Temporal dynamics of ectomycorrhizal fungi and persistence of Tuber melanosporum in inoculated Quercus robur seedlings in North Europe.

Tuber melanosporum is widely cultivated outside its natural habitat in various climatic conditions. This study aims to monitor the persistence of T. melanosporum in inoculated oak seedlings and document temporal changes of native ectomycorrhizal fungi in an Estonian 5-year-old plantation. Sampling of ectomycorrhizal fungi was carried out in June-July 2011-2013 to provide DNA-based identification of the inoculated truffle species and other co-occurring ectomycorrhizal fungi. The mycorrhiza of T. melanosporum proved resistant to cold winters, and the fungus persisted well in the root systems of surviving seedlings albeit slight decline in relative colonization level over 3 years. We identified the genera Hymenogaster and Hebeloma to be the dominant ectomycorrhizal competing fungi in root systems. Good vegetative growth of mycelia and the presence of two compatible mating types suggest that cultivation of T. melanosporum is possible in the Nordic climate. Evaluation of fruit-body production will be a critical next step, because fruiting efficiency allows to determine economic feasibility and ecological sustainability of the Périgord truffle cultivation in northern climate.