Diversity of endophytic fungi from extreme habitats and their promising biochemical markers

Climate change exacerbates abiotic stresses, including drought and salinity, significantly affecting agriculture. Overreliance on chemical fertilizers compounds environmental pollution, necessitating sustainable alternatives. Endophytic fungi adapted to extreme habitats present a viable solution by promoting plant growth and enhancing stress tolerance. This study explored the potential of endophytic fungi from harsh environments as eco-friendly substitutes for chemical fertilizers. A total of 174 fungal isolates, representing 13 genera, were recovered from nine wild plant species along the coasts of Port Said Governorate, Egypt. Alternaria dominated the isolates (52.3%), while Talaromyces was the least represented (0.6%). Isolates were tested for drought and salinity tolerance using polyethylene glycol (PEG-6000) and NaCl. Ten highly tolerant isolates were further evaluated for plant growth-promoting traits, including enzymatic activities, nutrient mobilization, antioxidant properties, and phytohormone production. Notable findings included Aspergillus terreus (P2R2M1) and Chaetomium globosporum (P5S1M1), which exhibited multiple enzymatic activities, and Trichoderma viride (P14R3M1), which showed exceptional phosphate solubilization (256 µg/mL). Cladosporium tenuissimum (P4R3M1) demonstrated strong siderophore production (89%), while Trichoderma viride (P12R1M1) exhibited the highest antioxidant capacity (77%) and phenolic content (44 µg GAE/mg DW). Acremonium hyalinulum (P14R1M1) produced the most indole acetic acid (16 µg/mL), and P12R1M1 synthesized the highest gibberellic acid (671 µg/mL). Additionally, this study identified new records of endophytic fungi in Egypt, such as Chaetomium globosporum and Pseudoseptoria sp. These findings underscore the potential of endophytic fungi as sustainable agricultural inputs and highlight their role in reducing reliance on chemical fertilizers.