Adding compost to soil can result in plant disease suppression through the
mechanisms of antagonistic action of compost microflora against plant
pathogens. The aim of the study was to select effective antagonists of
Pythium aphanidermatum from compost, to assess the effect of its
extracellular metabolites on the plant pathogen, and to characterize
antifungal metabolites. The fungal isolate selected by a confrontation test
was identified as Aspergillus piperis A/5 on the basis of morphological
features and the internal transcribed spacer (ITS) region, ?-tubulin and
calmodulin partial sequences. Liquid chromatography-mass spectroscopy
(LC-MS) analysis showed that gluconic and citric acid were the most abundant
in the organic culture extract. However, the main antifungal activity was
contained in the aqueous phase remaining after the organic solvent
extraction. The presence of considerable amounts of proteins in both the
crude culture extract as well as the aqueous phase remaining after solvent
extraction was confirmed by SDS-PAGE. Isolated Aspergillus piperis A/5
exhibits strong antifungal activity against the phytopathogen Pythium
aphanidermatum. It secretes a complex mixture of metabolites consisting of
small molecules, including gluconic acid, citric acid and itaconic acid
derivatives, but the most potent antifungal activity was associated with
proteins resistant to heat and organic solvents. Our findings about the
activity and characterization of antagonistic strain metabolites contribute
to the understanding of the mechanism of interaction of antifungal
metabolites as well as fungal-fungal interaction. The obtained results
provide a basis for further application development in agriculture and food
processing. [Projekat Ministarstva nauke Republike Srbije, br. TR31080 i br.
ON173048, i EU Commission project AREA, br.316004]