Abstract
Endophytic fungi in symbiotic association with their host plant are well known to improve plant growth and reduce the adverse effects of both biotic and abiotic stresses. Therefore, fungal endophytes are beginning to receive increased attention in an effort to find growth-promoting strains that could be applied to enhance crop yield and quality. In our study, the plant growth-promoting activities of endophytic fungi isolated from various parts of Sophora flavescens (a medicinally important plant in Mongolia and China) have been revealed and investigated. Fungal isolates were identified using molecular taxonomical methods, while their plant growth-promoting abilities were evaluated in plate assays. Altogether, 15 strains were isolated, representing the genera Alternaria, Didymella, Fusarium and Xylogone. Five of the isolates possessed phosphate solubilization activities and twelve secreted siderophores, while all of them were able to produce indoleacetic acid (IAA) in the presence or absence of tryptophan. The endogenous and exogenous accumulation of IAA were also monitored in liquid cultures using the HPLC-MS/MS technique to refine the plate assay results. Furthermore, for the highest IAA producer fungi, the effects of their extracts were also examined in plant bioassays. In these tests, the primary root lengths of the model Arabidopsis thaliana were increased in several cases, while the biomasses were significantly lower than the control IAA treatment. Significant alterations have also been detected in the photosynthetic pigment (chlorophyll-a, -b and carotenoids) content due to the fungal extract treatments, but these changes did not show any specific trends.
Highlights
Endophytic fungi live in the tissues of various plants without causing any symptoms of disease in the host [1]
For the first time, the plant growth-promoting activities of endophytes isolated from various organs of S. flavescens were analyzed in order to compare and evaluate their effects on root growth, biomass and the photosynthetic pigments in A. thaliana
The fungal isolates represented the genera of Alternaria, Didymella, Fusarium and Xylogone, which have not been previously reported as fungal endophytes of S. flavescens
Summary
Endophytic fungi live in the tissues of various plants without causing any symptoms of disease in the host [1] This ecological niche with the continual metabolic interactions between the endophytic microorganism and the host plant seem to serve a remarkable strong evolutionary pressure enhancing the synthesis of secondary metabolites of endophytes with novel properties [2]. Previous investigations of these microorganisms indicated that they are excellent producers of compounds that can be exploited for agrochemical or medicinal purposes due to their biological activity (e.g., antiviral, antimicrobial, anticancer, insecticidal, immunosuppressive and antioxidant effects) [3]. According to Zhang et al, the A. terreus strain was isolated from the seeds of this plant and the fungal production of a host metabolite was confirmed and optimized [16]
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