الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 253 |  |  |
| | | from | 253 | | |
Abstract
The present study was carried out at the Experimental Farm of the Kafer El Hamam Agriculture Research Station, Agriculture Research Center, Egypt during the two successive seasons of 2009/2010 and 2010/2011. Six parental bread wheat genotypes i.e., Line 1 (P1), Line 2 (P2), Line 3 (P3), Gemmeiza 10 (P4), Sakha 93 (P5) and Giza 168 (P6) were evaluated under three N-Levels. The studied parental materials were chosen on the basis of wide differences among them in respect to earliness, morph physiological characters, yield and its attributes, nitrogen use efficency. The results indicated that the most superior wheat genotypes were Gemmeiza 10 and their F1 cross Gemmeiza 10 × Giza 168 for flag leaf chlorophyll content, stay green, number of spikes/plant, number of grains/spike and grain yield/ plant; Line 1, Line 2 and the cross Line 2 × Sakha 93 for broader flag leaf area, 1000-grain weight and grain yield/ plant at L1, L2 and L3 levels; Gemmeiza 10 and Giza 168 and the crosses Line 2 × Sakha 93 and Line 1 × Line 2 for N- use efficiency. The most promising crosses in the desired direction of heterosis were Gemmeiza 10 × Giza 168 for earliness under L1, L2 and L3; Line 2 × Line 3 at L2 for stay green duration; Line 1×Line 3 and Line 2 × Sakha 93 for flag leaf area at L1; Line 1 × Gemmeiza 10 and Line 1 × Giza 168 for flag leaf chlorophyll content at L2 level; Line 1 × Sakha 93 and Line 2 × Line 3 for grain yield / plant at L1; Line 1 × Line 2, Line 2 × Sakha 93 and Line 3 × Sakha 93 for N-use efficiency and most crosses for N-stress index. The results indicated that both additive and dominance genetic components were highly significant for days to heading, days to maturity, plant height, flag leaf area, stay green duration at L1, L2, and L3 levels as well as N-use efficiency and N stress index. The dominance genetic component was significant for flag leaf chlorophyll content, grain and biological yields at L2 and L3 levels. Narrow sense heritability was high for the abovementioned characters while it was varied from low to moderate for grain, straw and biological yields and appeared to be increased with increasing N levels. Positive and significant correlation coefficient was observed between grain yield/plant and each of number of spikes/plant and biological yield/plant at L1 level; between grain yield /plant and each of plant height, spike length, 1000-grain weight and biological yield/plant under L2 as well as between grain yield and each of plant height, flag leaf area, leaf chlorophyll content, spike length and biological yield/plant at L3 level. The relative importance of the studied characters to wheat grain yield variation differed from nitrogen level to another. Stay green duration, number of spikes/plant, number of grains/spike and 1000- grain weight were found to be more important as direct and indirect contribution in wheat grain yield variation.