A method for differentiating between Coffea arabica and C. canephora plants and their hybrids

Abstract

Coffea canephora (Robusta) is diploid (2n=22) and C. arabica is tetraploid (2n=44). Both species are highly polymorphic and some of their forms overlap, making it impossible to always differentiate them on the basis of morphology alone. The experiment reported here describes how a number of leaf surface characters, such as stomatal frequency and size, epidermal cell count, and venation and mesophyll types, were used to differentiate the two species and their hybrids. A liquid plastic compound, duco cement, was used to make impressions of the leaf epidermis. Possible applications of this technique, which uses plastic impressions of leaf surfaces, to study introgression in populations, and the origin and evolution of C. arabica in particular, are discussed.