Genetic studies on several bean traits of Coffea canephora coffee in Cameroon

The genetic parameters of several bean traits of coffee from the species Coffea canephora were estimated using two mating designs: a triangular diallel with 6 parents and a partial diallel with 18 parents. The traits studied were: normal bean weight, the percentage of peaberries, the length, width and thickness of the beans. These characteristics were studied along with yield. The yield data came from harvests obtained over 14 years divided into an initial cycle of 6 years, a second cycle of 5 years after cutting back and a third cycle of 3 years after topping. The general combining abilities (GCA) were the principal sources of significant variation for the traits studied. Transmission of these traits was therefore mostly additive. Yield over 14 years was the most heritable trait. The rank correlations between the GCA of the bean traits and those of yield were not significant. The genetic correlations estimated in the partial diallel did not reveal any link between bean traits and yield. Only one genetic correlation between the peaberry rate and yield was significant. The peaberry rate was linked to fertility, which thus appeared to be a genetic component of yield. Index-based selection combining an increase in yield with improved bean traits could therefore be carried out without any particular difficulty. (Résumé d'auteur