Relationships between endophytic and pathogenic strains of Inonotus (Basidiomycota) and Daldinia (Ascomycota) from urban trees

The mycelia of wood-decay fungi can persist at a latent endophytic phase in living plant tissues and switch their trophic state under certain environmental conditions. Wood-decay models that take into account these organisms would improve predictability importance in urban environments. In this study, we evaluated the relationship between endophytic and pathogenic strains of Inonotus and Daldinia from urban London plane trees. In vitro wood-decay tests, oxidase reactions and phylogenetic analyses (ITS region, beta-tubulin and nLSU genes) were used to differentiate endophytic and wood-decay strains. All strains significantly reduced the weight of London Plane wood in vitro and had positive oxidase reactions. Endophytic and pathogenic strains of both genera were phylogenetically indistinguishable as evidenced by high sequence similarities, suggesting that endophytic strains can switch their trophic state and can cause wood decay. The capacity of endophytic fungi to switch from a quiescent to a degradative trophic state should be incorporated into predictive models of tree longevity. These revised models could help to predict the impact of wood decay in urban landscapes.