Using morphological and physiological factors to evaluate six cowpea varieties for drought tolerance

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A potted experiment was conducted from August to October 2011, in a planthouse at Soil Research Institute (SRI), Kwadaso/Kumasi. The objective was to evaluate the performance of cowpea varieties for drought tolerance using morphological and physiological traits. A completely andomized design replicated three times with two water treatments (control and water-stressed conditions) and six cowpea varieties was used. Data collected included biomass (BM), water use efficiency (WUE), relative water content (RWC), plant height (PHT), number of leaves per plant (NL), stem diameter (SD), root dry mass (RDM) and leaf senescence (LS). There were significant differences among the cowpea genotypes, as regards the water treatments and their interaction for these morpho-physiological parameters. Water stress significantly decreased growth and development of cowpea genotypes, and the variety Dan illa showed no significant difference between the two water regimes in relative water content, plant height, number of leaves per plant and stem diameter. Highly strong positive relationships were obtain between biomass and water use efficiency, and between water use efficiency and number of leaves per plant among water-stressed cowpea varieties with r2 = 0.92 and r2 = 0.82, respectively. With relatively better performance under water-stressed condition, as indicated by the drought susceptibility index, the three varieties Dan illa, TN88-63 and Asontem were the genotypes recommended to be used as source for drought tolerance in a cowpea breeding programme.
A Thesis submitted to the School of Graduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirements for the Degree of Master of Science in Plant Breeding (Agronomy), August-2012