Abstract [Objective] Soil salinization seriously affects the growth, development, and yield of the forage
grass E. frumentacea. We aim to investigate the regulatory effects of epibrassinolide (EBR) on salt tolerance
of E. frumentacea and its mechanism, in order to provide a theoretical basis for its application in forage
production. [Methods] Seedlings of ‘Ningji 1’ variety were used as materials. Based on the screening
of suitable salt concentrations, control, salt (150 mmol/L NaCl), and EBR (1, 10, 100 μg/L), either
alone or in combination, were set up. A hydroponic test was used to investigate the changes in seedling
growth, stress tolerant physiology, photosynthesis, ionic homeostasis, and the expression of genes related
to the signaling pathway (SOS) and antioxidant enzymes. [Results] Compared with control, seedling
growth, including plant height, root length, biomass, etc., was inhibited under salt stress. Photosynthesis
indexes, including chlorophyll content and actual photochemical efficiency of PSⅡ [Y(Ⅱ)], maximum
photochemical efficiency of PSⅡ (Fv'/Fm'), electron transport rate (ETR), photochemical quenching coefficient
(qP), etc., as well as osmoregulatory substance (proline, soluble proteins) content and antioxidant
enzyme (SOD, POD, CAT, and APX) activities were reduced under salt stress. Root K+ , Ca2+ ,
and Mg2+ contents were decreased, while root Na+ content was increased under salt stress. Leaf reactive
oxygen species (superoxide anion, hydrogen peroxide) content, and cell membrane permeability (malondialdehyde
content, relative conductivity) were increased under salt stress; gene expression was significantly
down-regulated. Most of the above indexes were not significantly affected by EBR treatment alone. Spraying
different concentrations of EBR could effectively alleviate the unfavorable changes of the above indexes
under salt stress, and the best effect was achieved by 10 μg/L EBR. [Conclusion] Foliar spraying of
EBR up-regulated the expression of SOS signaling pathway and antioxidant enzyme-related genes in the
leaves of E. frumentacea seedlings under salt stress, enhanced the antioxidant and osmoregulatory abilities,
maintained ion homeostasis in the root, protected photosynthesis and growth, and improved salt tolerance
