Figure A. Spherosporella brunnea ascocarps on a truffle-mycorrhized seedling (courtesy of Sergio Sanchez);
B. Mycelial culture of S. brunnea, isolate Sb_GMNB300 (courtesy of Gian Maria Niccolò Benucci);
C. S. brunnea ectomycorrhizal mantle (courtesy of Gian Maria Niccolò Benucci);
D. S. brunnea ectomycorrhizae with cystidia (courtesy of Gian Maria Niccolò Benucci).

Within the framework of the "1000 Fungal Genomes Project (1KFG): Deep Sequencing of Ecologically-relevant Dikarya" we sequenced the genome and transcriptome of Sphaerosporella brunnea Sb_GMNB300. In the 1KFG project, genome sequences will be generated for keystone lineages of saprophytic, mycorrhizal, and endophytic fungi that are of special ecological importance and will provide comparative genomics resources. Dozens of sequenced species were harvested from Long-Term Observatories to serve as the foundation for a reference database for metagenomics of fungi and for a comprehensive survey of the soil fungal metatranscriptome.

Sphaerosporella brunnea belongs to Ascomycota within Pyronemataceae, and similar to other members of the family it produces small, brownish cup-shaped fruiting bodies containing ascii having 8 ascospores within (Fig A). Spores are forcibly discharged through the air. Sphaerosporella brunnea also produces conidiospores (i.e. mitospores) in characteristic tree-shaped conidiophores that are dichotomous branched. They may serve as vegetative inoculum.

Sphaerosporella brunnea occurs naturally across North America, Europe, Asia, and is an important pioneer ectomycorrhizal symbiont that is able to associate with a diversity of tree and shrub species in the Angiospermae and Pinaceae. Sphaerosporella brunnea can also be grown in pure culture and isolates are presumed homothallic (Fig B). Fruit bodies erupt from the soil surface under high moisture conditions. Ectomycorrhizas of S. brunnea vary in color from ochre to dark brown. The mantle is plectenchymatous, cystydia are long and ramified (Fig C). Sphaerosporella brunnea is a common unwanted ectomycorrhizal contaminant of truffle-mycorrhized seedlings produced by commercial nurseries in Europe (Sánchez et al., 2014).

References

Sánchez, S., Gómez, E., Martín, M., De Miguel, A.M., Urban, A., Barriuso, J., 2014. 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. Fungal Ecology. 8:59-64 https://doi.org/10.1016/j.funeco.2013.12.003