| Summary: | Important losses in forest production are caused by fungi of the genus Heterobasidion in the Scandinavian region. After thinning, spores germinate on the surface of stumps, they infect the root system and they spread to neighbouring trees through root contacts. In this study we explore the
preference of different species of Heterobasidion for different areas of stumps (heartwood and sapwood) and whether or not the preference of infection is associated with moisture content. In two stands, inoculations of H. annosum s.s. and H. parviporum were done in 56 stumps of Pinus sylvestris and in 84 stumps of Picea abies. To know the infection preference, spores of both species of pathogenic fungi were inoculated in sapwood, border and heartwood stump zone of spruce and sapwood and heartwood zone of pine. We calculated the moisture content from a wet sample of each zone in the stump. On spruce, heartwood was the most infected area by H. parviporum (72.4%), followed by
border (44%) and, at last, sapwood (30.2%). Infection on stumps tended to spread towards the heartwood, independently from where the inoculation was done. On spruce, H. annosum s.s. behaved similarly to H. parviporum but the percentage of infection and spread between areas was smaller. In pine stumps, infected areas were very low (5.1%). No clear association with moisture was found, although both Heterobasidion spp. tended to have a preference for infected areas with low moisture content.
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