First report and diversity analysis of endophytic fungi associated with Ulva sp. from Iran.

Endophytic fungi are diverse microorganisms that colonize plants symbiotically without causing overt infections. While numerous studies have focused on endophytes in terrestrial plants, there are no prior reports of endophytes associated with algae in Iran. Samples of Ulva sp. were collected during the fall of 2022 from the Bandar Abbas Fishery Coast, Iran, and transported to the laboratory. Following surface sterilization, the samples were cultured on potato dextrose agar (PDA) medium and incubated at 25 °C for 3 weeks. The resulting isolates were purified using the hyphal tip method. This study identified 33 fungal isolates from Ulva sp. collected at the Bandar Abbas Fishery Coast, Iran. Morphological and molecular analyses classified these isolates into 7 species across 6 genera: Alternaria, Aspergillus, Chaetomium, Cladosporium, Penicillium, and Syncephalastrum. Aspergillus was the most abundant genus (34% of isolates), while Alternaria and Syncephalastrum were the least frequent (9% each). Phylogenetic analyses of ITS, β-tubulin, GAPDH, TEF, and LSU gene sequences supported the morphological identification of the isolates. Species identified included Alternaria alternate, Aspergillus caespitosus, Aspergillus terreus, Chaetomium globosum, Cladosporium cladosporioides, Penicillium digitatum, and Syncephalastrum racemosum. All species are reported here for the first time as endophytes of Ulva sp. in Iran. Furthermore, this study represents the first documentation of endophytic fungi associated with the marine alga Ulva sp. in Iranian waters. This research enhances understanding of the ecological interactions between fungal endophytes and marine algae in Iranian ecosystems, emphasizing the diversity of symbiotic relationships in aquatic environments.