A Strain of Cylindrocarpon spp. Promotes Salt Tolerance in Acer buergerianum

Global soil salinization is becoming increasingly severe. Many excellent garden trees cannot be planted in coastal or saline-alkali parks. Traditional methods such as freshwater washing and deep tilling consume substantial financial and human resources; hence, it is a promising strategy to search for a biological alternative. Seventy-eight fungal endophytic strains were isolated from the roots of alive Acer buergerianum (trident maple). Through a salt-resistance test, a strain was found to improve the salt tolerance of the seedlings. We explored the mechanism of improvement of salt resistance of the seedlings with this isolate by determining the levels of compounds and enzyme activities associated with salt resistance of the seedlings. ACS53 was identified as a species of the genus Cylindrocarpon by morphological and molecular evaluation. This strain substantially increased the contents of abscisic acid (ABA), proline, and soluble sugar and the activities of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD), which are related to stress tolerance, in seedlings under salt stress. The isolate also showed an ability to secrete abundant extracellular ABA, which may trigger salt tolerance of the seedlings. Biological methods are considered a potential strategy to cope with saline land. In this study, strain ACS53 belonging to the genus Cylindrocarpon was found to substantially improve the salt resistance of trident maple seedlings under salt stress. This may provide a potential sustainable method against salinization. It may also be helpful to better understand how a fungal endophyte improves the salt resistance of host plants.