Eco-Friendly Fungal Allies from Freshwater: Exploring Their Role in Plant Defense and Development 

Eco-Friendly Fungal Allies from Freshwater: Exploring Their Role in Plant Defense and Development 

Gil Han, Wonsu Cheon, Hye Yeon Mun, Yunjeong Heo, Yoosun Oh, Sangkyu Park, Hye Jin Hwang Sanghee Lee, Jeong Tae Kim, Yunji Cho, and Chang Soo Lee*

Fungi Research Division, Biological Resources Research Department, Nakdonggang National Institute of Biological Resources, Sangju 37242, Republic of Korea

*Email: cslee@nnibr.re.kr

Freshwater ecosystems serve as crucial reservoirs of microbial biodiversity, with approximately 20–30% of global freshwater utilized in industry and nearly 70% in agriculture. Despite this, the microbial communities residing in freshwater environments remain largely unexplored, particularly in the context of sustainable agriculture. In this study, we investigated the biocontrol and plant growth-promoting potential of fungal strains isolated from freshwater ecosystems in South Korea. 9 fungal isolates were obtained and screened for their antagonistic activity against four Colletotrichum species known to cause significant plant diseases. Dual culture assays demonstrated that several isolates effectively suppressed the growth of these phytopathogens. To assess their agricultural utility, we further evaluated each isolate for key functional activities, including siderophore production and phosphate solubilization. Additionally, given their roles in organic matter turnover and rhizosphere interactions, hydrolytic enzyme activities such as glycosidase, amylase, cellulase, xylanase, and protease, were tested. The ability to produce indole-3-acetic acid (IAA), a phytohormone associated with root development, was qualitatively assessed as well. Based on these preliminary findings, three fungal strains (F0006, F0020, and F0047) were selected for in vivo evaluation. The results indicate that these freshwater-derived fungi exhibit promising activities for development as microbial inoculants in sustainable crop production. This study highlights the potential of freshwater fungal resources and supports their application in eco-friendly strategies for plant disease management and growth enhancement.