Salt Stress Tolerance, Antioxidant Response, and the Effectiveness of Seed-Applied Stress Attenuators in Pumpkin Cultivars

Salinity compromises seed germination and early seedling growth, highlighting the need to identify tolerant cultivars and effective management strategies. This study aimed to evaluate tolerance to salt stress, antioxidant activity, and the effectiveness of seed-applied stress attenuators in pumpkin cultivars. The research was conducted in two stages. In the first stage, six cultivars (Tetsukabuto, Soberana, Kin, Bahiana Tropical, Sergipana, and Adele) were subjected to three levels of osmotic potential induced by NaCl (0.0, −0.2, and −0.4 MPa). Germination, growth, and biochemical variables were evaluated. In the second stage, two contrasting cultivars were subjected to six treatments: control (0.0 MPa), salt stress (−0.4 MPa), hydropriming, gibberellic acid, ascorbic acid, and salicylic acid, all under salt stress (−0.4 MPa). In addition to germination and growth variables, oxidative damage (H2O2 and lipid peroxidation) and antioxidant activity (SOD, CAT, and APX) were evaluated. Salt stress significantly reduced germination, growth, and biomass accumulation. Cultivar Adele showed greater tolerance, whereas Tetsukabuto was more sensitive. Hydropriming, gibberellic acid, ascorbic acid, and salicylic acid mitigated the effects of salinity, with hydropriming showing the greatest reduction in lipid peroxidation. It is concluded that Adele, combined with gibberellic acid, and Tetsukabuto, combined with hydropriming and gibberellic acid, showed better performance under salinity stress, highlighting the potential of physiological and biochemical traits for identifying contrasting responses to salinity.