Antifungal Activity of Endophytic Nigrospora Species Isolated from Pluchea Plants against Some Fungal Phytopathogens

Endophytic fungi represent promising biocontrol agents due to their ecological compatibility and production of diverse bioactive metabolites. In this study, two endophytic Nigrospora species N. sphaerica and N. osmanthi were isolated from healthy leaves of Pluchea dioscoridis and evaluated for their antagonistic activity against eight phytopathogenic fungi, including foliar pathogens (Alternaria sp., Stemphylium sp. and Myrothecium verrucaria) and soilborne pathogens (Fusarium oxysporum, F. solani, Rhizoctonia solani, Macrophomina phaseolina, Sclerotium rolfsii). Dual culture assays revealed that N. sphaerica exhibited superior inhibitory effects, achieving up to 60% inhibition against Alternaria sp. and 53% against M. verrucaria, alongside moderate suppression of soilborne pathogens. Correspondingly, filtrate assays showed significant biomass reduction, particularly in foliar fungi, suggesting the presence of potent diffusible antifungal metabolites. GC–MS profiling of Nigrospora sphaerica and N. osmanthi culture extracts revealed the predominance of phenol, 2,4-bis (1,1-dimethylethyl)-, along with several key antifungal metabolites. N. sphaerica, in particular, exhibited a broader chemical spectrum, producing α-linolenic acid, arachidonic acid, lactic acid, citric acid, 2-butenedioic acid, glycerol, and aromatic hydrocarbons compounds with well-documented antifungal properties. This highlights the value of isolating safe endophytic fungi capable of naturally synthesizing potent bioactive metabolites for sustainable fungal disease management. These findings highlight N. sphaerica as a strong candidate for further development in sustainable plant disease management. However, additional in vivo and field-based investigations are essential to validate the practical application of endophytic Nigrospora spp. as biological control agents against fungal phytopathogens.