Evaluation of Salt Tolerance at Germination Stage in USDA Cowpea Germplasm

Cowpea is a leguminous versatile crop and can be used as either dry seeds or vegetables for human consumption because of its high nutritional value. However, soil salinity is one of the most important constraint for cowpea production. The effects of salinity could be insidious at earlier stage of cowpea development such as germination. Screening for cowpea lines which would be tolerant to salinity enables cowpea producers to address this issue. The aim of this research is to evaluate salt tolerance at germination stage in cowpea. A total of 102 accessions of USDA cowpea germplasm with two treatments (water and 150mM salinity water) were used in this study. A relative salt tolerance (RelST) defined as the germination rate of a cowpea genotype under salt stress divided by non-stress was used as the salt tolerance parameter. The RelST ranged from 0 to 100% with an average of 49.7%. The standard deviation of RelST was 25.5 and the broad-sense heritability was 93.8%. Results suggested that there was large variation of salt tolerance among the 102 cowpea genotypes with very high inheritance. Four accessions, PI582551, PI582422, PI339611, and PI225922 had 92.0% or high RelST, significantly higher than other cowpea genotypes, indicating the four accessions may be used as good source for salt tolerance. Eight different salt tolerance parameters were also estimated and their correlations were discussed in the study, which will provide information to use proper methods to estimate salt tolerance in cowpea. The results from this study would also be valuable to select high salt tolerant cowpea germplasm utilized in cowpea breeding to develop salt tolerant cowpea varieties.