Kingdom : Myceteae (Fungi)

Kingdom : Myceteae (Fungi)

Include achlorophyllous, saprophytic or parasitic organisms with Unicellular or multicellular (Mycelium) thallus surrounded by chitinous cell wall. Nutrition is absorptive except slime molds.Reproduction is through asexual and Sexual methods.

Division : I Gymnomycota

Nutrition Phagotrophic, members of this group lack cell wall. Example. Dictyostelium

Division :II Mastigomycota

Flagellate  cells  are  present(Gamete/ Zoospore) . Nutrition absorptive, mycelium coenocytic. Example : Albugo

Division : III Amastigomycota

Unicellular to multicellular forms are included. The mycelium is septate.

Asexual reproduction occurs by budding, fragmentation, sporangiospores, conidia etc., Meiosis is zygotic. Example : Peziza

Recently, with the advent of molecular methods myxomycetes and oomycetes were reclassified and treated under chromista.

 The salient features of some of the classes – Oomycetes, Zygomycetes, Ascomycetes, Basidiomycetes and Form class Deuteromycetes are discussed below.

Oomycetes

Coenocytic mycelium is present. The cell wall is made up of Glucan and Cellulose. Zoospore with one whiplash and one tinsel flagellum is present. Sexual reproduction is Oogamous. Example: Albugo.

Zygomycetes

•            Most of the species are saprophytic and live on decaying plant and animal matter in the soil. Some lead parasitic life (Example: Entomophthora on housefly)

•            Bread mold fungi (Example: Mucor, Rhizopus) and Coprophilous fungi (Fungi growing on dung Example: Pilobolus) belong to this group (Figure 1.21).

• The mycelium is branched and coenocytic

•            Asexual reproduction by means of spores produced in sporangia.

•            Sexual reproduction is by the fusion of the gametangia which results in thick walled zygospore. It remains dormant for long periods. The zygospore undergoes meiosis and produce spores.

Ascomycetes

• Ascomycetes  include  a  wide  range of fungi such as yeasts, powdery mildews, cup fungi, morels and so on (Figure 1.22).

•            Although majority of the species live in terrestrial environment, some live in aquatic environments both fresh water and marine.

•            The mycelium is well developed, branched with simple septum.

•            Majority of them are saprophytes but few parasites are also known (Powdery mildew – Erysiphe).

•            Asexual reproduction takes place by fission, budding, oidia, conidia, chlamydospore.

•            Sexual reproduction takes place by the fusion of two compatible nuclei.

•            Plasmogamy is not immediately followed by karyogamy, instead a dikaryotic condition is prolonged for several generations.

•            A special hyphae called ascogenous hyphae is formed.

•            A crozier is formed when the tip of the ascogenous hyphae recurves forming a hooked cell. The two nuclei in the penultimate cell of the hypha fuse to form a diploid nucleus. This cell form young ascus.

•            The diploid nucleus undergo meiotic division to produce four haploid nuclei, which further divide mitotically to form eight nuclei. The nucleus gets organised into 8 ascospores.

•            The ascospores are found inside a bag like structure called ascus. Due to the presence of ascus, this group is popularly called "Sac fungi".

•            Asci gets surrounded by sterile hyphae forming fruit body called ascocarp.

•            There are 4 types of ascocarps namely Cleistothecium (Completely closed), Perithecium (Flask shaped with ostiole), Apothecium (Cup shaped, open type) and Pseudothecium.

Basidiomycetes

•            Basidiomycetes include puff balls, toad stools, Bird’s nest fungi, Bracket fungi, stink horns, rusts and smuts (Figure 1.23).

•            The members are terrestrial and lead a saprophytic and parasitic mode of life.

•            The mycelium is well developed, septate with dolipore septum(bracket like). Three types of mycelium namely Primary (Monokaryotic), Secondary (Dikaryotic) and tertiary are found.

•            Clamp connections are formed to maintain dikaryotic condition.

•            Asexual reproduction is by means of conidia, oidia or budding.

•            Sexual reproduction is present but sex organs are absent. Somatogamy or spermatisation results in plasmogamy. Karyogamy is delayed and dikaryotic phase is prolonged. Karyogamy takes place in basidium and it is immediately followed by meiotic division.

•            The four nuclei thus formed are transformed into basidiospores which are borne on sterigmata outside the basidium (Exogenous ). The basidium is club shaped with four basidiospores, thus this group of fungi is popularly called “Club fungi”. The fruit body formed is called Basidiocarp.

Deuteromycetes or Fungi Imperfecti

The fungi belonging to this group lack sexual reproduction and are called imperfect fungi. A large number of species live as saprophytes in soil and many are plant and animal parasites. Asexual reproduction takes place by the production of conidia, chlamydospores, budding, oidia etc., Conidia are also produced in special structures called pycnidium, Acervulus, sporodochium and Synnema (Figure 1.24). Parasexual cycle operates in this group of fungi. This brings genetic variation among the species.