Classification of fungi into four main groups is based primarily on the type of their sexual reproductive structures and methods of reproduction. However, these groups also differ in the type of hyphae and some other characters (table 8.1).

Table 8.1 c=Classification of fungi

Phylum (group) Typical examples Sexual reproduction Asexual reproduction Hyphae
Zygomycota (zygomycetes) Rhizopus, (black bread mold) pilobolus (spitting. Fungus) zygospores Non-motile spores form in sporangia Non-septate, multi mucleate
Ascomycota (Ascomycetes of sac- fungi Yeasts, morels, truffles, powdery mildews, molds Ascospores inside sac-like asci Conidia cut off from tips of conidiophores Septate, lengthy dikaryotic phase.
Basidiomycota (basidiomycetes or club-fungi Mushrooms, rusts, smuts, puff balls, bracket fungi Basidiospores borns on club shaped basidia Uncommon Septate, lengthy dikaryotic phase
Deuteromycota (Deuteromycetes/Imperfect fungi Aspergillus, Penicillium, Alternaria Sexual phase has not been observed Conidia varied

Zygomycota (zygomycetes or conjugating fungi)

During their sexual reproduction, zygote formed directly by the fusion of hyphae forms temporary, dormant, thick walled resistant structure called zygospore, hence the name zygomycetes. Meiosis takes place when zygospore germinates and haploid spores are produced. Spores on germination produce new mycelium. Asexual reproduction by spores is common. Hyphae are coenocytic.
Example: Rhizopus, found growing on spoiling moist bread, fruit etc.

Rhizopus_black_bread_mold

Fig. 8.8: Life cycle, of Rhizopus (black bread mold), a Zygomycete. Zygote formed by fusion of gametangia directly develops into a resting zygospore.

Ascomycota (Ascomycetes or Sac – Fungi)

It is the largest group of fungi, including over 60,000 species, 50% or so occurring in lichens and some, such as morels, are mycorrhizal. Most are terrestrial, though some are marine or fresh water. The group shows diversity from unicellular yeasts to large cup fungi and morels. They produce haploid sexual spores called ascospores by meiosis inside their characteristic sac like structures called asci (sing. Ascus). Meiosis follows nuclear fusion inside the ascus, commonly 8 ascospores are produced inside each ascus. Most sac – fruiting bodies called ascocarps-the visible morels etc. their hyphae are septate. They have lengthy dikaryotic phase that forms ascocarps. They reproduce asexually by conidia that are often dispersed by wind.

Asci_and_Ascospores

Fig, 8.9: Asci and Ascospores. Each aseus contains eight haploid ascospores

Yeasts are unicellular microscopic fungi, derived from all the three different groups of fungi but mostly ascomycetes, and reproducing mostly asexually by budding (Fig. 8.7). however yeasts reproduce sexually by forming asci/ascospores or basidia/basidiospores. They ferment carbohydrate ( glucose) to ethanol and carbondioxide. Because of this feature and many other reasons, these are of great economic importance (see economic importance of fungi). Saccharomyces cerevisiae is the most commonly exploited yeast.

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