Phylum Basidiomycota: Club fungi have long-lived dikaryotic mycelia

•Approximately 25,000 fungi, including mushrooms, shelf fungi, puffballs, and rusts, are classified in the phylum Basidiomycota.

•The name of the phylum is derived from the basidium, a transient diploid stage.

•The clublike shape of the basidium is responsible for the common name club fungus.

•Basidiomycetes are important decomposers of wood and other plant materials.

•Of all fungi, these are the best at decomposing the complex polymer lignin, abundant in wood.

•Two groups of basidiomycetes, the rusts and smuts, include particularly destructive plant parasites.

•The life cycle of a club fungus usually includes a long-lived dikaryotic mycelium.

(1) Two haploid mycelia of opposite mating type undergo plasmogamy,

(2) creating a dikaryotic mycelium that ultimately crowds out the haploid parents.

(3) Environmental cues, such as rain or temperature change, induce the dikaryotic mycelium to form compact masses that develop into basidiocarps.

•Cytoplasmic streaming from the mycelium swells the hyphae, rapidly expanding them into an elaborate fruiting body, the basidiocarp (mushrooms in many species).

•The dikaryotic mycelia are long-lived, generally producing a new crop of basidiocarp each year.

(4) The surface of the basidiocarp’s gills are lined with terminal dikaryotic cells called basidia.

(5) Karyogamy produces diploid nuclei which then undergo meiosis, (6) each yielding four haploid nuclei.

•Each basidium grows four appendages, and one haploid nucleus enters each and develops into a basidiospore.

(7) When mature, the basidiospores are propelled slightly by electrostatic forces into the spaces between the gills and then dispersed by the wind.

(8) The basidiospores germinate in a suitable habitat and grow into a short-lived haploid mycelia.

•Asexual reproduction in basidiomycetes is much less common than in ascomycetes.

•A billion sexually-produced basidiospores may be produced by a single, store-bought mushroom.

•The cap of the mushrooms support a huge surface area of basidia on gills.

•These spores drop beneath the cap and are blown away.

•By concentration growth in the hyphae of mushrooms, a basidiomycete mycelium can erect basidiocarps in just a few hours.

•A ring of mushrooms may appear overnight.

•At the center of the ring are areas where the mycelium has already consumed all the available nutrients.

•As the mycelium radiates out, it decomposes the organic matter in the soil and mushrooms form just behind this advancing edge.

•The four fungal phyla can be distinguished by their reproductive features.