Abstract:
Bread wheat variety development is vital to improve the productivity and product quality in Ethiopia which could be achieved by the information generated from the pre-breeding activity. Thus, this research was conducted to assess the genetic variability among bread wheat genotypes for quantitative and grain quality traits, estimate association of traits and determine the direct and indirect effect of traits on grain yield. The experiment was laid out in 10 x 10 simple lattice design at two locations (Kulumsa and Bekoji) in southeast Ethiopia during main cropping season of 2021/2022. The genotypes were evaluated for 17 quantitative and grain quality traits. Analysis of variance for each location and over locations revealed significant differences among the genotypes for most of the traits. The pooled mean of genotypes showed that grain yield varied from 2.28 to 3.01 t/ha over the two locations. Genotypic coefficient of variation (GCV) over locations ranged from 0.35% (days to 90% maturity) to 13.71% (thousand kernels weight) and phenotypic coefficient of variation (PCV) ranged from 0.60% (grain yield) to 20.53% (thousand kernels weight). Heritability in broad sense (H2 ) ranged from 16.22% (days to 90% maturity) to 76.91% (days to 50% heading), and genetic advance as percentage of mean (GAM) ranged from 0.43% (days to 90% maturity) to 12.36% (number of total tillers). Heritability was low for days to 90% maturity (16.22%); moderate for biomass yield (52.95%), hectoliter weight (43.89%) and total gluten content (32.17%); and high for days to 50% heading (76.91%), plant height (63.53%), spikes per plant (65.17%), spike length (60.20%), number of total tillers (65.82%), number of productive tillers (63.64%), number of spikelets per spike (62.29%), thousand kernels weight (66.75%), grain yield (64.71%) and percent protein (67.82%). This suggested that selection based on mean performances of genotypes is rewarding. Grain yield had positive and significant genotypic correlations with number of total tillers, number of productive tillers, thousand kernels weight and biomass yield, and negative and significant correlation with percent protein. Grain yield had positive and highly significant phenotypic correlation with number of total tillers, number of productive tillers, spikes per plant, spike length and biomass yield; positive and significant with thousand kernels weight. Grain yield also showed negative and significant phenotypic correlation with percent protein and total gluten content. Number of total tillers followed by biomass yield exerted highest positive direct effect on grain yield at phenotypic level. Biomass yield followed by number of total tillers exerted the highest positive direct effect on grain yield at genotypic level. The first five principal components (PCs) with Eigen values >1 accounted for 68.9% of total variation of genotypes. The pooled mean genetic distance for all possible pairs of 100 bread wheat genotypes ranged from 1.72 to 10.04 with the mean genetic distance, standard deviation and coefficient of variation of 5.13, 1.3 and 25.34%, respectively. The genotypes were grouped into ten distinct clusters. Generally, the result of this research showed the presence of variations among bread wheat genotypes for yield that could be exploited in future breeding programs. Therefore, G8, G31, G36, G39, G45, G49, G60, G63, G65, G92 and G99 (Lemu, the check variety) were the promising genotypes for grain yield, maturity, hectoliter weight, grain protein percent and total gluten content for future breeding programs.