Yaser Zanganeh Asadabadi - Former Graduate Student, Department of Plant Breeding, Karaj Branch, Islamic Azad University, Karaj, Iran
Manoochehr Khodarahmi - Seed and Plant Improvement Institute,Karaj, Iran
Sayed Mahmoud Nazeri - Agricultural Research Center, Mashhad, Iran
Abdollah Mohamadi - Department of Plant Breeding, Karaj Branch, Islamic Azad University, Karaj, Iran
Sayed Ali Peyghambari - Department of Agronomy and Plant Breeding, University of Tehran, Tehran, Iran

Abstract In order to study the inheritance of grain yield and its components in bread wheat, two cultivars, Karchyya(drought and salinity tolerant) and Gaspard (sensitive to drought and salinity stress) were crossed.Parents together with F۱, F۲, F۳, BC۱and BC۲ generations were evaluated using a randomized complete block design with three replications in ۲۰۰۸-۲۰۰۹ growing season.Grain weight per spike, number of grains per spike, ۱۰۰۰ grain weight, number of spikes per plant and grain yield per plant were recorded. Analysis of variance indicated significant differencesamong generationsforall traits. Mid-parent heterosis for number of grains per spike and high-parent heterosisfor rest of the traits indicated the role of dominance gene action in governing the studied characters. Furthermore, estimates of  degree of dominance was in the over-dominance range for all traits. Based onthe generation mean analysis and the subsequent joint scaling test,additive-dominance model wasinsufficient for explaining the inheritance of the agronomic characters under study. Therefore, different models consisting of four to six parameterswere fitted to the generation means.Considering all traits, at least one epistaticeffect was significant in the fitted models.These results suggest the importance of non-additive gene action in controlling the grain yield and its components in the terminal water stress condition. Therefore, breeding programs utilizing this type of gene action are recommended if hybridization problems could be solved in this important crop. The broad-sense and narrow-sense heritability of the traits were estimated from ۰.۳۱ to ۰.۴۲ and from ۰.۱۰ to ۰.۴۲, respectively. The narrow-sense heritability of ۱۰۰۰ grain weight and number of grains per spike were higher than that of grain yield per plant. This suggests that selection for grain yield in segregating generations would not be as effective as the yield components such as ۱۰۰۰ grain weight and number of grains per spike.

Keywords: Bread wheat, Gene action, Generation mean analysis, Generation variances, Heritability