Seaweed-associated fungal endophytes from southern Sri Lanka and their biocontrol potential against selected fungal phytopathogens

Abstract

Fungal endophytes are an endosymbiotic group of fungi that live asymptomatically in healthy tissues of plants and macroalgae. Due to their ability to produce bioactive compounds with potential antifungal properties, fungal endophytes that inhabit seaweed have gained significant attention in the search for sustainable biocontrol agents against phytopathogenic fungi and bacteria. The present study is aimed at identifying fungal endophytes that reside inside seaweeds found in the coastal waters of Southern Province, Sri Lanka, and investigating their biocontrol potential against two fungal phytopathogens; Neopestalotiopsis cubana (Sporocadaceae, Amphisphaeriales) and Colletotrichum siamense (Glomerellaceae, Glomerellales). This is the first study to discover fungal endophytes associated with seaweeds found in the waters of Sri Lanka. Eight fungal endophytic strains were isolated from seaweeds; Padina antillarum (Dictyotaceae), Sargassum ilicifolium (Sargassacea), and Ulva lactuca (Ulvophyceae), found in Thalpe, Madiha, and Koggala beaches. Based on ITS-rDNA sequence analyses, they were preliminarily identified as four distinct endophytic fungal species belonging to the genera Aspergillus and Penicillium. Isolated fungal endophytes were tested for their biocontrol potential against two selected fungal pathogens using a dual culture assay. Percent growth inhibition (PI) of the test pathogens was calculated. Among the isolated fungal endophytes, Aspergillus sp. GMBUCC 24–013 showed the strongest antagonistic activity against both C. siamense UKCC 24-012 and N. cubana GMBUCC 24–001 closely followed by Aspergillus sp. GMBUCC 24–007, GMBUCC 24–008, GMBUCC 24–009, and GMBUCC 24–012. Aspergillus sp. GMBUCC 24–006 exhibited the least biocontrol potential against both phytopathogens, while Penicillium sp. GMBUCC 24–010, and GMBUCC 24–011 showed moderate activity.