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True Fungi (Eumycophyta) 1
Deuteromycota – Fungi Imperfecti
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Tables Plates
Introduction This group of fungi comprises over
20,000 species and is very important in breaking down organic matter, as plant
and animal pathogens and for industrial importance. They are all higher true fungi, which lack a known perfect
stage. Their mycelium is like that in
the Ascomycota and vegetative reproduction structures are common to both
groups. Over 90 percent of the
important fungi that have been shown to possess a perfect, or sexual, stage
have been Ascomycota. Most of the
Deuteromycota produce conidia of one kind or another. There is substantial evidence that at
least the majority of these fungi are of Ascomycetous affinities. Indeed, it is probable that a great many
of them are Ascomycota whose perfect stages have simply escaped
discovery. Mycologists continue to
report finding ascigerous stages of several fungi previously included in this
group. Thereafter these drop out of
the Fungi Imperfecti and are renamed and reclassified on the basis of the
newly acquired information. How many
other members of the Fungi Imperfecti will in a similar way ultimately be
eliminated from the group can only be conjectured. However, it seems likely that among the large number of species
at present catalogued as Deuteromycota, there are some that never do produce
a perfect stage, perhaps having lost the ability in the course of evolution,
reproduction by conidia or other vegetative means having proved adequate for
survival. Four orders that will be
discussed here are Sphaeropsidales, Melanconiales, Moniliales and Mycelia
Sterilia. In 1952 Alexopoulos gave a
detailed narrative of the Deuteromycota, and the following description is
derived therefrom [Alexopoulos, C. J. 1952. Introductory
Mycology. John Wiley & Sons,
NY. 482 p.]. ------------------------------------- A great many
fungi are known which have septate mycelium and which, so far as anyone has
been able to discover, re- produce only by means of conidia. Since these
fungi apparently lack a sexual phase (perfect stage), we call them commonly
"imperfect fungi," and technically "Fungi Imperfecti."
Many of these are saprobic, but many are of great importance to us because
they are parasites that cause diseases of plants, animals, and human beings.
The same methods
employed for the formation of pycnidia also serve for the formation of.
acervuli, the origin of which may be simple meristogenous, compound
meristogenous, or symphogenous. This undoubtedly explains the fact that
intermediate forms, between pycnidia and acervuli are produced by some fungi
which ~re, therefore, difficult to classify.
------------------------------------- Sphaeropsidales In this order the spores are borne in a flask-shaped pycnidium on
the inside of which are conidiophores bearing conidia (pycnospores). Four form-families
have been distinguished as follows:
(1) Sphaeropsidaceae (pycnidia
dark colored, leathery to carbonous, stromatic or non-stromatic generally
provided with a circular opening).
(2) Zythiaceae (pycnidia as in the Sphaeropsidaceae but light colored instead of
dark, and soft or waxy instead of leathery).
(3) Leptostromataceae (pycnidia shield-shaped or elongated, flattened). (4) Excipulaceae (mature pycnidia somewhat
deeply cup-shaped). In the family Sphaeropsidaceae
species of the genus Darluca are
hyperparasitic on rusts. Species of Cicinnobolus are hyperparasites of
powdery mildew. Their mycelium is
grown longitudinally in the mycelium of their hosts. ------------------------------------- Please refer to
the following plates for characteristic structures in the Sphaeropsidales: Deuteromycota (Fungi
Imperfecti): Sphaeropsidales Plate 150 = Pycnidia types: Zythis fragariae, Dendrophoma
abscurans, Chaetomella atra, Diplodia zeae,
Fusicoccum viticolum & Endothia parasitica. Plate 151 = Pycnidial development: Phoma herbarum, P. pirina
& Zythia fragariae. Plate 153 = Sphaeropsidales: Pycnidiospore types. Plate 240 = Example
Structures: Deuteromycota:
Sphaeropsidales: Sphaerioidaceae ------------------------------------- Melanconiales Spores are borne on an acervulus
in this order (as in the genus Higginsia of the Ascomycota) Only one
form-family has been designated: Melanconiaceae. Many species are
parasitic on plants and cause a group of diseases called anthracnoses.
The acervuli that are the characteristic structures of this family
usually develop below the cuticle or below the epidermis of the host
plant. They release their conidia in
characteristic droplets, which may be white, cream-colored, pink, orange or
black depending on the pigmentation of the conidia. In the family Melanconiaceae the genus Gloeosporium has
setae, the genus Colletotrichum does
not have setae and Cylindrosporium is
lit the genus Higginsia of the Ascomycota: Helotiales. ------------------------------------- Please refer to the following plates for characteristic
structures in the Melanconiales: Deuteromycota (Fungi Imperfecti): Melanconiales Plate
152 = Acervuli:
Gloeosporium sp. & Colletotrichum lindemuthianum. Plate
154 = Melanconiales: Conidia types. Plate 241 = Example Structures: Deuteromycota: Melanconiales & Mycelia Sterilia ------------------------------------- Moniliales This order includes all the other spore-producing forms and
contains the greatest number of species.
Many species are of great importance and the group contains most of
the fungal pathogens of humans. It is
also the group that has many of the fungi that or of industrial
importance. Species of Penicillium
and Aspergillus that are not known to form cleistothecia are
included. The so-named "false
yeasts" that are not known to produce ascospores are grouped here. There are a number of serious plant
pathogens as well and some common contaminants of the biological laboratory
and many soil fungi what are saprobic and may play a significant role in the
soil economy. Eight family are
included here. The family Stilbaceae has a
coremium or synnema. The majority of
species are saprobic. The form-genus Graphium is economically important because several
species are responsible for blue stain of lumber that reduces market
value. The imperfect stage of Ophiostoma ulmi (= Graphium ulmi) belongs here also. The family Tuberculariaceae has a sporodochium, which is a cushion-like mass of hyphae. The genera Tubercularia, Volutella
and Fusarium are well known.
In Tubercularia the sporodochium is usually shaped like a
mushroom, with a very short stalk and a smooth surface. In Volutella the sporodochium produces
setae that arise here and there over the entire fructification. Volutella
fructi causes Dry Rot of Apples. The form-genus Fusarium
is the largest in this family and taxonomically one of the most
difficult of all fungal groups. Fusarium
produces long, crescent-shaped, multiseptate macroconidia usually borne on
sporodochia, and very small spherical, oval elongated or crescent shaped
microconidia on simple or branched single hyphae. Chlamydospores are also regularly produced by the mycelium, and
sclerotia are often formed. Parasitic
species are generally vascular parasites that cause wilts of plants by
plugging the conducting tissues and by toxin secretions. Among the most destructive species are Fusarium
solani on potato, Fusarium cubense on banana and Fusarium
lini on flax (Plate
159). The families Moniliaceae and Dermatiaceae have spores scattered over the mycelium. The Moniliaceae have hyaline spores
whereas the Dermatiaceae have dark pigmented spores. The genus Thielaviopsis has endoconidia,
but they may also produce macroconidia or chlamydospores in chains. The Moniliaceae is
the larges of all the form-families.
It includes all imperfect fungi that produce conidia on unorganized,
hyaline conidiophores or directly on the somatic hyphae. Most species are saprobic, but many are
important plant parasites and others are human pathogens. The imperfect stages of Aspergillus and
Penicillium belong here (Plate 102,f). The family Dermophyta is
related to Gymnoascaceae of the Ascomycota. In the family Cryptococcaceae there are asporagenous yeasts, which are related to Saccharomyces
of the Ascomycota. The Genus Candida incites a human disease called "Thrush."
The Genus Cryptococcus includes animal
pathogens and Torulopsis is a food yeast that
is used for animal food. The family Rhodotorulaceae is asporagenous yeasts
that are possibly related to the Basidiomycota: Dacryomycetales. The family Sporobolomycetaceae is also asporagenous yeasts that are possibly related to the
Basidiomycota: Dacryomycetales. Sporobolomyces
species have pink or orange-pigmented forms. They may reproduce by simple budding or they may produce
sterigmata with spores that are shot off forcibly (= ballistospores). ------------------------------------- Please refer to the following plates for characteristic
structures in the Moniliales: Deuteromycota (Fungi Imperfecti): Moniliales Plate
155 = Capsules of Cryptococcus neoformans. Plate
156 = Structures of Candida albicans
& Geotrichum sp. Plate
157 = Budding & spore production: Nectaromyces spp. & Sporobolomyces
spp. Plate
158 = Moniliales: Conidia types. Plate
159 = Sporodochium of Fusarium lini &
Fusarium sp. Plate 242 = Example
Structures: Deuteromycota: Moniliales ------------------------------------- Mycelia Sterilia includes a group of
fungi in which no conidia or other reproductive cells are known. Sclerotia are formed, but there are no
fruiting bodies (= spores). Many of
the Mycelia Sterilia proved to be Basidiomycota when their perfect stages
were discovered. Of the over two
form-genera in this group, Rhizoctonia and
Sclerotium are the best known and most
widely distributed. Rhizoctonia
is usually found in soils causing damping-off and root rot of their host
plants. Pellicularia filamentosa, a
basidiomycete, has Rhizoctonia solani as its imperfect stage. It causes Black
Scurf of potatoes and attacks other plants as well. Sclerotium cepivorum known
in the form of small black slcerotia produced on white, cottony hyphae,
causes white rot of onions and garlic.
Sclerotium rolfsii is omnivorous and can be very
destructive on plants. ------------------------------------- Please refer to the following plates for characteristic
structures in the Mycelia Sterilia: Deuteromycota (Fungi Imperfecti): Mycelia
Sterilia Plate 241 =
Example Structures:
Deuteromycota: Melanconiales
& Mycelia Sterilia ------------------------------------- Recognition Of Tribes And Sub-Tribes The final subdivision of most of the families into the
equivalent of tribes and sub-tribes is done on the basis of spore form,
structure and color, and utilizing the "Saccardo
Spore Sections" (= Italian mycologist: 1880-1925) with the
following possibilities: Amerosporae = spores 1-celled but not long, notstellate, spiral, or
filiform Hyalosporae = spores hyaline Phaeosporae = spores dark Didymosporae = spores 2-celled, not stellate, spiral, or filiform Hylodidymae = spores hyaline Phaeodidymae = spores dark Phragmosporae = spores more than 2-celled (variable), not stellate,
spiral, or filiform Hyalophragmiae = spores hyaline Phaeophragmiae = spores dark Scoloecosporae = spores long and slender (scolecospores) septate or non-septate Dictyosporae = spores muriform Hyalodictyae = spores hyaline Phaeodictyae = spores dark Helicosporae = spores spirally coiled, continuous or septate Staurosporae = spores stellate (star-shaped) or radiate, continuous or
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