Impact of the biological control agent Phlebiopsis gigantea on its resident genetic structure in the Baltic Sea area

The basidiomycete Phlebiop sis gigantea (Fr.) Julich has been used in Swedish forestry as a biocontrol agent against the root and butt-rot pathogen Heterobasidion annosum s.l. on freshly cut Picea abies stumps since the early 1990s. Until 2005, the commercial preparation of this biological stump treatment, Rotstop, has been based on a single strain of P. gigantea that has been applied on more than 47,000 ha annually in Fennoscandia. This paper reports on the spread of genetic material from the Rotstop biocontrol strain of P. gigantea to resident populations of P. gigantea. We conclude that the inoculated fungus remained to a large extent restricted to the treated plots and did not spread to the adjacent areas, dominated by the natural spore deposition from resident populations of the fungus. Furthermore, the study demonstrates high genetic diversity and low geographic differentiation in P. gigantea populations in the geographical area around the Baltic Sea.