The Turfgrass industry in saline soil is expanding, making it important to use salinity-tolerant turfgrasses. In this experiment, the effect of salinity stress on some biochemical content in salt-sensitive and salt-tolerant tall fescue was evaluated. The Sanandaj and Daran populations with commercial tall fescue (TF) were evaluated as salt-tolerant tall fescues and the Sanajan population was used as salt-sensitive TF. Five salinity levels of irrigation water (0, 45, 90, 135, and 180 mM NaCl) were applied to turfgrasses to identify the tolerance mechanisms in tolerant tall fescue under salinity stress. Results showed that salinity affected all turfgrasses in proline, chlorophyll, 1-1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, as well as sodium and potassium in their shoots. Sanajan population in 90, 135, and 180 mM salinity had the lowest chlorophyll content among all turfgrasses. Salt stress leads to an increase in the activity of proline compared to the control at the first stage (for evaluating osmotic stress) of measurement. In the second stage (to evaluate ionic stress), at concentrations of 135 and 180 mM NaCl, maximum proline was recorded in Daran and Sanandaj populations, respectively. The interaction effect of salinity and TF was significant for DPPH activity. The Na+/ K+ ratio in the Sanajan population was the highest at all salinity levels. In conclusion, the growth and antioxidant capacity of Festuca arundinaceae populations differ in their response to NaCl treatments. In salt-tolerant TF, proline and antioxidant activity increased with increasing NaCl. These may be a mechanism to protect tolerant TF in salt stress, leading to lower accumulated Na+ in tolerant TF, high K+ uptake, and high chlorophyll content. Based on these results, proline content, DPPH radical scavenging activity, chlorophyll contents, and potassium content could use to distinguish tolerant TF from sensitive TF.

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