C. × paradisi
|Citrus × paradisi|
The grapefruit (Citrus × paradisi) is a subtropical citrus tree known for its sour to semi-sweet, somewhat bitter fruit. Grapefruit is a hybrid originating in Barbados as an accidental cross between two introduced species, sweet orange (C. sinensis) and pomelo, or shaddock (C. maxima), both of which were introduced from Asia in the seventeenth century.  When found, it was named the " forbidden fruit";  and frequently, it has been misidentified with the pomelo. 
The evergreen grapefruit trees usually grow to around 5–6 meters (16–20 ft) tall, although they may reach 13–15 m (43–49 ft). The leaves are glossy, dark green, long (up to 15 centimeters (5.9 in)), and thin. It produces 5 cm (2 in) white four-petaled flowers. The fruit is yellow-orange skinned and generally, an oblate spheroid in shape; it ranges in diameter from 10–15 cm (3.9–5.9 in). The flesh is segmented and acidic, varying in color depending on the cultivars, which include white, pink, and red pulps of varying sweetness (generally, the redder varieties are the sweetest). The 1929 U.S. Ruby Red (of the Redblush variety) has the first grapefruit patent. 
The genetic origin of the grapefruit is a hybrid mix.  One ancestor of the grapefruit was the Jamaican sweet orange (Citrus sinensis), itself an ancient hybrid of Asian origin; the other was the Indonesian pomelo (C. maxima). One story of the fruit's origin is that a certain "Captain Shaddock"  brought pomelo seeds to Jamaica and bred the first fruit,  however, it probably originated as a naturally occurring hybrid between the two plants some time after they had been introduced there. 
The Trunk, Leaves, and Flowers of this Tree, very much resemble
those of the Orange-tree.
The Fruit, when ripe, is something longer and larger than the largest
Orange; and exceeds, in the Delicacy of its Taste, the Fruit of every
Tree in this or any of our neighbouring Islands.
It hath somewhat of the Taste of a Shaddock; but far exceeds that, as
well as the best Orange, in its delicious Taste and Flavour.
—Description from Hughes' 1750 Natural History of Barbados
The hybrid fruit, then called "the forbidden fruit", was first documented in 1750 by a Welshman, Rev. Griffith Hughes, who described specimens from Barbados in The Natural History of Barbados.   Currently, the grapefruit is said to be one of the "Seven Wonders of Barbados". 
The grapefruit was brought to Florida by Count Odet Philippe in 1823 in what is now known as Safety Harbor. Further crosses have produced the tangelo (1905), the Minneola tangelo (1931), and the oroblanco (1984).
The grapefruit was known as the shaddock or shattuck until the nineteenth century.  Its current name alludes to clusters of the fruit on the tree, which often appear similar to that of grapes.  Botanically, it was not distinguished from the pomelo until the 1830s, when it was given the name Citrus paradisi. Its true origins were not determined until the 1940s. This led to the official name being altered to Citrus × paradisi, the "×" identifying its hybrid origin.  
An early pioneer in the American citrus industry was Kimball Atwood, a wealthy entrepreneur who founded the Atwood Grapefruit Company in the late nineteenth century. The Atwood Grove became the largest grapefruit grove in the world, with a yearly output of 80,000 boxes of fruit.  It was there that pink grapefruit was first discovered in 1906. 
The 1929 Ruby Red patent was associated with real commercial success, which came after the discovery of a red grapefruit growing on a pink variety. Using radiation to trigger mutations, new varieties were developed to retain the red tones which typically faded to pink.  The Rio Red variety is the current (2007) Texas grapefruit with registered trademarks Rio Star and Ruby-Sweet, also sometimes promoted as "Reddest" and "Texas Choice". The Rio Red is a mutation bred variety that was developed by treatment of bud sticks with thermal neutrons. Its improved attributes of mutant variety are fruit and juice color, deeper red, and wide adaptation. 
The Star Ruby is the darkest of the red varieties. Developed from an irradiated Hudson grapefruit,  it has found limited commercial success because it is more difficult to grow than other varieties.  
|Top eleven grapefruit (inc. pomelos) producers — 2012|
|Country||Production ( metric tons)||Footnote|
|People's Republic of China||3,800,000||F|
|No symbol = official figure, P = official figure, F = FAO estimate, * = Unofficial/Semi-official/mirror data, C = Calculated figure A = Aggregate (may include official, semi-official or estimates);|
Grapefruit comes in many varieties. One way to differentiate between varieties is by the flesh color of fruit they produce.  The most popular varieties currently cultivated are red, white, and pink hues, referring to the internal pulp color of the fruit. The family of flavors range from highly acidic and somewhat sour, to sweet and tart.  Grapefruit mercaptan, a sulfur-containing terpene, is one of the substances which has a strong influence on the taste and odor of grapefruit, compared with other citrus fruits. 
This happens in two very different ways. In the first, the effect is from bergamottin, a natural furanocoumarin in both grapefruit flesh and peel that inhibits the CYP3A4 enzyme, (among others from the P450 enzyme family responsible for metabolizing 90% of drugs). The action of the CYP3A4 enzyme itself is to metabolize many medications.   If the drug's breakdown for removal is lessened, then the level of the drug in the blood may become too high or stay too long, leading to adverse effects.  On the other hand, some drugs must be broken down to become active, and inhibiting CYP3A4 may lead to reduced drug effects.
The other effect is that grapefruit can block the absorption of drugs in the intestine.  If the drug is not absorbed, then not enough of it is in the blood to have a therapeutic effect.  Each affected drug has either a specific increase of effect or decrease.
One whole grapefruit, or a glass of 200 mL (6.8 US fl oz) of grapefruit juice may cause drug overdose toxicity.  Typically, drugs that are incompatible with grapefruit are so labeled on the container or package insert.  People taking drugs should ask their health care provider or pharmacist questions about grapefruit and drug interactions. 
|Nutritional value per 100 g (3.5 oz)|
|Energy||138 kJ (33 kcal)|
|Dietary fiber||1.1 g|
|Pantothenic acid (B5)|
|†Percentages are roughly approximated using
US recommendations for adults. |
Source: USDA Nutrient Database
Grapefruit is a rich source of vitamin C (>20% of the Daily Value, DV in a 100 gram serving),   contains the fiber pectin,  and the pink and red hues contain the beneficial antioxidant lycopene.   Studies have shown grapefruit helps lower cholesterol,   and there is evidence that the seeds have antioxidant properties.  Grapefruit forms a core part of the " grapefruit diet", the theory being that the fruit's low glycemic index is able to help the body's metabolism burn fat. 
Although grapefruit seed extract (GSE) is promoted as a plant-based preservative by some natural personal care manufacturers, studies have shown that the apparent antimicrobial activity associated with GSE preparations is merely due to contamination with synthetic preservatives such as parabens.     
In Costa Rica, especially in Atenas, grapefruit are often cooked to remove their sourness, rendering them as sweets; they are also stuffed with dulce de leche, resulting in a dessert called toronja rellena (stuffed grapefruit).  In Haiti, grapefruit is used primarily for its juice (jus de Chadèque), but also is used to make jam (confiture de Chadèque).  
Grapefruit has also been investigated in cancer medicine pharmacodynamics. Its inhibiting effect on the metabolism of some drugs may allow smaller doses to be used, which can help to reduce costs. 
The grapefruit is a parent to many hybrids:
Tangelo is any hybrid of a
tangerine and either a
pomelo or a grapefruit
- ' Minneola': Duncan grapefruit × Dancy tangerine 
- 'Orlando' (formerly 'Take'): Bowen grapefruit × Dancy tangerine(pollen parent) 
- 'Seminole': Bowen grapefruit × Dancy tangerine 
- 'Thornton': tangerine × grapefruit, unspecified 
- ' Ugli': mandarin × grapefruit, probable (wild seedling) 
- 'Nova' is a second-generation hybrid: Clementine × Orlando tangelo cross 
- The Oroblanco and Melogold grapefruits are hybrids between pummelo (Citrus maxima) and the grapefruit
The grapefruit's cousins include:
- Common sweet orange: pummelo × mandarin hybrid
- Bitter orange: a different pummelo × mandarin hybrid
- Mandelos: pummelo × mandarine ( Citrus maxima)
- Hyuganatsu may also be a pumelo hybrid
- Carrington, Sean; Fraser, HenryC (2003). "Grapefruit". A~Z of Barbados Heritage. Macmillan Caribbean. pp. 90–91.
One of many citrus species grown in Barbados. This fruit is believed to have originated in Barbados as a natural cross between sweet orange (C. sinesis) and Shaddock (C. grandis), both of which originated in Asia and were introduced by Europeans in the seventeenth century. The grapefruit first appeared as an illustration entitled "The Forbidden Fruit Tree" in The Natural History of Barbados (1750) by Rev. Griffith Hughes. This accords with the scientific name which literally is "citrus of paradise". The fruit seems to have been fairly commonly available around that time, since George Washington in his Barbados Journal (1750-1751) mentions "the Forbidden Fruit" as one of the local fruit available at a dinner party he attended. The plant was later described in the 1837 Flora of Jamaica as the Barbados Grapefruit. The historical arguments and experimental work on leaf enzymes and oils from possible parents all support a Barbadian origin for the fruit.
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The Development of the Gully - The Gully was once part of a plantation owned by a Welshman called General William Asygell Williams over 200 years ago. Hence the name "Welchman Hall" gully. It was this man who first developed the gully with exotic trees and an orchard. Interestingly, the grapefruit is originally from Barbados and is rumoured to have started in Welchman Hall Gully.
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