A phylum of fungi, formerly classified as a class (Ascomycetes) or a subdivision (Ascomycotina). It contains about 65 000 described species, including the yeasts; many some species of filamentous fungi, some of which produce edible fruiting structures (e.g. the morels and truffles); Claviceps purpurea, which causes ergot in rye; and serious plant pests such as blight fungi and powdery mildews. Many are fungal partners of lichens. Sexual reproduction is by means of ascospores produced within a sac-like ascus. The asci are usually grouped together in an ascocarp. The phylum also now includes asexual fungi, such as Penicillium and Candida species, which were formerly placed in the taxon Deuteromycota.