Multivariate analysis of agro-morphological traits reveals diversity and population structure in cultivated yams (Dioscorea spp.) from Cameroon with implications for breeding

Abstract

Yam (Dioscorea spp.) is a major staple crop in West and Central Africa, but its productivity remains limited by the underutilization of available genetic diversity. This study evaluated the agro-morphological diversity and population structure of cultivated yams in Cameroon. A total of 224 accessions were collected from farmers’ fields and local markets across major yam-growing regions and established in an on-farm trial at the International Institute of Tropical Agriculture (IITA), Yaoundé, using a serpentine design without replication. A subset of 126 accessions, representing four healthy plants per landrace and sampling locality, was characterized using 42 agro-morphological descriptors encompassing tuber, vegetative, and inflorescence traits. Data were standardized using z-score transformation and analyzed using principal components analysis (PCA) for exploratory ordination. Based on PCA ordination, accessions with similar local names were aggregated to reduce the dataset to 88 landraces. Mean trait values were subjected to Gower distance-based hierarchical clustering. The first two principal components explained 45.4% of total variation, driven mainly by tuber traits, plant vigor, and leaf morphology. The population structure was resolved along gradients defined by productivity-, defense-, and growth cycle-related traits. Cluster analysis identified five stable groups, with further subdivision into seven clades, at Gower thresholds of 0.38 and 0.24, respectively. Silhouette analysis supported the five-cluster solution as the most robust. The observed diversity reflected a trade-off between adaptive defense strategies and productivity-related traits. The seven clades corresponded to seven presumptive Dioscorea species, suggesting possible genetic erosion compared to earlier reports. These findings highlight substantial morphological diversity, important for yam breeding and conservation. Integration of molecular markers is recommended to enhance finer genetic resolution of genetic diversity of yams.