الفهرس 
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Abstract
This study was carried out during 2017/2018 and 2018/2019 seasons at the Exp. Farm of Assiut University to evaluation of 20 bread wheat genotypes (Triticum aestivum L) for traits related to lodging resistance and yield under different three levels of nitrogen fertilization (50, 75 and 100 kg N/fed). The experiment using a randomized complete block design of three replications was used in both levels of nitrogen and seasons. The experimental space segment 2 m2, were planted wheat on December 5th, 2017 and November 28th, 2018 all appropriate agricultural operations for the wheat crop for both seasons were conducted.
The results could be summarized as follow:
There were highly significant differences among levels of nitrogen fertilization, genotypes and their interaction between nitrogen fertilization and genotypes for all traits under study for each seasons and the combined analysis of variance between the two seasons.
I- Yield traits and its components
The increase in nitrogen fertilization up to rate of 100 kg/fed led to an increase in yield traits (days to heading, spike length, number of spikes/m2, Number of kernels/grains and 1000-grain weight) and consequently an increase in yield for all genotypes in both seasons.
Days to heading
Nitrogen fertilization up to rate of 100 kg/fed delayed days to heading, the genotypes differed from each other in the days to heading. At the first level of nitrogen fertilization, the genotype 24 was the earliest (82.3 days), but the variety Misr 1 was the latest ones (90.3 days) in the first season. In the second season, the variety Sakha 93 was the earliest (82.3 days), while the genotype 21 was the latest (90.7 days) in the first and second season, respectively, under the first level of fertilization. As well as the lowest days to heading were two genotypes 42 (83.6 days) and Misr 1 (84.3 days), while the highest days to heading Sakha 94 (92.6 days) and genotype 23 (93.3 days) in the first and second season, respectively, under the second level of fertilization. The lowest days to heading genotype 20 (84.6 days) and Sakha 93 (84.7 days), while recorded the highest days to heading genotype Sids 13 (94.3 days) and genotype 21 (94.7 days) in the first and second season, respectively, under the third level of fertilization.
Spike length (cm)
Nitrogen fertilization increase to an rate of 100 kg/fed resulted in an increase in the length of the spike, giving the shortest spikes genotype 25 (10.4 cm) and the genotype 23 (10.5 cm), while gave the longest spikes Sids 1 (11.9 cm) and the genotype 13 (12.1 cm) in the first and second season, respectively, under the first level of fertilization. As well as gave genotype 25 the shortest spikes (11.2, 11.5 cm), while the genotype 24 gave the longest spikes (13 and 13.7 cm) in the first and second season respectively under the second level of fertilization. Gave genotype 25 the shortest spikes (12.8, 12.6 cm), gave the longest spikes genotype 16 (14.6 cm) and the Sids 1 (14.8 cm) in the first and second seasons respectively, under the third level of fertilization.
Number of spikes/m2
Number of spikes had a highly significant affected by nitrogen fertilizers and genotypes in both seasons. The lowest number of spikes/m2 was recorded genotype 42 (275.5 spike) and genotype 25