In Vitro Evaluation of Salt Tolerance and Melatonin-Mediated Stress Amelioration in Wild Potato (Solanum okadae)

Salinity is a critical abiotic stress influencing agricultural crop productivity in arid and semiarid environments. This study reports in vitro evaluation of NaCl tolerance of wild diploid potato species Solanum okadae and the effect of exogenous MT application on reducing the salt tress 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%, 167%, 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 study demonstrates that Solanum okadae exhibits inherent salt tolerance, which can be further enhanced by exogenous melatonin application. Melatonin treatment improved physiological and biochemical responses under high salinity, indicating its role as an effective stress ameliorant. These findings suggest that S. okadae holds promise for use in potato breeding programs aimed at developing salt-tolerant cultivars and for advancing our understanding of the genetic and molecular mechanisms of salinity tolerance in potato.