Abstract
Salinity is a critical abiotic stress influencing agricultural crop productivity in arid and semiarid environments. This study reports an in vitro evaluation of NaCl tolerance of wild diploid potato species Solanum okadae and the effect of exogenous MT application on reducing the salt stress effects. In vitro grown plantlets stressed with 50, 100, 150, and 200 mM NaCl had stress tolerance indices of 84.67%, 76.88%, 81.84%, and 67.94%, respectively. Compared to the control, 200 mM NaCl had severe adverse effects on growth parameters and decreased total chlorophyll and K + content by 88.12% and 25.91%, respectively, and increased Na + content by 50.17-fold. The rise in catalase activity, Ca 2+ and Mg 2+ contents, was 1.08-fold, 1.59-fold, and 1.25-fold, respectively. Melatonin (100 μM) treatment mitigated the growth inhibition caused by 200 mM NaCl, as demonstrated by an increase of 17.28%, 150%, 25.39%, 36.36%, and 6.72% in fresh weight, shoot length, total chlorophyll, chlorophyll b, and K + content, along with decreased Na + content and catalase activity by 1.79-fold and 1.08-fold, respectively. This preliminary in vitro study shows that Solanum okadae has natural salt tolerance, which is enhanced by exogenous melatonin improving physiological and biochemical responses under salinity stress. These findings highlight S. okadae ’s potential for breeding salt-tolerant potato cultivars and for understanding the genetic and molecular mechanisms of salinity tolerance. However, further validation in greenhouse and field conditions is needed to confirm the stability and practical relevance of these responses in real agricultural settings.