Endophytic fungi of Norway spruce roots in boreal pristine mire, drained peatland and mineral soil and their inhibitory effect on Heterobasidion parviporum in vitro

Most of the spruce-dominated pristine mires in South Finland have been drained for forestry, and a large proportion of these forest stands are currently approaching regeneration maturity. We investigated the potential impact of the drainage of pristine mire on the species composition of root endophytes compared to undisturbed mire and mineral soil. Additionally, we further evaluated the inhibitory effect of a subset of the isolated endophytes on the root rot pathogen Heterobasidion parviporum. A total of 113 isolates of fungal root endophytes were obtained from non-mycorrhizal Picea abies roots, which were assigned to 15 different OTUs. Most of the isolates consisted of dark septate endophytes (77 %); the Phialocephala fortinii s.l.-Acephala applanata species complex was the most dominant group, comprising 52 % of all the isolates. No significant differences in the frequency of isolates were observed between the sites. All the diversity indices suggest relatively low or mid-level versatility of the endophyte community, with mineral soil sites having the lowest index and drained peatland the highest. Nineteen of the isolates (17 %) inhibited the growth of the conifer root rot pathogen in vitro. The potential of these endophytes to serve as alternative antagonistic agents to control and manage Heterobasidion root rot disease is discussed.