Filamentous Ascomycota: Pyrenomycetes (Part 1)

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Filamentous AscomycotaPyrenomycetes (Part 1)

• General Mycology Pl P 421/521
• Lecture 8

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From Blackwell et al. 2006. Mycologia 98 834
Pyrenomycetes Sordariomycetes
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Sordariomycetes (Pyrenomycetes)

• Subclasses Hypocreomycetidae, Xylariomycetidae
  and Sordariomycetidae include 16 orders
• gt 600 genera, 3,000 species
• Mostly unitunicate asci formed in hymenium and
  perithecial ascocarps (Pyrenomycetes sensu
  Luttrell 1951)
• Asci forcibly discharge ascospores through ascus
  tip apparatus in most taxa
• Asci evanescent (prototunicate) with passive
  discharge of ascospores in a few taxa
• Diverse and often complex anamorphs

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From Zhang et al. 2006. An overview of the
systematics of the Sordariomycetes based on a
four-gene phylogeny. Mycologia 98 1076-1087.
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Order Hypocreales

• Soft textured, usually pale to brightly colored
  perithecia
• Unitunicate asci with thickened apices develop
  among apical periphyses
• Often with pale to brightly colored, fleshy
  stromata

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Hypocreales anamorphs

• Wet conidia produced from phialidic conidiogenous
  cells
• One-celled conidia
• Acremoniumsimple conidiophores
• Verticillium, Trichodermabranched conidiophores
• Gliocladiumcomplex conidiophores
• Stachybotryswhorl of phialides at conidiophore
  apex
• Volutella, Tuberculariaconidiomata (sporodochia)
• Septate conidia
• Fusarium, Cylindrocarpon, Cylindrocladium

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Stachybotrys
Enteroblastic/phialidic development,
macronematous conidiophores, dark amerospores in
wet masses
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Family Hypocreaceae

• Hypocrea (anamorph Trichoderma)
• Trichoderma is an important biological control
  agent
• Hypomyces (diverse anamorphs)
• Many species as parasites of mushrooms

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Hypomyces lactiflorum

• Parasitizes mushrooms early in their development
• Russula brevipes is most common host
• Lobster Mushroom
• Produces bright orange perithecia embedded in
  subiculum
• Ascospores two-celled
• Anamorph Sepedonium

From Hanlin, 1990
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Hypomyces lactiflorum Lobster Mushroom
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Non-parasitized Russula brevipes, the host for H.
lactiflorum
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Family Nectriaceae

• Species previously placed in Nectria with large,
  nonstromatic perithecia now in Nectriaceae and
  Bionectriaceae (not covered)
• Perithecia are orange to red, KOH
• Most species have two-celled ascospores
• Includes the teleomorphs of Fusarium,
  Cylindrocarpon, Cylindrocladium, Tubercularia

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Nectria cinnabarina

• Common parasite on dead branches
• Orange perithecia formed on cushion-shaped
  stromata that previously formed Tubercularia
  anamorph

From Hanlin, 1990
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Nectria cinnabarina from http//www.grzyby.pl/gatu
nki/Nectria_cinnabarina.htm
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Cosmospora photo by B. Callan
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Family Clavicipitaceae

• Characterized by threadlike ascospores and
  perithecia embedded in stromata
• Produce a wide range of secondary metabolites
• Parasitic on plants and animals
• Balansia, Claviceps and Epichloë are plant
  parasites
• Cordyceps parasitizes insect larvae and hypogeous
  fungal fruiting bodies
• Anamorphic genera Beauveria, Hirsutella,
  Metarhizium and Tolypocladium parasitize insects

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Claviceps purpurea from Hanlin, 1990
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Claviceps purpurea stromata and sclerotium
(left), and perithecia (above)
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Claviceps purpurea lifecycle

• Sclerotia fall to ground in fall and overwinter
• Sclerotia germinate in spring to produce stromata
  with perithecia
• Thread-like ascospores are wind-disseminated
• Ascospores that land on susceptible flower
  germinate and grow into the ovary
• Sphacelia anamorph develops in honey dew formed
  on infected florets
• Conidia are dispersed to uninfected flowers by
  rain or insects

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Claviceps purpurea

• Causes ergot of rye and other grasses
• Sclerotia formed in grass ovary composed of
  pseudoparenchymatous fungal tissue
• May contain high levels of 3 types of alkaloids
• Secoergolenes
• Ergolines
• Lysergic acid derivatives

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Ergotism

• Ergotism is a disease in animals (including
  humans)
• Vascular constriction that may lead to gangrene
• Hallucinations
• Ergotism involved in/responsible for
• St. Anthonys Fire (Middle Ages)
• Salem Witch Trials (1692)
• Modern outbreaks in France, Ethiopia, India

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Balansia and Epichloë

• Grass and sedge endophytes
• Endophytes are fungi that cause symptomless
  infections in plant hosts
• Anamorph Neotyphodium grows intercellularly in
  plant host
• Seed transmitted (vertical transmission) if
  flowers are produced by infected plants
• Horizontally transmitted in species inhibiting
  flower production
• Beneficial to plant
• Secondary metabolites (alkaloids) produced by
  endophyte protects plants from herbivores
  (Ryegrass Staggers)
• May confer drought resistance to infected plants

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Epichloe typhina
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Cordyceps

• Infects insect larvae (e.g., caterpillars) or
  underground fungal fruiting bodies
• Club-like stromata emerge from host, perithecia
  embedded in apical region
• Threadlike ascospores break apart while in ascus
• Cordyceps militaris has medicinal properties and
  has a long history of use in Asia

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Cordyceps
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Order Xylariales

• Dark, leathery, woody or carbonaceous perithecia
  usually embedded in well-developed stromata
• Ascus tips have ring that turns blue in Melzers
  reagent (amyloid reaction)
• Anamorphs usually holoblastic
• Wood decompers, endophytes, plant pathogens
• Two families
• Xylariaceae
• Diatrypaceae

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From Hanlin 1990)
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Hypoxylon spp. from Home of the
Xylariaceae http//mycology.sinica.edu.tw/Xylariac
eae/
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Xylaria hypoxylon from www.mykoweb.com/CAF/species
/Xylaria_hypoxylon.html
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Order Microascales

• Family Ceratocystidiaceae
• Ceratocystis (Chalara anamorphs)
• Perithecia with long necks, ascospores passively
  discharged
• Cyclohexamide sensitive, lacks cellulose and
  rhamnose in walls
• Ascospores dispersed by bark beetles
• May cause wilt diseases, blue stain

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Chalara anamorph
From Nag Raj and Kendrick, 1975
From Hanlin, 1990
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Blue stain in pine http//forestpathology.coafes.
umn.edu/biocontrol.htm
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Family Glomerellaceae

• Monotypic family characterized by black,
  nonstromatic perithecia, abundant paraphyses and
  asci with a J- apical ring
• Glomerella
• Glomerella cingulata (anamorph Colletotrichum
  gloeosporioides) causes anthracnose type
  diseases in gt 100 species of plants
• Anamorphs characterized by acervuli with
  prominent setae, production of appressoria upon
  conidial germination

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Hanlin, 1990
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Colletotrichum coccoides
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Order Ophiostomatales

• Ophiostoma differs from Ceratocystis
• Cyclohexamide insensitive
• Cellulose and rhamnose in cell walls
• Nonphialidic anamorphs (Sporothrix and
  Leptographium)
• Ophiostoma ulmi, causal agent of Dutch Elm
  Disease, killed many of the North American elm
  trees in 1920s
• Second pandemic of elm disease that occurred
  later was caused by N. novo-ulmi, a more
  aggressive pathogen due to formation of toxin
  (see Brasier Buck, 2001 Brasier Kirk, 2001)

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Ophiostoma and Leptographium
From D. Malloch www.botany.utoronto.ca
From Hanlin, 1990
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Perithecial necks and ascospores
Beetle galleries
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Order Diaporthales

• Black perithecia in stromata composed of host
  fungal tissues, asci float free at maturity, most
  with refractive ascus tip
• Important genera
• Diaporthe (Phomopsis anamorphs)
• Phomopsis characterized by ?- and ?-conidia
• Cryphonectria parasitica (Chestnut blight)
• Gaeumannomyces graminis var. tritici (Take-all
  disease of wheat)

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Diaporthe and Phomopsis
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Soybeans infected by Phomopsis http//www.ent.iast
ate.edu/imagegal/plantpath/soybean/phomopsis/phomp
sisseeddamxb.html
Phomopsis Cane Spot on Grapes
Phomopsis on alfalfa stem (USDA ARS Systematic
Mycology Lab)
http//winegrapes.tamu.edu/grow/diseases/photos/ph
omopsis1.jpg
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Cryphonectria parasitica

• Chestnut blight pathogen introduced to North
  America in 1904, by 1940 had destroyed all the
  chestnut trees in the eastern US

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Chestnut blight - virulent canker
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Cryphonectria parasitica
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Family Magnaporthaceae

• Magnaporthe grisea, anamorph Pyricularia grisea
  causes Rice Blast

From Valent (2004). Nature 431 516-517
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Magnaporthe and Pyricularia
From Hanlin, 1990
From Carmichael et al., 1980
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Order Sordariales

• Mostly wood or dung inhabiting taxa
• Asci with thin, refractive apical ring, one or
  two-celled ascospores, often with appendages or
  sheaths
• Phialophora-like anamorphs (phialidic) when known
• Taxa to be covered
• Chaetomium, Gelasinospora, Neurospora, Sordaria

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Neurospora

• Asci with refractive apical ring
• Ascospores one-celled, darkly pigmented, apical
  germ pore
• Grow rapidly in culture, sporulate abundantly
• Chrysonilia (Monilia) anamorph
• common on burnt substrates
• N. sitophila is the red bread mold
• G. W. Beadle and E. L. Tatum used mutated strain
  of Neurospora to demonstrate that enzymes are
  controlled by genes

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Chrysonilia anamorph http//www.botany.utoronto.ca
/Research Labs/MallochLab/Malloch/Moulds/Contents.
html
Hanlin, 1990
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Neurospora tetraspora
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Sordaria and Gelasinospora
Hanlin, 1990
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Chaetomium

• Asci deliquesce at maturity
• Ascospores one-celled, with germ pore(s)
• Conspicuous hairs on ascomata
• Cellulolytic, occur on paper and cotton

Hanlin 1990