الفهرس 
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Abstract
The present study was carried out at EI-Mattana Agric. Res Station, \gric. Res. Center, Egypt, during the three successive seasons of 2008/ :009,2009/2010 and 2010/2011.
The objectives of the present investigation were to study the .’esponse to selection in two durum wheat populations using the pedigree ielection method, also to study the interrelationships among the studied traits for improving grain yield and its components.
The materials used in these studies were two wheat populations, as follows:
]- Population I : (Bani-sweaf 1 x Line 2). 2- Population II: (Sohag 3 x Line 4).
The F3 plants were used as a base population for selection to drive F4
and F 5 generations. Selection was based on one of the following criterion:
1) Number of kernels/spike.
2) Number of spikes/plant.
3) 1000-kernel weight (gm).
4) Grain yield/plant (gm).
In addition, the parents of each cross, and the bulk population, were used for comparison of the selected families in each generation.
The studied traits were:
A - Morpho-physiological traits
1- Days to heading.
2- Days to maturity.
3- Plant height (em)
1- Number of spikes/plant. 2- Number of kernels/spike
Summary
3-1000-kernel weight (gm). 4- Grain yield/plant (gm).
The obtained results could be summarized as follows:
1- Selection for No. of spikes/plant:
Population I:
A. Variances and means:
The results indicated significant or highly significant differences among genotypes (selected families). The average of no. of spikes/plant for the selected families under normal and drought conditions increased from 13.2 and 12.1 in F4 generation (cycle I) to 14.9 and 12.7 in Fs generation (cycle 2), respectively. The average of no. of spikes/plant for the bulk population was 12.0 under normal condition in the two cycles of selection and 11.0 and 11.3 under drought condition, in F4 and Fs generations, respectively.
Also GCV of No. of spikes/plant decreased from 18.23% in the first. cycle (Cl) to 7.08% of the second cycle (C2), also for No. of kernels/ spike, 1000-kernel weigh, and grain yield/plant. For phenotypic coefficient of variability (PCV) decreased from 19.28% in the first cycle (C1) to 8.10% ofthe second cycle (C2).
B- Heritability estimates:
Estimates of heritability in broad sense after two cycles of selection were moderate or high estimates for heading date (73.82 and 77.41 %), maturity date (55.06 and 56.31 %), plant height (87.69 and 77.64%), no. of spikes/plant (89.36 and 76.31%), no. of kernels/plant (99.13 and 95.98%), 1000-kernel weight (99.61 and 82.29%) and grain yield/plant (80.69 and 81.59%), respectively.