |date=1 March 2013 |title=Citrus fruit intake and breast cancer risk: a quantitative systematic review |journal=Journal of Breast Cancer |volume=16 |issue=1 |pages=72–76 |doi=10.4048/jbc.2013.16.1.72 |pmc=3625773 |pmid=23593085}}

{{Cookbook|Citrus}}

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.{{cite web |url=http://www.aihd.ku.edu/foods/grapefruit.html |title=Foods Indigenous to the Western Hemisphere: Grapefruit |publisher=Aihd.ku.edu |first=Scott |last=Sheu |website=American Indian Health and Diet Project|archive-url=https://web.archive.org/web/20100818035403/http://www.aihd.ku.edu/foods/grapefruit.html|archive-date=18 August 2010|url-status=dead}} Lemonade is a popular beverage prepared by diluting the juice and adding sugar.{{cite web |url=https://dictionary.cambridge.org/dictionary/english/lemonade |title=Lemonade |website=dictionary.cambridge.org |access-date=October 25, 2018 |archive-date=October 25, 2018 |archive-url=https://web.archive.org/web/20181025190037/https://dictionary.cambridge.org/dictionary/english/lemonade |url-status=live}} Lemon juice is mixed in salad dressings{{cite web |title=Simple green salad with lemon dressing |url=https://www.jamieoliver.com/recipes/vegetables/simple-green-salad-with-lemon-dressing/ |publisher=Jamie Oliver |access-date=21 October 2024}} and squeezed over fruit salad to stop it from turning brown: its acidity suppresses oxidation by polyphenol oxidase enzymes.{{cite web |title=Fruit and vegetables: enzymic browning |date=15 May 2017 |url=https://www.ifst.org/lovefoodlovescience/resources/fruit-and-vegetables-enzymic-browning |publisher=Institute of Food Science and Technology |access-date=21 October 2024}}

A variety of flavors can be derived from different parts and treatments of citrus fruits. The colorful outer skin of some citrus fruits, known as zest, is used as a flavoring in cooking.{{Cite book |last=Bender |first=David |author-link=David A. Bender |title=Oxford Dictionary of Food and Nutrition | publisher=Oxford University Press |year=2009 |isbn=978-0-19-923487-5 |location=New York |pages=[https://archive.org/details/dictionaryoffood00bend/page/215 215] |edition=third |url-access=registration |url=https://archive.org/details/dictionaryoffood00bend/page/215}}

The whole of the bitter orange (and sometimes other citrus fruits) including the peel with its essential oils is cooked with sugar to make marmalade.{{cite news |url=https://www.bbc.co.uk/legacies/work/scotland/perth_tayside/article_2.shtml |publisher=BBC News |title=Legacies: Keiller's: Sticky Success |access-date=20 October 2024}}

File:Fried chicken legs!.JPG|Fried chicken garnished with lemon and onion

File:Calamansi (sliced) - Philippines.jpg|Calamansi, ubiquitous in Philippine condiments

File:Pomeranzen.jpg|Bitter oranges (Citrus × aurantium) are used for marmalade.

File:Bottled Sunshine.jpg|Marmalade, with orange peel

File:Lemonade 2.jpg|Lemonade

File:Orangerie du château de Versailles le 11 septembre 2015 - 78.jpg, 1686]]

By the 17th century, orangeries were added to great houses in Europe, both to enable the fruit to be grown locally and for prestige, as seen in the Versailles Orangerie.{{Cite journal |last1=Thacker |first1=Christopher |author2-link=Louis XIV |last2=Louis XIV |date=1972 |title="La Manière de montrer les jardins de Versailles," by Louis XIV and others |journal=Garden History |volume=1 |issue=1 |pages=53, 55 |doi=10.2307/1586442 |issn=0307-1243 |jstor=1586442}} Some modern hobbyists grow dwarf citrus in containers or greenhouses in areas where the weather is too cold to grow it outdoors; Citrofortunella hybrids have good cold resistance.{{Cite book |title=Citrus : complete guide to selecting & growing more than 100 varieties for California, Arizona, Texas, the Gulf Coast and Florida |last=Lance |first=Walheim |date=1996 |publisher=Ironwood Press |isbn=978-0-9628236-4-0 |location=Tucson, Arizona |oclc=34116821 |url-access=registration |url=https://archive.org/details/citruscompletegu00walh |pages=24–28, 90–91}}

File:Giovanna Garzoni (Italian) - Still Life with Bowl of Citrons - Google Art Project.jpg's Still Life with Bowl of Citrons, late 1640s]]

Lemons appear in paintings, pop art, and novels. A wall painting in the tomb of Nakht in 15th century BC Egypt depicts a woman in a festival, holding a lemon. In the 17th century, Giovanna Garzoni painted a Still Life with Bowl of Citrons, the fruits still attached to leafy flowering twigs, with a wasp on one of the fruits. The impressionist Edouard Manet depicted a lemon on a pewter plate. In modern art, Arshile Gorky painted Still Life with Lemons in the 1930s.{{cite news |last=Reidy |first=Tess |title=The king of zing: lemons in art – in pictures |url=https://www.theguardian.com/artanddesign/gallery/2024/mar/23/the-king-of-zing-lemons-in-art-in-pictures |work=The Guardian |date=23 March 2024}}

Citrus fruits "were the clear status symbols of the nobility in the ancient Mediterranean", according to the paleoethnobotanist Dafna Langgut. In Louisa May Alcott's 1868 novel Little Women, the character Amy March states that "It's nothing but limes now, for everyone is sucking them in their desks in schooltime, and trading them off for pencils, bead rings, paper dolls, or something else… If one girl likes another, she gives her a lime; if she’s mad with her, she eats one before her face, and doesn’t offer even a suck."{{cite web |last=Huang |first=Jean |title=When Life Gives You Lemons, It's a Status Symbol: On the Evolving Literary and Cultural History of Citrus |url=https://lithub.com/when-life-gives-you-lemons-its-a-status-symbol-on-the-evolving-literary-and-cultural-history-of-citrus/ |website=LitHub |access-date=20 October 2024 |date=1 October 2021}}

• Japanese citrus

{{reflist|30em}}

• [http://www.crec.ifas.ufl.edu/ Citrus Research and Education Center] of IFAS

{{Citrus}}

{{Taxonbar|from=Q81513}}

{{Authority control}}

Category:Cocktail garnishes

Category:Garden plants

Citrus fruits

Category:Lists of plants

Category:Ornamental trees

Category:Aurantioideae genera

Category:Taxa named by Carl Linnaeus