Genetic and environmental links between traits of cocoa beans and pods clarify the phenotyping processes to be implemented

Abstract

The average weight of cocoa beans is not generally taken into account during breeding processes, although it is a trait of interest. Several studies indicate that the weight of the beans has a high heritability in Theobroma cacao. However, the values obtained from different countries for the same clone often vary. In this study, we analyzed the effect of different factors on the weight of the beans. Apart from the clone effect, three main factors had an impact: i) the number of beans per pod: a good filling of the pod with beans tended to limit the weight of the beans, ii) the position of the beans in the pod: beans in the apical part of the pod were significantly lighter than the others and iii) the longer the duration of the fructification cycle the heavier the beans were (positive genetics correlation). These results lead us to propose protocols aimed at normalizing the phenotypic values of the genetic material. To obtain a reliable estimate of the bean weight, the following is proposed: either to use beans obtained from manual pollination to saturate the pods with beans, or to systematically use the number beans in the pods as a covariable.