Agaricus bisporus basidiospores

A basidiospore is a reproductive spore produced by Basidiomycete fungi. Basidiospores typically each contain one haploid nucleus that is the product of meiosis, and they are produced by specialized fungal cells called basidia. In gills under a cap of one common species in the phylum of Basidiomycota, there exist millions of basidia. Mature state of basidia has the base usually topped with four basidiospores in which contains one from the two haploid nucleus obtained from the process of meiosis. Because of this, a single mushroom has the ability to release a billion spores. Most basidiospores are forcibly discharged, and are thus considered ballistospores.

Basidiomycetes form sexual spores externally from a structure called a basidium. Four basidiospores develop on appendages from each basidium. These spores serve as the main air dispersal units for the fungi. The spores are released during periods of high humidity and generally have a night-time or pre-dawn peak concentration in the atmosphere.

When basidiospores encounter a favorable substrate, they may germinate, typically by forming hyphae. These hyphae grow outward from the original spore, forming an expanding circle of mycelium. The circular shape of a fungal colony explains the formation of fairy rings, and also the circular lesions of skin-infecting fungi that cause ringworm. Some basidiospores germinate repetitively by forming small spores instead of hyphae.

General structure and shape

Basidiospores are generally characterized by an attachment peg (called a hilar appendage) on its surface. This is where the spore was attached to the basidium. The hilar appendage is quite prominent in some basidiospores, but less evident in others. An apical germ pore may also be present. Many basidiospores have an asymmetric shape due to their development on the basidium. Basidiospores are typically single-celled (without septa), and typically range from spherical to oval to oblong, to ellipsoid or cylindrical. The surface of the spore can be fairly smooth, or it can be ornamented.

Basidiospores occur in the members of the Phylum Basidiomycota, which includes mushrooms, shelf fungi, rusts, and smuts.


  • Tree of Life: Basidiomycota
  • Basidiospores