Biostimulant Priming Modulates Photosynthesis and Storability of Salt-Stressed Garlic in a Cultivar-Dependent Manner

Soil salinization severely limits the stable production of garlic (Allium sativum L.) and compromises the postharvest storability of seed cloves as industrial planting materials. This study evaluated the morpho-physiological, photosynthetic (JIP-test), and postharvest responses of a shoot-dominant ('C-P') and a root-dominant ('J-L') garlic cultivar to graded salinity (0, 50, 200 mM NaCl) in a hydroponic system, with or without seed-clove priming using a novel commercial biostimulant. Results showed 50 mM NaCl significantly inhibited shoot growth, while 200 mM nearly arrested growth and induced clove decay. Under moderate salinity, LE priming exhibited cultivar-dependent mitigation. In 'C-P', it promoted root branching, enhanced soluble sugar accumulation, and improved postharvest tissue hydration. In 'J-L', biostimulant elevated leaf SPAD values, fully reversed stress-induced clove yellowing, and significantly suppressed postharvest fungal decay during cold storage. In conclusion, garlic's response to salinity is fundamentally dictated by intrinsic resource allocation strategies. Rather than merely promoting growth, biostimulant priming optimizes photosynthetic energy fluxes and reshapes metabolism. This tailored approach effectively preserves the visual marketability of susceptible cultivars while enhancing Osmo protectant accumulation and hydration in vigorous morphotypes, providing a sustainable strategy to safeguard industrial raw materials in salinized controlled cultivation systems.