Although salt stress affects all growth stages of a plant, seed germination and seedling growth stages are known to be more sensitive for most plant species. The current research was carried out to find the most effective indicators when screening melons for salt tolerance. For this purpose, a factorial experiment as a completely randomized design was performed in order to investigate the effects of salinity (0, 20, 40, 60 and 80 mM NaCl) on seed germination parameters, hydrogen peroxide content, lipid peroxidation and some antioxidant enzymes (guaiacol peroxidase, ascorbate peroxidase and superoxide dismutase) in five Iranian melon landraces and one melon cultivar ‘Galia’ F1 at early seedling growth stage. The ‘Galia’ F1 was included for comparison as a salt-tolerant cultivar. The data collected from all salinity treatments across six landraces were used for analysis of variance and principal component analysis (PCA) using SPSS software as well as for obtaining Pearson’s correlation coefficients (r) among all physiological parameters. Obtained results indicated that averaged all landraces across all treatments, increased NaCl significantly affected all the parameters measured. In all landraces, salt tolerance index (STI) decreased as the salt concentrations increased. The principal component analysis revealed variations among the traits and determined four main factors that explained 97.53% of the total variance. Simple correlation coefficient analyses showed the existence of significant positive and negative correlations among characteristics. Our study suggests that the salt tolerance index and principal component analysis can be used as accurate and easy indicators when screening melons for salt tolerance.
