Experiments on the life cycle and factors affecting reproduction of Sphaerosporella brunnea provide evidence for rapid asexual propagation by conidiospores and for homothallism in an ectomycorrhizal competitor of cultivated truffle species

Sphaerosporella brunnea is a pioneer and opportunist ectomycorrhizal species, and the most common fungal competitor in nurseries producing plants mycorrhized with Tuber species. Our objective was to learn more about its life cycle as the first step to manage its presence in greenhouses. Conidiation and formation of resting spore-like structures were found to be triggered by aeration and to be highest on CMA medium. In pot experiments S. brunnea was able to form ectomycorrhizas and ascocarps rapidly, in 2 and 3 months respectively, if substratum moisture was high. Both mycelia and conidiospores were effective sources of inoculum for mycorrhization. This species seems to be homothallic as apothecia have been obtained after inoculations with single monospore isolates. Propagation by mitospores and homothallism are poorly documented in ECM fungi, therefore these results may be of fundamental interest beyond the question of greenhouse management.