الفهرس 
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Abstract
Two sets of field experiments were conducted at the Experimental Farm, Faculty of Agriculture, Zagazig University during 2011/2012 and 2012/2013 growing seasons. The first set of experiments included six parental wheat genotypes and their all possible cross combination excluding reciprocals (15 F1 crosses). the 21 genotypes were grown in three adjacent exp. on three sowing dates (early, normal and late). The second set included eight wheat genotypes grown in three adjacent experiments in the same above sowing dates for two growing seasons 2011/2012 and 2012/2013. Genotypes grown in both sets of experiments were evaluated the main objectives of these experiments were to generate information about mean performance, heterosis, combining ability, gene action, heritability and stability parameters of bead wheat genotypes for the studied characters. The results revealed highly significant differences due to genotypes, parents and F1 crosses for all studied characters. The mean square due to parents VS F1s were highly significant for all traits, indicating heterotic pattern. Late sowing date (heat stress) reduced all studied characters compared to the normal (favorable) sowing date. Heat susceptibility index (HIS) values were less than unity for wheat cultivar Sids12 and F1 crosses Gemmeiza9×Misr1, Gemmeiza9×Line1 and Line1×Misr2, indicating that these genotypes were more tolerant to heat stress. The mean squares due to general (GCA) and specific (SCA) combining ability were highly significant for all traits, indicating that both additive and non-additive gene action controlled the genetic mechanism of these traits. The ratio of GCA variance to SCA variance was above one for earliness, plant height flag leaf area, spike length, peduncle length and number of spikelets/spike, indicating the major role of additive gene action in the inheritance of these characters. On the other hand, it was less than unity for number of grains/spike, 1000-grain weight and grain yield/plant on the three sowing dates. Narrow sense heritability was estimated to be high for earliness characters and peduncle length; moderate to high for plant height and number of spikelets/spike; low to moderate for flag leaf area and spike length; and low for number of grains/spike, 1000-grain weigh and grain yield/plant. The mean square of genotypes (G), environment (E) and G×E interaction for grain yield (ard./fad.) were significant. Wheat cultivar Sids12 had bi (1.20) and the lowest S2di (0.126), showing that this cultivar is stable and adapted to favorable environment. The most desirable genotypes were Line1 and Misr2. The AMMI stability showed that Line1, Line2 and Misr2 were the most stable genotypes. EG biplot indicated that environments E1, E3, E4 and E6 were the most differentiating environments, the genotype Line1 was the ideal genotype it had the highest vector length of the higher genotype and with zero GE.