Coffea is agenus offlowering plants in thefamilyRubiaceae.Coffea species areshrubs or smalltrees native to tropical and southernAfrica and tropicalAsia. Theseeds of some species, calledcoffeebeans, are used to flavor various beverages and products. The fruits, like the seeds, contain a large amount ofcaffeine, and have a distinct sweet taste.
The plant ranks as one of the world's most valuable and widely tradedcommodity crops and is an importantexport 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, andCoffea canephora (known as "Robusta"), which accounts for about 20–40%.[2][3]
In 2008, two new species were discovered inCameroon:Coffea charrieriana, which is caffeine-free, andCoffea anthonyi.[9] By crossing the new species with other known coffees, two new features might be introduced to cultivated coffee plants: beans withoutcaffeine andself-pollination.
In 2011,Coffea absorbed the twenty species of the former genusPsilanthus due to the morphological and genetic similarities between the two genera.[10] Historically, the two have been considered distinct genera due to differences in the length of thecorolla tube and theanther 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 expandedCoffea from 104 species to 124, and extended its native distribution to tropical Asia and Australasia.
The coffeegenome was published in 2014, with more than 25,000genes identified. This revealed that coffee plants make caffeine using a different set of genes from those found intea,cacao and other such plants.[11]
A robust and almost fully resolved phylogeny of the entire genus was published in 2017.[12] In addition to resolving the relationships ofCoffea species, this study's results suggest Africa or Asia as the likely ancestral origin ofCoffea 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.[13] For the study, scientists used DNA extraction andSSR marker analysis. This technique or similar ones 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.
Thecaffeine in coffee beans serves as atoxic substance that protects against insects and other pests, a form of naturalplant defense against herbivory. Caffeine simultaneously attractspollinators, specifically honeybees, by creating an olfactory memory that signals bees to return to the plant's flowers.[12] Not allCoffea species contain caffeine, and the earliest species had little or no caffeine content. Caffeine has evolved independently in multiple lineages ofCoffea in Africa, perhaps in response to high pest predation in the humid environments of West-Central Africa.[12]
Caffeine has also evolved independently in the more distantly related generaTheobroma (cacao) andCamellia (tea).[14] This suggests that caffeine production is anadaptive trait in coffee and plant evolution. The fruit and leaves also contain caffeine, and can be used to makecoffee cherry tea andcoffee-leaf tea. The fruit is also used in many brands of soft drink as well as pre-packaged teas.[15][16][17][18]
There are over 130 species ofCoffea, which is grown from seed. The two most popular areCoffea arabica (commonly known simply as "Arabica"), which accounts for 60–80% of the world's coffee production, andCoffea canephora (known as "Robusta"), which accounts for about 20–40%.[2][3]C. arabica is preferred for its sweeter taste, whileC. canephora has a higher caffeine content.C. arabica has its origins in the highlands of Ethiopia and theBoma Plateau of Sudan, and came about as the result of a hybrid betweenC. canephora andC. eugenioides.[19]
The trees produce edible red or purple fruits that are eitherepigynous berries orindehiscentdrupes.[20] The fruit is often referred to as a "coffee cherry", and it contains two seeds, called "coffee beans".[21] Despite these terms, coffee is neither a truecherry (the fruit of certain species in the genusPrunus) nor a truebean (seeds from plants in the familyFabaceae).
In any coffee crop, about 5–10% of fruits contain only a single bean. Called apeaberry, 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 (10–11+1⁄2 ft). Most commonly cultivated coffee species grow best at high elevations, but do not tolerate freezing temperatures.[22]
TheCoffea arabica tree grows fruit after three to five years, producing for an average of 50 to 60 years, though up to 100 years is possible.[23] The white flowers are highly scented. The fruit takes about nine months to ripen.
^ab"Coffee: World Markets and Trade"(PDF). United States Department of Agriculture – Foreign Agricultural Service. 16 June 2017.Archived(PDF) from the original on 10 October 2017. Retrieved8 December 2017.
^Lashermes, Philippe; Andrade, Alan Carvalho; Etienne, Hervé (2008). "Genomics of Coffee One of the World's Largest Traded Commodities". In Paul H. Moore; Ray Ming (eds.).Genomics of Tropical Crop Plants. Vol. 1. New York: Springer. pp. 203–226.doi:10.1007/978-0-387-71219-2_9.ISBN978-0-387-71219-2.Consequently, bean quality may be lowered and supply become less stable to adversely affect the coffee market of consumer countries. Furthermore, in the light of climate changes and increasing awareness of the negative impacts of the nonsustainable use of natural resources, coffee production will have to evolve. This is particularly relevant for perennial plants such as coffee whose productive life is very long and for which rapid genetic gains are tedious to obtain.
^abcHamon, Perla; Grover, Corrinne E.; Davis, Aaron P.; Rakotomalala, Jean-Jacques; Raharimalala, Nathalie E.; Albert, Victor A.; Sreenath, Hosahalli L.; Stoffelen, Piet; Mitchell, Sharon E.; Couturon, Emmanuel; Hamon, Serge; de Kochko, Alexandre; Crouzillat, Dominique; Rigoreau, Michel; Sumirat, Ucu; Akaffou, Sélastique & Guyot, Romain (2017). "Genotyping-by-sequencing provides the first well-resolved phylogeny for coffee (Coffea) and insights into the evolution of caffeine content in its species: GBS coffee phylogeny and the evolution of caffeine content".Molecular Phylogenetics and Evolution.109:351–361.Bibcode:2017MolPE.109..351H.doi:10.1016/j.ympev.2017.02.009.PMID28212875.
^Lashermes, P.; Combes, M.-C.; Robert, J.; Trouslot, P.; D'Hont, A.; Anthony, F.; Charrier, A. (1999). "Molecular characterisation and origin of theCoffea arabica L. genome".Molecular and General Genetics.261 (2):259–266.doi:10.1007/s004380050965.PMID10102360.S2CID7978085.
