Diverse Plant-Associated Pleosporalean Fungi from Saline Areas: Ecological Tolerance and Nitrogen-Status Dependent Effects on Plant Growth

Abstract

Similar to mycorrhizal mutualists, the rhizospheric and endophytic fungi are also considered to act as active regulators of host fitness (e.g., nutrition and stress tolerance). Despite considerable work in selected model systems, it is generally poorly understood how plant-associated fungi are structured in habitats with extreme conditions and to what extent they contribute to improved plant performance. Here, we investigate the community composition of root and seed-associated fungi from six halophytes growing in saline areas of China, and found that the pleosporalean taxa (Ascomycota) were most frequently isolated across samples. A total of twenty-seven representative isolates were selected for construction of the phylogeny based on the multi-locus data (partial 18S rDNA, 28S rDNA, and transcription elongation factor 1-α), which classified them into seven families, one clade potentially representing a novel lineage. Fungal isolates were subjected to growth response assays by imposing temperature, pH, ionic and osmotic conditions. The fungi had a wide pH tolerance, while most isolates showed a variable degree of sensitivity to increasing concentration of either salt or sorbitol. Subsequent plant–fungal co-culture assays indicated that most isolates had only neutral or even adverse effects on plant growth in the presence of inorganic nitrogen. Interestingly, when provided with organic nitrogen sources the majority of the isolates enhanced plant growth especially aboveground biomass. Most of the fungi preferred organic nitrogen over its inorganic counterpart, suggesting that these fungi can readily mineralize organic nitrogen into inorganic nitrogen. Microscopy revealed that several isolates can successfully colonize roots and form melanized hyphae and/or microsclerotia-like structures within cortical cells suggesting a phylogenetic assignment as dark septate endophytes. This work provides a better understanding of the symbiotic relationship between plants and pleosporalean fungi, and initial evidence for the use of this fungal group in benefiting plant production.

Identification, ecological evaluation and phylogenetic analysis of non‐symbiotic endophytic fungi colonizing timothy grass and perennial ryegrass grown in adjacent plots

“…In a study by Qin et al. (), the phylogenetic groups isolated in a multilocus sequence analysis (MLSA) were partially similar to the fungal families isolated in our study despite considerable geographic distance. The Chinese isolates belonged to the families Pleosporaceae , Phaeosphariaceae , Didymellaceae , Lepthosphaeriaceae , Lentithecieae , Massarinaceae , Didymosphaeriaceae and Sporormiaceae .…”

“…In a study by Qin et al (2017), the phylogenetic groups isolated in a multilocus sequence analysis (MLSA) were partially similar to the fungal families isolated in our study despite considerable geo- Suaeda salsa. According to Qin et al (2017), these fungi strongly influence plant tolerance to stress and nitrogen redistribution. These findings have been confirmed in dark septate endophytic (DSE) fungi colonizing edible plants (Vergara et al, 2017).…”

“…According to Qin et al. (), these fungi strongly influence plant tolerance to stress and nitrogen redistribution. These findings have been confirmed in dark septate endophytic (DSE) fungi colonizing edible plants (Vergara et al., ).…”

A window into fungal endophytism in Salicornia europaea: deciphering fungal characteristics as plant growth promoting agents

“…For instance, endophytic fungi isolated from plants in geothermal soils demonstrate thermotolerance (Rodriguez et al 2004), those from heavy metal contaminated areas revealed significant mechanisms of metal tolerance (An et al 2015) and strains obtained from medicinal plants produced bioactive compounds (Ganley et al 2004). Endophytic fungi isolated from the halophyte Suaeda salsa conferred salt stress tolerance in rice seedlings (Qin et al 2017). Thus it is clear that the traits of endophytic fungi are imposed by the type and conditions of their host plant (e.g.…”

Grazing Intensity Affects Communities of Culturable Root‐Associated Fungi in a Semiarid Grassland of Northwest China

“…However, for the majority of culturable RAF (c-RAF), that is, a number of ascomyceteous and non-mycorrhizal basidiomycetous fungi with septate hyphae, their effects on host plants are little explored. There is increasing evidence that several groups of c-RAF can enhance the tolerance of host plants to abiotic stresses such as heat and salt (Rodriguez et al, 2008;Qin et al, 2017) and to biotic stresses such as pathogens and herbivores (Hartley & Gange, 2009). For example, dark septate endophytes (DSE), a major group of c-RAF which are characterized by dark melanized hyphae and commonly occur in all climate regions (Mandyam & Jumpponen, 2005;Rodriguez et al, 2009), have been found to confer fitness benefits to host plants, especially in extreme environments (Newsham, 2011).…”