Mycorrhizal Fungi Prevent Disease in Stressed Pine Seedlings

The common rhizospheric fungus Cylindrocarpon destructans caused severe root damage leading to mortality in light-starved, stunted seedlings of Pinus sylvestris. This effect was, however, almost fully prevented by the presence of mycorrhizal fungi; i.e. Laccaria laccata, Pisolithus tinctorius, or unidentified species present in small amounts of conifer soil. Protection took place even before visible mycorrhizae were found on the roots. This is the first time that protection ofstressed plants against non-parasitic (non-invasive) pathogens has been reported. The results indicate that root protection by mycorrhizal fungi may not only be effective inside the root but probably also extends out into the rhizoplane or rhizosphere.