Mitigación del estrés salino en cultivares de caupí mediante brasinoesteroides: respuestas fisiológicas y antioxidantes

Cowpea (Vigna unguiculata (L.) Walp.) is a crucial crop for food security in tropical regions, but its productivity is severely limited by soil salinity. Brassinosteroids (BR) have emerged as promising natural regulators that can enhance plant resilience to abiotic stresses. This study aimed to evaluate the mitigating effect of BR on salt stress in two cowpea cultivars with contrasting tolerance (BRS Tapaihum, tolerant; Manteiguinha, sensitive) by analyzing physiological and biochemical parameters. A completely randomized design was employed in a 2x3x3 factorial scheme, combining two cultivars, three NaCl concentrations (0, 75, and 150 mM), and three BR concentrations (0, 0.2, and 0.4 µM). Key analyses included electrolyte leakage, leaf Na⁺ and K⁺ content, and the activity of antioxidant enzymes, alongside lipid peroxidation (MDA) assessment. Salinity stress (150 mM NaCl) significantly increased electrolyte leakage and sodium accumulation while decreasing potassium content. The activity of antioxidant enzymes was elevated under salt stress. Foliar application of BR significantly mitigated these effects by reducing Na⁺ accumulation, enhancing K⁺ retention, improving the K⁺/Na⁺ ratio, and modulating antioxidant enzyme activity, which consequently decreased oxidative membrane damage (MDA). The tolerant cultivar, BRS Tapaihum, consistently exhibited a superior response to BR application compared to the sensitive Manteiguinha. These results demonstrate that BR application effectively enhances salt stress tolerance in cowpea by improving ionic homeostasis and reinforcing the antioxidant system. This suggests its strong potential as a biostimulant for sustainable cultivation in salinity-affected areas.