Extending the hyphal area of the ectomycorrhizal fungus Laccaria parva co-cultured with ectomycorrhizosphere bacteria on nutrient agar plate

The members of Proteobacteria have been frequently detected from ectomycorrhizal roots; however, their function in the mycelial growth of ectomycorrhizal fungi remains uncertain. This study examined the extension of the hyphal area of Laccaria parva co-cultured with the ectomycorrhizosphere bacteria. One mycelial disk of L. parva was placed on the center of a plastic dish containing diluted modified Melin-Norkrans agar media, and each bacterial strain was incubated 2?cm away from the mycelial disk at four orthogonal directions. Several strains of Rhizobiaceae, including those closely related to Bradyrhizobium, significantly increased the extension of the hyphal areas of several strains of L. parva; however, the majority of bacteria tended to decrease them. The effects of bacteria on the hyphal growth area differed according to the combination of strains of bacteria and L. parva in several cases, indicating that the interactions between bacteria and L. parva can be specific at the strain level.