الفهرس 
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Abstract
The purpose of the present study were to: 1- Identify physiological and biochemical traits related to the tolerance of water deficits that could distinguish sensitive and tolerant cotton plant genotypes 2- Study the effect of water stress on cotton yield and fiber quality. 3- Detection and estimation of general and specific combining ability under water stress condition to isolate superior parents and cross combination for tolerance water deficit which are characterized by bearing water deficit to be used in various breeding programs. 4- Study the genetic behavior of some physiological and morphological as well as fiber quality characteristics under water stress conditions. 5- Detect the magnitude of genetic divergence among parental cotton genotypes and their F1s cross combinations to select most suitable combinations for tolerant water deficient. 6- Construct of some selection procedures to enhance selection of superior families in early segregating generations. Experimental design and laboratory procedures:- 1- First experiment: Line x Tester mating design. Thirteen cotton parents were crossed, in such away Line x Tester (9x4) mating design by using four Testers i.e. Dandra, Pima S6, Australy and 10229 and nine Lines i.e. Giza 45, Minufy, Giza 67, Giza 68, Giza 86, Giza 77, Giza 94, Giza 96 and Giza 69, in 2014 crop season. In 2015 season the 36 F1 hybrids and their parents were grown in a randomized complete block (RCB) design with three replicates under water stress and non-stress conditions. 2- Second experiment:- The material used in this part includes three generations F2, F3 and F4 of the intraspecific cotton (Gossypium barbadense L.) cross Giza 67 x Pima S6. In the first season 2014 F2generation consisted of 250 single plants with the original parents were grown. One plant was left/hill at thinning time, self-pollination was practiced for all F2 plants. F2 plants were selected on the basis of their performance in various characters by using various selection procedures. In 2015 season, the selfed seeds of F3 progenies were evaluated with their original parents in a randomized complete block design with three replicates. In 2016 selfed seed of selected families were evaluated with the original parents as same like in 2015. The following characteristics were studied:- Water relations and leaves chemical composition, Physiological measurements related drought, Growth habits and earliness characters, Yield and yield components characters, Fiber quality characters, Drought tolerance indices. conclusion and recomendation Sharp reduction in cotton yield and deterioration in fiber quality occur when cotton plant grown under water stress condition. The Egyptian variety Giza 67 recorded the best GCA for most studied characters followed by Giza 94 and Giza 86. The breeder can use these varieties as parents in breeding programs aiming to improve yield and fiber quality for the tolerant of water stress. The cross combinations Giza 86 x Pima S6, Giza 77 x Pima S6 and Giza 94 x Dandra showed significant positive SCA values for most studied characters under stress condition, so the breeder can use these combinations in breeding programs for the tolerant of water stress. Nine selection families were isolated in F4 generation by superiority of these families from better parents, F3 families and point start of F2 plants mean. The breeder may utilize such selected families in breeding programs aiming to improve yield and quality.