AUTHOR=Ugarelli Kelly , Jagels Annika , Choi Chang Jae , Loesgen Sandra , Stingl Ulrich 

TITLE=Fungal endophytes from Thalassia testudinum show bioactivity against the seagrass pathogen, Labyrinthula spp.

JOURNAL=Frontiers in Marine Science

VOLUME=Volume 11 - 2024

YEAR=2024

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2024.1359610

DOI=10.3389/fmars.2024.1359610

ISSN=2296-7745

ABSTRACT=Thalassia testudinum has undergone die-offs in the past century due to seagrass was�ng disease caused by Labyrinthula sp. Litle is known about how seagrasses resist Labyrinthula infec�ons, but metabolites that inhibit Labyrinthula were previously extracted from seagrass leaves. Furthermore, leaf fungal endophytes from seagrasses possess an�pathogenic poten�al, but their ac�vity against Labyrinthula is unknown. Here, we aimed to iden�fy whether fungal endophytes of T. testudinum can aid in disease defense against Labyrinthula. Through Illumina amplicon sequencing of the leaves' mycobiome, we iden�fied fungi that are known to produce an�microbials. We also isolated and extracted organic compounds from endophytes to test their an�-Labyrinthula poten�al using disk diffusion assays. Twentytwo isolates inhibited Labyrinthula, from which two isolates, Trichoderma sp. P1a and Diaporthe sp.M14, displayed strong inhibi�on. LC-HRMS/MS analysis determined the likely bioac�ve compounds of Trichoderma as peptaibols, and of Diaporthe as cytosporone B. Cytosporone B was confirmed bioac�ve against Labyrinthula via disk diffusion assays. While these organisms are low in abundance in the mycobiome, this study demonstrates that seagrass endophytes have the poten�al to play an important role in defense against Labyrinthula.