Mastigomycotina : General features of Mastigomycotina | Mycology

In this article we will discuss about General features of Mastigomycotina

Mastigomycotina (Zoosporic Fungi)

The subdivision Mastigomycotina is com­monly known as zoosporic fungi.

The important characteristics of Mastigo­mycotina are:

i. The Mastigomycotina are zoosporic fungi, adapted mostly in aquatic habitat.
ii. Three types of zoospores are common in this group. These are:

(a) Laterally biflagellate,
(b) Posteriorly uniflagellate, and
(c) Anteriorly uniflagellate type having “9 + 2” arrange­ment of component fibrils.

iii. Members of this group vary from unicellular plant body (with or without rhizoid) to fila­mentous coenocytic mycelium.
iv. Sexual reproduction takes place by gametic copulation, gametangial copulation and gametangial contact.



Ainsworth (1973) classified the subdivision Mastigomycotina into following classes:

A. Chitridiomycetes
B. Oomycetes

A. Class. Chitridiomycetes:

Their main distinguishing characteristics are:

i. The vegetative body is unicellular or chain of cells attached with the substratum by rhizoids.
ii. Cell wall is mainly made up of chitin and glucans.
iii. The plant body is normally haploid, except Allomyces.
iv. Asexual reproduction takes place by zoospores produced in zoosporangium; zoospores are uniflagellate, flagellum whiplash type and posteriorly placed.
v. Sexual reproduction takes place by piano- gametes developed in gametangia. The fused gametes form zygote. After resting period, it undergoes meiosis and forms new haploid thallus.



Members of this group are mostly aquatic. Some of them are terrestrial and parasitic. Important parasitic members are Synchytrium endobioticum causes wart disease of potato; Olpidium brassicae, in roots of Crucifers; Urophlyctis alfalfae causes crown wart of alfalfa (Medicago); and Physoderma maydis causes brown spot of maize.

Coelomomyces anophelescia is an endoparasite on mosquito larvae and can be utilized for the biological control of Anopheles mosquito.

B. Class. Oomycetes:

The members are mostly aquatic, either free- living or parasitic on water molds, algae and small animals. Some are terrestrial and few are parasitic on higher plants. The class Oomycetes is characterised by oogamous type of sexual reproduction.

The main distinguishing characteristics are:

i. Members of this class are generally aquatic, but some are terrestrial, grows saprophyticaily on soil or parasitically on shoots of higher plants.
ii. The plant body ranges from unicellular, holocarpic, endobiotic parasites to well- developed coenocytic and branched myce­lium.
iii. The cell wall is composed mainly of cellulose-glucan and devoid of chitin.
iv. Asexual reproduction takes place by biflagellate zoospore without cell wall. The zoospores may be either pear-shaped with anteriorly placed flagella (primary) or reni-form with laterally placed flagella (secon­dary). The flagella are unequal in length, the shorter one tinsel (Flimmer or Pantonematic) type and longer one whiplash (Peitschen or Acronematic) type. Some members produce conidia as asexual spore.
v. Members of Oomycetes are generally eucar­pic, except Lagenidiales those are holocarpic.
vi. Sexual reproduction is of oogamous type. The non-motile gametes are produced in male (antheridium) and female (oogonium) gametangium. The male gametes are trans­ferred to the egg through fertilisation tube, results in the formation of oospore.
vii. The vegetative thallus is diploid and meiosis takes place in gametangium rather than in zygote.



Some important parasitic members of this group are:

i. Pythium. Different species of Pythium cause foot rot, fruit rot, rhizome rot and damping off (detail in Table 4.1).
ii. Phytophthora. Different species of Phytoph­thora cause stem and leaf blight, foot rot, leaf rot, corm rot, fruit rot etc. (detail in Table 4.2).
iii. Plasmopara. P. viticola causes downy mildew of grape vine.
iv. Albugo. Different species of Albugo cause white rust disease of different hosts like crucifers(cabbage, Brassica, radish, rurnip etc.), spinach, sweet potato, morning glories etc. The A. Candida is very common causing white rust of crucifers.
v. Saprolegnia. S. parasitica, a parasite on fish, is an aquatic member.