True fungi are classified into two major classes viz. Lower true fungi and higher true fungi.
Flowchart: Classification of Fungi
Lower True Fungi:
They are also known as water fungi. They have aseptate
mycelium. Based on the category they are of two types: Oomycetes and
Zygomycetes.
Oomycetes are eukaryotic cells and pathogenic in
nature and hence they have disreputable properties. They have well-defined cell
walls, composed of β-1,3, and β-1,6 glucans, and the body is composed of
mycelium formed by hyphal networks. They absorb nutrition by heterotrophic
mode. They cannot do photosynthesis due to lack of chlorophyll and hence they
are parasitic. They undergo sexual reproduction and produce spores as a mode of
reproduction. They cause seedling blights, damping-off (Pythium aphanider matum
and P. ultimum), root rots (Phytophthora cinnamomi), foliar blights and downy
mildews (Plasmopara viticola) diseases.
Saprolegnia is the only genus of oomycete pathogens that
does not contain plant pathogens but contains pathogens of different
water-borne organisms such as crayfish.
Zygomycetes are conjugated fungi made up of a fusion
of the protoplasts of two equal or unequal gametangia. They have mainly three
parasitic orders viz. Mucorales, Entomophthorales, and Zoopagales. They
reproduce by both sexual and asexual methods. They have sexual spores which are
known as zygospores whereas asexual reproduction occurs by sporangiospores.
Zygospore germinates to produce a hypha and the hyphae are generally aseptated.
The hypha wall is composed of chitin chitosan. Example: Black bread mold
(Rhizopus stolonifer), Mucor, Basidiobolus, Conidiobolus.
Higher Fungi:
They have septate mycelium. The septa have each a central
pore and no motile cells are produced in the life cycle. They have three
classes viz. Ascomycetes, Basidiomycetes, and Deuteromycetes.
(i) Ascomycetes:
- Sexual spores are produced within a sac-like structure called ascus.
- Sexual spores are called ascospores.
- Asexual reproduction occurs by single-celled or multi-celled conidia.
- Ascomycetes are also known as sac mycetes. Hyphae are generally separated.
- Examples: Saccharomyces, Arthroderma, Gibberella.
(ii) Basidiomycetes:
- Sexual spores are produced externally on a basidium.
- Sexual spores are known as basidiospores.
- Asexual reproduction occurs by budding, fragmentation, or conidia formation.
- They are commonly called as mushroom groups.
- Hyphae are generally separated.
- Examples: Amanita, Agaricus, Filobasidiella.
(iii) Deuteromycetes:
- No sexual stage is present.
- Deuteromycetes are also known as fungi imperfection.
- Asexual reproduction occurs by means of conidia.
- Most of the human and animal pathogens are present in this class.
- Examples: Candida, Cryptococcus, Trichophyton, Epidermophyton, Histoplasma.