Seed priming with glycinebetaine improves germination, yield, gas exchange and photosynthetic attributes in Sesamum indicum under saline stress

Increased salinity stress in environment challenges the seed germination, emergence, and crop yield. The issue carefully demands the seed priming strategies to mitigate the drastic effects of salinity. Current study was conducted to appraise the modulation in germination, photosynthetic pigments, yield, and gas exchange attributes of sesame cultivars (TS-5 and TH-6) to pre-sowing seed treatment with glycinebetaine (GB) under salt stress. Seeds were treated with GB (25 mM) and water prior to sowing for 16 h. Ten seeds of each cultivar were laid down on moistened filter paper (0 mM and 70 mM NaCl) in petri plates to assess the germination attributes under salt stress. In a separate pot experiment, GB primed and water primed seeds were sown in 10 kg sand filled plastic pots. After two weeks of seed sowing, two concentrations of salinity (0 mM and 70 mM) were maintained by dissolving NaCl in full strength Hoagland nutrient solution. Data for germination, gas exchange and yield parameters were collected after one week, two week and ten weeks respectively. Salt stress decreased the germination percentage, plumule/radicle length, number of seeds/plant, Chl a, net photosynthetic rate (P-N), stomatal conductance (g(s)) and transpiration rate (E), while intercellular CO2 concentration (C-i) and ratio of internal to atmospheric CO2 concentration C-i/C-a ratio were increased. However, seed mass/plant, Chl b and carotenoids remained unaffected under salinity. GB mitigated the saline effects by increasing the germination percentage, plumule length, number of seeds/plant and P-N and showed non-significant effect on radicle length, seed mass per plant and Chl a, b and carotenoid contents. Sesame cultivar TH-6 showed better performance as compared to TS-5 under saline conditions. GB is powerful osmoregulator to minimize salt effect in sesame by enhancing physiological and yield attributes.