Intraspecific Variability in Agro-Morphological Traits of African Yam Bean Sphenostylis Stenocarpa (hochst Ex. A. Rich) Harms

Intraspecific variabilities in 40 accessions of African yam bean (AYB) were assessed through characterization of 48 agromorphological traits for two cropping seasons between June and December 2011 and 2012. Data were analyzed using descriptive statistics, analysis of variance (ANOVA), correlation analysis, principal component analysis, and cluster analysis (Semi-partial R squared method). The accessions showed significant differences (P ≤ 0.05, P ≤ 0.01, P ≤ 0.0001) in 16 reproductive traits. Accessions TSs 66 (144.50 days), TSs 51 (144.67 days) and TSs 154 (144.67 days) were identified as early maturing accessions. The first five principal component axes explained 69.7% of the total variation with PC1 and PC2 contributing 38.9% to the total variation. Correlation coefficients were high and significant for yield traits. A highly significant correlation (r = 0.99***) was observed between seed yield (kg ha-1) and weight of total pods per plant. Tubers were produced from 42.5% of the accessions. The accessions of AYB were meaningfully grouped into five clusters at the R-squared distance of 0.04 similarity index. Phenotypically, AYB 57 and TSs 123 were the most similar accessions with the closest distance of 0.0071. Four seed shapes were identified; oval (82.5%), globular/round (5%), oblong (10%), and rhomboid (2.5%). In order to improve the yield of AYB, the number of seeds per pod, number of pods per plant, weight of total seeds per pod, and weight of total seed per plant are important determinant factors. The genetic variabilities observed in the traits studied could be utilised for improvement of AYB.