Abstract

A survey of fungal endophytes associated with xylem of presumably healthy trees was conducted. Wood-inhabiting fungal endophytes of Prumnopitys andina, Podocarpus saligna, Drimys wintert and Nothofagus obliqua were isolated from surface sterilized xylem core samples. Five basidiomycetes (Inonotus sp, Bjerkandera adusta and three unknown strains), two ascomycetes (Xylaria sp., Bipolaris sp.) and one anamorphic strain were detected. Xylaria sp and Bjerkandera adusta were the most frequent fungal isolates. Ultrastructural observations of wood cores samples by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and light microscopy showed the presence of fungal hyphae attached to the inner cell surface inhabiting xylem elements even before the induction of wood degradation. Evidence of latent infection was found mainly along the parenchyma rays indicating fungal colonization and distribution. Results showed simultaneous decay of all wood components, characterized by a thinning cell-wall from the cell lumen to the middle lamella and erosive wood degradation typical of non selective white rot. By using SEM, TEM and light microscopy it was possible to detect natural incidence of latent infections, to visualize spreading of colonization and the ability to produce wood degradation under suitable conditions.