Colonization by dark septate endophytes improves the growth of Hedysarum scoparium under multiple inoculum levels

Abstract

Despite the abundance of studies on the interactions between dark septate endophytes (DSEs) and host plants, little is known about the effects elicited by different DSE species and inoculum levels, especially in desert plants. Here, we examined the colonization status and species composition of DSEs in roots of Hedysarum scoparium, a xerophyte plant endemic to arid desert, northwest China. Subsequently, we assessed the performance of host plants inoculated with Paraphoma chlamydocopiosa and Alternaria doliconidium under different inoculum levels. DSE colonization was characterized by spatial and interannual variability, and hyphal colonization was dominant (17.2%–76.7%). Alternaria doliconidium, Edenia gomezpompae, Paraphoma pye, Subramaniula flavipila and Herpotrichia striatispora are reported here in desert ecosystems for the first time. Both P. chlamydocopiosa and A. doliconidium established positive symbiosis with H. scoparium, however, the growth-promoting effects differed significantly depending on the DSE species and inoculum level (P < 0.05). Specifically, P. chlamydocopiosa promoted plant height and shoot biomass, whereas A. doliconidium enhanced stem branching and total biomass. The greatest benefits associated with DSEs occurred at 20-mL inoculum level. Variance partitioning analysis indicated inoculum level explained 13.7% of variation in plant growth, while substrate properties and enzymatic activity explained respectively 38.0% and 12.2% of variation in DSE–host associations. Total root length and root surface area were significantly correlated with substrate pH and phosphorus, whereas root diameter was affected by organic carbon and phosphatase. These data provide basis for evaluating the potential application of DSEs for vegetation restoration in arid ecosystems.