Lichen substances and the growth of root associated fungi Phialocephala fortinii and Rhizoscyphus ericae (Ascomycetes) in pure culture

Ruotsalainen A.L.*, Koopmann R. & Hyvärinen M. (2009) Lichen substances and the growth of root associated fungi Phialocephala fortinii and Rhizoscyphus ericae (Ascomycetes) in pure culture.

Sydowia 61 (1): 79–89

Mat-forming lichens are key components of field-layer vegetation of the oligotrophic boreal forests. Hence lichen residues containing secondary substances have a great potential to affect soil microbial processes and both positive and negative impacts on, for example, mycorrhizae have been reported. However, apart from mycorrhizae little is known about the responses of other root-associated fungi to these compounds. Here, we report results from an in vitro experiment where impacts of biologically meaningful concentrations of selected lichen secondary metabolites and lichen extracts on the radial growth of two ubiquitous root-associated fungi were under scrutiny. The growth of both fungal species, Phialocephala fortinii, a fungus belonging to the dark-septate endophyte complex, and Rhizoscyphus ericae, a mycorrhizal associate of Ericaceous plants, responded negatively to the studied concentrations of lichen phenols, whereas lichenan did not affect the growth of either of the species. Extracts from epiphytic Hypogymnia physodes had variable effects on the fungi. We conclude that lichen phenols are potentially antibiotic towards root-associated fungi, and lichenan is not readily degradable by the fungal species studied. In order to resolve the dispute about the ecological significance of lichen substances, the degradation processes of these compounds in real microbial community should be traced.

Keywords: allelopathy, dark septate endophytes, ericoid mycorrhiza, facilitation, lichen phenols.