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Classification of Fungi (Ainsworth 1966, 1971, 1973)

G.C Ainsowrth (1966,71,73) included all fungi in the kingdom Mycota which he divided into two division in a research article entitled “A general-purpose classification of fungi”. This system of classification is followed in the present text.

Division

Sub division

Classes

Myxomycota

(Slime moulds)

 

§  Acrasiomycetes(Cellular slime molds)

§  Hydromyxomycetes (Net slime molds)

§  Myxomycetes (True slime molds)

§  Plasmodiophoromyeetes  (Endoparistic)

Eumycota

(True Fungus)

Mastigomycotina

3 classes

§  Chytridiomycetes.

§  Hyphochytridiomycetes.

§  Oomycetes.

Zygomycotina

2 classes:

§  Zygomycetes.

§  Trichomycetes.

Ascomycotina

6 classes:

§  Hemiascomycetes

§  Loculoascomycetes

§  Plectomycetes.

§  Laboulbeniomycete.

§  Pyrenomycetes.

§  Discomycetes.

Basidiomycotina

3 classes:

§  Teliomycetes.

§  Hymenomycetes.

§  Gasteromycetes.

 

Deuteromycotina (Fungi Imperfecti).

3 classes:

§  Blastomycetes.

§  Hyphomycetes.

§  Coelomycetes.

ZYGOMYCOTINA

  • Habitat: Mostly terrestrial living in soil or on decaying plant or animal material.

  • Nutrition: They consist of both parasitic and saprophytic species.

  • Vegetative structure: The thallus is usually aseptate and coenocytic. The septum is not present in early stage but formed during the reproductive stage.

  • Cell wall: Composed of chitin and chitosan.

  • Asexual reproduction: Thin walled aplanospores (non-motile spores) are formed.

  • Sexual reproduction: Shows gametangial copulation followed by zygospore formation. The zygospore formation is the characteristic feature that contains sporopollenin which is present in the outer wall of spores.

  • Motile stage: Flagellated cells are absent.

  • Common genera: Mucor, Rhizopus, Phycomyces, etc.

 

ASCOMYCOTINA (SAC FUNGUS)

  • Habitat: The majority species are terrestrial but few are aquatic.

  • Nutrition: They consist of both parasitic and saprophytic species.

  • Vegetative structure: Mycelium is well developed with branched and septate hyphae except yeast.

  • Cell wall: Composed of chitin and glucans, but in unicellular form, it is composed of glucans and mannans.

  • Vegetative reproduction: takes place by fragmentation (in filamentous form), fission and budding (in unicellular form).

  • Asexual reproduction: by non-motile conidia, oidia or chlamydospores.

  • Sexual reproduction: Takes place by gametangial copulation (Saccharomy­ces), gametangial contact (Penicillium), somatogamy (Morchella) or spermatization (Polystigma). Ascomycetous also called as sac fungi due to formation of  sexual ascospores (8 in number) inside a sac-like structure called ascus.

  • The ascocarps are fruiting body in which ascus develops. The ascocarps vary in shape and it may be of four types: Apothecium (Peziza, Morchella), Cleistothecium (Aspergillus, Penicilli­um), Peritheci­um (Clavicpes), Ascostroma (Mycosphaerella).

  • Motile stage: absent

  • Common genera: Peziza, Morchella, Aspergillus, Penicilli­um, Clavicpes.


BASIDIOMYCOTINA (CLUB FUNGUS)

  • Habitat: Most abundant and advanced group of fungus. The majority species are terrestrial but few are aquatic.

  • Nutrition: They consist of both parasitic and saprophytic species.

  • Vegetative structure: Mycelium is well developed with branched and septate hyphae having simple or dolipore septum. The mycelial cells contain one nucleus, called monokaryotic i.e., primary mycelium or two nuclei, called dikaryo­tic i.e., secondary mycelium. The secon­dary mycelia may organise and form fruit body, called tertiary mycelium.

  • Cell wall: made of chitin. 

  • Vegetative reproduction: Vegetative reproduction takes place by budding and fragmentation.

  • Asexual reproduction: Asexual reproduction takes place by conidia, oidia or chlamy­dospores.

  • Sexual reproduction: Sex organs are absent. During sexu­al reproduction, the monokaryotic cell of opposite strains fuse (somatogamy) and these results in the formation of dikaryon. The dikaryotic phase persists for long period of time. Karyogamy occurs in basidium mother cell and forms diploid nucleus, which is ephemeral (short lived) and soon form 4-haploid basidiospores by meiosis. Basidiospores are developed exogenously on the horn-shaped structure, the sterigmata (generally 4) on the basidium.

  • Motile stage: absent

  • Common genera: Agaricus, Polyporus, Puccinia, Ustilago

 

DEUTEROMYCOTINA (FUNGI IMPERFECTI)

  • Habitat: They might be terrestrial or aquatic.

  • Nutrition: Members of this group are mostly saprobes, but some are parasitic on plants and animals, including man.

  • Vegetative structure: Septate well-developed mycelium but some have a unicellular thallus.

  • Cell wall: chiefly contains chitin-glucan.

  • Vegetative reproduction: It might occur by budding.

  • Asexual reproduction: The reproduction mostly occurs by conidia, however, a few are purely mycelial, developing no spores.

  • Sexual reproduction: Sexual reproduction absent or not reported yet so its life cycle is incomplete in nature and therefore also called Fungi imperfecti

  • Common genera: Fusarium, Cercospora, Colletotrichum

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