Plant growth-promoting endophytic fungi of the wild halophytic rice Oryza coarctata

Abstract Background Plant growth-promoting endophytic fungi (PGPEF) that are associated with halophytes have the potential to boost crop salinity tolerance and productivity. This in turn has the potential of enabling and improving cultivation practices in coastal lands affected by salt stress. Methods Endophytic fungi from the wild halophytic rice Oryza coarctata were isolated, characterized, identified, and studied for their effects on all developing stages of rice plant growth and their yields both with and without salt stress. Key results In this study, three different fungal endophytes were isolated from the halophytic wild rice Oryza coarctata. Two isolates were identified as Talaromyces adpressus (OPCRE2) and Talaromyces argentinensis (OPCRh1) by ITS region sequencing. The remaining isolate NPCRE2 was confirmed as a novel strain named Aspergillus welwitschiae Ocstreb1 (AwOcstreb1) by whole genome sequencing. These endophytes showed various plant growth-promoting (PGP) abilities in vitro (e.g., IAA, ACC-deaminase and siderophore production, phosphate, and zinc solubilization as well as nitrogen fixation), where AwOcstreb1 was significantly more efficient compared to the other two isolates at high salinity (900 mm). Independent application of these fungi in commercial rice (Oryza sativa) showed significant elevation in plant growth, especially in the case of the AwOcstreb1 inoculants, which had enhanced metabolite and chlorophyll content at the seedling stage in both no-salt control and 100-mm salt-stressed plants. At the same time, AwOcstreb1-treated plants had a significantly lower level of H2O2, electrolyte leakage, and Na+/K+ ratio under saline conditions. Higher expression (1.6 folds) of the SOS1 (salt overly sensitive 1) gene was also observed in these plants under salinity stress. This strain also improved percent fertility, tillering, panicle number, and filled grain number in both no-salt control and 45-mm salt-stressed inoculated plants at the reproductive stage. Consequently, the differences in their yield was 125.16% and 203.96% (p < 0.05) in colonized plants in normal and saline conditions, respectively, compared to uninoculated controls. Conclusions We propose that AwOcstreb1 is a potential candidate for an eco-friendly biofertilizer formula to improve the cultivation and yield of rice or any other crop in the highly saline coastal regions of Bangladesh.