Filamentous fungi a background
Lecture 2
Fungi are important in nature
As decomposers
As pathogens of plants, animals
and humans, and in food spoilage
As producers of secondary
metabolites, e. g. penicillin
In cheese, bread and wine making
Four phyla of fungi
o Chytridiomycota - no sexual spore
o Zygomycota - zygospore
o Ascomycota - ascospore
o Basidiomycota - basidiospore
Fungal reproduction
Asexually, by forming conidia
Sexually (three steps):
•Plasmogami (dikaryon)
•Karyogami (zygote forms)
•Meiosis (sexual spore forms):
•Zygospore
•Ascospore
•Basidiospore
Chytridiomycota
Zygomycota
Gametangia fuse to produce a
zygospore (Rhizopus stolonifer)
Ascomycota
Ascomycota 32 300 described species
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Powdery mildews
Nectria cankers of trees (Nectria galligena)
Brown rot of stone fruit (Monilia fructicola)
Chestnut blight (Cryphonectria parasitica)
Dutch elm disease (Ophiostoma ulmi)
Most yeasts
Morels and truffles
Characteristics of Ascomycota
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Septate hyphae
Uninucleate or multinucleate hyphae
Heterothallic or homothallic
Sexual spore = ascospore, produced in sac
called ascus. Usually 8 ascospores per
ascus.
• Ascocarp (fruiting body) can be of three
different types: cleistothecium,
perithecium or apothecium.
Botrytis cinerea - a fungus -causes
grey mold
Powdery mildew of cucumber
Cleistothecia of powdery mildew
Anthracnose of cucurbits
Anthracnose of
melon caused by
Colletotrichum
orbiculare
Eye spot disease of strawberry
Ramularia grevilleana,
Mycosphaerella fragariae
Canker, Nectria galligena
Perithecium of Nectria galligena
Penicillium and Aspergillus
Examples of
conidiophores of other
imperfect fungi or
Deuteromycetes
Wilts caused by Fusarium
oxysporum
Darkened vascular
tissue
of
cucumber
Wilt of field grown melon
caused by F. ox.
caused by F. ox. formae
f.sp.
cucumerinum
speciales melonis
Life cycles of fusarium wilts
Basidiomycota 22 300 described species
• Mushrooms, stinkhorns, puffballs
(Basidiomycetes)
• Rusts (Teliomycetes)
• Smuts (Ustomycetes)
Basidiospores (sexual spore) made on clublike structure, called basidium.
Basidiomycota
Characteristics of Basidiomycota
• Mycelium is septate
• Septa are perforated - sometimes with
dolipore (doughnut shaped)
Characteristics of Basidiomycota
• Mycelium passes two phases monokaryotic and dikaryotic.
• Two hyphal ends of the monokaryotic
mycelium (of different mating types)
fuse and produce the dikaryotic
mycelium.
• The dikaryotic mycelium can divide at
the apical cell and form clamp
connections.
Basidiomycetes have clamp
connections
“Fairy ring”
Fruiting bodies
Fly agaric
(flugsvamp)
Hallocinogenic fungi
Psilocybe mexicana
Psilocybin
• Mushrooms are part of many religious ceremonies in Mexico
and Central America. Psilocybe mexicana is a fungus that
contains the hallucinogenic drug psilocybin, which is related to
LSD and mescaline.
Rhizoctonia solani
• It is a basidiomycete;
teliomorph
(Thanatephorus
cucumeris) is rare.
• Has very characteristic
mycelium; typical of
basidiomycete.
• Differentiated into
anastomosis groups (AG)
(fusion of hyphae only
occur if same anastomosis
group)
The disease cycle of Rhizoctonia
solani
Characteristics of the rusts
(Teliomycetes)
• Sori, in which uredospores are formed.
• Were thought to be obligate parasites, but some can
be grown in the laboratory.
• Can live on one host - autoecious, or two hosts heteroecious.
• New races appear constantly; difficult to control.
• Spore forms: basidiospore (n), aeciospore (n+n),
uredospore (n+n) and teliospore (2n).
Rusts
Wheat stem rust (Puccinia
graminis)
Stem rust of wheat
Rust of roen (rönn)
Rust of raspberry
Disease cycle of cedar-apple rust
Rust of rose
Uredospores of rose rust
Teleutospores, rose rust
Corn smut
Corn smut
Teliospores (2N) (sexual spores)
Infection
Filamentous
Dikaryon (N+N)
Meiosis
Mating
Budding cells (1N)
The life cycle of smut fungi
Chlamydospores (1N)
(asexual spores)