Antifungal activity of an endophytic strain of Phomopsis sp. on Sclerotinia sclerotiorum, the causal agent of Sclerotinia disease

Ethyl acetate crude extract obtained from fermented cultures of Phomopsis sp. strain S4 (strain S4 extract) was effective in the control of mycelial growth and influenced to some extent sclerotia germination and the number of sclerotia formed by Sclerotinia sclerotiorum, the major agent of Sclerotinia disease. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies showed that in the presence of strain S4 extract, the general hyphal morphology and cells ultrastructure of S. sclerotiorum exhibited drastic changes, including hyphae shriveled and full of holes, damaged cell wall, incomplete plasma membrane, empty cells deprived of cytoplasm, and organelles. Leakage of carbohydrates in S. sclerotiorum exposed to strain S4 extract was also detected. Moreover, the methane dicarboxylic aldehyde (MDA) content increased whereas the catalase (CAT) content was lower. In addition, strain S4 extract was analyzed by gas chromatography mass spectrometry (GC-MS). Of the 86 compounds identified in the strain S4 extract the most frequent were those with a benzene ring (60.91%). These findings suggest that strain S4 extract has potential as natural antifungal agent against S. sclerotiorum and that may be due to its ability to cause oxidative damage to the pathogen cells.