الفهرس 
ACKNOWLEDGEMENT
The performance of traits under drought stressOnly 14 pages are availabe for public view
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Abstract
The present study was conducted at the Experimental Station of Desert Research Center, Toshka, Egypt, during 2008/2009, 2009/2010, 2010/2011 and 2011/2012 to evaluate 30 genotypes under four irrigation treatments (I0=1800, I1=1500, I2=1200 and I3=900 m3/fed/season) for yield and related traits. Also, to study the genetic analysis of yield and its components of 9-parents diallel (excluding reciprocals) crosses in both F1 and F2-generations under different irrigation treatments. Drip irrigation system was applied in these experiments. Each experiment was designed in a randomized complete block design with three replications.
Results obtained will be summarized as follows:
i. Performance of genotypes
• Mean squares due to irrigation treatments, genotypes and their interaction (G×I) were highly significant for all traits in the combined analysis, except interaction (G×I) for total chlorophyll and number of spikes/plant which were non-significant.
• Stress conditions reduced number of days to heading, flag leaf area, plant height, spike length, total chlorophyll, yield and its components as compared with non-stress condition.
• The reduction in days to heading by drought stress accounted for 2.2, 5.1 and 9.0% under I1, I2 and I3, respectively as compared to non-stress conditions (I0). The genotype No. 1 was the earliest (52.17 days), while genotype No. 4 was the latest ones (73 days) under the all irrigation treatments and in the combined.
• For number of grains/spike, the average over all genotypes was 49.52 grains under normal irrigation condition but it was reduced to 40.50, 29.02 and 23.28 grains under I1, I2 and I3, respectively.
• Drought stress decreased 100-grain weight by 6.2, 16.5 and 37.4% as compared to normal irrigation (I0) under the I1, I2 and I3, respectively.
• The reduction in biological yield/plant by drought stress accounted for 25.0, 55.5 and 77.7% from normal irrigation (I0) in the treatments I1, I2 and I3, respectively. Also, the reduction in grain yield/plant was 26.9, 58.4 and 79.8%.
• The calculated water stress susceptibility index (DSI) and sensitivity test based on grain yield/plant revealed that genotype No. 1 could be considered as relatively water stress tolerant or less susceptible and less sensitive to drought.
ii. Genetical analysis
• Mean squares due to irrigation treatments and genotypes, as well as components (i.e. parents, crosses and parents vs. crosses) were highly significant for all traits in the combined analysis, except irrigation for number of spikes/plant in F2 which was non-significant.
• Stress conditions reduced number of days to heading, flag leaf area, plant height, spike length, total chlorophyll, yield and its components as compared with non-stress condition in parents, F1 and F2 generations.
• The reduction in days to heading from non-stress as percentage was 2.7, 7.2 and 11.2% for parents, 3.7, 6.9 and 11.4% for F1-generation and 3.8, 9.3 and 16.3% for F2-generation under I1, I2 and I3, respectively.
• The reduction in number of grains/spike from non-stress as percentage was 14.9, 32.4 and 55.8% for parents, 9.8, 22.4 and 37.3% for F1-generation and 6.6, 15.6 and 27.0% for F2-generation under I1, I2 and I3, respectively.
• Drought stress decreased 100-grain weight by 7.3, 20.0 and 33.9% for parents, 7.0, 17.0 and 34.2% for F1-generation and 6.4, 16.1 and 34.1% for F2-generation as compared to normal irrigation (I0) under the I1, I2 and I3, respectively.
• The reduction in biological yield/plant by drought stress accounted for 21.8, 45.7 and 73.8% for parents, 16.9, 39.2 and 64.3% for F1-generation and 13.5, 32.6 and 54.2% for F2-generation from normal irrigation (I0) in the treatments I1, I2 and I3, respectively. Also, the reduction in grain yield/plant was 23.0, 48.9 and 73.8% for parents, 18.8, 39.8 and 63.1 % for F1-generation and 12.9, 29.7 and 51.4% for F2-generation.
• The parental genotype; P1 and the hybrids; P2×P6 and P6×P9 in F1 and F2 gave drought susceptibility index less than one (less susceptible), gave also values less than one (less sensitive) in sensitivity test.
• Mean square due to general and specific combining abilities were also highly significant for all traits in both generations. The ratio of the genetic variance components of GCA/SCA was less than one were detected for all traits in both generations, indicating predominance of non-additive gene effects in the inheritance.
• Estimates of GCA effects revealed that the parental genotype P1 seemed to be the best general combiner for earliness, and the parental genotypes P4, P6, and P8 for grain yield/plant in both generations. The crosses combinations P4×P9 and P6×P7 showed high SCA effects for the mentioned traits.