Evaluating the impact of different salinity levels on morphological, physiological and yield traits of various onion genotypes (Allium cepa L.)

Onion (Allium cepa L.) is a universally significant vegetable crop, but its yield is severely limited by soil salinity, particularly in large onion-producing areas of India. This research evaluates the morphological, physiological and yield reaction of four improved onion genotypes (Bhima Kiran, Bhima Shakti, Bhima Shweta and Bhima Red) to six levels of salinity (0, 0.5, 1, 2, 4 and 6 dS m-1) in pot experiments over 2023-24 and 2024-25 Winter- spring seasons at the ICAR-Directorate of Onion and Garlic Research, Pune. Results indicated that salinity increases resulted in substantial declines in plant height, number of leaves, thickness of the neck, leaf area, dry matter accumulation, chlorophyll content, bulb diameter, bulb weight and total bulb yield with significant genotypic variation. Bhima Shakti and Bhima Shweta exhibit higher salinity tolerance, maintaining higher growth and yield parameters under salinity conditions, whereas Bhima Kiran and Bhima Red were extremely sensitive, recording drastic reductions. Low salinity (0.5 dS m-1) sometimes triggered growth and yield in tolerant genotypes, which indicated potential osmotic priming effects. Extreme salinity (6 dS m-1) reduced total bulb yield in sensitive genotypes (Bhima Kiran and Bhima Red) to only 3 %-12 % of controls, while tolerant genotypes (Bhima Shakti and Bhima Shweta) maintained higher yields of 33.94 g and 53.59 g pot-1, about 7 % and 10 % of their controls respectively. The research emphasizes the need for genotype selection for salt-susceptible environments and focuses on the physiological and biochemical processes involved in salt tolerance of onion.