Aromatic Substances in Leaves of Populus tremula as Inhibitors of Mycorrhizal Fungi

The inhibitory principles of aqueous extracts of aspen leaves, acting upon mycorrhizal fungi of forest trees, were isolated by extraction with ethyl acetate and chromatography on silicic acid. Two inhibitors were identified as benzoic acid and catechol by gas chromatography and mass spectrometry. When added to a synthetic medium, these substances had a strong inhibitory effect on the growth of different Boletus-species and a weaker inhibitory effect on litter-decomposing Marasmius-species. When the fraction of the extract which was not soluble in ethyl acetate was included in the medium, the aromatic compounds still inhibited the mycorrhizal fungi while the growth of the litter-decomposers was stimulated.