Soil fungal community and mating type development of Tuber melanosporum in a 20-year chronosequence of black truffle plantations

Abstract

Black truffle plantations are established on the basis that Tuber melanosporum Vittad. spreads from artificially inoculated trees. Although truffle cultivation has progressed tremendously over the past 30 years, the ecological processes underlying T. melanosporum mycelium expansion and its interactions with the rest of the fungal community over time are not completely understood. Controversy exists on how mating type distribution evolves with time and its incidence on truffle production. We studied the soil fungal community and mating type distribution in plantations before truffle production (3, 5 and 7 years and after plantation establishment) and during the production period (10, 14 and 20 years) at three distances from the tree stem: 40, 100 and 200 cm. We found that T. melanosporum developed steadily over the years as extraradical mycelium, first at the nearest part of the tree and later up to 200 cm. T. melanosporum development was not correlated with changes in other ectomycorrhizal fungi and was negatively correlated with lower relative abundance of arbuscular mycorrhizal fungi and of non-root associated guilds such as moulds, yeasts and plant pathogens. Mating type frequency did not change across years. Twenty years after establishment no signs of replacement of T. melanosporum by other fungi nor biases in mating type abundance were observed in soil mycelia, indicating that T. melanosporum can colonize and dominate the surrounding soil in mature Quercus ilex L. plantations.