A contribution to the studies of actinorhizal symbioses of Alnus spp. in Slovenia

Alders (Alnus spp) can form multiple symbiosis with ectomycorrhizal fungi a nd nitrogen fixing bacteria from the genus Frankia. We have tried to isolat e Frankia from root nodules of Alnus glutinosa and A. incana, to culture th em in different culture media and inoculate the seedlings of A. glutinosa, A. incana and A.viridis. The root nodules were surface sterilized and cultu red in a modified BAP medium (LI & al. 1996), a combination of BAP and nutr ient medium (BAKER & al. 1979) and in a liquid medium. No growth was observ ed, although a reference strain of Frankia sp. from a culture collection in Oregon did grow in the combined medium. For inoculation, crushed surface s terilized nodules and sterile two-week old seedlings of alders, grown on th e medium PNS (HACIN & al. 1997), were used. The nodulation was observed on A. glutinosa and A. incana in two growth conditions: in growth pouches and in vitro. PCR amplification with specific primers was performed to confirm the presence of a part of nitrogenase coding genes and to confirm isolates as Frankia alni species/group. We plan to continue with a screening for gro wth conditions and molecular characterization of Frankia strains from Slove nia and with combined inoculations with ectomycorrhizal fungi.