Abstract

A field trial was carried out on the Al-Sofia regon on the right side of the Euphrates in Ramadi. Six genotypes of wheat (Triticum aestivum L.) were crossed in half diallel, in winter season of 2005, to produce fifteen crosses. The parent and crosses were grown in winter season 2006 using R. C. B. D. with three replications to determine heterosis, general and specific combining ability effects and gene action. Significant differences were found among parents and their crosses for all traits. The results showed that the cross IPA (95×Sali) gave the highest hybrid vigor in each of grain yield/ plant and number of spike/ m2 and number of grain/ Spike (19.47 %, 12.34 %, 11.39 %) respectively. The variance due to GCA and SCA were highly significant for all traits studied expect number of grain/spike where only GCA،SCA was significant. The cultivr IPA 95 had the best GCA effects for grain yield of single plant. The highest SCA effect was expressed in (IPA 95×Sali) for grain yield, number of grain/ spike number of spike/ m2. The variance ratio of GCA to SCA was less than one for all characters except number of spike/ m2. The traits were controlled by dominance effect while the number of spike /m2 was controlled by additive effect. The values of dominance variance was more than additive variance for all characters except number of spike /m2. These results reduce the value of the narrow sence heritability for all characters except number of spike /m2, which is an indication, that heterosis for these characters due to dominant gene action. The results indicate that some genotypes could be used in a breeding program to develop new version of high yield per plant and SCA to produce better grain yield selects.