Differences In The Virulence Of Sphaeropsis Sapinea Strains Originating From Scots Pine And Non-Pine Hosts

The virulence of 15 endophytic and pathogenic Sphaeropsis sapinea strains was tested towards Scots pine (Pinus sylvestris). Two-thirds of the strains had been isolated from Scots pines with varying health status: five isolates originated from healthy tissue (endophytic fungal stage) and five from diseased tissue (pathogenic stage). One-third of the strains were isolated from symptomatic tissues of non-pine hosts: black alder (Alnus glutinosa), European beech (Fagus sylvatica), European larch (Larix decidua), Norway spruce (Picea abies) and Douglas fir (Pseudotsuga menziesii). The S. sapinea strain isolated from black alder is the first proof that this fungus can form associations with alder species. On four-year-old P. sylvestris, one isolate per plant was inoculated on three side-shoots of seven plants in a greenhouse (21 inoculations/strain). Differences in necrosis size caused by the isolates were measured 55 days after inoculation. The pathogenic S. sapinea isolates originating from diseased Scots pine and from non-pine hosts were found to cause significantly longer necroses when compared to the endophytic isolates of S. sapinea from symptomless pines.