Rusts

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Rusts Smuts
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Three Classes of Basidiomycota
Hymenomycetes dolipore septum holobasidia
phragmobasidia Ustilaginomycetes
"simple dolipore"
phragmobasidia teliospores
Urediniomycetes simple septum
phragmobasidia teliospores
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Urediniomycetes Uredinales - the Rusts 5000
species 140-150 genera Ustilagniomycetes
Ustilaginales - the Smuts 1200 species 50
genera All are parasitic on plants, often
causing great damage to many cultivated crops
Heterothallic Obligate biotroph - incapable
of completing life cycle saprobically
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Teliomycetes - old class, included Uredinales
and Ustilaginales based on possession of the
teliospore Teliospore site of
karyogamy technically part of the basidium

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teliospore germinates, gives rise to a short germ
tube of determinate growth known as the
promycelium. Promycelium site of meiosis
formation of sterigmata and basidiospores
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• Uredinales
• Rust fungi may produce as many as five different
• spore-producing stages (0, I, II, III, IV) in
  their life cycles
• Heteroecism
• two taxonomically different host plants in order
  to
• complete life cycle
• alternate host stages 0, I
• primary host stages II, III
• Autoecism
• - entire life cycle completed on a single host
  species

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Stage 0 and I produced on alternate host
Stage 0 Spermogonia bearing spermatia (n) and
receptive hyphae (n)
helios.bto.ed.ac.uk/bto/microbes/biotroph.htm

• fertilization of the receptive hyphae by
  spermatia initiates
• the dikaryon and the formation of aecia

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Stage I Aecia bearing aeciospores (nn)

• aeciospores infect primary host
• e.g., aeciospores produced on alternate host
  (e.g., Barberry)
• infect primary host (e.g., grasses)

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Stage II Uredinia (j) bearing urediniospores
(nn)
helios.bto.ed.ac.uk/bto/microbes/biotroph.htm

• reinfect primary host
• amplifies disease within primary host
• uredinia can eventually develop into telia

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Stage III Telia bearing teliospores (nngt2n)

• final stage on primary host
• overwinters as dikaryon

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Stage IV Basidia bearing basidiospores (n)

• in the spring teliospore germinates a
  promycelium
• diploid nucleus migrates into the promycelium
  and
• undergoes meiosis
• four haploid nuclei migrate into developing
  sterigmata
• are incorporated into basidiospores
• basidiospores reinfect alternate host

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Life Cycle of Puccinia graminis
I
SUMMER
aecia on barberry (nn)
urediniospores (nn) airborne
spermatia (n) insect transported to receptive
hyphae (n) heterothallic
II
aeciospores (nn) airborne
O
F A L L
uredinia on grass from infection by aeciospores
or urediniospores
spermagonia on barberry from infection by
basidiospores
basidiospore (n) airborne
meiosis
III
S P R I N G
IV
telia on grass
teliospore (2n) germinating on straw
with promycelium and basidiospores (n)
teliospore on straw (nn)
karyogamy (2n)
WINTER
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Life cycle patterns of the Uredinales 1.
macrocylic forms- all five reproductive stages
2. demicyclic forms- the uredinial stage is
absent 3. microcyclic forms- both aeciospores
and urediniospores are absent teliospore is
the only binucleate spore produced
Heteroecism- two taxonomically different host
plants in order to complete their life cycles.
Autoecism- completes its entire life cycle on a
single host species
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Examples of distantly related hosts Puccinia
graminis 0 and I on barberry bushes (Berberis
vulgaris dicot) II and III on various grasses
(monocot) Cronartium ribicola 0 and I on white
pines (gymnosperms) II and III on currants
gooseberries (angiosperms) Uredinopsis osmundae
0 and I on the balsam fir (Abies balsamea
gymnosperm) II and III on the cinnamon fern
(Osmunda cinnamomia)
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• Ustilaginales
• no sex organs
• monokaryons nonpathogenic
• dikaryon pathogenic
• heterothallic mating of
• compatible spores
• teliospores