Exploring genetic variability in robusta coffee ( <i>Coffea canephora</i> ) for berry and bean attributes

The study was undertaken to assess genetic diversity and inheritance for bean and berry attributes and ascertain correlation among these attributes in robusta coffee (Coffea canephora L.) to guide and facilitate future breeding programmes. Fifty-four field-planted robusta coffee clones in a randomized complete block design with three replications were assessed for 10 berry and bean attributes over two crop seasons (2021/2022 and 2022/2023). Significant (p < 0.05) variation was observed for all assessed attributes. Moderate-to-high broad-sense heritability, ranging from 0.58 (dry berry to wet berry ratio) to 0.89 (100-bean weight), was found among the attributes, which reflects variability and suggests these attributes would be amendable to selection. Further, our analysis showed that selection for 100 wet or dry berry weight could result in an increase in 100-bean weight (rg = 0.82, p = 0.0001). Also, selection for an increased dry bean to dry berry ratio would result in an increase in outturn (rg = 0.83, p = 0.0001), whereas selection for increased outturn would result in decreased peaberry beans (rg = -0.62, p = 0.0001). Principal component analysis showed that three principal components were important in explaining the total variability (81.1%) in the assessed attributes. Cluster analysis grouped the clones into three distinct categories, confirming their varied bean and berry attributes, and grouped the attributes into three distinct classes to guide attribute selection in future improvement endeavors. The implications of the observed variations in robusta coffee breeding are further discussed.