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Coffea

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Coffea is a genus of flowering plants in the family Rubiaceae. Coffea species are shrubs or small trees native to tropical and southern Africa and tropical Asia. The seeds of some species, called coffee beans, are used to flavor various beverages and products. The fruits, like the seeds, contain a large amount of caffeine, and have a distinct sweet taste.

The plant ranks as one of the world's most valuable and widely traded commodity crops and is an important export product of several countries, including those in Central and South America, the Caribbean and Africa. The coffee trade relies heavily on two of the over 120 species, Coffea arabica (commonly known simply as "Arabica"), which accounts for 60–80% of the world's coffee production, and Coffea canephora (known as "Robusta"), which accounts for about 20–40%. Both coffee species are vulnerable to shifting growing zones caused by climate change, likely to result in a decline in production in some of the most important growing regions.

Cultivation and use

Freshly harvested coffee cherries
Freshly harvested coffee cherries
Coffea fruits, Bali

There are over 120 species of Coffea, which is grown from seed. The two most popular are Coffea arabica (commonly known simply as "Arabica"), which accounts for 60–80% of the world's coffee production, and Coffea canephora (known as "Robusta"), which accounts for about 20–40%. C. arabica is preferred for its sweeter taste, while C. canephora has a higher caffeine content. C. arabica has its origins in the highlands of Ethiopia and the Boma Plateau of Sudan, and was the result of a hybrid between C. canephora and C. eugenioides.

The trees produce edible red or purple fruits, which are described either as epigynous berries or as indehiscent drupes. The fruit is often referred to as a "coffee cherry," and it contains two seeds, called "coffee beans." Despite these terms, coffee is neither a true cherry (the fruit of certain species in the genus Prunus) nor a true bean (seeds from plants in the family Fabaceae).

In about 5–10% of any crop of coffee fruits, only a single bean is found. Called a peaberry, it is smaller and rounder than a normal coffee bean.

When grown in the tropics, coffee is a vigorous bush or small tree that usually grows to a height of 3–3.5 m (9.8–11.5 ft). Most commonly cultivated coffee species grow best at high elevations, but do not tolerate freezing temperatures.

The tree of Coffea arabica will grow fruits after three to five years, producing for an average of 50 to 60 years, although up to 100 is possible. The white flowers are highly scented. The fruit takes about nine months to ripen.

Coffea flower
Coffea fruit cross section
Coffea arabica beans germinating
Ripe Coffea arabica fruits
Beans inside a Coffea arabica fruit
Coffea branches

Ecology

The caffeine in coffee beans serves as a toxic substance protecting the seeds of the plant, a form of natural plant defense against herbivory. Caffeine simultaneously attracts pollinators, specifically honeybees, by creating an olfactory memory that signals bees to return to the plant's flowers. Not all Coffea species contain caffeine, and the earliest species had little or no caffeine content. Caffeine has evolved independently in multiple lineages of Coffea in Africa, perhaps in response to high pest predation in the humid environments of West-Central Africa. Caffeine has also evolved independently in the more distantly related genera Theobroma (cacao) and Camellia (tea). This suggests that caffeine production is an adaptive trait in coffee and plant evolution. The fruit and leaves also contain caffeine, and can be used to make coffee cherry tea and coffee-leaf tea. The fruit is also used in many brands of soft drink as well as pre-packaged teas.

Several insect pests affect coffee production, including the coffee borer beetle (Hypothenemus hampei) and the coffee leafminer (Leucoptera caffeina).

Coffee is used as a food plant by the larvae of some Lepidoptera (butterfly and moth) species, Dalcera abrasa, turnip moth and some members of the genus Endoclita, including E. damor and E. malabaricus.

Research

New species of Coffea are still being identified in the 2000s. In 2008 and 2009, researchers from the Royal Botanic Gardens, Kew named seven from the mountains of northern Madagascar, including C. ambongensis, C. boinensis, C. labatii, C. pterocarpa, C. bissetiae, and C. namorokensis.

In 2008, two new species were discovered in Cameroon. Coffea charrieriana, which is caffeine-free, and Coffea anthonyi. By crossing the new species with other known coffees, two new features might be introduced to cultivated coffee plants: beans without caffeine and self-pollination.

In 2011, Coffea absorbed the twenty species of the former genus Psilanthus due to the morphological and genetic similarities between the two genera. Historically, the two have been considered distinct genera due to differences in the length of the corolla tube and the anther arrangement: Coffea with a short corolla tube and exserted style and anthers; Psilanthus with a long corolla tube and included anthers. However, these characteristics were not present in all species of either respective genus, making the two genera overwhelmingly similar in both morphology and genetic sequence. This transfer expanded Coffea from 104 species to 124, and extended its native distribution to tropical Asia and Australasia.

In 2014, the coffee genome was published, with more than 25,000 genes identified. This revealed that coffee plants make caffeine using a different set of genes from those found in tea, cacao and other such plants.

In 2017, a robust and almost fully resolved phylogeny of the entire genus was published. In addition to resolving the relationships of Coffea species, this study's results suggest Africa or Asia as the likely ancestral origin of Coffea and point to several independent radiations across Africa, Asia, and the Western Indian Ocean Islands.

In 2020 a technique of DNA fingerprinting, or genetic authentication of plant material was proven effective for coffee. For the study, scientists used DNA extraction and SSR marker analysis. This technique or ones similar may allow for several improvements to coffee production such as improved information for farmers as to the susceptibility of their coffee plants to pests and disease, a professionalized coffee seed system, and transparency and traceability for buyers of green, un-roasted coffee.

Species

  1. Coffea abbayesii J.-F.Leroy
  2. Coffea affinis De Wild.
  3. Coffea alleizettii Dubard
  4. Coffea ambanjensis J.-F.Leroy
  5. Coffea ambongenis J.-F.Leroy ex A.P.Davis
  6. Coffea andrambovatensis J.-F.Leroy
  7. Coffea ankaranensis J.-F.Leroy ex A.P.Davis
  8. Coffea anthonyi Stoff. & F.Anthony
  9. Coffea arabica L.
  10. Coffea arenesiana J.-F.Leroy
  11. Coffea augagneurii Dubard
  12. Coffea bakossii Cheek & Bridson
  13. Coffea benghalensis B.Heyne ex Schult.
  14. Coffea bertrandii A.Chev.
  15. Coffea betamponensis Portères & J.-F.Leroy
  16. Coffea bissetiae A.P.Davis & Rakotonas.
  17. Coffea boinensis A.P.Davis & Rakotonas.
  18. Coffea boiviniana A.P.Davis & Rakotonas.
  19. Coffea bonnieri Dubard
  20. Coffea brassii (J.-F.Leroy) A.P.Davis
  21. Coffea brevipes Hiern
  22. Coffea bridsoniae A.P.Davis & Mvungi
  23. Coffea buxifolia A.Chev.
  24. Coffea canephora ("Coffea robusta") Pierre ex A.Froehner
  25. Coffea carrissoi A.Chev.
  26. Coffea charrieriana Stoff. & F.Anthony
  27. Coffea cochinchinensis Pierre ex Pit.
  28. Coffea commersoniana (Baill.) A.Chev.
  29. Coffea congensis A.Froehner
  30. Coffea costatifructa Bridson
  31. Coffea coursiana J.-F.Leroy
  32. Coffea dactylifera Robbr. & Stoff.
  33. Coffea decaryana J.-F.Leroy
  34. Coffea dubardii Jum.
  35. Coffea ebracteolata (Hiern) Brenan
  36. Coffea eugenioides S.Moore
  37. Coffea fadenii Bridson
  38. Coffea farafanganensis J.-F.Leroy
  39. Coffea floresiana Boerl.
  40. Coffea fotsoana Stoff. & Sonké
  41. Coffea fragilis J.-F.Leroy
  42. Coffea fragrans Wall. ex Hook.f.
  43. Coffea gallienii Dubard
  44. Coffea grevei Drake ex A.Chev.
  45. Coffea heimii J.-F.Leroy
  46. Coffea homollei J.-F.Leroy
  47. Coffea horsfieldiana Miq.
  48. Coffea humbertii J.-F.Leroy
  49. Coffea humblotiana Baill.
  50. Coffea humilis A.Chev.
  51. Coffea jumellei J.-F.Leroy
  52. Coffea kapakata (A.Chev.) Bridson
  53. Coffea kianjavatensis J.-F.Leroy
  54. Coffea kihansiensis A.P.Davis & Mvungi
  55. Coffea kimbozensis Bridson
  56. Coffea kivuensis Lebrun
  57. Coffea labatii A.P.Davis & Rakotonas.
  58. Coffea lancifolia A.Chev.
  59. Coffea lebruniana Germ. & Kester
  60. Coffea leonimontana Stoff.
  61. Coffea leroyi A.P.Davis
  62. Coffea liaudii J.-F.Leroy ex A.P.Davis
  63. Coffea liberica Hiern
  64. Coffea ligustroides S.Moore
  65. Coffea littoralis A.P.Davis & Rakotonas.
  66. Coffea lulandoensis Bridson
  67. Coffea mabesae (Elmer) J.-F.Leroy
  68. Coffea macrocarpa A.Rich.
  69. Coffea madurensis Teijsm. & Binn. ex Koord.
  70. Coffea magnistipula Stoff. & Robbr.
  71. Coffea malabarica (Sivar., Biju & P.Mathew) A.P.Davis
  72. Coffea mangoroensis Portères
  73. Coffea mannii (Hook.f.) A.P.Davis
  74. Coffea manombensis A.P.Davis
  75. Coffea mapiana Sonké, Nguembou & A.P.Davis
  76. Coffea mauritiana Lam.
  77. Coffea mayombensis A.Chev.
  78. Coffea mcphersonii A.P.Davis & Rakotonas.
  79. Coffea melanocarpa Welw. ex Hiern
  80. Coffea merguensis Ridl.
  81. Coffea millotii J.-F.Leroy
  82. Coffea minutiflora A.P.Davis & Rakotonas.
  83. Coffea mogenetii Dubard
  84. Coffea mongensis Bridson
  85. Coffea montekupensis Stoff.
  86. Coffea montis-sacri A.P.Davis
  87. Coffea moratii J.-F.Leroy ex A.P.Davis & Rakotonas.
  88. Coffea mufindiensis Hutch. ex Bridson
  89. Coffea myrtifolia (A.Rich. ex DC.) J.-F.Leroy
  90. Coffea namorokensis A.P.Davis & Rakotonas.
  91. Coffea neobridsoniae A.P.Davis
  92. Coffea neoleroyi A.P.Davis
  93. Coffea perrieri Drake ex Jum. & H.Perrier
  94. Coffea pervilleana (Baill.) Drake
  95. Coffea pocsii Bridson
  96. Coffea pseudozanguebariae Bridson
  97. Coffea pterocarpa A.P.Davis & Rakotonas.
  98. Coffea racemosa Lour.
  99. Coffea rakotonasoloi A.P.Davis
  100. Coffea ratsimamangae J.-F.Leroy ex A.P.Davis & Rakotonas.
  101. Coffea resinosa (Hook.f.) Radlk.
  102. Coffea rhamnifolia (Chiov.) Bridson
  103. Coffea richardii J.-F.Leroy
  104. Coffea sahafaryensis J.-F.Leroy
  105. Coffea sakarahae J.-F.Leroy
  106. Coffea salvatrix Swynn. & Philipson
  107. Coffea sambavensis J.-F.Leroy ex A.P.Davis & Rakotonas.
  108. Coffea sapinii (De Wild.) A.P.Davis
  109. Coffea schliebenii Bridson
  110. Coffea semsei (Bridson) A.P.Davis
  111. Coffea sessiliflora Bridson
  112. Coffea stenophylla G.Don
  113. Coffea tetragona Jum. & H.Perrier
  114. Coffea togoensis A.Chev.
  115. Coffea toshii A.P.Davis & Rakotonas.
  116. Coffea travancorensis Wight & Arn.
  117. Coffea tricalysioides J.-F.Leroy
  118. Coffea tsirananae J.-F.Leroy
  119. Coffea vatovavyensis J.-F.Leroy
  120. Coffea vavateninensis J.-F.Leroy
  121. Coffea vianneyi J.-F.Leroy
  122. Coffea vohemarensis A.P.Davis & Rakotonas.
  123. Coffea wightiana Wall. ex Wight & Arn.
  124. Coffea zanguebariae Lour.

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