الفهرس 
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Abstract
Wheat (Triticum aestivum, L.) is considered as one of the major cereal crops in Egypt, as well as, in many parts all over the world which has been used in human food and animal feed. Recently, under Egyptian conditions increasing wheat yield and its production is considered as one important strategy goals to minimize the great gab between production and consumption that reached 55% especially under the increase in population size than wheat production. Solving these problems need to increase total wheat yield by producing highly productive varieties. It could be achieved by exploring maximum genetic potential from available wheat germplasm. - Based on the above, the current study seeks to achieve the following objectives: 1. Estimation means performance. 2. Calculate Heterosis effects (mid-parent and better parent). 3. Estimation of general and specific combining ability. 4. Estimation heritability in (narrow broad and narrow senses). 5. Partitioning the total genetic components of variation to its separate parts. - To achieve those goals, The present study was carried out at the experimental farm of Tag El-Ezz Agricultural Research Station El-Dakahlia Governorate (Clay saline soil), Egypt during the three wheat growing seasons of 2012/2013, 2013/2014 and 2014/2015 to create new combinations characterized by high yielding ability. The experimental materials comprised of eight wheat cultivars which genetically differ in their earliness, yield and its components viz.; Giza 168, Misr1, Sakha93, Sids12, Sakha94, Misr2, Gemmeiza9, and Gemmeiza10. The previous eight parental cultivars were employed to produce 28 F1 hybrids following 8 x 8 half Diallel crossing scheme excluding reciprocals during wheat growing season of 2012/2013. The female plants were hand emasculated and covered with butter paper bags. The emasculated ears were pollinated with hands carefully. The seeds of the 28 F1 hybrids and their parents were planted on 20 November and evaluated in winter wheat growing season of 2013/2014. At the same time, seeds of four parental cultivars from the same previous parental and their six F1 hybrids were sown on 20 November at the two winter wheat growing seasons of 2013/2014 and 2014/2015 in a separate experiment. Layout of the experiment was done according to the Randomized Complete Block Design with three replications, during evaluation seasons of 2013/2014 and 2014/2015. The obtained results were subjected according to Griffing (1956), Jones (1956) and Hayman 1954a and b Diallel analysis biometrical approaches. - The study reached several results summarized as follows: Results indicated mean squares due to parents and their crosses which were significant for all studied traits. The parental variety P3 was the best parent for earliness. However, P8 was the best for remained traits. The crosses (P1 x P4) and (P2 x P4) were the best combinations for earliness traits, while the six crosses were the best for remained traits. Highly significant negative desirable heterotic effects were detected for earliness, on the contrary for remained traits relative to mid and better parent. The mean squares associated with general and specific combining abilities detected significant and highly significant estimates for all studied traits. Results indicated that P4 (Sids12) was good combiner for earliness traits and most of yield and its component traits. The best cross combinations displayed fair amount of SCA effect were obtained from (P2 x P4) and (P4 x P5) for earliness traits, the six crosses for remained traits. The graphical analysis Wr/Vr indicated the importance of over dominance gene effects in controlling all traits. The results indicated the importance of additive and dominance genetic variances in controlling these traits. The ”a” item was significant for most studied traits and more than ”b” item. Narrow sense heritability was less than (0.50) for all traits except plant height trait (0.80).