Morphological Variabilities and Identification of Yam (Dioscorea spp.) Genotypes from Major Growing Regions in Tanzania

Abstract

Yam (Dioscorea  spp.) is a vegetatively propagated crop that belongs to the family Dioscoreaceae. In Tanzania, yam is mainly grown as a source of food and income generation, especially for smallholder farmers. In this study, an assessment of morphological variations among 74 genotypes of  Dioscorea  spp. collected from six major growing regions was conducted. Yam genotypes were maintained and planted at Tanzania Agricultural Research Institute-Kibaha for characterization. Data from fifty morphological variables were subjected to multivariate analysis using principal component analysis and cluster analysis. The first nine principal components with Eigenvalues > 1 accounted for 86.28% of the total variations. Some traits that contributed to the variabilities include stem length, leaf margin colour, vein colour, absence/presence of wings, wing colour, hairiness, spines on stem base, aerial tubers, and inner skin colour. The dendrogram separated the 74 yam genotypes into two major clusters with six sub-clusters. Based on the results, four yam species were identified from the collected genotypes, and these included  D. alata,  D. bulbifera,  D. cayenensis, and  D. dumetorum. The results revealed high morphological variabilities among the yam genotypes. Information obtained in this study is very useful in yam breeding programs in Tanzania.

Keywords:  Cluster analysis, multivariate analysis, phenotypic variabilities, yam in Tanzania