2018 ASHS Annual Conference

With poor quality of irrigation water, cultivated areas facing salinity keep increasing, hence preventing cowpea from being cultivated in areas where its optimal growth and development conditions are found. However, to date, few salt-tolerant cowpea cultivars have been reported, which has resulted in a less performing cowpea breeding program for salt tolerance. Previous investigations showed that accumulations of Na⁺ and Cl^- in leaves resulted in reduction in chlorophyll content, thus affecting photosynthesis. Understanding how chlorophyll content evolves over time will assist plant breeders in selecting cowpea genotypes with better tolerance to salinity by choosing those with more stable chlorophyll content under salt stress. Therefore, the objective of this study was to evaluate the chlorophyll content of cowpea genotypes over 24 days of salt stress at seedling stage. A total of 30 cowpea accessions previously shown as having different responses were used in this study. Salt treatments were 0 mM and 200 mM NaCl. Experiment design was completely randomized (CRD) with three replications per genotype and salt treatment combination, and organized in a split-plot manner. Salt stress was imposed for 24 days. Results revealed that: (i) time X genotype interaction was significant in both salt conditions and without salt conditions; (ii) chlorophyll content slowly decreased in the salt-tolerant genotypes; (iii) chlorophyll content slightly increased at 6 and 9 days of salt stress in both moderate and sensitive genotypes, but decreased at a faster rate than in the salt-tolerant ones; and (iv) the salt sensitive genotypes were completely dead at 24 days of salt stress, whereas the salt-tolerant ones were able to maintain a significant amount of chlorophyll content at that time. These results can be used for advancing breeding programs for salt tolerance in cowpea.