PopW improves salt stress tolerance of red clover (Trifolium pratense L.) via activating phytohormones and salinity related genes

Red clover, a perennial forage legume, is globally significant because of its high nutritional value and nitrogen fixation capacity. However, one of the disadvantages of red clover is its sensitivity to salinity conditions. The aim of this study was to investigate the effect of the PopW pre-treatment on physiological and molecular responses of red clover under salinity stress conditions. Different salinity levels (0, 30, 60, 90, 120, 150, 180, 210 mM NaCl) were applied to the red clover plants. The results indicated that the PopW pre-treated plants had lower yield/quality losses, and better physiological state than the non-pretreated ones under salinity stress. The PopW pre-treatment enabled to maintain K, Na, and Ca contents in red clover plants under all salinity stress levels, compared to non-pretreated ones (p < 0.01). Moreover, after salinity stress treatment, the increased levels of GR, SOD, crude protein rate, IAA, GA, ABA, JA, stress-related genes and decreased levels of leaf senescence genes were determined in the PopW pre-treated plants, compared to non-pretreated ones (p < 0.01). The findings indicate that endogenous hormone content changes and modulation of stress-related and leaf senescence genes played significant preventive roles against salt stress conditions in the PopW pre-treated red clover plants. The results of this study suggest that the PopW pre-treatment could be utilized for marginal areas having salinity problems in red clover.