Inheritance of agronomic and physiological characteristics of spring wheat (Triticum aestivum L.) lines at normal and salinity-stress conditions

Inheritance of several physiological and agronomic traits in 92 F4 lines derived from the cross between two wheat (Triticum aestivum L.) cultivars (Arg and Moghan3, tolerant and sensitive to salinity, respectively) was studied in a greenhouse at normal and salinity stress conditions using a hydroponic system in 2018. The experiment was carried out as a split-plot design based on randomized complete blocks with two replications. The two salinity levels (control and application of 150 mM NaCl at the three-leaf stage) were arranged in the main plots and the lines in the subplots. Analysis of variance showed significant differences among lines for all of the investigated characteristics, except the K+/Na+ ratio. The line × salinity interaction was significant for the majority of the traits including grain yield. Salinity stress increased leaf temperature, electrolyte leakage, 1000-grain weight, and Na+ content, and decreased other traits significantly. Transgressive segregation was detected for some traits at both normal and salinity stress conditions. At both normal and salinity stress conditions, broad-sense and narrow-sense heritability for the studied traits were estimated high (0.72 to 0.99) and moderate to low (0.11-0.62), respectively. The lowest broad-sense (0.72 and 0.66 at normal and salinity-stress conditions, respectively) and narrow-sense heritability (0.13 and 0.11 at normal and salinity-stress conditions, respectively) belonged to the grain yield. At both conditions, the magnitude of dominance genetic variance was higher than the additive genetic variance for the majority of the traits investigated. The average degree of dominance for all traits at both conditions was greater than one, which showed the existence of over-dominance gene action in controlling these traits. This research highlights the necessity of exploiting dominance gene effects in breeding programs of wheat at salinity stress conditions.