Molecular Breeding in Coffee (Coffea Arabica L.)

Abstract

The cultivated coffee Coffea arabica L. (2n=4x=44) is an allotetraploid species native to Africa, containing two diploid genomes that originated from two different diploid wild ancestors (2n=2x=22), C. canephora and C. eugenioides or ecotypes related to those species (Lashermes et al., 1999). It is the only polyploid species in the genus and is self-fertile while other Coffea species are diploid and generally self-incompatible. C. arabica is characterised by a very low genetic diversity (Fig. 1), which is attributable to its origin, reproductive biology, and evolution. In addition, most cultivars are derived from the few trees which survived various efforts to spread arabica growing world-wide (Van der Vossen, 1985; Lashermes et al., 1996a). It is believed that the encountered agro-morphological variation which gave rise to so many named varieties, results from few major-gene spontaneous mutations conditioning plant, fruit and seed characters (Carvalho, 1988). The cultivars, therefore, present a homogeneous agronomic behaviour characterised by a high susceptibility to many pests and diseases, and very low adaptability (Bertrand et al., 1999).