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Six populations; P1, P2, F1, F2, BC1 and BC2 were used in this study to determine quantitative genetic parameters. The means of the six generations were recorded for number of days to heading , days to physiological maturity, plant height, number of spikes per plant, number of kernels per spike, 100-kernel weight and grain yield per plant in three crosses namely; Giza 168 × Gemmiza 10, Giza 168 × Sakha 69 and Sakha 69 × Giza 163 generated from four diverse parents. The experiment was conducted in 2005/06, 2006/07 and 2007/08 wheat-growing seasons at Sakha Agric. Res. Station. Analyzed data revealed that sufficient genetic variations were found among generations for all the characters studied in all crosses. The results of the genetic analysis showed that the genetic variance among F2 plants were genetically different for all studied characters in the three wheat crosses except for 100-kernel weight in the cross Giza 168 × Gemmiza 10. The additive, dominance and epistatic gene effects were important in controlling the inheritance of number of days to heading, number of spikes per plant, number of kernels per spike and grain yield. Heritability estimates in broad and narrow senses were generally moderate to high for most studied characters in the three crosses. The expected genetic advance estimates from selection in the F2 were low for days to heading and days to physiological maturity, 100-kernel weight in crosses Giza 168 × Gemmiza 10 and Giza 168 × Sakha 69 and for plant height in cross Sakha 69 × Giza 163. Average degree of dominance was less than unity for days to physiological maturity in cross Giza 168 × Gemmiza 10, for plant height in cross Giza 168 × Sakha 69 and for grain yield per plant in the three crosses indicating the presence of partial dominance. Significant heterosis estimates were obtained for days to heading, days to physiological maturity, plant height and 100-kernel weight in most crosses.

This investigation was made to evaluate three bread wheat hybrids and their six populations generated from each of them under normal and late sowing dates. The three hybrids were obtained where hybrid 1 was a result of crossing (Late × Late) cultivars; hybrid 2 was a result of crossing (Early × Early) cultivars and hybrid 3 was a result of crossing (Late × Early) ones. The early parental in breed lines included: Line1, Line2 and Line3 while, the late parental ones included: Misr2 and Gemmeiza9. The two sowing dates were: normal sowing on 29 November 2011 and the late sowing on 29 December 2011. Therefore, the total genetic materials were obtained from the three hybrids included 18 genotypes which were evaluated at Sakha Agricultural Research Station Farm, Wheat Section, Egypt. Earliness traits showed that late sowing date required fewer days than normal sowing date for days to heading; days to maturity and grain filling period. This trend was present for all populations of the three hybrids. It appeared that late sowing shorten the life span of plants. Yield component characters which included: plant height; 100kernel weight and grain yield/ plant showed the advantage of hybrid 1 for plant height and grain yield/plant than the other two hybrids. These two characters showed a modest amounts of heterosis for the three hybrids. Nature of gene action which estimated from the six populations and evaluated using the scaling test analysis proposed by Mather and Jinks (1971). The results indicated the importance of additive genetic variance than dominance genetic variance one for most studied traits. These results were also supported by the results obtained from the scaling test analysis as the quantities A,B and C indicated the adequacy of the additive dominance model.

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