Mycobiota inhabiting sapwood of healthy and declining Scots pine (Pinus sylvestris L.) trees in the Alps

In this study we examined the endophytic mycobiota of the outermost sapwood of Scots pine trees. We aimed at understanding whether endophytic fungal communities are affected by site and tree conditions, including the health status of trees. A total of 673 trees showing different degree of decline were sampled in four forests of the western Alps. Fungal endophytes were isolated from woody microcores and identified on the basis of their macroscopic and microscopic features. Molecular methods were used to identify sterile Basidiomycota and Heterobasidion isolates. A total of 143 fungal taxa were identified. Ascomycota and anamorphic fungi were dominant, followed by Basidiomycota and Zygomycota. Different fungal communities were identified in the sequence “healthy – intermediate declining – declining trees”. Declining trees were found to harbour a higher number of taxa and are characterized by higher colonization frequencies than healthylooking trees. Canonical Correspondence Analysis (CCA) indicates that fungal assemblages are significantly affected by the degree of decline of trees and to a lesser extent by their diameter and by presence of mistletoes. Our observations