Transcript 6-Ascomycete anamorphs and Imperfect fungi

Ascomycete Anamorphs and the
Imperfect Fungi
Mycology (Bio 594, Special Topics)
M. Marshall 2013
Shippensburg University
(See last slide for credits)
Ascomycete
anamorphs
Have mitospore types
that are produced on
hyphal conidiophores,
or on or in structures
made from
aggregated hyphae =
conidiomata
Most micro-fungi are first encountered as
the imperfect stage
Although many fungi may in fact be the imperfect asexual
(anamorphic) form of a fungus with an perfect
(teleomorph) stage, usually the production of the latter
stage requires two opposite mating types to unite on
specific substrates and/or under limited conditions. Years
may elapse between the discovery of an asexual isolate
and its sexual form. So many fungi that are important in
human affairs are known only by their asexual designation.
Some later prove to have a sexual stage and some not.
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Deuteromycetes
“deuter-” Gk., meaning “second”
• > 20,000 species of fungi in 2600 genera that
have no known sexual state
• Most belong in phylum Ascomycota
• These fungi are also called:
 Anamorphic fungi
 Mitosporic fungi
 Conidial fungi
 Imperfect fungi
 Fungi imperfecti
Asexual Propagules I – Other than Conidia
• Chlamydospore
– 1-celled spore (usually thickwalled) designed for
perennation; formed inside
an existing hyphal cell
• Sclerotium (pl. sclerotia)
– Rounded mass of hyphae,
often differentiated into rind
and medulla. Usually
melanized
Asexual propagules II Conidia
Conidium (pl. conidia)
– Non-motile spore designed
for dispersal
– Wide range of shape, size,
color and septation among
taxa (details discussed in
later slides).
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Saccardoan Spore Types & Imperfect
Classification
• P.A. Saccardo (18451920)
– “Sylloge Fungorum”
(1882-1972)--names &
descriptions of all known
fungi
– Developed system of
classifying fungi based
on type of spore (shape,
septation, color)
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Types of Deuteromycetes
• Hyphomycetes—fungi that produce conidia from
conidiogenous cells free on their mycelia ( on
conidiophores).
– May be formed on the surface of synnematal or
sporodochial types of conidiomata
• Coelomycetes—fungi that produce conidia from
conidiogenous cells formed in closed or semi-closed
conidiomata such as an ascervulus or pycnidium
Variations of Deuteromycete grouping
As with all things mycological, the Saccardoan system has been
modified over the years (there are different versions) and other
systems have been proposed as well:
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Saccardoan Hyphomycete (form) Families
• Moniliaceae—conidiophores formed singly, hyphae
and conidia pale-colored
• Dematiaceae—conidiophores formed singly, hyphae
and/or conidia dark-colored
• Tuberculariaceae—conidiophores aggregated on
cushion-like sporodochium (pl. sporodochia)
• Stilbaceae—conidiophores aggregated in a synnema
(pl. synnemata), an erect bundle with conidia formed
at apex
An alternative, Saccardoan Form Orders according to
Barnett*
Moniliales – Conidia directly on mycelium, on conidiogenous cells or
conidiophores which may be separate, in clusters, or tightly packed
groups. The largest and most commonly represented group.
Sphaeropsidales – Conidia produced in well defined pycnidia
Melanconiales – Conidia naturally produced in acervuli ; in culture
possibly singly or in compact groups resembling sporodochia
of the Moniliales.
Mycelia Sterilia – No conidia production. Form sclerotia or other
survival structures.
Some authors include the conidial Oomycetes (old: Phycomycetes)
here also because of their superficial similarity to the true fungi
imperfects.
Barnett’s Saccardoan Families and Sections of the Moniliales I
Moniliales – Conidia directly on mycelium, on conidiogenous cells or conidiophores
which may be separate, in clusters, or tightly packed groups. The largest and most
commonly represented group.
Moniliaceae – hyaline conidia
Dematiaceae – darkly pigmented conidia (either singly or en mass).
Both have conidiophores single and separate or in loose
clusters.
Sections:
Amerosporae – conidia one-celled = amerospores
Didymosporae – conidia two-celled = didymospores
Phragmosporae – conidia with transverse septa only = phragmospore
Dictyosporae – conidia with both transverse and oblique septation
= dictyospore
Scolecosporae – conidia filiform = scolecospore
Staurosporae – conidia stellate or branched = staurospore
Helicosporae – conidia coiled = helicospore
The prefixes Hyalo- or Phaeo- are sometimes used with the above spore
names to indicate hyaline or darkly pigmented respectively
Barnett’s* Saccardoan Families and Sections of the Moniliales II
Tubiculariaceae – Conidiophores compacted into a rounded or flat
sporodochium which may not be produced in culture.
Stilbaceae
–
Conidiophores compacted into synnemata, but may also
produce single conidiophores of the Moniliaceous or
demateaceous type (previous slide).
* H.L. Barnett was an accomplished mycologist who
worked at west Virginia University. At various times he
was President of the American Phytopathological
Society and the Mycological Society of America. His
book, Illustrated genera of Imperfect Fungi has gone
through 4 editions and is still a major “Imperfect”
reference today.
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Conidiophores
Hyphae bearing conidiogenous cells
– Morphologically differentiated from vegetative
hyphae (=macronematous)
– Morphologically not differentiated
(=micronematous)
Conidiophores
Closed Conidiomata (Coelomycetes)
Acervulus
Pycnidium
Conidium containing structures that rupture through host epithelium.
An acervulus is more open, not within walls of fungal tissue. The
pycnidium is perithecium like, but contains short conidiophores and
mitosporic conidia, not asci. In some ascomycete fungi the pycnidial
walls develop into stroma within which true perithecia develop.
Pycnidium details
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Open conidiomata: Synnemata
• Conidiophores united at
base grow in parallel to
give a “tree trunk” like
configuration.
• Conidiogenous cells at
apex.
• Conidia may be
produced dry or formed
in a liquid matrix.
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Open Conidiomata: Sporodochium
• A compact, cushion-like
aggregation of hyphae
on which conidiophores
are formed in a dense
layer
• The aggregation of
hyphae is called a
stroma (pl. stromata)
Saccardoan Spore Types
amerospore
scolecospore
staurospore
helicospore
dictyospore
phragmospore
didymospore
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More Saccardoan Spore Type Terminology
• Color (prefixes)
– Hyaline or bright (hyalo-)
– Pigmented (phaeo-)
• Shape and septation
–
–
–
–
1-celled —amerospore
2-celled —didymospore
Multicelled —phragmospore
Muriform —dictyospore (with both vert. & horiz.
cross walls)
– Filiform —scolecospore (hair-like)
– Helical — helicospore
– Branched — staurospore
(see also slide 11)
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Arrangement of conidia at locus
• Solitary
• Catenate = true chains
• Seriate = false chains, spore heads
– Dry spores
– Wet spores (gleoid)
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Succession of conidia
• Basipetal = a chain of conidia in which new spores
are formed at the base, the oldest conidia are at the
apex
• Acropetal = a chain of conidia with the new spores
formed at the end of the chain, oldest spores are at
the base. In order for this type of conidial formation
to occur, the conidia must function as conidiogenous
cells (e.g., Alternaria, Cladosporium)
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Synanamorph
• Two or more types of
asexual spores formed
by the same fungus
• Example:
– Ceratocystis fibriata
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Conidiogenous Cells
• A cell that forms one or
more conidia
• May be formed on a
specialized, simple, or
branched hypha called a
conidiophore
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From D. Malloch
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Conidial Development (Ontogeny)
• Blastic—blowing out of conidial initial prior to
formation of delimiting septum
• Thallic—conversion of segment of existing
hyphae into conidia
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Blastic versus thallic
Cole, 1986
Blastic vs thallic conidiogenesis & spore separation
Blastic = cross wall follows “budding”, thallic = cross wall defines the
spore as separate.
Schizolytic separation = septae split; rheolytic = wall of basal cell
splits.
Blastic Anamorph and Hyphomycete (imperfect)
examples
Blastic types: precurrent, phialidic, and retrogrssive
Precurrent = leaves ring-like scar
on conidiogenous cell (Venturia).
Phialidic = Conidia pushed out
of end of conidiogenous phialid
(Penicillium, Aspergilous).
Retrogressive = sepatate form
down the conidiophore
underneath the first (?)
Basauxic retrogressive-like
alternative = chain of blaststic
conidia where new growth is
added from a mother cell below .
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Blastic development
• Holoblastic
– single conidium is formed from conidiogenous
locus, all wall layers involved in formation of
conidium wall
• Enteroblastic
– more than one conidium formed from locus, only
the inner wall layer(s) involved in formation of
conidium wall
Holoblastic
Enteroblastic
Enteroblastic development detail
• Phialidic—a basipetal
succession of conidia is
formed from a fixed
locus on the
conidiogenous cell
(phialide)
collarette
Enteroblastic development detail
• Annellidic—a basipetal
succession of conidia
formed by repeated
percurrent proliferation
of conidiogenous locus,
leaving the distal end of
locus with transverse
scars (annellations)
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More Enteroblastic development
• Tretic—the inner wall of
the conidiogenous cell
blows out through a
hole (pore) in the outer
wall like a balloon to
form a conidium.
Thallic arthric, alt. arthric, and solitary
Arthric = growth stops hyphae divided up
by arrising septae. Fracture at sepatae.
Alternate-arthric = some intervening
cells in the arthric chain degenerate to
release the others as conidia.
Solitary = single large spores develop,
may be multicellular.
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Arrangement of conidia at locus
• Solitary
• Catenate = true chains
• Seriate = false chains, spore heads
– Dry spores
– Wet spores (gleoid)
@
Succession of conidia
• Basipetal = a chain of conidia in which new spores
are formed at the base, the oldest conidia are at the
apex
• Acropetal = a chain of conidia with the new spores
formed at the end of the chain, oldest spores are at
the base. In order for this type of conidial formation
to occur, the conidia must function as conidiogenous
cells (e.g., Alternaria, Cladosporium)
Credits
This presentation has been modified from one posted on
the web by Dr. Lori Carris, Washigton State University
Plant Pathology Dept. from her course: Plant Path 521,
Mycology.
Fungal symbiosies