A simple and cost-effective approach for salt tolerance evaluation in cowpea (Vigna unguiculate) seedlings

Authors: RAVELOMBOLA, WALTRAM - University Of Arkansas; QIN, JUN - University Of Arkansas; WENG, YUEJIN - University Of Arkansas; Mou, Beiquan; SHI, AINONG - University Of Arkansas

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/16/2019
Publication Date: 8/1/2019
Citation: Ravelombola, W., Qin, J., Weng, Y., Mou, B., Shi, A. 2019. A simple and cost-effective approach for salt tolerance evaluation in cowpea (Vigna unguiculate) seedlings. HortScience. 54(8):1280-1287. https://doi.org/10.21273/HORTSCI14065-19.
DOI: https://doi.org/10.21273/HORTSCI14065-19

Interpretive Summary: Salt stress has been increasingly threating crop production globally, affecting more than 830 million hectares of croplands worldwide. Little is known with respect to breeding for salt-tolerant cowpea cultivars despite of salt stress becoming a growing threat to cowpea production. Seedling stage is one the most susceptible stages to salt stress in cowpea. Establishing a streamlined methodology for rapidly screening a large number of varieties will significantly contribute toward enhancing cowpea breeding for salt tolerance. Therefore, the objective of this study was to establish and validate a simple approach for salt tolerance evaluation in cowpea seedlings. A total of 30 varieties including two controls (PI582468, a salt-tolerant variety, and PI255774, a salt-sensitive variety) were grown under no-salt and salt treatments in a greenhouse. A total of 14 above-ground traits were evaluated. Results revealed: 1) There were significant differences in average number of dead plants per pot, leaf injury, chlorophyll, plant height, and leaf and stem weight among the 30 varieties; 2) All PI255774 plants were completely dead, whereas those of PI582438 were fully green after two weeks of salt stress, which validated this methodology, 3) Chlorophyll content was associated with number of dead plants and leaf injury; 4) Leaf weight was moderately associated with number of dead plants and leaf injury; and 5) Plant height was not associated with number of dead plants and leaf injury. Therefore, less number of dead plants per pot, high chlorophyll content, and less leaf injury were good criteria for salt tolerance evaluation in cowpea. This study provided a simple methodology and suggested straightforward criteria to evaluate salt tolerance at seedling stage in cowpea.

Technical Abstract: As salt-stress is becoming a growing threat to cowpea production, there is a need to breed for salt-tolerant cowpea cultivars. Seedling stage is one the most susceptible stages to salt stress in cowpea. Establishing a streamlined methodology for rapidly screening a large number of genotypes will significantly contribute toward enhancing cowpea breeding for salt tolerance. Therefore, the objective of this study was to establish and validate a simple approach for salt tolerance evaluation in cowpea seedlings. A total of 30 genotypes including two controls (PI582468, a salt-tolerant genotype, and PI255774, a salt-sensitive genotype) were grown under 0 mM and 200 mM NaCl in a greenhouse. A total of 14 above-ground traits were evaluated. Results revealed: 1) There were significant differences in average number of dead plants per pot, leaf injury scores, relative salt tolerance for chlorophyll, plant height, and leaf and stem biomass among the 30 genotypes; 2) All PI255774 plants were completely dead, whereas those of PI582438 were fully green after two weeks of salt stress, which validated this methodology; 3) Relative salt tolerance for chlorophyll content was highly correlated with number of dead plants and leaf injury scores, 4) Relative salt tolerance for leaf biomass was moderately correlated with number of dead plants and leaf injury scores, and 5) Relative salt tolerance in plant height was poorly correlated with number of dead plants and leaf injury scores. Therefore, less number of dead plants per pot, high chlorophyll content, and lower leaf injury scores were good criteria for salt tolerance evaluation in cowpea. This study provided a simple methodology and suggested straightforward criteria to evaluate salt tolerance at seedling stage in cowpea.