FUNGI AND OTHER ORGANISMS (PLANT) - PowerPoint PPT Presentation

1 / 29
About This Presentation
Title:

FUNGI AND OTHER ORGANISMS (PLANT)

Description:

A relationship between Fungus + Root = Mycorrhiza. Construction of Haustaria Biotrophic fungi frequently produce haustaria. Haustoria: ... – PowerPoint PPT presentation

Number of Views:467
Avg rating:3.0/5.0
Slides: 30
Provided by: marych9
Category:

less

Transcript and Presenter's Notes

Title: FUNGI AND OTHER ORGANISMS (PLANT)


1
MYCOLOGY (MIC 206)
  • FUNGI AND OTHER ORGANISMS (PLANT)

2
FUNGI AND PLANTS
  • Fungi can be
  • Facultative symbionts can live freely or within
    plants
  • Obligate symbionts can only grow in association
    with plants.
  • Hyphae of symbiotic fungi can penetrate plant
    cells, some grow through tissues without entering
    or penetrating plants cells.
  • Two way of parasitic relationships of fungi with
    plants
  • Biotrophic
  • Necrotrophic

3
Biotrophic vs Necrotrophic
  • Some fungi have phases where they became
    biotrophic or necrotrophic.
  • Fungi can penetrate plant tissues through
  • aerial surfaces (stems, leaves, flowers, fruits).
  • root surfaces (root epidermis).
  • wounds (normal process where internal tissues are
    exposed due to breakage of plants surfaces (e.g.
    when fruits and leaves are formed).

4
MOA of Plant Pathogen
  • Examples of fungi penetrating plant tissues
  • Aerial surfaces
  • Examples are Cladosporium (leaf), Rhizopus
  • stolonifer (fruit), Colleototrichum (fruit
    and leaf),
  • Armillaria mellea (wood/ bark).
  • Root surfaces
  • Fusarium spp. (root), Sclerotinia sclerotonum
    (root).
  • Wounds
  • Sclerotinia fructigena (wasps or birds break
  • epidermis of fruit and introduce conidia of
    fungus).
  • Other internal tissues
  • Armillaria mellea (tree pathogen and able to
    enter
  • living trees but can live as saprotrops
    when trees
  • die).

5
BIOTROPHIC ASSOCIATIONS
6
Biotrophic Associations
  • From the Greek
  • bios life,
  • trophy feeding.
  • Live within the plant and obtain nourishment
    without causing cell death to plants.
  • Long-term feeding relationship with the living
    cells of their hosts, rather than killing the
    host cells as part of the infection process.

7
Characteristics of Biotrophic Associations
  • Characteristics
  • Do not kill hosts so either parasitic or
    saprophytic.
  • Tissues that are invaded remain alive.
  • Symbiotic because two organisms live together.
  • A relationship between Fungus Root
    Mycorrhiza.

8
Construction of Haustaria
  • Biotrophic fungi frequently produce haustaria.
  • Haustoria specialized hyphae that penetrate the
    cells of other organisms that obtains food from a
    host.
  • Fungi grow between the host cells and invade only
    a few of the cells to produce nutrient-absorbing
    structures termed haustoria.

9
MOA of Haustaria
  • Fungal haustoria will be produced from spores
    that germinate on the surface of plants, on
    leaves or stems.
  • The germinating spores may produce a penetration
    peg known as an appressorium and penetrate the
    plants cell wall.
  • After penetration, the hyphal tip forms an
    invagination within the cell that becomes the
    haustorium.
  • Haustorium is a structure of an extended
    extracellular mycelium, or filaments, of the
    fungus.

10
Magnaporthe oryzae Rice Blasts Diseases
appressorium
penetration of leaf
penetration peg
11
CLASSIFICATION OF BIOTROPHICS ASSOCIATION
  • Two importants groups

12
BIOTROPHIC ASSOCIATIONS - RUST FUNGI
13
The Rust Fungi
  • The infection behaviour of rust fungi is broadly
    similar to that of the powdery mildews.
  • Involving nutrient absorption by haustoria to
    support abundant sporulation for epidemic spread.

Close-up of lower surface of the leaf, showing
cup-shaped pustules of aeciospores.
Small lesions on the upper surface of a barberry
leaf, with spermogonia in their centres.
14
Penetration and Colonization by Rust Fungi
15
Growth of barley rust germ tubes on a barley leaf
replica
16
Growth of barley rust germ tubes on a barley leaf
replica
17
Bean Rust Uromyces appendiculatus
18
Bean Rust Uromyces appendiculatus
19
Bean Rust Uromyces appendiculatus
20
Black Rot of Grape - Phyllosticta ampelicida
21
Phyllosticta ampelicida germinated conidia and
melanized appressoria
22
BIOTROPHIC ASSOCIATIONS POWDERY MILDEW FUNGI
23
The Powdery Mildew Fungi (Ascomycota)
  • The Powdery Mildew Fungi (Ascomycota)
  • Powdery mildews produce mycelium (fungal threads)
    that grow only on the surface of the plant.
  • They never invade the tissues themselves.
  • The fungi feed by sending haustoria, into the
    epidermal (top) cells of the plant.
  • Typical forms many powdery mildews, where the
    fungus forms a powdery coating of white spores on
    the leaf surface.

24
Powdery Mildew Fungi
  • Other common examples in Britain are powdery
    mildew of hawthorn (Podosphaera oxyacanthae),
    gooseberry (Sphaerotheca morsuvae), and cereals
    and grasses (Erysiphe graminis).

Powdery mildew of roses, caused by the fungus
Sphaerotheca pannosa.
Localised lesions of Erysiphe graminis on wheat
leaves.
25
NECROTROPHIC ASSOCIATIONS
26
Necrotrophic Associations
  • Term necro relating to death.
  • Necrotrophic Kill cells and absorb nutrients
    from dead cells.
  • How?
  • ? Frequently secrete enzymes that degrade plant
  • components or toxins that kill the
    plants tissue.
  • Subsequently live on nutrients from the tissue
    they have killed.

27
Characteristics of Necrotrophic Associations
  • Characteristics
  • Kills host cells.
  • Can be recognised by patches of dead, blackened
    tissue.
  • Produce toxins which kill plant cells and their
    enzymes to degrade plant constituents so that
    fungus can use them as food.
  • Can change to saprophytic or biotrophic in later
    stages.
  • Show low specificity to host plants.
  • They are easy to culture in the absence of their
    hosts.
  • They can survive in the absence of their hosts by
    production of spores or sclerotia in the dead
    tissue.

28
Necrotrophic Associations (cont)
  • Examples
  • Botrytis cinerea cause grey moulds in young
    plants or grapes when conditions are cold and
    damp.
  • Grey mould rot causes damage on stored carrot,
    parsnip, mangel, beet, endive, chicory, turnip,
    and many others.

29
Necrotrophic Associations (cont)
  • Examples
  • Phytophthora spp. Cause black pod disease in
    cocoa plant and brown rot disease on orange
    fruit.
Write a Comment
User Comments (0)
About PowerShow.com