Abstract

In the present investigation, the genetic variability of 64 speckled type common bean genotypes were evaluated at Haramaya University during 2015 cropping season using 8 × 8 simple lattice design with three replications. The analysis of variance indicated highly significant (P<0.01) differences among genotypes for all the nine characters studied. High genotypic coefficient of variation (GCV) was observed for grain yield, while high phenotypic coefficients of variation (PCV) were recorded for number of seeds plant^-1, grain yield ha^-1 and common bacterial blight resistance. For all the traits, estimates of PCV were higher than GCV indicating the presence of environmental influence. High heritability values and genetic advances were recorded in grain yield. Cluster analysis using Mahalanobis distance delineated the genotypes into six main groups. Cluster I contain the largest number of genotypes (43.75%) followed by clusters II (26.56%) and III (10.94%) while clusters IV, V and VI contain four genotypes each. The D² analysis indicated that there was a significant difference among the clusters. The maximum inter cluster distance was observed between cluster IV and V. Principal component analysis (PCA) was performed to assess the variation and correlation among genotypes for the traits and grouped them based on their performance.  The combination of the first four principal components explained more than 85.74% of the genotypic variations. Therefore, exploiting the genetic diversity among clusters would broaden the genetic base of speckled bean breeding populations.

Key words: Clustering, genetic distance, genetic variability, Phaseolus vulgaris, speckled bean.