Influence of NaCl stress on germination, growth and vigour of onion (Allium cepa L.) seedlings

Onion (Allium cepa L.), a globally important vegetable crop, is highly sensitive to salinity stress, particularly during its early developmental phases, especially the germination stage. This study evaluated the effect of varying sodium chloride (NaCl) concentrations (0, 50, 100, 150, 200 and 250 mM) on seed germination and early seedling growth of four improved onion cultivars-Bhima Shweta, Bhima Red, Bhima Shakti and Bhima Kiran-under controlled laboratory conditions using a factorial completely randomised design (FCRD) with three replications. Germination percentage, shoot and root length, fresh and dry weights, survival and mortality rates and seed vigour indices were measured. Results demonstrated that NaCl concentrations exceeding 50 mM significantly reduced germination, growth and vigour parameters in all cultivars, with the most severe inhibition observed at 250 mM (37-49 % germination, 70-80 % reduction in seedling elongation and > 50 % mortality). Among the cultivars tested, Bhima Shakti exhibited the highest salt tolerance, maintaining greater germination percentages, biomass accumulation, survival rates and vigour indices compared to other cultivars. The findings indicate that increasing salinity delayed emergence, impaired water uptake, disrupted ion homeostasis and reduced seedling survival, underscoring the importance of selecting salt-tolerant cultivars for sustainable onion production in saline-affected regions.