Genetic differentiation between Coffea liberica var. liberica and C. liberica var. Dewevrei and comparison with C. canephora

Coffea liberica Hiern includes C. liberica var. liberica (LIB) from western Africa and C. liberica var. dewevrei (DEW) from central Africa. This geographical distribution also includes cultivated C. canephora for which a within-species clustering in two interfertile groups is known. In this study, genetic differentiation between LIB and DEW was evaluated on the basis of morphological traits, molecular markers (AFLP) and male fertility of F1 hybrids. The results were also compared with the within-species differentiation in C. canephora. The morphological traits differed significantly but the distributions overlapped. By contrast, LIB and DEW constituted two distinct groups with high genetic differentiation (G_st=0.25) when using AFLP markers. In addition, the pollen viability of F1 hybrids between LIB and DEW was weak (44.2%) and similar to interspecific C. canephora x DEW F1 hybrids or C. canephora x LIB F1 hybrids, indicating that there are marked reproductive barriers between LIB and DEW.