Melatonin as a protective signal in oats: enhancing salinity tolerance for sustainable agriculture on marginal lands

Abstract Soil salinity poses a major constraint and a primary threat to global food security, demanding sustainable strategies to maintain crop productivity on marginal lands. This study evaluated the role of exogenous melatonin (50 and 100 µM) in enhancing salt stress resilience in two oats (Avena sativa L.) varieties exposed to 120 mM NaCl in a completely randomized design. Salinity stress markedly reduced plant biomass, chlorophyll stability, and relative water content while promoting excessive accumulation of toxic ions and reactive oxygen species. Melatonin pretreatment-particularly at the 50 µM, effectively mitigated these adverse effects by acting as a physiological priming agent. Melatonin induced a coordinated plant’s stress response reprogramming, evidenced by elevated activities of antioxidant defense system (CAT, POD, and APX) and a significant reduction in oxidative damage indicators such as H2O2 and malondialdehyde (MDA). Additionally, melatonin improved ionic homeostasis, resulting in significant recovery of vegetative growth and approximately a 50% increase in grain yield under saline conditions. These findings highlight melatonin as a promising eco-friendly approach for improving oat performance in salinity stressed environment.