الفهرس 
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Abstract
The present study was carried out during the two seasons 2002/2003 and 2003/2004 using six parental bread wheat cultivars and/or lines ( Triticum aestivum L.). These genotypes were Line 1, Sakha 61, Sakha 93, Sakha 94, Gemmeiza 9 and Gemmeiza 10. All possible parental combinations without reciprocals were made among the six genotypes, giving 15 crosses. The six parental genotypes and their 15 F1’s were planted in two experiments. The first experiment, was irrigated with four irrigations (Normal conditions). The second one, was irrigated with only two irrigations (Stress conditions). In each experiment, the genotypes were grown in a randomized complete block design using three replications. Finally, the important results indicated that : 1-The parent Line 1 was the best for some traits i.e. days to maturity, flag leaf area, total chlorophyll content, plant height, weight of 100 kernels, grain yield per plant and it had low drought susceptibility index. While, the cross Line 1 × Sakha 94 was the best for some traits i.e. grain filling rate, plant height, number of kernels/ spike, grain yield/plant and it had low drought susceptibility index. 2- Estimation of useful heterosis over better parent for grain yield/plant proved that it never exceeds 25.26% at normal conditions ( cross Sakha 93× Gemmeiza 9) and 23.67% at stress conditions (cross Sakha 61×Gemmeiza 9). 3-The parents Line 1 and Sakha 94 were a good combiners for most traits. It could be used in breeding program for drought tolerance. 4-Selection for most traits could be applied in early segregating generations . It could be recommended that the Line 1 , cultivar Sakha 94 and the cross Line1 × Sakha 94 could be used in breeding program for drought tolerance in bread wheat