Can lichen secondary compounds impact upon the pathogenic soil fungi Fusarium oxysporum and F. avenaceum?
The antifungal activity of secondary lichen metabolites extracted by means of acetone and ethanol from Cetraria islandica, Cladonia mitis, C. rangiferina, Pseudevernia furfuracea and Usnea dasopoga on the pathogenic fungi Fusarium oxysporum and F. avenacuem was examined. The activity of extracted compounds was tested after their mixture with PDA medium before solidification. The most active extracts inhibiting the growth of fungal mycelia contained fumarprotocetraric, salazinic and usnic acids, and atranorin. Unparalleled activity was demonstrated by an ethanol extract from mixed C. islandica and P. furfuracea thalli, which accelerated the growth of F. avenaceum compared with the control test with ethanol. The growth rate of the two Fusarium representatives was strongly inhibited by both alcoholic extracts from C. mitis and from C. rangiferina, more strongly than by the extracts from the mixed thalli of the two terricolous taxa. A dose of 1 ml of acetone added to the medium had no significant effect on the growth of the tested fungi; it indicates usefulness of acetone as a solvent for some lichen compounds in this type of experiment.