Genetic Parameters and Stress Tolerance Index for Quantitative Traits in Barley under Different Drought Stress Severities

To determine genetic parameters and drought resistance in barley, an experiment was conducted at Kafr El-Hamam Agricultural Research Station in Zagazig, El-Sharqiyah Governorate, Egypt. The fourteen and two checks genotypes were evaluated under a diverse set of conditions that ranged from non-stress condition to conditions with moderate to severe. The analysis of variance displayed that yield, and other studied traits were significantly affected by seasons and genotypes (p<0.01), while, the genotypes x seasons interaction showed significant or highly significant for most studied characteristics during non-stress, moderate stress and severe stress conditions. The highest values of the mean performance for most studied traits were recorded under non-stress, followed by mild pressure and then severe stress for all or most the studied genotypes. Most studied genotypes were better than the checks varieties during non-stress, moderate, severe stress conditions. The variance components and heritability showed significant or highly significant for most studied traits under non-stress, moderate and severe stress conditions. The maximum values of genetic variance were found for most studied traits under drought stress conditions followed by the environmental and genotypes × season variances. High heritability coupled with high genetic advance as percent of the mean was observed for most studied traits under non-stress, moderate and severe stress conditions. The differences between phenotypic coefficients of variation (PCV%) were higher than the values of genotypic coefficients of variation (GCV%) for all studied traits during non-stress, moderate and severe stress conditions. The highest values of GCV% and PCV% were recorded for most studied characteristics during severe stress condition. The values of the relative coefficient of variation were higher than the unity for most studied traits during non-stress and drought stress conditions. Hence, these genetic parameters can be used as direct selection criteria for barley improvement under drought stress conditions. The values of stress tolerance (STI) based on moderate stress were better than the benefits of STI based on severe stress. Cluster analysis classified the genotypes into three groups, i.e., tolerant, semi-tolerant and susceptible. Based on mean performances, stress tolerance and cluster analysis, 1, 4, 6 and ten genotypes recorded the best values and are identified as the best drought-tolerant genotypes for most studied traits and can be used in future barley breeding programme during moderate stress condition in Egypt.