Orange (fruit)


Orange (fruit)
Orange
Orange blossoms and oranges on tree
Scientific classification
Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Rosids
Order: Sapindales
Family: Rutaceae
Genus: Citrus
Species: C. × sinensis
Binomial name
Citrus × sinensis
(L.) Osbeck[1]

An orange—specifically, the sweet orange—is the citrus Citrus × ​sinensis (Citrus Sinensis (L.) Osbeck) and its fruit.[2] It is the most commonly grown tree fruit in the world.[3]

The orange is a hybrid of ancient cultivated origin, possibly between pomelo (Citrus maxima) and mandarin (Citrus reticulata).[4] It is an evergreen flowering tree generally growing to 9–10 m in height (although very old speciments have reached 15 m).[5] The leaves are arranged alternately, are ovate in shape with crenulate margins and are 4–10 cm long.[6] The orange fruit is a hesperidium, a type of berry.[7]

Orange trees are widely cultivated in tropical and subtropical climates for the delicious sweet fruit, which is peeled or cut (to avoid the bitter rind) and eaten whole, or processed to extract orange juice, and also for the fragrant peel.[8] In 2008, 68.5 million tons of oranges were grown worldwide, primarily in Brazil and the state of Florida in the US.[9]

Oranges probably originated in Southeast Asia[8] and were cultivated in China by 2500 BC. The fruit of Citrus sinensis is called sweet orange to distinguish it from Citrus aurantium, the bitter orange. The name is thought to derive ultimately from the Sanskrit[10] for the orange tree, with its final form developing after passing through numerous intermediate languages.

In a number of languages, it is known as a "Chinese apple" (e.g. Dutch Sinaasappel, "China's apple", or northern German Apfelsine).[11] (In English, however, "Chinese apple" generally refers to the pomegranate).[12]

Contents

Terminology and scope

Orange fruit and cross section

All citrus trees are of the single genus, Citrus, and remain almost entirely interfertile; that is, there is only one "superspecies" which includes grapefruits, lemons, limes, oranges, and numerous other types and hybrids.[13]

Nevertheless, names have been given to the various members of the genus. The name "orange" applies primarily to the sweet orange, Citrus sinensis, which accounts for about 70% of world citrus production.[14] This article is limited to Citrus sinensis and its hybrids.

Other citrus species known as oranges include:

  • The bitter orange, Citrus aurantium, also known as Seville orange, sour orange (especially when used as rootstock for a sweet orange tree), bigarade orange, and marmalade orange.
  • The bergamot orange, Citrus bergamia Risso, which is grown primarily in Italy and used primarily for the peel, which flavours Earl Grey tea.
  • The mandarin orange Citrus reticulata, which itself has an enormous number of cultivars (most notably the satsuma (C. unshiu), tangerine (Citrus × tangerina) and clementine (C. clementina). In some cultivars the mandarin resembles the sweet orange and is difficult to distinguish from it, but it is generally smaller and/or oblate rather than round in shape, easier to peel, and less acid.[15]
  • The trifoliate orange (Poncirus trifoliata) is sometimes included in the genus and classified as an orange (Citrus trifoliata). It is often used as rootstock for sweet orange trees, especially as a hybrid with other Citrus cultivars. The trifoliate orange is a thorny shrub or small tree grown primarily for its foliage and flowers, or as a barrier hedge; however, it bears a downy fruit resembling a small citrus fruit, from which marmalade is sometimes made. It is native to northern China and Korea, and is also known as "hardy orange" (because it can withstand sub-freezing temperatures) or "Chinese bitter orange".[16]

Taxonomy of the orange (and citrus in general) presents difficulties; the interfertility of citrus has resulted in numerous hybrids, bud unions, and cultivars; taxonomy is often controversial, confusing, or inconsistent.[4][14]

The fruit of a member of the genus Citrus is considered a hesperidium, a kind of modified berry, because it has numerous seeds, is fleshy and soft, derives from a single ovary, and is covered by a rind created by a leathery thickening of the ovary wall.[7][17] An orange seed is called a "pip".[18] The white thread-like material attached to the inside of the peel is called pith.[19]

Although the sweet orange will grow to different sizes and colours according to local conditions, it most commonly has ten carpels, or segments, inside. Unripe fruit is green. The pebbled exterior of ripe fruit can be bright orange to yellow-orange, but often retains a considerable amount of the green colour of unripe fruit.

Orange trees are generally grafted; the bottom part of the tree, including the roots and trunk, is called the rootstock, while the fruit-producing top part of the tree is called budwood (when talking about the process of grafting) or scion (when talking about the variety of orange).[20]

Citrus Sinensis (L.) Osbeck is broken down into four groups with distinct characteristics: Common oranges, blood oranges, navels, and acidless oranges.[21][22][23]

Varieties

Common oranges

Common oranges (also called "white", "round" or "blond" oranges) make up about two-thirds of all oranges grown and include all oranges not described in one of the other three groups. They are used primarily for juice production.[21][23]

Valencia

The Valencia or Murcia orange is one of the sweet oranges used for juice extraction. It is a late-season fruit, and therefore a popular variety when the navel oranges are out of season. For this reason, the orange was chosen to be the official mascot of the 1982 FIFA World Cup, which was held in Spain. The mascot was called "Naranjito" ("little orange"), and wore the colours of the Spanish football team uniform.

Hart's Tardiff Valencia

Thomas Rivers, an English nurseryman, imported this variety from the Azores Islands and catalogued it in 1865 under the name Excelsior. About 1870, he provided trees to S. B. Parsons, a Long Island nurseryman, who sold trees to E. H. Hart of Federal Point, Florida.[24]

Hamlin

The Hamlin orange was once the most important juice orange in Florida, replacing the inferior Parson Brown variety as the principal early-season juice orange. Today it is the predominant early-season orange grown in Florida and Brazil. It thrives in humid subtropical climates and is for that reason found primarily in Florida and Brazil; cooler, more arid climates (such as California) produce edible fruit, but the size is too small for commercial use.[5]

The cultivar was discovered in 1879 near Glenwood, Florida, in a grove later owned by A.G. Hamlin. It is small, smooth, not highly coloured, seedless and juicy, but the juice is pale. The fruit is of poor to medium quality but the tree is high-yielding and cold-tolerant. The fruit is harvested from October to December and this cultivar is now the leading early orange in Florida and possibly the world's principal variety of very early maturing common sweet orange.[5]

On pineland and hammock soil it is budded on sour orange which gives a high solids content. On sand, it does best on rough lemon rootstock.[3]

Other varieties of common oranges

  • Balta (Pakistan)
  • Belladonna (Italy)
  • Berna – Grown mainly in Spain
  • Biondo Commune ("common blond") is widely grown in the Mediterranean basin, especially in North Africa and Egypt; Greece, where it is called the Koines; Italy, where it is also known as the Liscio; and Spain. It is also called the Beledi and Nostrale.[21] In Italy, this variety ripens in December, earlier than the competing Tarocco.[25]
  • Biondo Riccio (Italy)
  • Cadanera is a seedless orange of excellent flavour grown Algeria, Morocco and Spain, where it is quite popular. It is known by a wide variety of trade names, including Cadena Fina, Cadena sin Jueso, Precoce de Valence (early Valencia), Precoce des Canaries, and Valence san Pepins (seedless Valencia).[21] It was first grown in Spain in 1870. It begins to ripen in November.[26]
  • Calabrese or Calabrese Ovale (Italy)
  • Carvalhal (Portugal)
  • Castellana (Spain
  • Clanor (S. Africa)
  • Don Jao (Portugal)
  • Fukuhara (Japan)
  • Gardner (Florida) This midseason orange ripens around February 1, about the same time as Midsweet. Gardner is about as cold hardy as Sunstar and Midsweet.[27]
  • Hamlin (worldwide)
  • Homosassa (Florida)
  • Jaffa
  • Jincheng – the most popular orange in China.
  • Joppa (S. Africa, Texas)
  • Khettmali (Israel, Lebanon)
  • Kona is a type of Valencia orange introduced to Hawaii in 1792 by Captain George Vancouver, whose ship's surgeon and naturalist, Archibald Menzies, raised the seedlings on board and gave them to several Hawaiian chefs. In Kailua-Kona, some of this original stock still bears fruit. For several decades in the 19th century, these oranges were the leading export from the Kona district on the Big Island of Hawaii.
  • Lue Gim Gong (Florida) An early scion developed by Lue Gim Gong, a Chinese immigrant known as the "Citrus Genius". In 1888, Lue cross-pollinated the "Harts late" Valencia and "Mediterranean Sweet" orange varieties, which produced a fruit both sweet and frost-tolerant. Originally considered a hybrid, the "Lue Gim Gong" orange was later found to be a nucellar seedling of the "Valencia" variety,[28] which is properly called the "'Lue Gim Gong". Distributed by Glen St. Mary Nurseries, the variety was awarded the Silver Wilder Medal by the American Pomological Society in 1911, the first such award for a citrus fruit.[3][29] As of 2006, the "Lue Gim Gong" variety is still grown in Florida, but is sold under the general name "Valencia".
  • Macetera (Spain) Known for its unique flavour.
  • Maltaise Blonde (North Africa)
  • Maltaise Ovale (South Africa), grown in California as Garey's or California Mediterranean Sweet.
  • Marrs (California, Iran, Texas) relatively low in acid
  • Midsweet (Florida) Midsweet is a newer scion similar to the Hamlin and Pineapple. It ripens later than Pineapple and is cold-hardier. Fruit yield and quality are similar to the Hamlin although the juice is deeper-coloured.[27]
  • Moro Tarocco is popular in Italy and is ovoid in shape, resembling a tangelo, with a distinctive caramel-coloured endocarp. The original mutation occurred in the 17th century in Sicily, creating the striking caramel-toned endocarp. This colour is the result of the pigment called anthocarpium, not usually found in citrus, but is common in other red fruits and flowers.
  • Mosambi (India, Pakistan) So low in acid and insipid-tasting that it might be classified as acidless.
  • Parson Brown (Florida, Mexico, Turkey) 'Parson Brown', once a widely-grown Florida juice orange, has declined in popularity as new varieties with more juice, better yield, and higher acid and/or sugar content have been developed. It originated as a chance seedling at the home of Reverend N. L. Brown near Webster, Florida, in 1865. Its fruit are round, medium large, has a thick, pebbly peel and contains 10–30 seeds. It is still grown because it is the earliest maturing fruit in the United States; it usually matures in early September in the Valley district of Texas,[23] and from early October to January in Florida.[27] Both peel and juice colour are poor, as is juice quality.[23]
  • Pera (Brazil) – popular in the Brazilian citrus-producing industry, yielding 7.5 million tons in 2005.
  • Pera Coroa (Brazil)
  • Pera Natal (Brazil)
  • Pera Rio (Brazil)
  • Pineapple (North and South America, India)
  • Premier (S. Africa)
  • Rhode Red is a mutation of the Valencia orange, but has a more highly coloured flesh, more juice, and less acidity than the Valencia. It also has less Vitamin C. It was discovered in 1955 in a grove near Sebring, Florida, by Paul Rhode.
  • Roble was first shipped from Madrid, Spain, in 1851 by Joseph Roble to his homestead in what is now Roble's Park in Tampa, Florida. It is known for high sugar content.
  • Queen (S. Africa)
  • Salustiana (North Africa)
  • Sathgudi (South India)
  • Seleta, Selecta (Australia, Brazil) High in acid
  • Shamouti (Africa, Asia, Greece) Sweet
  • Shamouti Jaffa (Israel) is a mutation of an earlier and inferior Palestinian variety, dating from around 1850. The tree is considered ornamental due to dense foliage, large leaves, and absence of thorns. It is harvested in Israel from December through May.
  • Shamouti Masry (Egypt) A richer variety than Shamouti
  • Sunstar (Florida) A newer cultivar, the Sunstar ripens mid-season (December–March. The juice colour is darker than the competing Hamlin and it is more resistant to cold and fruit-drop than the competing mid-season Pineapple variety.[27]
  • Tomango (S. Africa)
  • Verna (Algeria, Mexico, Morocco, Spain)
  • Vicieda (Algeria, Morocco, Spain)
  • Westin (Brazil)

Navel oranges

Navel oranges are characterized by the growth of a second fruit at the apex, which protrudes slightly and resembles a human navel. They are primarily used for eating, as the skin is thicker and easier to peel than a common orange, they are less juicy, and a bitterness from limonin during processing renders them less satisfactory for juice.[21] They are very popular because of their use as an eating orange, their widespread distribution, and their long growing season; in the United States, they are available from November through April, with peak supplies in January, February and March.[30]

A peeled sectioned navel orange. The underdeveloped twin is located on the bottom right.

According to Dorsett, Shamel, and Popenoe (1917) of the U.S. Department of Agriculture who conducted a study at first hand, a single mutation in 1810 to 1820 in a Selecta orange tree planted at a monastery near Bahia in Brazil, probably yielded the navel orange, also known as the Washington, Riverside, or Bahia navel.[31] However, a researcher at the University of California, Riverside, believes that the parent variety was more likely the Portuguese navel (Umbigo) orange described by Risso and Poiteau (1818–22).[31] The mutation causes the orange to develop a second orange at the base of the original fruit, opposite the stem, as a conjoined twin in a set of smaller segments embedded within the peel of the larger orange. From the outside, it looks similar to the human navel, hence its name.

Because the mutation left the fruit seedless, and therefore sterile, the only means available to cultivate more of this new variety is to graft cuttings onto other varieties of citrus tree. It was introduced into Australia in 1824 and Florida in 1835. Twelve such cuttings of the original tree were transplanted[32] to Riverside, California in 1870, which eventually led to worldwide popularity.[31] The California Citrus State Historic Park preserves this history in Riverside, California, as does the Orcutt Ranch Horticulture Center in Los Angeles County, California.

Today, navel oranges continue to be produced through cutting and grafting. This does not allow for the usual selective breeding methodologies, and so not only do the navel oranges of today have exactly the same genetic makeup as the original tree, and are therefore clones, all navel oranges can be considered to be the fruit of that single nearly two-hundred-year-old tree. The case is similar to that of the common yellow seedless banana, the Cavendish. On rare occasions, however, further mutations can lead to new varieties.[31]

Cara cara navels

Cara cara orange slices on the left.

Cara cara oranges (also called "red navel") are a type of navel orange grown primarily in Venezuela, South Africa, and California's San Joaquin Valley. The bright orange exterior of cara cara oranges is similar to other navels, but their interior is a distinctive pinkish red. They are sweet and comparatively low in acid.[33]

It is believed to have developed as a cross between the Washington navel and the Brazilian Bahia navel.[34] It was discovered at the Hacienda de Cara Cara in Valencia, Venezuela in 1976.[35]

From the major growing regions, South African cara caras are ready for market starting in August, Venezuelan fruits arrive in October and Californian fruits make their seasonal debut in late November.[33][34]

Other varieties of navels

  • Dream Navel
  • Bahianinha or Bahia
  • Late Navel
  • Washington or California Navel

Blood oranges

Blood oranges, which are very widely grown in Spain and Italy (as "sangüina" or "sanguigna", respectively) are characterized by dark red pigmentation. They are considered, in general, the most delicious juice orange.[21]

Comparison between the inside and the outside of both the regular and blood orange.

Blood oranges are a natural variety of C. sinensis derived from abnormal pigmentation of the fruit that gives its pulp a streaked red colour. The juice produced from such oranges is often dark burgundy, hence reminiscent of blood. Original blood oranges were first discovered and cultivated in the 15th century in Sicily; since then, however, their cultivation spread worldwide, and most blood oranges today are hybrids.

The fruit has found a niche as an interesting ingredient variation on traditional Seville marmalade, with its striking red streaks and distinct flavour. The scarlet navel is a variety with the same dual-fruit mutation as the navel orange.

Other varieties of blood oranges

  • Tarocco is a relatively new variety developed in Italy. It begins to ripen in late January.[25]
  • Sanguinelli is cultivated in Sicily and is actually a mutant of the Doble Fina. It was discovered in 1929 at Almenara, in the Castellón province of Spain.
  • Moro (Italy) Originally from Sicily, it is common throughout Italy. The medium-sized fruit has a relatively long harvest, lasting from December through to April.
  • Maltese is small and highly-coloured. It is often used in sorbets and other desserts due to the rich burgundy colour. It is generally thought to have originated in Italy as a mutation (although the Maltese claim origin) and has been cultivated there for centuries. It is also extensively grown in southern Spain and Malta.

Acidless oranges

Acidless oranges are an early-season fruit with very low levels of acid. They are also called "sweet" oranges in the US, with similar names in other countries: douce in France, sucrena in Spain, dolce (or maltese) in Italy, meski in North Africa and the Near East (where their peculiar rather bland taste is especially popular), lokkum in Turkey, succari in Egypt, and lima in Brazil.[21]

The lack of acid, which protects orange juice against spoilage in other groups, renders them generally unfit for processing, due to spoilage, so that they are primarily eaten rather than juiced. They remain profitable in areas of local consumption, but rapid spoilage renders them unsuitable for export to major population centers of Europe, Asia, or the United States.[21]

History of cultivation

The sweet orange does not occur in the wild. It is believed to have been first cultivated in southern China, northeastern India, or perhaps southeastern Asia (formerly Indochina).[3]

The Persian orange, grown widely in southern Europe after its introduction to Italy in the 11th century, was bitter. It was used primarily for medicinal purposes.[3]

Italian traders might have introduced it to the Mediterranean area after 1450. Portuguese navigators have also been credited with bringing orange trees to the Mediterranean region around 1500.[3] After introduction of the sweet orange, it was quickly adopted as an edible fruit; it was so highly regarded that wealthy persons grew oranges in private conservatories, called orangeries. Certainly by 1646 it was well-known in Europe.[3]

In some South East Indo-European languages the orange was named after Portugal, which was formerly the main source of imports of sweet oranges. Examples are Bulgarian portokal портокал, Greek portokali πορτοκάλι, Persian portaghal پرتقال, Albanian portokall, Macedonian portokal портокал, and Romanian portocală. In Italian the word portogallo to refer to the orange fruit is dialectal.[36] It means literally "Portugal". Similar words are in common use in most Italian dialects across the whole country.[37] Related names can also be found in other languages: Turkish portakal, Arabic al-burtuqal البرتقال, Amharic birtukan, and Georgian p'ort'oxali ფორთოხალი.

Portuguese, Spanish, Arab, and Dutch sailors planted citrus trees along trade routes to prevent scurvy. On his second voyage in 1493, Christopher Columbus took the seeds of oranges, lemons and citrons to Haiti and the Caribbean. They were introduced in Florida (along with lemons) in 1513 by Spanish explorer Juan Ponce de León, to California by the Franciscans in the 18th century, and were introduced to Hawaii in 1792.

Spaniards undoubtedly introduced the sweet orange into South America and Mexico in the mid-1500s, and probably the French took it to Louisiana. It was from New Orleans that seeds were obtained and distributed in Florida about 1872 and many orange groves were established by grafting the sweet orange onto sour orange rootstocks. Arizona received the orange tree with the founding of missions between 1707 and 1710. The orange was brought to San Diego, California, by those who built the first mission there in 1769. An orchard was planted at the San Gabriel Mission around 1804. A commercial orchard was established in 1841 on a site that is now a part of Los Angeles. In 1781, a surgeon and naturalist on the ship Discovery collected orange seeds in South Africa, grew seedlings on board and presented them to tribal chiefs in the Hawaiian Islands on arrival in 1792. In time, the orange became commonly grown throughout Hawaii, but was virtually abandoned after the arrival of the Mediterranean fruit fly, and the fruit is now imported from the United States mainland.[3]

Attributes

Nutritional value

Orange, raw, Florida
Nutritional value per 100 g (3.5 oz)
Energy 192 kJ (46 kcal)
Carbohydrates 11.54 g
- Sugars 9.14 g
- Dietary fiber 2.4 g
Fat 0.21 g
Protein 0.70 g
Thiamine (vit. B1) 0.100 mg (9%)
Riboflavin (vit. B2) 0.040 mg (3%)
Niacin (vit. B3) 0.400 mg (3%)
Pantothenic acid (B5) 0.250 mg (5%)
Vitamin B6 0.051 mg (4%)
Folate (vit. B9) 17 μg (4%)
Vitamin C 45 mg (54%)
Calcium 43 mg (4%)
Iron 0.09 mg (1%)
Magnesium 10 mg (3%)
Phosphorus 12 mg (2%)
Potassium 169 mg (4%)
Zinc 0.08 mg (1%)
Percentages are relative to US recommendations for adults.
Source: USDA Nutrient Database

Acidity

Like all citrus fruits, the orange is acidic: pH levels have been reported by reliable sources as low as 2.9[38] and as high as 4.0[38][39]

Grading

Florida

  • Whole oranges: The USDA has established the following grades for Florida oranges, which primarily affects oranges sold as fruit: U.S. Fancy, U.S. No. 1 Bright, U.S. No. 1, U.S. No. 1 Golden, U.S. No. 1 Bronze, U.S. No. 1 Russet, U.S. No. 2 Bright, U.S. No. 2, U.S. No. 2 Russet, and U.S. No. 3.[40] The general characteristics graded are colour (both hue and uniformity), firmness, maturity, varietal characteristics, texture, and shape.

Grade numbers are determined by the amount of unsightly blemishes to the skin and firmness of the fruit (which do not affect consumer safety). The USDA separates blemishes into three categories:

    • General blemishes, including: ammoniation, buckskin, caked melanose, creasing, decay, scab, split navels, sprayburn, undeveloped segments, unhealed segments and wormy fruit.
    • Injuries to fruit, including: bruises, green spots, oil spots, rough, wide, or protruding navels, scale, scars, skin breakdown, and thorn scratches.
    • Damage caused by dirt or other foreign material, disease, dryness or mushy condition, hail, insects, riciness or woodiness, and sunburn.[40]
The terms Bright, Golden, Bronze and Russet apply solely to discolouration. Fancy, the highest grade, requires the highest grade of both colour and blemishes.
  • Fruit for juice: The USDA uses a separate grading system for oranges used for juice (where appearance and texture is irrelevant). There are only two grades, U.S. Grade AA Juice and U.S. Grade A Juice. (Note that this is a grade given to the oranges prior to processing.) Juice grades are determined by three factors: (1) the juiciness of the orange; (2) the amount of solids in the juice (at least 10% solids being required for the AA grade); and (3) the proportion of anhydric citric acid to fruit solids.

Orange peel

Orange peel contains citral, an aldehyde that antagonizes the action of vitamin A. Therefore, anyone eating quantities of orange peel should make certain that their dietary intake of Vitamin A is sufficient.[41]

Production

Two areas dominate orange growth and especially production of orange juice. The southeast coast of Brazil, surrounding São Paulo, produces more oranges than the next three countries combined. As almost 99% of the fruit from this region is processed for export, it is the overwhelming giant in worldwide orange juice production.

Mid-south Florida produces about half as many oranges as Brazil; however, the bulk of its orange juice is sold domestically. The Indian River area of Florida is known for the high quality of its juice, which is often sold fresh in the US. Because of the low yield and high quality of Indian River oranges, their juice is often blended with juice from other regions.[42]

Production of orange juice between these two makes up roughly 85% of the world market. Brazil exports 99% of its production, while 90% of Florida's production is consumed in the US.[43]

Orange juice is traded internationally in the form of frozen concentrated orange juice to reduce the volume used, so that storage and transportation costs are lower.[44]

Orange output in 2005
Top orange producers
(million tons)
2005 2008
 Brazil 17.8 18.5
 United States 8.4 9.1
 India 3.1 4.4
 Mexico 4.1 4.3
 China 2.4 3.7
 Spain 2.3 3.3
 Iran 2.0 2.6
 Italy 2.2 2.5
 Indonesia 2.2 2.3
 Egypt 1.8 2.1
 Pakistan 1.6 1.7
World Total 61.7 68.5
Source:
UN Food & Agriculture Organisation (FAO)
[45]

Oranges grown for commercial production are grown in groves and are produced throughout the world. Brazil is by far the greatest producing area, followed by Florida, which accounts for 80% of the United States' crop.

Brazil

Brazil is the largest orange-producing nation in the world, and production is located primarily in the state of São Paulo, which accounts for approximately 80% of Brazil's production and 53% of total global FCOJ (frozen concentrated orange juice) production (in the region of Campinas, São Carlos, São José do Rio Preto and Barretos, and the western part of the state of Minas Gerais). In Brazil, the four major orange varieties of orange used for processing orange juice are the Hamlin, Pera Rio, Natal and Valencia.[46][47]

Cultivation

Propagation

Propagation of orange trees is deceptively difficult, because hardy edible oranges are not generally grown from seed. Cultivars that produce good quality fruit are highly susceptible to root diseases. Grafted trees also begin bearing fruit many years earlier than trees reproduced by seed.[48]

Other benefits of grafting include more accurate reproduction of good fruit traits than plants derived from seed, and the opportunity to alter tree size, productivity, and other traits through rootstock influence, while maintaining identical fruit characteristics.[48]

Almost all orange trees are propagated in two stages. First, rootstock is grown from seed. When the seedling is well-established, the leafy top is cut off, and budwood from an existing tree is grafted onto the rootstock. It is the budwood that determines the variety of orange that is grown.

Sour orange, resistant to phytophthora parasitica (root rot or "foot rot"), was the preferred rootstock in Florida, especially in low hammock and flatwoods soils with high water table, until the discovery of the virus disease tristeza in Florida orange groves in 1952. Some were grown on sweet orange or rough lemon rootstock, but these are poor choices. Sweet orange is highly vulnerable to numerous pests and diseases, especially root rot, and lemon rootstock results in oranges that lack juice and sugar. Lemon rootstock, however, produces rapid growth and early fruiting. Sour rootstock is itself susceptible to a number of diseases, most notably the tristeza virus, which is carried by nematodes.

As citrus-growing stretched southward into high pineland, rough lemon (Citrus jambhiri) rootstock gained favour and was found to induce more rapid and vigorous growth and earlier bearing, counterbalancing its sensitivity to cold and tendency toward foot rot. Rough lemon became the dominant rootstock in Florida until it was found to be extremely susceptible to blight and was abandoned. Sour orange has been reinstated in recent years because tristeza has been more or less dormant since the 1940s and sour orange is now the prevailing stock for 50% of the orange trees in the state.[3]

Principle rootstocks – United States

Today, five types of rootstock predominate in (comparatively) cool climates where there is chance of cold, or especially freezing, weather (notably Florida and Southern Europe):

  • Sour rootstock ("standard sour orange") is still used and is the only one of the five that is actually an orange; it is highly drought resistant and generally vigorous.
  • Poncirus trifoliata. Poncirus trifoliata is a close relative of the Citrus genus, and is actually known as the "trifoliate orange" and "Chinese bitter orange"; in fact, it is sometimes classified as Citrus trifoliata. It is grown as an ornamental flowering shrub and is extremely cold tolerant compared to true citrus.
It makes excellent rootstock under certain conditions; it is especially resistant to cold, tristeza virus and phytophthora parasitica (root rot), and grows well in heavy clay/loam soil. It is the slowest growing of the rootstocks, however, and has poor resistance to heat and drought. It is primarily used in China, Japan, and parts of California with heavy soils.[49]
  • Swingle citrumelo. On April 1, 1974, the U.S. Department of Agriculture released to citrus nurserymen and growers the 'Swingle' citrumelo citrus rootstock. This rootstock selection was hybridized by Walter Tennyson Swingle at Eustis, Florida, in 1907, from Citrus paradisi Macf. 'Duncan' grapefruit X Poncirus trifoliata (L.) Raf. Swingle citrumelo is tolerant of tristeza virus and Phytophthora parasitica (root rot) and moderately tolerant of salt and freezing.[50]
  • Citrange (Troyer citrange and Carrizo citrange). Citranges are hybrids of the Washington navel orange and Poncirus trifoliata. The original crosses were made in the early 1900s by the United States Department of Agriculture with the intention of producing cold tolerant scion varieties. They were later identified as being suitable for use as rootstocks.
Commercial use of these rootstocks began in Australia in the 1960s. They have become very successful orange rootstock; the Troyer variety is generally found in California, while the Carrizo variety is used in Florida. The benefits are phytophthora (root rot) tolerance, nematode tolerance, tristeza virus tolerance, good cold tolerance, and reasonable vigor. They are also highly polyembryonic, so growers get multiple plants from a single seed. Citrange, however, does not do well in clay, calcareous, or high pH soil, and is sensitive to salinity (all except clay being characteristic of coastal areas). (It also is not usable as rootstock for mandarin scions, as it "overgrows" them, i.e. the rootstock will produce branches of its own in competition with the grafted budwood.)[51]
  • 'Cleopatra' mandarin. Cleopatra mandarin originated in India and was introduced into Florida from Jamaica in the mid 19th century. Cleopatra mandarin has been widely distributed and trialled as a rootstock throughout the world. It is used primarily in Florida, Spain and Australia for shallow alkaline soils, due to its rare ability to tolerate alkalinity and salinity often present in such otherwise ideal environments as south Florida. Dade County, Florida, for example, has 85% calcareous soil, as is typical of land previously under water.[52] In most other respects, it is an inferior rootstock.[53]

Other rootstock varieties – United States

  • African shaddock X trifoliate hybrid[31]
  • Benton citrange trifoliate hybrid[31]
  • Borneo Rangpur lime[31]
  • Bitters C-22 citrange ('X Citroncirus sp.' Rutaceae) Bitters C-22 is not related to the bitter orange, but was named in honor of William P. Bitters. It was hybridized at the USDA US Date and Citrus Station in Indio, California, and developed further by the University of California, Riverside. It is used primarily as rootstock for navel oranges in California; however, a recent report suggested its usefulness in Texas to replace sour orange due to its tolerance of calcareous soil conditions.[54][55]
  • Carpenter C-54 citrange[55]
  • C-32 citrange trifoliate hybrid[31]
  • C-35 citrange trifoliate hybrid[31]
  • Calamondin kumquat hybrid[31]
  • Carrizo citrange trifoliate hybrid[31]
  • Citradia trifoliate hybrid[31]
  • Citremon trifoliate hybrid (CRC 1449)[31]
  • Citrumelo trifoliate hybrid C190[31]
  • Citrumelo trifoliate hybrid (CRC 1452)[31]
  • Citrumelo trifoliate hybrid (CRC 4475)[31]
  • Citrus macrophylla (Alemow)[31]
  • Citrus volkameriana Volkamer lemon[31]
  • Cleopatra mandarin[31]
  • Cleopatra mandarin X trifoliate hybrid X639[31]
  • Flying dragon trifoliate (CRC 3330A)[31]
  • Fraser Seville sour orange[31]
  • Furr C-57 citrange[55]
  • Goutoucheng sour orange (CRC 3929)[31]
  • Goutoucheng sour orange (CRC 4004)[31]
  • Grapefruit seedling (CRC 343)[31]
  • Pomeroy trifoliate[31]
  • Rangpur lime X Troyer citrange hybrid[31]
  • Rich 16-6 trifoliate[31]
  • Rubidoux trifoliate[31]
  • Rusk citrange trifoliate orange[31]
  • Satsuma X trifoliate hybrid[31]
  • Schaub rough lemon[31]
  • Small-leaf trifoliate[31]
  • Smooth Flat Seville sour orange[31]
  • Sun Chu Sha Kat mandarin[31]
  • US 119 (Grapefruit X trifoliate) X Sweet Orange hybrid[31]
  • Vangassay rough lemon[31]
  • Yuma Ponderosa lemon pummelo hybrid[31]
  • Zhuluan sour orange hybrid (CRC 3930)[31]
  • Zhuluan sour orange hybrid (CRC 3981)[31]

Climate

Orange tree in the National Botanic Garden of Belgium – Plant Palace – Meise (Belgium).

Oranges can be grown outdoors in warmer climates, and indoors in cooler climates. Like most citrus plants, oranges will not do well unless kept between 15.5 °C – 29 °C (60 °F – 85 °F). Orange trees grown from the seeds of a store-bought fruit may not produce fruit, and any fruit that is produced may be different than the parent fruit, due to modern techniques of hybridization. To grow the seed of a store-bought orange, one must not let the seed dry out (an approach used for many citrus plants). One method is to put the seeds between the halves of a damp paper towel until they germinate, and then plant them. Many just plant them straight into the soil, making sure to water them regularly. Oranges require a huge amount of water and the citrus industry in the Middle East is a contributing factor to the desiccation of the region.

Oranges are sensitive to frost, and a common treatment to prevent frost damage when sub-freezing temperatures are expected is to spray the trees with water, since as long as unfrozen water is turning to ice on the trees' branches, the ice that has formed stays just at the freezing point, giving protection even if air temperatures have dropped far lower.[56]

Another strategy to prevent freezing of orange crops and trees is burning fuel oil in smudge pots (also known as a choofa or orchard heater). These burn with a great deal of particulate emission. Condensation of water vapor on particulate soot prevents condensation on plants and raises air temperature very slightly. Smudge pots were first developed after a disastrous freeze in Southern California in January 1913 wiped out a whole crop.[57]

Harvesting

Canopy-shaking mechanical harvesters are increasingly being used in Florida to harvest process oranges. Current canopy shaker machines use a series of six- to seven-foot long tines to shake the tree canopy at a relatively constant shaking stroke and frequency.[58]

Diseases and pests

Cottony cushion scale

The first major pest attacking orange trees in the United States was the cottony cushion scale (Icerya purchasi), which was imported from Australia to California in 1868. Within 20 years, it had wiped out the citrus industry around Los Angeles and seriously limited orange growth throughout California.

In 1888, the USDA sent Alfred Koebele to Australia to study the scale in its native habitat. He brought back with him specimens of an Australian ladybird beetle, Novius cardinalis, and within a decade the scale had been controlled or eradicated throughout the state.[24]

Citrus greening disease

As of 2010, the most serious threat to orange production is Citrus Greening Disease (Liberobacter asiaticum), an insect-vectored bacterium. Although common in parts of Asia, it was first reported in the Western Hemisphere in 2004 in Brazil, by Fundecitrus Brasil. (The insects that carry it were discovered in Florida in 1998.) Since then, it has attacked nearly 100% of the trees in Florida.[59] As of 2009, 87% of the trees in Brazil's primary orange growing areas (São Paulo and Minas Gerais) showed symptoms of greening, an increase of 50% over 2008.[60]

The disease is characterized by blotchy mottle on the leaves, and misshapen, poorly coloured, off-tasting fruit. In areas where the disease is endemic, citrus trees may live for only 5–8 years and never bear usable fruit.[59]

The Asian citrus psyllid (ACP), Diaphorina citri Kuwayama, is an invasive insect pest of citrus in Brazil and Florida. It is an efficient vector of the bacterium, Liberobacter asiaticum, causal organism of citrus greening disease or "Huanglongbing" (HLB). The pest was first detected in Florida in 1998 and now occurs on all citrus throughout the state. HLB was first detected in Florida 2005 and is spreading rapidly. Generalist predators such as the ladybeetles, Curinus coeruleus, Olla v-nigrum, Harmonia axyridis, and Cycloneda sanguinea, and lacewings such as Ceraeochrysa spp. and Chrysoperla spp. make significant contribution to the mortality of ACP, resulting in 80–100% reduction in psyllid populations.

In contrast, parasitism by Tamarixia radiata, a species-specific parasitoid of ACP, is variable and generally low in southwest Florida, averaging less than 12% during May through September and 50% in November 2006.

Foliar applications of insecticides reduced psyllid populations for a short time at best, but also suppressed the populations of predatory ladybeetles. Soil application of aldicarb provided limited control of ACP while drenches of imidacloprid to young trees were effective for two months or more.[61]

Management of citrus greening disease is difficult and requires an integrated approach including use of clean stock, elimination of inoculum via voluntary and regulatory means, use of pesticides to control psyllid vectors in the citrus crop, and biological control of psyllid vectors in non-crop reservoirs. Nowhere in the world where citrus greening disease occurs is it under completely successful management.[59]

Greasy spot

Greasy spot, caused by Mycosphaerella citri, produces leaf spots and defoliation of orange trees reducing tree vigor and yield. The fungus produces air-borne ascospores from pseudothecia in decomposing leaf litter on the grove floor.[62]

Storage and processing

After harvesting, oranges have a shelf life of about one week at room temperature and one month refrigerated.[63] In either case, they are optimally stored loosely in an open or perforated plastic bag.[63] Oranges produce odours that are absorbed by meat, eggs and dairy products.[63]

Degreening

Oranges cannot be artificially ripened and must be mature when harvested. (In Texas,[64] Arizona, California, and Florida, laws forbid harvesting immature fruit for human consumption.) Ripe oranges, however, often have some green or yellow-green colour in the skin. Ethylene gas is used to turn green skin orange. The process is called "degreening", or sometimes, "gassing", "sweating" or "curing". Its purpose is to remove the green colour from otherwise mature fruit.

Degreening is used primarily in the early fall when night temperatures have not been low enough for the peel to develop its characteristic mature colour. Late oranges such as Valencia sometimes regreen during the spring growth flush and may also be degreened.

Recommended degreening conditions include 82 to 85 °F temperature, 92 to 95% relative humidity and 1 to 5 ppm ethylene. Air circulation within the degreening room should produce about one change per minute. In addition, outside air ventilation should be adequate to maintain carbon dioxide level below one percent, which normally requires about one complete change of air per hour.

Degreening time varies with the amount of green colour, size of fruit and some cultural practices, e.g., excessive nitrogen fertilization promoting vigorous growth and oil-emulsion sprays after mid-July. Maximum degreening times in the US are 48 to 60 hours for oranges, but the degreening period should be as short as possible.[64]

Etymology

The word orange is derived from Sanskrit नारङ्ग nāraṅgaḥ "orange tree."[65] The Sanskrit word is in turn borrowed from the Dravidian root for 'fragrant'. In Tamil, a bitter orange is known as நரண்டம் 'Narandam', a sweet orange is called நகருகம் 'nagarugam' and நாரி 'naari' means fragrance.[66] In Telugu the orange is called నరిఙ‌ 'naringa'. The Sanskrit word was borrowed into European languages through Persian نارنگ nārang, Armenian նարինջ nārinj, Arabic نارنج nāranj, (Spanish-language naranja and Portuguese laranja), Late Latin arangia, Italian arancia or arancio, and Old French orenge, in chronological order. The first appearance in English dates from the 14th century. The forms starting with n- are older, and this initial n- may have been mistaken as part of the indefinite article, in languages with articles ending with an -n sound (e.g., in French une norenge may have been taken as une orenge), a process called juncture loss. The name of the colour is derived from the fruit, first appearing in this sense in 1542.

Some languages have different words for the bitter and the sweet orange, such as Modern Greek nerantzi and portokali, respectively. Or in Persian, the words are narang and porteghal (Portugal), in the same order. The reason is that the sweet orange was brought from China or India to Europe during the 15th century by the Portuguese. Some languages refer to it as Applesin (or variants), which means "Apple from China",[citation needed] while in Puerto Rico "jugo de china" refers to orange juice,[67] The bitter orange was introduced through Persia.

Several Slavic languages use the variants pomaranč (Slovak), pomeranč (Czech), pomaranča (Slovene), pomarańcza (Polish) from old French pomme d'orenge.[68]

Juice and other products

Oranges and orange juice
Kinnow, a variety of Mandarin orange widely cultivated in Pakistan
Octyl ethanoate is responsible for the fragrance of oranges.

Oranges are widely grown in warm climates worldwide, and the flavours of oranges vary from sweet to sour. The fruit is commonly peeled and eaten fresh, or squeezed for its juice. It has a thick bitter rind that is usually discarded, but can be processed into animal feed by removal of water, using pressure and heat. It is also used in certain recipes as flavouring or a garnish. The outer-most layer of the rind can be grated or thinly veneered with a tool called a zester, to produce orange zest. Zest is popular in cooking because it contains the oil glands and has a strong flavour similar to the fleshy inner part of the orange. The white part of the rind, called the pericarp or albedo and including the pith, is a source of pectin and has nearly the same amount of vitamin C as the flesh.

Products made from oranges

  • Orange juice is one of the commodities traded on the New York Board of Trade. Brazil is the largest producer of orange juice in the world, followed by the USA. It is made by squeezing the fruit on a special instrument called a "juicer" or a "squeezer." The juice is collected in a small tray underneath. This is mainly done in the home, and in industry is done on a much larger scale.
  • Frozen orange juice concentrate is made from freshly squeezed and filtered orange juice.[69]
  • Sweet orange oil is a by-product of the juice industry produced by pressing the peel. It is used as a flavouring of food and drink and for its fragrance in perfume and aromatherapy. Sweet orange oil consists of about 90% d-limonene, a solvent used in various household chemicals, such as to condition wooden furniture, and along with other citrus oils in grease removal and as a hand-cleansing agent. It is an efficient cleaning agent which is promoted as being environmentally friendly and preferable to petroleum distillates.

However, d-Limonene is classified from slightly toxic to humans[70] to very toxic to marine life[71] in different countries. Its smell is considered more pleasant by some than those of other cleaning agents.

Although once thought to cause renal cancer in rats, limonene now is known as a chemopreventive agent[72] with potential value as a dietary anti-cancer tool in humans.[73] There is no evidence for carcinogenicity or genotoxicity in humans. The Carcinogenic Potency Project estimates that it causes human cancer on a level roughly equivalent to that caused by exposure to caffeic acid via dietary coffee intake.[74] The IARC classifies d-limonene under Class 3: not classifiable as to its carcinogenicity to humans.[75]

  • The orange blossom, which is the state flower of Florida, is highly fragrant and traditionally associated with good fortune. It has long been popular in bridal bouquets and head wreaths for weddings.
  • Orange blossom essence is an important component in the making of perfume.
  • The petals of orange blossom can also be made into a delicately citrus-scented version of rosewater; orange blossom water (aka orange flower water) is a common part of both French and Middle Eastern cuisines, most often as an ingredient in desserts and baked goods.
  • In the United States, orange flower water is used to make orange blossom scones and marshmallows.
  • The orange blossom gives its touristic nickname to the Costa del Azahar ("Orange-blossom coast"), the Castellon seaboard.
  • In Spain, fallen blossoms are dried and then used to make tea.
  • Orange blossom honey, or actually citrus honey, is produced by putting beehives in the citrus groves during bloom, which also pollinates seeded citrus varieties. Orange blossom honey is highly prized, and tastes much like orange.
  • Marmalade, a conserve usually made with Seville oranges. All parts of the orange are used to make marmalade: the pith and pips are separated, and typically placed in a muslin bag where they are boiled in the juice (and sliced peel) to extract their pectin, aiding the setting process.
  • Orange peel is used by gardeners as a slug repellent.
  • Orange leaves can be boiled to make tea.
  • Orange wood sticks (also spelt orangewood) are used as cuticle pushers in manicures and pedicures, and as spudgers for manipulating slender electronic wires
  • Orange wood is a flavouring wood in meat grilling much as mesquite, oak, pecan and hickory are used.

See also

Footnotes

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  3. ^ a b c d e f g h i Morton, J., Fruits of Warm Climates (1987) Miami, FL, pp. 134–142.
  4. ^ a b Nicolosi, E.; Deng, Z. N.; Gentile, A.; La Malfa, S.; Continella, G.; Tribulato, E. (2000). "Citrus phylogeny and genetic origin of important species as investigated by molecular markers". TAG Theoretical and Applied Genetics 100 (8): 1155–1166. doi:10.1007/s001220051419. 
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  6. ^ Citrus sinensis – Encyclopedia of Life. EOL. Retrieved on 2011-10-02.
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  75. ^ IARC Monographs on the evaluation of carcinogenic risks to humans. 73-16. 1999. pp. 307–27. http://monographs.iarc.fr/ENG/Monographs/vol73/mono73-16.pdf. 

References

  • McPhee, John. Oranges (1966) – focuses on Florida groves.
  • Sackman, Douglas Cazaux. Orange Empire: California and the Fruits of Eden (2005) comprehensive, multidimensional history of citrus industry in California
  • Train, John. Oranges (2006)

External links


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