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Division of Kingdom Fungi

Division of the Kingdom Fungi into various classes is based on morphology of the mycelium, mode of spore formation and fruiting bodies. Kingdom fungi is divided into 4 classes /divisions/phylum basically:
i) Phycomycetes
ii) Ascomycetes
iii) Basidiomycetes
iv) Deuteromycetes

Phycomycetes
• These are considered as Lower fungi/ Algal fungi.
• Found in aquatic habitats, on decaying woods in moist and damp places; obligate parasites of plants
• Have Aseptate and Coenocytic hypha.
• Both sexual and asexual reproduction occurs
• Asexual reproduction occurs by Zoospore or by Aplanospores. These spores are endogeneously produced in sporangium.
• Sexual reproduction produes Zygospores . Zygospores are formed by fusion of two gametes.
• Phycomycetes is sub-divided into Zygomycetes & Oomycetes.
• Common examples are Mucor , Rhizopus stolonifer (bread mold) and Albugo (parasitic fungi on mustard).

Ascomycetes
• Commonly known as Sac-Fungi, because of production of spores (called Ascospores) in sac-like Asci.
• Fruiting body is Ascocarp.
• Ascomycetes are unicellular, e.g., Yeast (Saccharomyces) or multicellular, e.g., Penicillium.
• Are saprophytic, decomposers, parasitic or COPROPHILUS (growing on dung).
• Mycelium is branched and septate.
Live with green algae or Cyanobacteria in beneficial symbiotic associations called Lichens. Also form Ectomycorrhizae with plants.
• Asexual spores are Conidia produced exogenously on the special mycelium called Conidiophores, in cluster or long chain. Conidia on germination produce mycelium.
• Sexual spores are Ascospores which are produced endogenously in Asci. These asci are arranged in different types of fruiting bodies called Ascocarps.
• Examples are Aspergillus , Peziza, Claviceps, Morchella (true morel) and Neurospora, . Neurospora is used extensively in biochemical and genetic work. Others like Morels and truffles are edible ascomycetes. Yeast is useful in fermentation and Penicillium produces antibiotics.

Basidiomycetes
• Commonly known as Club Fungi, after basidium, the club-like cells.
Basidium is a swollen cell at the tip of a specialized hypha, is the characteristic sexual reproductive structure of the club fungi.
• Mycelium is branched and septate.
• Fruiting body is Basidiocarp; club shaped basidium are arranged in basidiocarp. Karyogamy and meiosis take place in the basidium producing four Basidiospores.
• In mushrooms, the basidium form on specialized structures of the basidiocarp known as Gills. The basidium plays the same role in the club fungi as the ascus does in the sac fungi.
• Vegetative reproduction by Fragmentation is common; asexual spores usually not found.
• Examples include Agaricus bisporus (edible Mushroom/White button), Bracket Fungi or Shelf Fungi (important decomposers of wood), Puffballs, Ustilago (Smut) and Puccinia (Rust fungus), Stinkhorns, Bird’s nest fungi
• Grow in soil, on logs and tree stumps and in living plant bodies as parasites, e.g., rusts and smuts

Deuteromycetes
• Known as Imperfect Fungi, because only Vegetative or Asexual Reproduction occurs in these fungi.
Lacks Sexual Reproduction; whenever perfect sexual stages are discovered in these fungi ,they were often moved to Ascomycetes and Basidiomycetes and out of Deuteromycetes.
• Asexual spores Conidia are produced.
• Mycelium is septate and branched.
• Few members are Saprophytes or Parasites, while a large number of them are Decomposers of litter and help in mineral cycling.
• Examples are Alternaria, Colletotrichum and Trichoderma.

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