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Phylum Ascomycota Orders Erysiphales & Laboulbeniales. General Mycology Pl P 421/521 Lecture 7. Pyrenomycetes. Plectomycetes (Eurotiales). Chaetothyriales. Loculoascomycetes 1. Loculoascomycetes 2. Filamentous ascomycetes. Inoperculate discomycetes. Lecanoralean discomycetes.

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phylum ascomycota orders erysiphales laboulbeniales

Phylum AscomycotaOrders Erysiphales & Laboulbeniales

General Mycology

Pl P 421/521

Lecture 7

slide2

Pyrenomycetes

Plectomycetes (Eurotiales)

Chaetothyriales

Loculoascomycetes 1

Loculoascomycetes 2

Filamentous ascomycetes

Inoperculate discomycetes

Lecanoralean discomycetes

Operculate discomycetes

Erysiphales (powdery mildews)

Laboulbeniales

Saccharomycetales

Archiascomycetes

Basidiomycota

erysiphales
Erysiphales
  • Common name = Powdery Mildews
  • Biotrophs of vascular plants
    • Biotroph: an obligate parasite growing on another living organism
  • 21 genera, 437 species infecting > 40,000 species of plants (mostly dicots)
  • Most species are host specific, a few are omnivorous, infecting hundreds of host species
powdery mildew symptoms
Powdery Mildew Symptoms

Photo by Claudia Nitschwitz

characteristics
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
slide9

appressorium

Plasma membrane

Penetration peg

haustorium

Host cytoplasm

Plasma membrane

Plant cell wall

fungus

asexual reproduction
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 > 30,000 conidia
conidia
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
slide12

Ovulariopsis

Oidium type anamorph

Oidiopsis

Streptopodium

Fibrosin bodies

From Braun, 1987

sexual reproduction
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
asci ascospores
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
identification
Identification
  • Anamorph type
  • Number of asci/ascocarp
  • Cleistothecial appendages
    • Mycelioid
    • Rigid
      • Spear-like with inflated base
      • With curled tips
      • With dichotomously branched tips
blumeria
Blumeria
  • B. graminis--only powdery mildew on grasses
  • Mycelial setae
  • Digitate haustoria
  • Several asci/ascocarp
  • Inflated base on conidiophore
mycelioid appendages
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
dichotomously branched appendage tips
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
spear like appendages phyllactinia
Spear-like appendages--Phyllactinia
  • 24 species
  • Appendages lift ascocarp off leaf surface
  • Brush cells on top of ascocarp
  • Ovulariopsis and Streptopodium anamorphs
appendages with curled tips
Appendages with curled tips
  • Uncinula (81 spp)
    • Oidium anamorph
    • Several asci/ascocarp
  • Uncinuliella
    • Differs by bristle-like appendages on top of ascocarp
molecular data vs morphology
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 77:150-168; Mori et al 2000, Mycologia 92:74-93)
class laboulbeniomycetes
Class Laboulbeniomycetes
  • Orders Laboulbeniales and Pyxidiophorales
    • 5 families, 140 genera, > 1800 species
    • Members of 4/5 families lack hyphae, reduced to thallus attached to host
  • Parasitize arthropods
laboulbeniomycetes
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)
slide33

Hosts of Laboulbeniales (From Meredith Blackwell)

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.

pyxidiophorales
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
slide35

Blackwell et al. 1986. Hyperphoretic dispersal of a Pyxidiophora anamorph. Science 232: 993-995

slide36

Pyxidiophora perithecia

Development of anamorph

Photos by M. Blackwell

slide37

Presumptive anamorph (above)

From Kirschner (2003). Mycological Progress 2: 209-218.

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