Taxonomy_of_the_coffee_plant

Coffea canephora it characterised by its great variation in forms or ecotypes, and therefore it is much more
difficult to distinguish varieties. This is due to its allogamous (cross-fertilizing) reproduction, where always
pollen from another tree is needed for fertilization. In contrast to self-fertilizing C. arabica, Robusta always
mixes DNA from a multitude of individuals, which generated many different genotypes.
Robusta coffee is also more bitter and has less favourable organoleptic qualities, which is also mirrored in
the trade prices, where Robusta is sold at 60 % lower prices than Arabica. However, quality of Robusta can
still be improved with higher post-processing efforts. Yet, quality is sufficient for soluble coffee production
and to be used in blends with Arabica. There was also a larger demand for cheap coffee after the second
world war, which boosted the share on world coffee production for Robustas from 0 % in 1920 to 40 %
today.
For selection of Robusta trees, a strategy is frequently applied, where genotypes with a good general
combining ability are selected. Doing that, one looks for individuals with a certain genotype that produce
hybrids of good quality with many different other genotypes. This way one can higher the probability that
the trees in the plantation produce an evenly good quality crop.
On the picture the geographic origins of the two main genetic groups of C. canephora are shown. The red
area marks the Guinean group of Robustas (Ivory coast and Guinea), whereas the green area marks the
Congolese group with few sub-groups, e.g. C (Cameroon, the Central African Republic and Congo).
Several geographic C. canephora varieties have been defined, e.g. Robusta in the Congo (around 1890
Gaillan collected seeds to start a nursery, now Robusta is commonly used for the whole species), Nganda
in Uganda and Kouilou from Central Africa. The latter species is now widely grown in Brazil, named
Conilon.
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