Author: Jan Scholten
Names: Basidiomycetes; Basidios.
Basidiomycota is a class in the Phylum of Fungi.
Botany: 3 subphyla (including six unassigned classes); 16 classes, 52 orders, 177 families, 1589 genera, 31515 species.
The most recent classification recognizes three subphyla Pucciniomycotina, Ustilaginomycotina and Agaricomycotina and two other class level taxa Wallemiomycetes and Entorrhizomycetes.
Traditionally Basidiomycota was divided into 2 classes, Homobasidiomycetes or Holobasidiomycetes, including true mushrooms and Heterobasidiomycetes, including jelly, rust and smut fungi.
1. Presence of well-developed, branched and septate mycelium having simple (e.g., Ustlaginales and Uredinales) or dolipore (e.g., Auriculariaceae, aphyllo- phorales and Agaricales) septum.
2. The mycelial cells contain one nucleus, called monokaryotic i.e., primary mycelium or two nuclei, called dikaryotic i.e., secondary mycelium. The secondary mycelia may organise and form fruit body, called tertiary mycelium.
3. The cell wall is mainly composed of chitin and glucans.
(a) Vegetative reproduction takes place by budding and fragmentation.
(b) Asexual reproduction takes place by conidia, oidia or chlamydospores. This is lacking in some higher taxa of this subdivision.
(c) Sex organs are absent. During sexual reproduction, the dikaryotic cell is formed by somatogamy, spermatisation or by buller phenomenon. The dikaryotic phase persists for long period of time. Karyogamy occurs in basidium mother cell and forms diploid nucleus, which is ephemeral (short lived). 4-haploid basidiospores are formed by meiosis. Basidiospores are developed exogenously on the horn-shaped structure, the sterigmata (generally 4) on the basidium.
5. Basidia are of two types: Holobasidium (aseptate) e.g., Agaricus, Polyporus etc. (Fig. 4.56A) and Phragmobasidium (septate) e.g., Puccinia, Ustilago (Fig.4.56B) etc.
6. Except in lower forms (Puccinia, Ustilago), secondary mycelia by aggregation form fruit body, the basidiocarp [Agaricus, Polyporus etc.). The number of spores’ on each basidium is commonly 4, but 2 or more than 4 are also present.