Evaluation of Phenotypic Variability for the Water Use and Water Use Efficiency Based on Physiological Determinants in Cotton (Gossypium hirsutum L.)

(Ihab Abu good)

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Abstract

A significant area of cotton production are located in limited rainfed areas. Being a commercially important crop, improvement of drought tolerance has received increasing attention in crop improvement programs. Currently, the emphasis is to identify and assess variability in specific traits of roots, water use efficiency (WUE), and other physiological traits that have relevance in enhancing drought stress tolerance. The objective of this study to assess the phenotic variability of some drought tolerant traits and establishing the use of carbon and oxygen stable isotopic signature as surrogate to WUE and transpiration respectively. Thirteen advanced breeding lines (F7) of cotton raised in containers holding 30 kg soil. After seedling establishment, 50 days after sowing (DAS) at the field facility of Department of Crop Physiology, University of Agricultural Sciences, Bangalore, India, physiological parameters influencing WUE and biomass accumulation during vegetative phase of crop development (50- 80 DAS) were assessed. Significant genotypic variation was observed in canopy cover (Leaf Area Duration), total dry biomass (TDM) and cumulative total water transpired (CWT). TDM accumulated showed a significant association with leaf area and CWT but not with WUE. Based on the relationships of WUE with physiological traits such as Mean Transpiration and Net Assimilation Rates, WUE of the examined cotton genotypes was under a strong stomatal control. Results of the stable carbon and oxygen isotopes ratios further revealed a lesser inference of chloroplast capacity on WUE. It is demonstrated that cotton lines with higher chloroplast capacity can still be identified from 65533;conductance types65533; lines. Through, the uses of a dual isotope approach as useful selectable strategy in yield improvement in cotton. Key Words: Carbon isotope discrimination, Cotton, Oxygen isotope enrichment, Water use efficiency.
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