In this article we will discuss about the classification of deuteromycetes into various orders.
Because the Deuteromycetes are classified mainly by the types of spores produced, they present many difficulties from the point of view of classification. A pure culture of a single fungus may contain more than one spore type, which would justify its placement in at least two different form-genera.
Since the conception of species is here most loose the arrangement of form-species is purely tentative, the names are to serve merely as handles for convenience in treating these imperfect fungi.
Several systems of classification of the Deuteromycetes have been proposed, of which the oldest one is that of Saccardo (1886) published in Sylloge Fungorum.
Saccardo’s classification has been modified by Ainsworth (1966) and outlined in the following manner:
A. Reproduction by thallospores or conidia
B. Thallospores or conidia not borne in any form of pycnidium or acervulus
Hyphomycetes
BB. Thallospores or conidia borne in a pycnidium or acervulus
Coelomycetes
AA. No reproductive structures known Agonomycetes or
Mycelia Sterilia
The Hyphomycetes include only one form-order:
Moniliales (or Hyphales) which may be subdivided into the following form-families;
A. Conidiophores discrete
B. Mycelium and conidia hyaline or light-coloured Moniliaceae
BB. Mycelium and/or conidia dark-coloured Dematiaceae
AA. Conidiophores synnemata Stilbellaceae
AAA. Conidiophores in sporodochia Tuberculariaceae
The Coelomycetes may be subdivided in the following form-orders:
A. Pycnidial fungi Sphaeropsidales
AA. Acervular fungi Melanconiales
The form-order Sphaeropsidales includes the following form-families:
Pycnidia dark, leathery or membranous Sphaeropsidaceae
Pycnidia light or brightly coloured, waxy or fleshy Zythiaceae
Pycnidia flattened, shield-shaped or elongated Leptostromataceae
Pycnidia deeply cupulate when mature Excipulaceae
The form-order Melanconiales has one form-family Melanconiaceae.
The Agonomycetes or Mycelia Sterilia include only one form-order: Agonomy- cetales having form-genera: Rhizoctonia, Sclerotium, Racedium, Ozenium, and Rhizomorpha.
But Saccardo in his original work divided the form-families into a number of sections taking colour, shape, and septation of conidia as the basis for such groupings.
Following are the sections:
Amerosporae: conidia one-celled, globose, oval or short-cylindrical.
Allantosporae: conidia cylindrical, curved (allantoid) hyaline to pale.
Hyalosporae: conidia hyaline or bright.
Phaeosporae: conidia dark-coloured.
Didymosporae: conidia two-celled, ovate or elongate.
Hyalodidymae: conidia hyaline or bright.
Phaeodidymae: conidia dark-coloured.
Phragmosporae: conidia oblong to fusoi transversely septate into three or more cells.
Hyalophragmiae: conidia hyaline or bright.
Phaeopihragmiae: conidia dark-coloured.
Dictyosporae: conidia ovate to elongate, divided by transverse and longitudinal septa.
Hyalodictyae: conidia hyaline or bright.
Phaeodictyae: conidia dark-coloured.
Scolecosporae: conidia filamentous, thread-like, one- to several-celled, hyaline or dark.
Helicosporae: conidia cylindric, spirally coiled, one- to several-celled, hyaline or dark.
Staurosporae: conidia stellate or irregular, one- to several-celled, hyaline or dark.
The Deuteromycetes are also subdivided in the following manner into four form- orders based on the presence or absence of spores and structures from which or in which the spores are produced.
A. Conidia and other spores present
B. Reproduction by conidia formed within pycnidia which open by a pore or a long slit, or finally become disk-like
Form-order Sphaeropsidales
BB. Conidia, when formed, not in pycnidia; conidia in acervuli which are immersed in substratum or erumpent, black or light-coloured, accompanied by setae or not
Form-order Melanconiales
BBB. Conidia not borne within a pycnidium or acervulus; conidia although produced sometimes as buds are usually found on conidiophores; besides conidia, other spores developed from the cells of the somatic hyphae or yeast-like forms
Form-order Moniliales
AA. Conidia and others spores lacking, sterile mycelium may or may not form sclerotia or masses of fungal cells present
Form-order Mycelia Sterilia
Form-Order Sphaeropsidales of Deuteromycetes:
The Sphaeropsidales are predominantly leaf-spotting fungi though many of them grow on fruit or stems causing blight, rot, cankers, etc. A great number are saprophytes or parasitic on tissues of weak vitality, but not a few are active parasites. The pycnidia characteristic of this group are with or without ostioles or other openings and are separate or joined by stromatic tissue.
The conidia produced in the pycnidia are slime spores. A simplified key to the form-families and form-genus is outlined below.
A. Pycnidia globose, conic or lenticular; membranous, carbonous or coriaceous; stromatic or non-stromatic; black
Form-family Sphaeropsidaceae
B. Pycnidia non-stromatic without setae; conidia filiform, one- to several- celled, several times longer than wide, hyaline
Form-genus Septoria (Fig. 304D & E)
AA. Pycnidia very similar to the Sphaeropsidaceae but light-coloured, soft or waxy
Form-family Zythiaceae
AAA. Pycnidia more or less irregular or shield-shaped to elongate, flattened, black
Form-family Leptostromataceae
AAAA. Pycnidia more or less deeply cup-shaped, black
Form-family Excipulaceae
Form-Order Melanconiales of Deuteromycetes:
The Melanconiales include a fairly large number of forms which are plant pathogens. The common name ‘anthracnose’ is applied to any disease caused by a member of this group. The mycelium is internal remaining within the host or substratum.
The conidiophores form a stratum. The strata typically bear conidia in acervuli which are immersed or erumpent like sporodochia or may be like pycnidia, but true pycnidia are never developed. They are corneous or even submembranous, may or may not be accompanied by setae. The conidia are variable.
This form-order has a single Form-family Melanconiaceae having following form-genera.
A. Conidia one-celled, short, hyaline without appendages; produced apically on conidiophores; acervulus with dark setae
Form-genus Colletotrichum (Fig. 305G)
AA. Conidia three- to several-celled with transverse septa only, not filiform; dark, but end cells hyaline , with appendages: two to three appendages at the apex of conidia
From – genus Pestalotia (fig. 304 A to C)
Form-Order Moniliales of Deuteromycetes:
This is the largest form-order under the Deuteromycetes.
The vast majority are of immense importance:
(i) For being human pathogens,
(ii) In industry,
(iii) As plant pathogens, and
(iv) As laboratory containments.
This group is one of very great diversity and contains a multitude of forms. Many are saprophytes while some are aggressive parasites. The Moniliales differ from the Sphaeropsidales in the absence of the pycnidium and from the Melanconiales in their somewhat loose, separate hyphae, not innate and closely aggregated as in the Melanconiales.
As such they are designated as conidial fungi without pycnidia or acervuli. The conidia, though produced sometimes as buds or by a hyphae becoming broken up, are commonly on conidiophores which have a wide distribution over the hyphae, or are united in groups, or massed in other ways. A simplified key to the form-families and form-genera is presented below.
A. Conidia and conidiophores hyaline or brightly coloured; conidiophores not united into sporodochia or synnemata; conidia seldom as oidia, usually on conidiophores which may or may not be differentiated from somatic hyphae; conidia one- to three- or more-celled, globose to cylindrical or elongated to filiform, sometimes irregular in shape hyaline or bright- coloured
Form-family Moniliaceae
B. Conidia pyriform to nearly ellispoid, two- to three-celled, hyaline; conidiophores long slender, simple or rarely branched, septate, single or in tufts; conidia lateral as well as apical; presence of conidial scars on the conidiophores
Form-genus Pyricularia (Fig. 305B)
AA. Conidia or conidiophores (or both) dark-coloured (brown or black); conidiophores not united into sporodochia or synnemata; conidiophores may or may not be sharply differentiated from the somatic hyphae, erect, simple or much-branched; conidia one- to several-celled, septation either only in a transverse plane or in longitudinal, transverse, and diagonal planes; conidia extremely variable in shape
Form-family Dematiaceae
B. Conidia one-celled globose to sub-spherical, smooth with distinct dark pigment, borne singly at the apex of short conidiophore; conidiophores inflated below the tip exhibiting jar-shaped appearance
Form-genus Nigrospora (Fig. 298E)
BB. Conidia long, slender to filiform, tapering upward, one- to several- celled, hyaline to dark; somatic hyphae produce stroma from which conidiophores arise in tufts of few or many; conidiophores simple or branched, continuous or septate, denticulate or geniculate, usually at the points of denticulation or geniculation scars are formed which bear conidia acrogenously
Form-genus Cercospora (Fig. 305F)
BBB. Conidia three- to several-celled with transverse septa only, ellipsoid or cylindrical, straight, or slightly curved or bent, ends rounded, smooth- walled, dark-coloured, exogenous, not catenulate; conidiophores stout, erect, short or long, septate, branched or unbranched, more or less irregular or bent, bearing conidia successively on new growing tips, often at the knee-like bents
Form-genus Helminthosporium (Fig. 305A)
BBBB. Conidia three- to five-celled with transverse septa only; dark, more or less fusiform, typically bent or curved with one or two of the central cells distinctly larger and darker than the terminal cells; conidiophores brown, unbranched sometimes branched, septate, bear conidia at the apex
Form-genus Curvularia (Fig. 305D)
BBBBB. Conidia dark, typically with both transverse and longitudinal septa, variously shaped, obclavate to elliptical or ovoid having a simple or branched appendage; conidiophores dark, simple, septate, short or elongated, conidia borne on conidiophores acropetally in long chains, less often borne singly
Form-genus Alternaria (Fig. 305C)
AAA. Conidia produced on sporodochia, the external form of the sporodochium is usually definite, occasionally extended as an unlimited crust; conidiophores usually thickly crowded and often forming a closed hymenium, simple or branched, rod-like; conidia various, usually terminal, single, but also in chains and lateral
Form-family Tuberculariaceae
B. Pyrictilaria. C. Alternaria. D. Curvularia. E. Fusarium. F. Cercospora. G. Colletotrichum.
B. Conidia hyaline, variable, principally of two kinds—macroconidia several-celled slightly carved or bent at the pointed ends, spindle- or sickle-shaped, and microconidia usually one-celled, may be two-celled, ovoid or oblong borne singly or in chains; conidia often held in a mass of gelatinous material; conidiophores variable, slender, stout, short, simple or branched irregularly or bearing a whorl of phialides, developed singly or grouped into sporodochia; sporodochia without setae; chJamydospores may or may not be developed
Form-genus Fusarium (Fig. 305E)
AAAA. Conidia produced on conidiophores which are pressed into a synnema
Form-family Stilbellaceae
AAAAA. Plant body consisting of more or less yeast-like forms, form-genera separated according to their ability to form pseudomycelium and true mycelium and on the basis of the kinds of spores
Form-family Cryptococcaceae
Form-order Mycelia Sterilia of Deuteromycetes:
Forms included under this group do not produce conidia and other spores. The sterile mycelium may or may not develop sclerotia. These sterile forms are among the worst of plant pathogens. Following are the form-genera- under this group.
A. Sclerotia variable in form, horny-fleshy, frequently small, formed of loose hyphae brown with long cells
Form-genus Rhizoctonia (Fig. 306)
AA. Sclerotia large, globose or irregular, cartilaginous-fleshy, formed of compact hyphae, mycelium usually light
Form-genus Sclerotium
AAA. Sclerotium-like compact clusters of small cells, mycelium light
Form-genus Papulaspora