Assessment of Genetic Diversity in Sphenostylis stenocarpa (Hochst Ex. A Rich Harms) Using Morphological Markers

Abstract

African Yam Bean [Sphenostylis stenocarpa (L.)] as an unexploited, neglected and underutilized crop, calls for urgent attention for its breeding and improvement to avoid extinction. Fifty AYB seed samples from Idomi, Obubra, Ekoli-Edda, Abakaliki, Jos as well as IITA, Ibadan, Nigeria was assessed for genetic diversity using morphological and rbcL gene markers. Morphological characterization of AYB was carried out on twenty yield-related and yield traits. Analysis of Variance (ANOVA), Principal Component Analysis and Clustering Analysis were done using Genstat discovery Edition 4 and PASW version 20.0 software. The results revealed low genetic variations in morphological traits like pod weight, pod length, number of leaves, days to 50 % maturity, seed length and width and days to 50% flowering in different accessions investigated. Principal Component analysis generated eight principal components accounting for 57.47 % of the total variation while the hierarchical cluster analysis revealed two major clusters without traceable pattern of clustering. The relatively low genetic variation observed in the AYB accessions indicates inter-national germplasm exchange of AYB which has been a common practice among countries in Africa and Asia. Accessions from Ekoli-Edda in cluster 2 distantly clustered away from those from Abakaliki even when they were from same state. The Principal component analysis lend credence to the analysis of variance results and stems from the low degree of morphological diversity possibly due to an interaction of genetic and environmental factors. The traits which had large loading values (pod weight and length) in the first two principal component should be considered for selection in S. sternocarpa breeding programme. We conclude that there was very narrow genetic diversity in the AYB collections investigated.