Diversity and Biocontrol Potential of Culturable Fungi Isolated from Deep-Sea Sediments

Deep-sea sediments harbor unique fungal communities adapted to extreme conditions, offering an untapped resource for novel bioactive compounds. However, systematic studies of their potential for agricultural biocontrol remain limited. This study assessed the diversity of culturable fungi from deep-sea sediments and screened their antago-nistic activity against important phytopathogens. Using a multi-method approach (dilution plating and plate stamping), we isolated 159 fungal isolates from sediments at four sites. Internal transcribed spacer (ITS)-based phylogenetic analysis identified Ascomycota as the dominant phylum, along with 35 genera dominated by Cladosporium, Penicillium, and Aspergillus. ITS sequence similarities of 34 strains to known species were < 95%, suggesting potentially novel taxa. Of 23 representative isolates tested, 82.6% inhibited at least one of the following pathogens: Colletotrichum gloeosporioides, Ganoderma pseudoferreum, or Phellinus noxius. Nine selected strains in-hibited pathogen growth through both sterile culture filtrates and volatile organic compounds (VOCs), with effects varying by the strain-pathogen combination. Notably, VOCs from certain strains stimulated the growth of specific pathogens, demonstrating complex fungal chemical interactions. These results highlight the diversity and bio-control potential of culturable deep-sea fungi and support their evaluation as envi-ronmentally friendly agricultural biocontrol agents.