The genome of the black truffle - one of the most popular truffles on the market - has been sequenced. This is the first genome of a symbiotic ascomycete to be analysed. Comparison with the genome of another ectomycorrhizal symbiotic fungus indicates that a genetic predisposition to symbiosis evolved differently in ascomycetes and basidiomycetes. The study also offers insight into fungal sex and fruiting