Download Basidiomycota

Basidiomycota
Class: Uredinomycetes (Rusts)
Class: Ustomycetes (Smuts)
Rusts and Smuts
Most economically important group
of fungi in Basidiomycota.
Basidiocarp absent.
Basidium and basidiospores borne
from germinating teliospore.
teliospore Basidia and
basidiospores
Teliospore
Rusts and Smuts
Septa simple, without dolipore septum.
Life cycle differs from Basidiomycetes.
Parasitic.
Class: Uredinomycetes
Only Basidiomycota with sexual organs.
All members obligate parasites.
Most complex life cycles of all organisms.
With at least two and up to five
spore stages.
Puccinia graminis (Wheat Rust) used
as representative life cycle:
Macrocyclic: has five spore stages.
Heteroeciouis: requires two hosts
to complete its life cycle.
Spore Stages of Puccinia graminis
Stage 0: Spermogonium also referred to
as a Pycnium.
Pycnium Produces spermatia and
receptive hyphae.
hyphae
Stage 1:Aecium produce aeciospores.
Stage 2:Uredium produce urediospores.
Stage 3:Telium produce teliospores.
Stage 4:Basidium produce
basidiospores.
Puccinia graminis Life Cycle
Summary
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Uredium and Urediospores
Begin life cycle, in early spring, with
binucleate urediospore stage.
Uredium and Urediospores
Prepared slide of uredium and
urediospores.
Urediospores
reinfect wheat
Telium and Teliospores
Telium and Teliospores
In late summer,
Uredium converts to
Telium, which
produces binucleate
teliospores.
Overwinters in
teliospore stage
Karyogamy occurs in
teliospore.
Basidium and Basidiospores
Prepared slide of two-celled teliospore
stage.
Basidium and Basidiospores
Basidium and basidiospores borne
from germinating teliospore
Karyogamy and meiosis occurs in teliospore.
Teliospore germinates to form basidium and
basidiospores.
Basidiospore infects Barberry (alternate
host)!
Basidiospore
Teliospore
Basidium
2
Spermogonium
Spermogonium
Basidiospores germinate to form
monokaryon.
Spermogonium with spermatia and
receptive hyphae produced.
Spermogonium
Spermatium of A1 must fuse with
receptive hyphae of A2 mating strain
and vise versa
Flies carry spermatia to receptive
hyphae. Attracted to spermogonium
by sweet exudates
Dikaryon reformed below
spermogonium to form aecium on
lower surface of barberry leaves.
Aecium and Aeciospores
Aeciospore must now infect wheat to
complete lifecycle.
Spermogonium and Aecium
Prepared slide of Spermogonium and
Aecium.
Spermogonium:
Spermogonium
Receptive
hyphae and
Spermatia
Aecium and
aeciospores
Aecium and Aeciospores
Prepared slide
of aecium and
aeciospores
Aeciospores held
together by
disjunctors
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Variations in Spore Stages
Demicyclic:
Demicyclic Rust is missing uredium
stage.
Microcyclic: Rust is missing uredium
and aecium stages.
Rust can complete entire life cycle
on one host: autoecious.
Teliospore is most variable in
morphology and is utilized in defining
genera.
Teliospore Variations
Puccinia
coronata
Class: Uredinomycetes
Variations in
teliospore
morphology on
right.
Teliospore Variations
Phragmidium
teliospores
commonly called
“crown rust”
because of the
horns on the
teliospore.
Teliospore Variations
Gymnosporangium
libocedri has
gelatinous
teliospores.
Native Rusts
Atelocauda
digitata: Close-up
of infected
phyllodes with
spermogonial and
aecial stages.
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Native Rusts
Endoraecium
hawaiiense: A
species of native
Hawaiian koa
rust.
Class: Ustomycetes
Commonly called smut fungi because
teliospores give plant a black, sooty
appearance.
Parasitic on flowering plants.
Many are dimorphic:
Mycelial stage is obligate parasite.
Yeast stage is saprobic.
Class: Ustomycetes
In some ways similar to rusts, but
also very different:
Fewer spore stages: Only
basidiospore and teliospore stage
present.
Only one host is required to
complete life cycle.
Sex organs are absent!
Class: Ustomycetes
Ustilago maydis:
Smut sori filled
with teliospores.
Class: Ustomycetes
Will use Ustilago maydis (Corn Smut)
life cycle as representative of smuts.
Species dimorphic and parasitic on
corn.
Fungus replaces kernel with large
sorus of teliospores.
Ustilago maydis Life Cycle
Young sorus filled with dikaryotic mycelium
Square, septate
hyphal cells.
Ð
Hyphal cells
rounding off.
Ð
Globose, thickwalled telispores.
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Ustilago maydis Life Cycle
Teliospore
germinating to
produce
basidium and
basidiospores.
Basidiospores
“bud” produce
yeast.
Yeast stage
saprobic
Teliospore Variations
As in rust fungi,
teliospores
variable.
Used in defining
species.
Ustilago maydis Life Cycle
Compatible yeast
cells
fusion,followed by
formation of
dikaryon (arrow).
Dikaryon obligate
parasite.
Typical Host Appearance
Ustilago
cynodontis,
bermuda grass
smut. Common in
Hawai‘i.
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