1. The Finnish Forest Research Institute, Suonenjoki Research Station, 77600 Suonenjoki, Finland
2. University of Helsinki, Forest Field Station, 35500 Korkeakoski, Finland
3. Department of Forest Mycology and Pathology, Swedish University of Agricultural Sciences, Uppsala, Sweden
4. The Finnish Forest Research Institute, Rovaniemi Research Station, 96301 Rovaniemi, Finland
5. Department of Biochemistry and Biotechnology, University of Kuopio, 70211 Kuopio, Finland