# In Vitro Screening of NaCl-Tolerant Dark Septate Endophytes and Their Growth-Promoting Effects on Anemone tomentosa

## TL;DR

This study identifies a salt-tolerant fungus that promotes plant growth in saline soils, offering potential for ecological restoration.

## Contribution

The Pp strain of DSE is newly identified as highly NaCl-tolerant and effective in promoting plant growth in saline conditions.

## Key findings

- Six DSE strains showed varying levels of NaCl tolerance in vitro, with Pp performing best at 1.0 M NaCl.
- The Pp strain significantly enhanced seedling growth of Anemone tomentosa in pot experiments.
- All tested DSE strains formed symbiotic relationships with A. tomentosa under saline conditions.

## Abstract

NaCl is the main cause of natural soil salinization. Exploring dark septate endophytes (DSEs) with NaCl tolerance provides information for ecological remediation in saline soil areas. In this study, six DSE strains (Didymella macrostoma (Dm), Paraboeremia selaginellae (Ps), Paraphoma pye (Pp), Paraphoma aquatica (Pa), Acrocalymma ampeli (Aa), and Exophiala xenobiotica (Ex)) isolated from the root sections of Anemone tomentosa were subjected to in vitro NaCl stress experiments and inoculation tests. The results showed that six DSE strains can grow on solid media with different NaCl concentrations (0, 0.2, 0.4, 0.6, 0.8, and 1.0 M) and increase the antioxidant enzyme activities and soluble protein contents to adapt to a salt stress environment. Among these strains, the Pp strain exhibited the greatest biomass accumulation under high NaCl concentrations (1.0 M), indicating greater NaCl tolerance compared to the other five strains. In addition, in the pot experiment, all six DSE strains were able to successfully establish a symbiotic relationship with A. tomentosa, and the Pp strain also showed significant growth-promoting effects on seedlings. In summary, the Pp strain is identified as having strong NaCl tolerance and a significant growth-promoting impact, indicating that it has potential applications as a NaCl-tolerant microbial agent and can be used for bioremediation in saline soils. This research contributes to the basic material and theoretical basis for joint plant–microbe combined remediation in areas prone to soil salinization.