Physiological enhancements for alleviation of salt stress in wheat

Increased salinity is a severe problem to crop production while pre-sowing seed treatments can effectively induce salt tolerance in plants. The effect of different pre-sowing seed treatments (hydropriming, halopriming (50 mM CaCl ₂.2H₂O), ascorbate priming (50 mg L^-1) and pre-sowing chilling treatment (-19°C) on seed germination, vigor, antioxidants and total soluble protein content was investigated in two wheat (Triticum aestivum L.) cultivars Auqab-2000 (salt tolerant) and MH-97 (salt sensitive) under saline (15 dS m^-1) or non-saline (4 dS m ^-1) conditions. Of all the seed pretreatments, halopriming followed by hydropriming was the most effective in alleviating the adverse effect of salinity by improving germination and seedling growth of both cultivars. In addition, the effect of ascorbate priming was more pronounced in salt tolerant cultivar as revealed from curtailed mean germination time, improved seedling vigor and enhanced ascorbate contents and catalase (CAT) activity. Salinity significantly increased leaf protein content in both cultivars but the magnitude of increase in protein content was higher in Auqab-2000 as compared to that in MH-97. All pre-sowing seed treatments significantly enhanced superoxide dismutase (SOD) activity in MH-97 while priming with CaCl₂· 2H₂O and ascorbate were very effective in Auqab-2000 during stress conditions. The salt-tolerant cultivar Auqab-2000 had a better protection against reactive oxygen species (ROS) as shown by increased SOD amd CAT activities under salt stress. In conclusion, halopriming and hydropriming successfully improved the seed performance in both cultivars whereas priming with ascorbate was only effective in salt tolerant cultivar under saline conditions. This benefit was attributed to early and synchronized germination, vigorous stand establishment, and decreased oxidative damage due to enhanced antioxidant system.