Change in chlorophyll content over time well-differentiated salt-tolerant, moderately salt-tolerant, and salt-susceptible cowpea genotypes

Authors: DONG, LINGDI - University Of Arkansas; RAVELOMBOLA, WALTRAM - University Of Arkansas; WENG, YUEJIN - University Of Arkansas; QIN, JUN - University Of Arkansas; ZHOU, WEI - University Of Arkansas; BHATTARAI, GEHENDRA - University Of Arkansas; ZIA, BAZGHA - University Of Arkansas; YANG, WEI - University Of Arkansas; SHI, LINGI - University Of Arkansas; Mou, Beiquan; SHI, AINONG - University Of Arkansas

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/13/2019
Publication Date: 9/1/2019
Citation: Dong, L., Ravelombola, W., Weng, Y., Qin, J., Zhou, W., Bhattarai, G., Zia, B., Yang, W., Shi, L., Mou, B., Shi, A. 2019. Change in chlorophyll content over time well-differentiated salt-tolerant, moderately salt-tolerant, and salt-susceptible cowpea genotypes. HortScience. 54(9):1477-1484. https://doi.org/10.21273/HORTSCI13889-19.
DOI: https://doi.org/10.21273/HORTSCI13889-19

Interpretive Summary: Cowpea [Vigna unguiculata (L.) Walp] is one of the most consumed legumes in Africa. In the western part of the U.S., there is increasing interest in cowpea as a cover crop. Previous investigations showed that excessive accumulation of sodium and chlorine in leaves under saline conditions resulted in reduction in chlorophyll content, thus affecting photosynthesis. Understanding how chlorophyll content changes over time will assist plant breeders in selecting cowpea genotypes with tolerance to salinity by choosing those with more stable chlorophyll content under salt stress. We assessed, therefore, changes in chlorophyll content of cowpea genotypes at the seedling stage. Twenty-four cowpea genotypes known to differ in their responses to salt stress were treated with 0 mM and 200 mM of sodium chloride. Salt sensitive genotypes were completely dead after 24 days of salt stress, whereas the salt-tolerant ones maintained a significant amount of chlorophyll content. Chlorophyll content slowly decreased in the salt-tolerant genotypes. Chlorophyll content slightly increased at 6 and 9 days of salt stress in moderate and sensitive genotypes, but decreased at a faster rate than in the salt-tolerant genotypes. These results can be used to help select plants with different responses to salt stress in cowpea breeding programs for salt tolerance.

Technical Abstract: Accumulation of sodium and chlorine in leaves in saline conditions reduces chlorophyll content of plants, thus reducing photosynthesis. Understanding how chlorophyll content changes over time will assist plant breeders in selecting cowpea genotypes with better tolerance to salinity by enabling them to identify those with more stable chlorophyll content under salt stress. The objective of this study was to assess changes in chlorophyll content of cowpea genotypes over 24 days of salt stress at the seedling stage. Twenty-four cowpea accessions known to differ in responses to salt stress were used in this study. The experimental design was completely randomized design (CRD) with three replicates per genotype and salt treatments of 0 mM and 200 mM NaCl, and organized in a split-plot manner. Time X genotype interaction was significant at both salt levels. Chlorophyll content slowly decreased in the salt-tolerant genotypes. In contrast, chlorophyll content slightly increased at 6 and 9 days of salt stress in moderate and sensitive genotypes, but decreased at a faster rate than in the salt-tolerant genotypes. 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. These results can be used for advancing breeding programs for salt tolerance in cowpea.