Abstract
The objective of this study is to estimate the nature of inheritance of grain yield and it's components in bread wheat. Half diallel crossing (6×6) performed in 2010 season including six parents (Line A-60 , Line3-7 , IPA99 , Abu-Ghraib3 , Bancal and Sham6) and grown in comparison experiment in 2010 season. Plant height(cm), flag leaf area (cm), no. of spikes per plant, no. of grains per spike,1000 grains weight (g) and grain yield per plant(g) were studied. Highly significant differences appear among genotypes in all traits studied reflected in high significant difference of GCA and SCA except grain yield. plant-1(g). P˂0.01 differences in IPA99 and Bancal parents had significant GCA effects toward desired direction in most grain yield components traits, were regarded as good combiners, while (Line3-7×IPA99) and (Line3-7×Abu-Ghraib3) crosses have significant positive SCA effects, also exhibiting high significant hybrid vigor in grain yield and many other of it's component traits followed by (Line A-60× Bancal) cross. δ2GCA/δ2SCA less than 1 for all traits.That refers to an important non additive type of gene action regarded as the major genetic variance component controlling inheritance traits, though regardless of environmental variances. Low Narrow sense heritability was seen in grain components traits, while heritability in broad sense were high and ranged from 85.5-94.3,therefore, gain from selection were low in all traits. Therefore, selection should be delayed on late generation and recurrent selection may be affective method of breeding the bread wheat genotypes.