Macroalgae-Derived Fungal Endophytes Promoted the Growth of Mexican Lime Seedlings Under Heat Stress in Greenhouse Condition

Fungal endophyte associated with algae represents a rich source of bioactive metabolites and biostimulants, which can be used practically in agriculture as biofertilizers. Here, we aimed to study the associated symbiotic fungi collected from intertidal areas of the southern coastlines of the Persian Gulf and Oman Sea. The extracted endophytic fungi were identified based on morphological, physiological, and molecular (based on ITS1-5.8S-ITS4rRNA regions) analyses. 566 fungal isolates were obtained from 190 seaweed segments. Results showed that the genera Aspergillus and Penicillium were the most frequent isolated fungi. The highest frequency of fungal isolates (48.29%) was observed in seaweeds collected from Bushehr province. In vitro, most of the fungal isolates (85%) could grow properly on a PDA medium incorporated with one molar NaCl concentration. Fungal isolates showing the highest resistance to NaCl in vitro assays and with the highest frequency were used as biofertilizer agents to study their effects on the morphological characteristics of Mexican lime seedlings. The inoculation results showed that the fungal endophytes could increase the fitness of Mexican lime seedlings under heat stress by improving morphological attributes.