الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
The present study was carried out at Mansoura University, Faculty of Agriculture, Agronomy Department Farm, Dakahlia Governorate, Egypt, during the two seasons 2017/2018 and 2018/2019 seasons using six parental bread wheat cultivars (Triticum aestivum L.). These genotypes were Giza 168, Sakha 94, Shandweel 1, Gemmeiza 11, Sids 12 and Misr 1. All possible parental combinations without reciprocals were made among the six varieties, giving 15 crosses Mean squares of genotypes, parents, crosses, and parents versus crosses were significant or highly significant for most of the studied flowering and morpho-physiological, yield and its components and grain quality traits under both normal and N-stress conditions, reflecting a sort of heterosis for these characters The highest desirable heterosis and heterobeltiosis were detected by crosses No. 7 (P2 x P4) and No.8 (P2 x P6) for earliness; crosses No.14, No.8 and No.3 for 100-Kernel weight; most of the studied crosses for spike length; crosses No.8 and No.13 for number of spikelets/spike; crosses No.9, No.7 and No.13 for number of grains per spike; cross No.4 for number of spikes/plant; crosses No.3 (33.90 and 23.23%), No.12 (30.01 and 27.77%) and No.10 (30.61 and 17.13%) for grain yield per plant, hence, it could be concluded that these crosses may be useful for improving wheat grain yield program under low or high N conditions The obtained results revealed that the ratios of GCA/SCA were less than unity for all earliness and morpho- physiological and yield and its components traits under normal and nitrogen stress conditions, indicating that these studied traits are predominantly controlled by non-additive gene action. Therefore, it could be concluded that selection would be successful in improving these traits and selection would be more effective in the late segregated generation.