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The potential of any crop variety is subjected to various environmental conditions and a large fraction of the potential yield cannot be attained. For this study, fifty cotton genotypes of different origin were collected from gene pool of Central Cotton Research Institute, Multan and screened in the glass house. These genotypes were also evaluated under the field condition to obtain parents that possess better tolerance against drought. Initial screening of these genotypes was conducted in the glass house under three moisture levels 100, 70 and 40% at field water capacity. Data were recorded for root length, fresh root weight, dry root weight, root shoot length ratio, shoot length; fresh shoot weight, dry shoot weight, fresh root shoot weight ratio and dry root shoot weight ratio in glass house. Five drought tolerant genotypes (BH-176, MPS-11, DPL-45, Tree cotton and Cyto-62) and three susceptible genotypes (GS-444, Cooker-315, MS-64) were identified. Highly significant differences found among genotypes for all seedling characters. Further evaluation was done in field on the basis of various physiological parameters i.e. relative water content, excised leaf water loss, cell injury, leaf water potential, osmotic potential, net photosynthesis rate, transpiration rate and stomatal conductance under normal and water stress conditions. Same genotypes were confirmed under field studies. Highly significant genotypic variation existed among genotypes for all the physiological traits. The predicting genotypes may be selected and exploited to improve drought tolerance for the cotton crop.
Keywords: Cotton; Drought; Physiological traits; Pakistan; Seedling traits; Tolerance