Alleviation of salinity stress in spring onion by a novel halophytic extract biostimulant via seed priming

Salt stress contributes to reduced vegetable productivity worldwide. Plant-based biostimulants have emerged as a promising technique in improving stress tolerance in crops. To our knowledge, the potential of T. decumbens -derived aqueous extract as a seed-priming biostimulant for improving salt tolerance in A. fistulosum has not previously been investigated. Thus, this study evaluated the effect of T. decumbens -derived aqueous extract as a priming agent in improving seed germination indices, morpho-physiological and phytohormonal responses of spring onion under salt stress (100 mM NaCl). Seeds were pretreated with 50% halophytic crude extract (HCE), 25% HCE, 12.5% HCE, and distilled water (hydro-priming) for 24 h, while non-primed seeds acted as a control. Results reveal that saline irrigation (100 mM NaCl) significantly reduced germination performance (26.5%), seed vigour index (SVI) (35.85), total fresh weight (TFW) (1.35 g), and increased mean germination time (MGT) (7.3 days) in non-primed seeds. Remarkably, halophytic extract priming at the concentration of 12.5%, significantly enhanced germination performance (76%), SVI (391.4), TFW (5.15 g), and shortened the MGT (3.9 days) under saline irrigation (100 mM NaCl) as compared to hydro-priming and the control (non-primed). Additionally, saline irrigation in non-primed and hydro-primed treatments triggered a significant reduction of crucial ions (K + , Mg 2+ and Ca 2+ ), while Na + levels, hydrogen peroxide (H 2 O 2 ), malondialdehyde (MDA) and stress-related phytohormones (Abscisic acid (ABA), Salicylic Acid (SA), Melatonin (MEL), and Jasmonic Acid (JA)) levels were significantly elevated, suggesting that spring onion seedlings were severely affected by salt-induced oxidative stress. However, priming with HCE suppressed salt-induced oxidative stress by lowering MDA and H 2 O 2 and increased antioxidative enzymes (superoxide dismutase and catalase). Furthermore, HCE priming caused a significant reduction of stress-related phytohormones (ABA, SA, MEL, and JA), thus reversing the stress-induced behaviour. These results support the use of halophytic extracts as priming agents in enhancing seed germination performance and seedling growth of spring onion under saline cultivation.