Basidiomycetes

The basidiomycetes are filamentous fungi, with the exception of those forming yeasts. They include mushrooms, puffballs, stinkhorns, bracket fungi, jelly fungi, boletes, chanterelles, earth stars, smuts, bunts, rusts, mirror yeasts, and the humanpathogenic yeast Cryptococcus.

  

Czech Puffballs

  

Anemone_stinkhorn

 

Rainbow-bracket-fungi

   

yellow-jelly-fungus-mat-su-carbon-crew

  
   

Boletes

   

Geastrum_saccatum earth star mushroom

  

Smuts

   

Corn smut caused by Ustilago maydis

Together, basidiomycetes and ascomycetes form the subkingdom Dikarya, referred to collectively as the "higher fungi."


Basidiomycetes are characterized by the presence of large structures called basidiocarps which are the sexual structures, or fruiting bodies of the fungus.

  

Bbasidium

Spores are borne at the tips of basidia (singular basidium). The basidium is a specialized, club-shaped cell where karyogmay is carried out, followed by meiosis.  Many basidia are contained in or on the basidiocarp and are released into the air.
  

Basidium in electronic microscope

The basidia are contained in rows or gills on the underside of the mushroom cap. A single mushroom, with a surface area of about 200 cm2 may release a billion spores, which drop from the basidia-containing gills and are blown away.

  

Gills on the underside of the mushroom cap

Basidiomycota (except for the rusts (Pucciniales)) tend to have mutually indistinguishable, compatible haploids composed of filamentous hyphae. 

Typically haploid, Basidiomycota mycelia fuse via plasmogamy, followed by compatible nuclei migrating into each other's mycelia to pair up with the resident nuclei. Karyogamy is delayed so that the compatible nuclei remain in pairs, called a dikaryon. The hyphae are then said to be dikaryotic; conversely, the haploid mycelia are called monokaryons.

  

Basidiomycota lifecycle

Basidiomycetes have either a bipolar (unifactorial) or a tetrapolar (bifactorial) mating system. Following meiosis, the resulting haploid basidiospores have nuclei that are compatible with 50% (if bipolar) or 25% (if tetrapolar) of their sister basidiospores, because the mating genes must differ for them to be compatible. However, there are many variations of these genes in the population; therefore, over 90% of monokaryons are compatible with each other, as if there were multiple sexes.

Basidiomycetes are particularly important in nature as decomposers of plant material, especially dead wood and trees. They contain enzymes able to break down the lignin in wood. Shelf fungi are the most efficient at this. Some species of basidiomycetes form mycorrhizal relationships with plants, and others (rusts and smuts in particular) are plant parasites.
   

Club fungus. Sulfur Shelf ( Laetiporus sulphureus)