Abstract

Knowledge of the sources and magnitude of variability among genotypes plays a pivotal role in any crop improvement program to maximize gains from selection. This experiment was conducted at Bako Agricultural Research Center in 2011 cropping season with the objective of studying and estimating the extent of genetic variability in common bean genotypes under sole and mixed cropping systems. Meanwhile, the wider range of variability observed from the mean of various quantitative traits. The genotypes that varied by cropping system depicted the presence of high level of variability. The highest genotypic coefficient of variation (GCV) and phenotypic coefficient of variation (PCV) values were recorded for hundred grain weight (29.56 and 35.46 g), biological yield (27.22 and 31.37) and grain yield (26.60 and 31.54 q/ha), whereas the lowest GCV and PCV values were recorded for days to maturity of sole common bean genotypes. Phenotypic variance in both sole and mixed cropping systems was higher than that of genotypic variances. This implies that, considerable contribution of environmental factors to the phenotypic expression of the genotypes. High broad sense heritability as observed under both sole and intercropping systems indicated that, genetic improvement can be obtained through further selection programme. Important agronomic traits: pods per plant, seeds per pod and branches per plant had positive and significant correlation with grain yield in most cases. Path coefficient analysis at genotypic level indicated that all traits except plant height, seeds per pod and hundred grain weights exerted their positive direct effect on grain yield.  Hence, the current study identified the presence of wide variability between those common bean genotypes which can be used for further breeding program and selection can be made using those traits associated to yield.

Key words:  Genotypic variance, heritability, intercropping, phenotypic variance, quantitative traits, sole cropping.