Club Fungi

Phylum Basidiomycota

The Club Fungi, or Basidiomycetes, are one of the commonly recognized groups of true fungi, and form a monophyletic group of fungi. This group includes the mushrooms and toadstools, as well as shelf fungi, coral fungi, jelly fungi, stink horns, rusts, smuts, earth stars, and fairy rings. These fungi are major decomposers of plant leaf litter in moist and forested systems, especially with their ability to decompose the lignin in wood. They are found in practically every terrestrial ecosystem, as well as freshwater and marine habitats. Many form mutualistic relationships with the roots of plants (mycorrhizae), but others are parasitic on plants, such as the rusts/smuts.

Ecology and Form

- Major decomposers of plant litter
- The body of a fungus are aggregated hair-like strands called mycelium (plural = mycelia), which creeps along the ground releasing enzymes and digesting plant material for energy.
- Basidiomycete mycelium have crosswalls (=septate), and the crosswalls are perforated
- In their "vegetative" feeding phase, the mycelia are monokaryotic, in which they have 1 nucleus per cell, which is typical of most eukaryotes. During reproduction, these fungi become dikaryotic, in which they have 2 nuclei per cell. See Life Cycle below for more details.
- Clamp connections connect two cells and allow accurate segregation of nuclei during mitosis and growth

Diversity

Group with about 25,000 species
Examples include mushrooms, toadstools, shelf fungi, coral fungi, jelly fungi, stink horns, rusts, smuts, earth stars, and fairy rings

“Hymenomycetes”

Class Basidomycetes, e.g., Coprinus or Agaricus
- e.g Mushrooms, Bracket/shelf fungi, Coral fungi, Jelly fungi, and Tooth fungi
- Basidiocarp is the mushroom
  - Cap or pileus: spore-producing portion
  - Stalk or stipe: elevates cap above ground

Largest, terrestrial organism?

One of the largest land organisms is reported to be a honey mushroom (Armillaria ostoyae) growing in Oregon's Blue Mountains
The fungus covers 2,384 acres (965 hectares) or nearly 4 square miles (10 square kilometers)
This organism covers more acreage than Pando, the quaking aspen patch in Utah (106 acres), even though Pando would be greater in weight
The largest organism on Earth is usually reported to be a seagrass patch off Australia, which is 200 sq km or 77 sq miles or over 49,000 acres

Above: Fairy ring around a pine tree

Above: Cap fungus or toadstool (Amanita) basidiocarp

Above: Jelly fungus (Dacrymyces) basidiocarp

Above: Coral fungus basidiocarp

"Gasteromycetes”

Class Basidomycetes
e.g. puffballs, stinkhorns, bird’s-nest fungus, earthstars
Polyphyletic group evolved from hymenomycetes
Basidiospores develop inside the basidioma

Above: Stink horn (Phallus) basidiocarp

Above: Puffball basiocarp

Above: Earth star (Geastrum) basidiocarp

Above: Bird's nest fungus (Cyathus) basidiocarp

Rust/Smuts

Classes Teliomycetes and Ustomycetes
Rusts (Teliomycetes) ~7,000spp.; Smuts (Ustomycetes), ~1,070spp., e.g. Puccinia
Tremendously important due to agricultural damage
e.g. wheat rust, white pine blister, cedar-apple rust, coffee rust & peanut rust; corn smut, wheat bunt smut
Do not form basidioma, but possess dikaryotic hyphae and basidia
Extremely complex lifecycle
- Heteroecious: require two different hosts
- Autoecious: require one different hosts

Left: apple cedar rust (Gymnosporangium)

Right: white pine blister rust (Cronartium)

Life cycle

Club fungi can reproduce both sexually and asexually
- Basidiomycetes exhibit a complex, haplontic life cycle
- Sexual reproduction in club fungi begins when monokaryotic mycelia strands come in contact with mycelia from another individual
- The tips of the mycelia, from each organism, fuse together. This creates new cells that combine the protoplasm and organelles of both organisms, but the nuclei do not fuse. This is a process called plasmogamy, and creates cells with two nuclei (=dikaryotic or binucleate)
- From these fused cells, these two organisms will begin to produce a large fruiting body, called a basidiocarp, such as a mushroom. This basidiocarp continues to grow and mature creating areas of fertile tissue, such as the gills on a mushroom.
- Along the edge of the gills are special cells called basidia (singular = basidium). Inside these cells, the two nuclei fuse (called "karyogamy") to form a diploid zygote. This is the only diploid cell in the life cycle.
- The diploid zygote will then go through meiosis to produce four haploid spores. These spores are then dispersed into nature
- The spores then germinate into monokaryotic mycelia

Above: life cycle of basidiomycetes

Above: Growth of a basidiocarp

Classification

Eukaryotes

└Unikonts

└Fungi

└Dikarya

└Basidiomycota

Geologic Age

Devonian - present

Additional Resources

Single Mushroom Dose Fights Cancer Depression for 2 Years (Science Blog 16Jun2025)

└Agrawal et al. (2025) Long-term benefits of single-dose psilocybin in depressed patients with cancer

A crown rust fungus could help manage two highly invasive plants in Minnesota (Phys.org 5Mar2024)

└Greatens et al. (2024) Aecial and Telial Host Specificity of Puccinia coronata var. coronata, a Eurasian Crown Rust Fungus of Two Highly Invasive Wetland Species in North America

Coffee Rust Battle Intensifies - (Scientific American 18May2014)
Apple-Cedar Rust (In Defense of Plants 2017)
How mushroom disperse their spores (NY Times, 2017)
Rust: the Fungi that Attack Plants (YouTube 2017)

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