Salt tolerance of cowpea genotypes in the emergence stage

The effect of NaCl salinity (0, 85 and 170 mmol/L) during emergence of 25 genotypes of cowpea [Vigna unguiculata (L.) Walp.] was studied under growth chamber conditions. Seed emergence percentage and rate, root:shoot ratio, and biomass per plant were affected by genotype, salinity and genotype x salinity interaction; this interaction showed that salinity effects differed among genotypes. The criterion used to classify genotypes with respect to their salt tolerance was based on their germination percentages in both 85 and 170 mmol NaCl/L. One genotype was grouped into class 'A' (CB27) which had the highest salt tolerance at emergence, and was classified as salt tolerant. Another group consisting of Paceno, CB88, CB3, CB5, Tardon, Cuarenteno and CB46 was placed into class 'B'; these genotypes showed total emergence percentages up to 75% in both 85 and 170 mmol NaCl/L. A third group of genotypes was placed into class 'C' which had the lowest emergence percentages in both 85 and 170 mmol NaCl/L. It was confirmed that salinity treatments affect the emergence of cowpea, delaying both emergence percentage and rate. We conclude that selection and classification for salt tolerance in cowpea genotypes can be successfully undertaken at early seedling stages, because the same genotypes were classified similarly during the germination stage in previous research.