12 Asexual Sporulation in Agaricomycetes

Production of mitotic spores has been reported for various species of the Agaricomycetes but is generally rather neglected and the extent of asexual sporulation in this class of Basidiomycetes is unknown. The typical life cycle of Agaricomycetes comprises of two alternate mycelial stages, the sterile monokaryon and the fertile dikaryon. The monokaryon contains only one type of haploid nuclei. The dikaryon is formed by mating of two compatible monokaryons and has two distinct haploid nuclei in its hyphal cells, each one per parental monokaryon. Both types of mycelia may produce asexual spores but species differ in whether mitospores are formed at the monokaryon, at the dikaryon, at both or at none. Mitospores produced on the dikaryon might be homokaryotic or heterokaryotic. Here, we present an overview on species of the Agaricomycetes and their spores. Types of sporulation include thallic spore formation (arthroconidia), blastic sporulation (blastoconidia) and intracellular production of thick-walled chlamydospores. Where known, we discuss functions of spores and regulation of mitospore production.