TheKey lime, also known asWest Indian lime, Mexican lime, orEgyptian lime (Citrus ×aurantiifolia orC. aurantifolia)[1] is a type oflime. While it is treated as a species in botanical classification, it originated as a natural hybrid betweenCitrus micrantha (a wild papeda) andCitrus medica (citron).
The Key lime has thinnerrind and is smaller, seedier, more acidic, and more aromatic than thePersian lime (Citrus × latifolia). It is valued for its characteristic flavor. The name comes from its association with theFlorida Keys, where it is best known as theflavoring ingredient inKey lime pie. The Key lime is not to be confused with bartender's lime or the Omani lime, which are slightly different. The last is classified as a distinctrace, with a thicker skin and darker green color. Philippine varieties have various names, including "dayap" and "bilolo".[2]
The English wordlime was derived, viaSpanish thenFrench, from the Arabic wordليمةlīma, which is, in turn, a derivation of thePersian wordlimuلیمو.[3]Key is fromFlorida Keys, where the fruit was naturalized. The earliest known use of the name is from 1905, where the fruit was described as "the finest on the market. It is aromatic, juicy, and highly superior to the lemon."[4]
C. aurantiifolia is a shrubby tree, growing to 5 metres (16 feet), with manythorns. Dwarfvarieties 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 the trunk. Theleaves are ovate, 2.5–9 centimetres (1–3+1⁄2 inches) long, resemblingorange leaves (the scientific nameaurantiifolia referring to this resemblance to the leaves ofCitrus aurantium). Theflowers 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 the Northern Hemisphere.[5][6]
Termed small-fruited acid lime, as opposed to large-fruited acid lime (Tahitian or Persian lime), it has a spherical fruit, 3-6 cm in diameter, sometimes with apical papillae, greenish-yellow; peel very thin, very densely glandular; segments with yellow-green pulp-vesicles, very acid, juicy and fragrant. Seeds are small, plump, ovoid, pale, smooth with white embryos (polyembryonic). The Key lime is usually picked while it is still green, but it becomes yellow when ripe.
Map of inferred original wild ranges of the mainCitrus cultivars, and selected relevant wild taxa[9]
'Mexican' lime and its clonal derivatives like 'West Indian' lime, 'Kagzi' lime and 'Key' lime are the most common cultivars ofCitrus aurantifolia[10]. Other small-fruited acid limes are cultivated in certain regions only; examples are, 'Abhayapuri' lime, 'Everglade' lime, 'Egyptian' lime, and 'India' lime.
The Key lime has given rise to several other lime varieties. The best known, thetriploid progeny of a Key lime-lemon cross, is thePersian lime (Citrus × latifolia), the most widely produced lime, globally. Others are, like their parent, classed withinC. aurantiifolia.Backcrossing withcitron 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 amandarin-pomelo cross similar to the oranges has produced the Kirk lime. The New Caledonia and Kaghzi limes appear to have resulted from anF2 Key lime self-pollination, while a spontaneous genomic duplication gave us thetetraploid Giant Key lime.[11][12] The potential to produce a wider variety of lime hybrids from the Key lime due to its tendency to formdiploid gametes may reduce the disease risk presented by the limited diversity of the current commercial limes.[13]
In California in the late 19th century, "Mexican" limes were more highly valued than lemons; however, in Florida, they were generally considered weeds. Then, in 1894–95, theGreat 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 the1926 Miami hurricane ripped them up, they were replanted with the hardier, thornless Persian limes.[15]
There are various approaches to the cultivation of Key limes. This variety ofcitrus can be propagated from seed and will grow true to the parent. The seeds must be kept moist until they can be planted, as they will not germinate if allowed to dry out.[citation needed] If the plants are propagated from seed, the seeds should be stored at least 5–6 months before planting.[16] Alternatively, vegetative propagation from cuttings or byair layering may permit fruit production within one year, and from genetically more predictable lines of plants. Another method, digging around a mature tree to sever roots, will encourage new sprouts that can be transplanted to another location.[citation needed] Clones are often bud grafted[17] into roughlemon orbitter orange to obtain strong root stocks.
It is often advisable to graft the plants onto rootstocks with low susceptibility togummosis because seedlings generally are highly vulnerable to the disease. Useful rootstocks include wild grapefruit,cleopatra mandarin andtahiti limes.[16]C. macrophylla 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,[18][19] good air circulation, and protection from cold wind. Because its root system 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.[16]
The method of cultivation greatly affects 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 andair 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 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.[16]
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 arelative humidity of 75–85%. Special procedures are employed to control the shelf life; for example, applications ofgrowth 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 is a coating ofcoconut oil that improves shelf life, thereby achieving a constant market supply of Key limes.[20]
Key limes are made intoblack lime by boiling them inbrine 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.[16]
The annual Key Lime Festival inKey West, Florida, has been held every year since 2002 over theIndependence Day weekend and is a celebration of Key limes in food, drinks, and culture, with a significant emphasis onKey lime pie.[21]
^Ali, Muhammad Amjad; Nawaz, Muhammad Azher (2017), "Advances in Lime Breeding and Genetics", in Khan, M. Mumtaz; Al-Yahyai, Rashid; Al-Said, Fahad (eds.),The Lime: Botany, Production and Uses, CAB International, pp. 37–53
^Bisen A., Pandey S.K., Patel N.:Effect of skin coatings on prolonging shelf life of kagzi lime fruits (Citrus aurantiifolia Swingle). Journal of Food Science and Technology (2012) 49(6).753-759. (page 139–145)
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