Genetic Variability, Correlation and Path Analysis on the Storage Tuber Yield and Yield Components of Yam (Dioscorea spp.) from Southwest Ethiopia

Abstract

The study was conducted to estimate the extent of genetic variation, association between storage tuber yield and yield related traits and to identify the most persuasive character(s) involving 36 yam genotypes for selection and conservation. Field evaluation was conducted at Jimma Agricultural Research Center in Ethiopia using a 6x6 lattice design with two replications. Variance analysis of characters revealed significant differences (p<0.01) among the genotypes. Estimate of phenotypic and genotypic coefficients of variation showed variability among the genotypes. High genotypic (14.87, 8.36 and 5.38%) and phenotypic coefficients of variation (40.11, 24.03 and 15.17%) were observed for tuber fresh weight, petiole length and number of vine hill^-1 in the order of magnitudes. Heritability (13.70% and 12.10%) coupled with genetic advance as percent of mean (11.56% and 5.94%) were recorded for tuber fresh weight and petiole length, respectively. Correlation study between different traits showed highly significant association among characters. At genotypic level, tuber fresh weight showed significant and positive correlated with leaf length (r=97), leaf width (r=1.00), vine length (r=0.99), petiole length (r=1.00), days to maturity (r=1.00), number of internodes vine¹ (r=0.57), internodes length (r=1.00), tuber length (r=1.00), tuber diameter (r=1.00) and harvest index (r=0.73). Tuber fresh yield is a complex agronomic trait induced by many associated traits directly and indirectly and thus, selection of yams based on these traits will enhance tuber yield and need high concern towards tuber yield improvement. Analysis of path coefficients at genotypic level revealed that days to maturity (p=1.0183) had maximum positive direct effect on tuber fresh weight followed by tuber length (p=0.2126). This study revealed that selection of later maturing genotypes may improve genetic gain in storage tuber yield in yam breeding. Based on the above results, genotypes: 27/02, 56/76, 08/02, 10/002, 39/87, 45/03, 6/02, 116, and 7/83 were selected for breeding and conservation.