Dark septate endophytes (DSEs) usually colonize plant roots, especially in stress environments. However, their relationship with plants ranges from beneficial to harmful and has remained largely uncharacterized. In the present study, 14 DSE species grouped into 11 genera were isolated from the roots of a desert plant, Artemisia ordosica, which is widely distributed in northwest China. Three dominant DSE species—Paraphoma chrysanthemicola (Pc), Alternaria chartarum (Ac), and Acrocalymma vagum (Av)—were selected and tested for their resistance to drought in vitro. Furthermore, we characterized the responses of A. ordosica under drought conditions in relation to the presence of these DSEs following inoculation. The results showed that all three strains grew well under in vitro drought stress, and the biomass of Ac and Av was significantly higher than that of the unstressed control. The effects of DSE inoculation on the growth of A. ordosica under drought stress varied according to the different DSE species but were generally beneficial. Under drought stress, Av and Pc promoted plant growth, antioxidant enzyme activity, and root development of the hosts. The Ac strain conferred obvious positive effects on the antioxidant enzyme activity of the hosts. In general, Av and Pc demonstrated better application potential for improving the drought resistance of A. ordosica.

To evaluate the applicability of desert dark septate endophytes (DSEs) in crop cultivation, Alternaria alternata (Fr.) Keissl. (Aa), Paraphoma pye Moslemi & P.W.J. Taylor (Pp), and Paraphoma radicina (McAlpine) Morgan-Jones & J.F. White (Pr) were inoculated into nonhost wheat growing under three water conditions. The plants’ biomass, vegetative growth, and physiological parameters were investigated. At harvest, all DSE strains were effective colonizers under all treatments. These DSEs generally positively affected wheat growth but varied among different DSE species, and this promoting effect was more obvious under drought conditions. Under mild drought (MD) treatments, Aa and Pr increased the leaf number and plant height of hosts. Pr showed a significant beneficial influence on the wheat’s total biomass under all treatments, while Aa and Pp showed benefits only under the well-watered or MD treatment. The response mechanisms of DSE-inoculated wheat under stress may be due to the enhanced photosynthetic efficiency and antioxidant system. Generally, Pr had a stronger beneficial effect. The improved growth and fitness of the inoculated hosts under drought stress may reduce their water supply requirements during seedling growth. We speculate that inoculating wheat with this strain could be a promising approach for water-saving cultivation in arid environments.

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