Combining Ability Analysis , Estimation of Heterosis and Some Genetic Parameters Using Half Diallel Cross in Bread wheat (Triticum aestivum L.)

Five varieties of bread wheat (<em>Triticum aestivum L.</em>) Tamuz-3 Adnaniya, Abu-Greebe-3, IPA-99 and Sham-6 and their half diallel crosses were used to study general and specific combining ability for plant height, number of tillers per plant, number of spikes per plant, spike length , number of grains per spike, 100 grains weight and grain yield per plant. The result of the analysis of variance showed that the mean square of genotypes, (GCA) and (SCA) were highly significant for all studied characters. The ratio between the component variance of (GCA) and the component of variance (SCA) was less than one for all studied characters except for plant height which was more than one this indicate the importance of additive and dominance gene effects for all characters, but the dominance gene effects is more important for determining these characters. The largest and positive value for (GCA) effect was in the following parental varieties : Abu- Ghreeb-3 for plant height and number of grains per spike, IPA-99 for number of tillers and number of spikes per plant, Adnaniya for spike length and 100 grains weight and grain yield per plant. The (SCA) effects value in some hyprids was positive with desirable direction, but other hyprids showed negative with undesirable direction for all studied characters therefor heterosis can be utilized for improve these characters. The hyprids (1x3), (1x4), (2x3),(2x4),(2x5),(4x5) revealed desirable and high significant heterosis for all studied characters. The broad sense heritability were high for all studied, however the narrowsense heritability were high for plant height and medium to remained characters. There were over dominance for all characters except partial dominance for plant height.