The Coffea genus belongs to the Rubiaceae family, which has over 500 different genus and over 6,000 species. The majority of these are either trees or bushes. Taxonomically, the plants classified under the Coffea genus are characterized by a cleft in the ventral part of their seeds (sutura coffeanum). This genus varies from small bushes up to trees that grow over 10 meters (3x feet) tall; its leaves are simple, opposite; its stipules vary as much in size as in shape; its flowers are hermaphrodites, white and tubular; and its fruits consist of drupes of different shapes, colors and sizes; each fruit normally contains two seeds.
Linneo (1737) classified the plant as a new genus, Coffea, with only one known species at the time, C. arabica. Today 103 species have been identified. All native from Africa and Madagascar (including the Comoro Islands) Nonetheless, only two are responsible for 99% of the genus’s global commerce: Coffea arabica and Coffea canephora.
The Coffea canephora Pierre ex-Froehner, also known as Robusta, has an ample geographic distribution and is found wild in meridional Africa, in countries such as Congo, Cote d’Ivoire, Sudan and Uganda as well as in the northeastern part of Tanzania and Angola. Nowadays it is also grown in Indonesia and Vietnam. Approximately 35% of coffee that is commercialized comes from this species. This species developed throughout the years resistance to many plagues and diseases prevalent in harsh tropical climates.
Robusta coffee is cultivated generally in altitudes below 1,000 meters above sea level. It is cross pollinated and therefore it should be cultivated with different, yet compatible, genotypes. Its content of caffeine is usually greater than 2%, is bitterer and has a cereal-like taste. Recent research estimates that the Robusta species was originated more than 5 million years ago, and is even believed by some to be more than 25 million years old.
Coffea arabica L. is currently the primary species of the genus. It makes up nearly 65% of traded coffee in international markets. As opposed to Robusta, it is an autogamous or self-fertilizing plant. Scientific studies catalog Coffea arabica as relatively young species that was originated less than a million years ago. It is found wild in the mountains of eastern Africa, and came from somewhere in southeast Ethiopia, South Sudan and or northern of Kenya. It is a tetraploid (has 44 chromosomes), that derives the cross of ancient forms of two diploid species: Coffea eugenioides (22 chromosomes), as the female progenitor, and C. canephora (22 chromosomes), as the male progenitor. The caffeine content of the C. arabica bean usually varies between 1.0% and 1.4% in its dry state, and is less bitter than Robusta.
All the stories about coffee and its introduction to Arabia and Europe are primarily stories that focus on the C. arabica plant. Being a self-fertilizing plant, one can create a plantation out of one single seed, (something that cannot be done with Robusta). When the Dutch got hold of the coffee trade, they planted it in Ceylon (currently Sri-Lanka). However, the coffee leaf rust destroyed those plantations in the 19th century, and they decided to start planting Robusta in Java and other island of today’s Indonesia. This is why Robusta began to be commercially used. And this is also why the genetic diversity of the C. arabica varieties that ended up being cultivated in other regions of the world is very limited.
There are around 2000 possible variations of the Coffea arabica. Bear in mind that to be considered a variety, plants have to be stable (being able to reproduce and keep its characteristics throughout different generations). The most popular C. arabica varieties in the world include: Typica, Bourbon, San Bernardo, Villalobos, Caturra, Catuai, Pache Comum, Pache, Kent, Mundo Novo and Maragogype.
So where would C. arabica coffee grow to have the best conditions for higher quality? In the mild temperate tropical and subtropical climates similar to where it originated. Those regions of the world located as close as possible to the equatorial line, allowing them to enjoy similar sunlight year round, and high mountains that would allow for milder temperatures will be best. There are not many of them; if one takes a world tour above the equator, you will find the mountains of Eastern Africa, Indonesia and Colombia. This is where most of the truly high grown coffee is produced in the world, although there are interesting exceptions in certain parts of Central America. As it grows well in temperatures that range between 18° and 24°C, in Colombia the plantations are concentrated at altitudes that oscillate between 1,200 and 1,800 meters above sea level, although you can find plantations as high as 2,300 meters. Colombia is one of the few coffee producing countries that only produces C. arabica coffee in the world.
Some of the initial varieties to be sowed in Colombia were Typica, Bourbon and Maragogipe. These C. arabica varieties were then replaced in a significant way by the higher yielding Caturra. Most of the new varieties, (such as Castillo (R), more of these in a forthcoming article) are very similar to Caturra Colombia continues to be an exceptional country where only varieties from the C. arabica species are planted, all of them with 44 chromosomes.
Typica is the first coffee variety introduced to most coffee growing countries. In Colombia it was partially replaced with the Caturra variety in the 1960′s. Today Typica still represents about 25% of total coffee hectares of coffee cultivated in Colombia.
The Bourbon cultivar of the Coffea arabica, arrived later, from Bourbon Island, renamed as Reunion island, located in the Indian ocean. This variety was introduced in Africa and South America between 1860 and 1870, and it soon became as popular as Typica, though it hasn´t been very popular in Colombia because of it´s beans smaller than Typica.
The Caturra variety is the result of a natural mutation of the Bourbon variety that took place in Brazil.. Being a dwarf variety, more plants can be planted per hectare, allowing for higher productivity. It adapted extremely well to Colombian conditions, and it was heavily planted as from the 1970s.
In sum one can state that the C. arabica species has limited genetic variability, as well as susceptibility to most pests and diseases. Analysis made by researchers, in particular those from FNC’s Cenicafé, have shown that the cultivated varieties available in the Americas have small genetic variability (see graph below), and are very distant from their Robusta (diploid) forefathers.
The genetic variability among those varieties that are currently produced in Colombia is even lower as a result of the limited number of C. arabica “grandparents” that crossed the ocean some centuries ago, a portion of which actually reached Colombia and adapted to local conditions. However, the germplasm collection from Ethiopia, available for coffee breeding has a somewhat higher variability, which may allow the development of new varieties with interesting attributes to better adapt to climate change . In a forthcoming article we will be discussing plant breeding, genetic variability and resistant genes.
Originally posted in Colombian Coffee Hub