Assessment of genetic variability among bread wheat genotypes for agronomic and morphological traits under optimum and stress condition

Background Bread wheat is one of the most important cereal crops produced in almost all agro-ecologies of Ethiopia. Assessment of genetic variability in crop species is one of the major activities of plant breeding which helps to design breeding methods for further evaluation to meet the diversified goals. Methods The experiment was laid out in 8x8 simple lattice design under both optimum and stress conditions at middle Awash during 2019/20 growing season. Water stressed treatment was imposed by withholding three irrigation from 50% flowering up to physiological maturity. In the non-stressed water regime, plants were watered at every 10 days interval using furrow irrigation method. In order to avoid water leakage between treatments, the non-stressed water regime plots were established four meters away from the water stressed regime plots. Results Analysis of variance revealed highly significant (p ≤ 0.01) variation for all studied traits under both conditions. The variation observed for grain yield varied from 2.30-6.0 t ha− 1 and 1.01–4.36 t ha− 1 under optimum and stress conditions respectively. Genotypic and phenotypic coefficient of variation ranged from 3.88(days to maturity) to 20.84% (grain yield) and 4.76(days to maturity) to 24.73% (fertile tiller plant− 1) under optimum condition respectively. Under stress condition GCV and PCV ranged from 4.30(days to maturity) to 18.41% (fertile tiller plant− 1) and 5.19 (days to maturity) to 22.27% (fertile tiller plant− 1) respectively. Broad sense heritability and genetic advance as a percentage of mean ranged from 43(spike length) to 89% (biomass yield) and 6.51(days to maturity) to 40.33% (grain yield) under optimum condition respectively, whereas under stress condition it ranged from 23.40 (harvest index) to 86.1% (days to heading) and 5.69% (harvest index) to 33.34% (biomass yield) respectively. High heritability coupled with high genetic advance as a percentage of mean was recorded for biomass yield and grain yield under optimum condition, whereas for biomass yield and fertile tiller plant− 1under stress condition. Conclusions According to the mean performance of genotypes G3, G24, G26, G24 and G45 had yield advantage over checks under both conditions. Generally, the variation observed among the tested genotypes confirmed the possibility of improvement through selection and hybridization for the study area.