الفهرس 
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Abstract
Two sets of field experiments (Stability and diallel) were performed in the present study. The first experiment was conducted at two Agriculture Research Stations, i.e., Kafr Al-Hamam (El-Sharkia) and Sids (Bani-Sweif) during the winter successive growing seasons 2010/2011 and 2011/2012 to study mean performance and stability of twelve bread wheat genotypes across twelve environments (2 seasons × 2 locations × 3 sowing dates). The second experiment was carried out at the Kafr Al-Hamam Agriculture Research Station using diallel set among six parental genotypes under two sowing dates i.e. 20th (recommended sowing date) and 30th December (late sowing date) to assess types of gene action and heritability for earliness, morph-physiological characters and yield and its components.
Significant differences were observed among wheat genotypes under different environments for all the studied characters. The environmental factors, i.e. seasons, locations and sowing dates and their interactions were highly significant in most cases. The local wheat cultivars Sakha 93, Gemmeiza 11 and Sids 12 pronounced good level of earliness with 90.86, 91.17 and 91.75 days and accumulated 957.53, 961.22 and 963.06 growing degree days, respectively, of them Gemmeiza 11 and Sids 12 had high yield potentiality. The most promising wheat genotypes exhibited higher productivity were Misr 2, Misr 1, Gemmeiza 11 and Line 16 with 23.85, 23.62, 23.62 and 23.42 ard./fad., respectively.
Stability analysis of variance revealed highly significant G x E “linear” for yield and its components. The G x E “linear” interaction was significant when tested against the pooled deviation for number of spikes/m², 1000-grain weight and grain yield (ard./fad.). Phenotypic stability parameters indicated that wheat genotypes Misr1, Misr 2 and Shandweel 1 were highly adapted to favorable environments, whereas, Sids 13 was suitable to stress environments. The most desired and stable genotypes were Misr 1, Gemmeiza 11, Sids 12, Line 14 and Line 16 for grain yield (ard./fad). The AMMI analysis of variance showed that 70.79% of the total sum of squares was attributable to environmental effects, 6.70% to genotypic effects and 12.83% to GEI effects for grain yield (ard./fad.). According to GE bi-plot and ASV, the most desired and stable genotypes were Misr1, Sakha 93, Line 27 and Gemmeiza 11 for grain yield (ard./fad.).
The most important characters could be used as selection criteria for improving heat stress tolerance were early maturity, flag leaf area, canopy temperature depression, number of spikes/m² and grain protein content.
The results indicated high degree of genetic variability existed among parental wheat genotypes and their F1 crosses for earliness and grain filling characters, morph-physiological, yield and its components and protein content under both normal (20th Nov,) and late (30th Dec.) sowing dates. The parental wheat genotypes Sids 12, Gemmeiza 11 and Line 14 and their F1 crosses Sids 12 x Gemmeiza 11, Sids 12 × Line 14 and Gemmeiza 11 x Line 14 were the earliest under both sowing dates. The local parental genotypes Misr 1 and the Line 16 produced the best levels of productivity under both sowing dates. The F1 crosses (Sids 12 x Gemmeiza 11), (Sids 12 × Shandweel 1), (Sids 12 × Line 14), (Gemmeiza 11 × Shandweel 1), (Gemmeiza 11 × Line 14), (Gemmeiza 11 × Line 16) and (Misr 1 × Line 14) gave the highest productivity under both sowing dates.
The most desirable heterosis (over mid-parents and better parent ) were registered for days to heading in the wheat cross combination (Sids 12 × Gemmeiza 11) under both sowing dates, (Shandweel 1×Line 14) under normal sowing date as well as (Sids 12 × Gemmeiza 11) and (Gemmeiza 11 × Line 14) under late sowing one for days to maturity and the cross combinations (Sids 12 × Gemmeiza 11), (Sids 12 × Shandweel 1), (Sids 12 × Line 14), (Gemmeiza 11 × Shandweel 1), (Gemmeiza 11 × Line 14) and (Gemmeiza11 × Line 16) for grain yield/plant.
According to Hayman approach (1954 a and b) showed that, additive and dominance genetic components and their derived parameters differed in its magnitude from environment to another. In general, both additive and dominance genetic components were significant and involved in the inheritance of all characters. The dominance component was larger than the additive one for grain filling characters and grain yield and its components. Additive gene action was the prevailed type controlling earliness characters. Narrow sense heritability values were high for earliness characters, moderate for grain filling rate and low for grain yield/plant.