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Phylum Ascomycota Orders Erysiphales

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21 genera, 437 species infecting 40,000 species of plants ... Digitate haustoria. Several asci/ascocarp. Inflated base on conidiophore. Mycelioid Appendages ... – PowerPoint PPT presentation

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Title: Phylum Ascomycota Orders Erysiphales


1
Phylum AscomycotaOrders Erysiphales
Laboulbeniales
  • General Mycology
  • Pl P 421/521
  • Lecture 7

2
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3
Blackwell et al. 2006. Mycologia 98 834
4
Blackwell et al. 2006. Mycologia 98 834
5
Erysiphales
  • Common name Powdery Mildews
  • Biotrophs of vascular plants
  • Biotroph an obligate parasite growing on
    another living organism
  • 21 genera, 437 species infecting gt 40,000 species
    of plants (mostly dicots)
  • Most species are host specific, a few are
    omnivorous, infecting hundreds of host species

6
Powdery Mildew Symptoms
Photo by Claudia Nitschwitz
7
Characteristics
  • Mycelium is mostly superficial
  • Anchored to host epidermis by appressoria
  • Nutrients obtained via haustoria
  • Haustoria are intracellular structures
  • Overwinter as mycelium in infected buds or as
    ascomata
  • Asexual reproduction via conidia
  • Sexual reproduction via ascospores formed in
    cleistothecia

8
From APSnet.org
9
fungus
10
Asexual reproduction
  • Erect, hyaline conidiophores are usually formed
    on superficial mycelium
  • One-celled, hyaline thin-walled conidia are
    produced holoblastically in basipetal chains
  • One colony can produce gt 30,000 conidia

11
Conidia
  • Wind-dispersed
  • Germination can occur at low relative humidity
  • Germination involves germ tube, appressorium and
    penetration peg formation
  • Apex of penetration peg enlarges to form
    haustorium

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Microsphaera alni anamorph on Vaccinium
14
Sexual reproduction
  • Cleistothecia formed on superficial mycelium in
    late summer/early fall
  • Asci
  • Formed in basal layer
  • Globose to pyriform
  • Discharge by rupture of ascus tip

15
Asci/Ascospores
  • One to numerous asci/cleistothecium
  • Ascospores hyaline, one-celled, ovoid
  • 1-8 ascospores/ascus
  • Number of asci/cleistothecium is important
    character in identification

16
From APSnet.org
17
Identification
  • Anamorph type
  • Number of asci/ascocarp
  • Cleistothecial appendages
  • Mycelioid
  • Rigid
  • Spear-like with inflated base
  • With curled tips
  • With dichotomously branched tips

18
Microsphaera alni cleistothecia
19
Sawadaea bicornis cleistothecia
20
Sawadaea bicornis cleistothecial appendages
21
Blumeria
  • B. graminis--only powdery mildew on grasses
  • Mycelial setae
  • Digitate haustoria
  • Several asci/ascocarp
  • Inflated base on conidiophore

22
Mycelioid Appendages
  • Several asci/ascocarp
  • Eryisiphe (100 spp)
  • Oidium anamorph
  • Leveillula (8 spp.)
  • Internal mycelium
  • Oidiopsis anamorph (emerges through stomate)
  • One ascus/ascocarp
  • Sphaerotheca (50 spp.)
  • Appendages with curled tips
  • Oidium anamorph with fibrosin bodies

23
Dichotomously branched appendage tips
  • One ascus/ascocarp
  • Podosphaera (12 spp.)
  • Oidium anamorph with fibrosin bodies
  • Several asci/ascocarp
  • Microsphaera (125 spp.)
  • Oidium anamorph
  • Sawadaea (6 spp.)
  • Curved tips on appendages
  • Oidium anamorph with fibrosin bodies

24
Spear-like appendages--Phyllactinia
  • 24 species
  • Appendages lift ascocarp off leaf surface
  • Brush cells on top of ascocarp
  • Ovulariopsis and Streptopodium anamorphs

25
Appendages with curled tips
  • Uncinula (81 spp)
  • Oidium anamorph
  • Several asci/ascocarp
  • Uncinuliella
  • Differs by bristle-like appendages on top of
    ascocarp

26
Molecular data vs. morphology
  • Phylogeny analyses of powdery mildews based on
    rDNA sequence data shows lineages corresponding
    to anamorph type rather than teleomorph
    morphology (Saenz Taylor 1999, Can. J. Botany
    77150-168 Mori et al 2000, Mycologia 9274-93)

27
Saenz Taylor 1999
28
Class Laboulbeniomycetes
  • Orders Laboulbeniales and Pyxidiophorales
  • 5 families, 140 genera, gt 1800 species
  • Members of 4/5 families lack hyphae, reduced to
    thallus attached to host
  • Parasitize arthropods

29
Laboulbeniomycetes
  • Most species are highly host specific, found on
    only one arthropod species
  • Roland Thaxter (1858-1932) at Farlow Herbarium,
    Harvard was one of the leading experts on this
    group
  • Published a series of monographs on
    Laboulbeniales (1896-1931)

30
Roland Thaxters "Contributions towards a
monograph of the Laboulbeniaceae"
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32
Laboul images by Alex Weir
33
Hosts of Laboulbeniales (From Meredith
Blackwell)
Blattoidea (cockroaches and allies)  Coleoptera (beetles)  Dermaptera (earwigs)  Diptera (true flies)   Heteroptera (bugs) Hymenoptera Formicidae (ants)  Isoptera (termites)  Mallophaga (bird lice) Orthoptera (crickets and allies) Thysanoptera (thrips)  Acarina (mites)  Diplopoda (millipedes) 
Most species of. Laboulbeniales have been
reported from beetles and flies in temperate
regions, but recent studies in the tropics
indicate that diversity in these regions may be
much greater than in temperate areas, primarily
because diversity of hosts, especially beetles,
is much higher.
34
Pyxidiophorales
  • 2 genera, 16 species
  • Specialized for dispersal by arthropods (bark
    dung beetles, phoretic mites)
  • Perithecia with ascospores that undergo extreme
    morphological changes during maturation

35
Blackwell et al. 1986. Hyperphoretic dispersal
of a Pyxidiophora anamorph. Science 232 993-995
36
Pyxidiophora perithecia
Development of anamorph
Photos by M. Blackwell
37
Presumptive anamorph (above)
From Kirschner (2003). Mycological Progress 2
209-218.
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