Taxonomy of fungi

Taxonomy is the science of classification, i.e. the ‘assigning of objects to defined categories’.

Classification has three main functions:

it provides a framework of recognizable features by which an organism under examination can be identified;

it is an attempt to group together organisms that are related to each other;

and it assists in the retrieval of information about the identified organism in the form of a list or catalogue.

Traditional taxonomic methods

Early philosophers classified matter into three Kingdoms: Animal, Vegetable, and Mineral.
Fungi were placed in the Vegetable Kingdom because of certain similarities to plants such as their lack of mobility, absorptive nutrition, and reproduction by spores.

Indeed, it was at one time thought that fungi had evolved from algae by loss of photosynthetic pigmentation. This was indicated by the use of such taxonomic groups as Phycomycetes, literally meaning ‘algal fungi’. This grouping, approximately synonymous with the loose term ‘lower fungi’, is no longer used because it includes taxa not now thought to be related to each other (chiefly Oomycota, Chytridiomycota, Zygomycota).

Early systems:

of classification were based on morphological (macroscopic) similarity, but the invention of the light microscope revealed that structures such as fruit bodies which looked alike could be anatomically distinct and reproduce in fundamentally different ways, leading them to be classified apart.

Until the 1980s, the taxonomy of fungi was based mainly on light microscopic examination of typical morphological features, giving rise to classification schemes which are now known to be unnatural.

Examples of traditional taxonomic features include the presence or absence of septa in hyphae, fine details of the type, formation and release mechanisms of spores, or aspects of the biology and ecology of fungi.

Useful ultrastructural details, provided by transmission electron microscopy, concern the appearance of mitochondria, properties of the septal pore, details of the cell wall during spore formation or germination, or the arrangement of secretory vesicles in the apex of growing hyphae.

Biochemical methods have also made valuable contributions, especially in characterizing higher taxonomic levels. Examples include the chemical composition of the cell wall, the occurrence of pigments and the types and amounts of sugars or polyols.

Molecular methods of fungal taxonomy:

Only the most important molecular methods are outlined here. They are based either directly on the DNA sequences or on the properties of their protein products, especially enzymes.

1. KINGDOM PROTOZOA

     (A) Myxomycota

        i) Acrasiomycetes

        ii) Dictyosteliomycetes

        iii) Protosteliomycetes

(B) Myxomycetes

i) Plasmodiophoromycota

 ii) Plasmodiophorales

iii) Haptoglossales (Oomycota)

2. KINGDOM STRAMINIPILA

(A) Hyphochytriomycota

(B) Labyrinthulomycota

i) Labyrinthulomycetes

ii) Thraustochytriomycetes

(C) Oomycota

i) Saprolegniales

ii)Pythiales

iii) Peronosporales

3. KINGDOM FUNGI (EUMYCOTA)

 (A) Chytridiomycota

i) Chytridiomycetes

(B) Zygomycota

i) Zygomycetes

ii) Trichomycetes

(C) Ascomycota

 i) Archiascomycetes

ii)Hemiascomycetes

iii)Plectomycetes

iv)Hymenoascomycetes

a)Pyrenomycetes

b) Erysiphales

c) Pezizales

d) Helotiales

e) Lecanorales/lichens

v) Loculoascomycetes

(D)Basidiomycota

i) Homobasidiomycetes

ii) Homobasidiomycetes: gasteromycetes

iii) Heterobasidiomycetes

iv) Urediniomycetes

v) Ustilaginomycetes

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