Biological classification can be defined as a method used to categorize and group living organisms based on their characteristics and functions. And this is also known as taxonomy. R.H. Whittaker divided living organisms into 5 kingdoms based on their cellular structure, complexity, reproduction, mode of nutrition, and phylogenetic relationships. The five kingdoms are Monera, Protista, Fungi, Animalia, and Plantae.
Fungi
They are found all over the world. They are heterotrophic organisms and obtain nutrients from dead substrates by absorption. Their cell walls are composed of fungal or chitinous cellulose. Their bodies are long and have thread-like structures called hyphae. A cluster of hyphae forms a mycelium. They depend on living animals and plants and are called parasites. Fungi are further classified into 4 classes based on the structure of the mycelium and the method and type of spore formation:
- Phycomycetes
- Ascomycetes
- Basidiomycetes
- Deuteromycetes
Basidiomycetes
- Also known as club fungi.
- The reproductive structure is basidium.
- Spores that are produced are called basidiospores.
- The vegetative structure is made up of primary or secondary mycelium.
- Vegetative reproduction is done by fragmentation.
- Sexual reproduction is done by the two vegetative or somatic cells creating a basidium.
- Basidiospores are produced in the basidium by the development of fruiting bodies called basidiocarps.
- Examples – Agaricus (found in mushrooms), Puccinia.
- Basidiomycetes include these groups: mushrooms, puffballs, jelly fungi, boletes, chanterelles, earth stars, smuts, rusts, mirror yeasts, and Cryptococcus, the human pathogenic yeast.
Examples
- Mushrooms: The fleshy, spore-bearing fruiting body of a fungus that normally grows above ground, on soil, or food source is known as a mushroom or toadstool.
- Puffballs: The name puffballs come from the clouds of brown dust-like spores that are released when the adult fruit body bursts or is impacted.
- Smuts: The multicellular fungi known as smuts are distinguished by their abundant teliospore numbers. The smuts’ dark, thick-walled, and dust-like teliospores are what gave rise to their name, which is derived from a Germanic term for dirt.
- Rusts: Plant diseases called rusts are brought on by fungi of the Pucciniales group. Rusts are among the most dangerous infections for horticulture, forestry, and agriculture.
- Cryptococcus: In the fungi Cryptococcaceae, the genus of the fungi Cryptococcus contains both filamentous and yeast species.
- Jelly fungi: These fungi are named from the jelly-like substance of their foliose, irregularly branching fruiting body.
Classification of Basidiomycetes
Traditional Classification of Basidiomycetes
Basidiomycetes are classified into two subclasses based on the septation/partition of the basidium
Heterobasidiomycetes
- Also known as holobasidiomycetes.
- Have fragmented basidium.
- They are obligate parasites and can cause severe diseases in many crops.
- Includes true mushrooms.
- Includes three orders:
- Tremellales
- Uredinales
- Ustilaginales
Homobasidiomycetes
- Do not have fragmented basidia.
- They are grown in numerous habitats such as grassland, dung, termite mounds, and wooden logs.
- Includes rust and smut fungi.
- Includes two series: Hymenomycetes and Gastromycetes.
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Hymenomycetes
- The hymenium is exposed.
- It Includes 3 orders- Exobasidiales, Polyporales, and Agaricales.
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Gastromycetes
- The hymenium is enclosed.
- It Includes 5 orders- Hymenogastrales, Lycoperdales, Sclerodermatales, Phallales, and Nidulariales.
Recent Classification of Basidiomycetes
It is classified into 3 subclasses and 2 other class-level taxa-
Pucciniomycotina– includes rust fungi, the insect parasitic genus Septobasidium, a former group of smut fungi, and a mixture of different, infrequent seen recognized fungi. Includes 8 classes:
- Agaricostilbomycetes
- Atractiellomycetes
- Classiculomycetes
- Cryptomycocolacomycetes
- Crystobasidiomycetes
- Microbotryomycetes
- Mixiomycetes
- Pucciniomycetes
Ustilaginomycotina– most of them are former smut fungi and the Exobasidiales. Includes 3 classes:
- Exobasidiomycetes
- Entorrhizomycetes
- Ustilaginomycetes
Agaricomycotina– also known as Hymenomycetes comprises most fungi such as mushrooms, bracket fungi, and puffballs. Includes 3 classes:
- Agaricomycetes
- Dacrymycetes
- Tremellomycetes
2 Class-level taxa
- Wallemiomycetes- sister group of Agaricomycotina according to the genomic evidence.
- Entorrhizomycetes– possibly a close sister group to the rest of Basidiomycetes classes.
Economic Importance of Basidiomycetes
- Basidiomycetes are of beneficial as well as harmful nature but still, they possess great economic importance.
- Some basidiomycetes are the causative agents which cause destructive diseases in cereal crops including wheat, oats, barley, etc.
- Basidiomycetes like pore fungi are the wood rotters that destroy lumbar and timber.
- Basidiomycetes like Mushrooms are of great economic value as food. They are cultivated for being delicious and rich in various sources.
- Species of puffballs including Lycoperdon and Clavatia, their young fleshy sporophores can be eaten as Clavatia is consist of a substance called calvacin that is used in the treatment of cancer.
- However, the toadstools are poisonous. Some of these, like Amanita, are poisonous to the point of death, while others just cause discomfort. With the roots of forest trees, many members of this class develop ectotrophic mycorrhizal connections.
- While the mantle of the fungal partner serves to transfer nitrogen, phosphorus, and other elements received by the mycelium to the root, the fungus acquires sugars and other organic substances from the roots of the tree partner.
- Saprophytic Basidiomycetes are important in the decomposition of dead fallen leaves and other forest litter because they transform waste and bring it back into the soil.
Life Cycle of Basidiomycetes
The Basidiomycetes share several characteristics with Ascomycetes regarding their general life cycle pattern. The haplophase somatic body, represented by primary mycelium, is produced by the basidiospore following germ tube germination. Often, oidia are produced by the main mycelium. The oidia can act as spores and produce primary mycelia, or they can participate in the development of dikaryotic secondary mycelia by spermatizing with other primary mycelia that are compatible with one another. Somatogamy between two suitable primary mycelia can also produce secondary mycelium. The basidium forms from the dikaryotic apical cell of the hypha of the secondary mycelium.
The dikaryotic hyphal cells may produce resting spores. A basidium is produced by each spore that is resting on germination. Karyogamy occurs in the diplophase condition that produces basidiospores, which is followed immediately by meiosis and results in the production of haploid basidiospores. The haplophasic somatic body is produced when the basidiospores germinate. The life cycle is completed. The three phases of the life cycle are the haplophase, dikaryophase, and diplophase, with the dikaryophase being significantly longer than the other two and nutritionally distinct from the haplophase. Additionally, the haplophase is visible. The diplophase, which is relatively brief in nearly all fungi, is followed by meiosis.
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FAQs on Basidiomycetes
Question 1: Define taxonomy.
Answer:
The method used to categorize and group living organisms based on their characteristics and functions is known as taxonomy.
Question 2: Write classes of fungi.
Answer:
Fungi are further classified into 4 classes based on the structure of the mycelium and the method and type of spore formation:
1. Phycomycetes
2. Ascomycetes
3. Basidiomycetes
4. Deuteromycetes
Question 3: What are the characteristics of Basidiomycetes?
Answer:
Characteristics of Basidiomycetes-
- Also known as club fungi.
- The reproductive structure is basidium.
- Spores that are produced are called basidiospores.
Question 4: Write the traditional classification of Basidiomycetes.
Answer:
Basidiomycetes are classified into two sub-classes based on the septation/partition of the basidium:
1. Heterobasidiomycetes
2. Homobasidiomycetes
Question 5: Write about Agaricomycotina.
Answer:
Agaricomycotina- also known as Hymenomycetes comprises most fungi such as mushrooms, bracket fungi, and puffballs.