plant diseases caused by fungi: ascomycota 4 .pdf · fungi kingdom phylum class fungi (higher)...

Plant Diseases Caused By Fungi: Ascomycota

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Fungi

Kingdom Phylum Class

Fungi

(Higher)

Ascomycota Hemiascomycetes

Plectomycetes

Pyrenomycetes

Loculoascomycetes

Discomycetes

Deuteromycetes

Basidiomycota Teliomycetes

Hymenomycetes

Source: Ainsworth (1973)Note: Refer to Agrios (2005) for latest classification.


Higher Fungi

Source: Agrios (2005)


Ascomycota

Sac fungi

Important characteristics: Septate hyphae

Asexual reproduction (anamorph): Conidia produced on conidiophores or in

fruiting bodies such as acervuli & pycnidia

Sexual reproduction (teleomorph): Ascospores produced in asci (singular, ascus)

either naked or in fruiting bodies called ascocarps

Usually 8 ascospores per ascus


Sexual Reproduction

Types of ascocarps:1. Cleistotesium (spherical & closed)

2. Perithecium (flask-shaped & with opening)

3. Apothecium (saucer-shaped)

4. Ascostroma (matrix of mycelium with cavities or locules, either monolocular or multilocular)


Multilocular Monolocular


Asexual Reproduction



1. Hemiascomycetes

Saccharomyces cerevisiae (yeast)

Important in wine & bakery industries

Morphology: unicell

Asexual reproduction: budding

Sexual reproduction: ascospores

Source: Webster, 1988


2. Plectomycetes

Filamentous ascomycetes (Agrios, 2005)

Ascocarp: cleistothecium

Examples:i. Aspergillus sp.

ii. Penicillium sp.

iii. Erysiphe sp.

iv. Oidium sp.


2. Plectomycetes (cont’)

1. Aspergillus sp.

(anamorph/asexual stage)

Eurotium sp.

(teleomorph/sexual stage)

Aspergillus flavus: produces aflatoxins

Aspergillus niger:produces citric/gluconic acid




2. Penicillium sp. (anamorph)

Talaromyces sp. (teleomorph)

P. italicum (blue mold)

P. digitatum (green mold)

P. chrysogenum: produces penicillin

P. griseofulvum: producesgriseofulvin




iii. Erysiphe cichoracearum Disease: Powdery mildew

Host: Cucurbits

Obligate parasite

Produces haustorium

iv. Oidium heveae Disease: Powdery mildew

Host: Rubber

Causes secondary leaf fall

Attack young leaves

Oidium hevea: Powdery mildew on rubber.

Erysiphe cichoracearum: Powdery mildew on cucumber.

Source: JPT


3. Pyrenomycetes

Ascocarp: Perithecium

Order:

1. Meliolales

2. Chaetomiales

3. Clavicipitales


3. Pyrenomycetes (cont’)

i. Order: Meliolales

Disease: Black mildew

Obligate parasite

Produces hypopodia

Interfere with photosynthesis

Associated with honeydew of insects such as aphids & scale insects

Examples:

Meliola mangiferae (host: mango) Meliola butleri (host: citrus)

Hypopodia



ii. Order: Chaetomiales Ascocarp: Perithecium with appendages

& ostioles

Saprophyte

E.g.: Chaetomium sp.



ii. Order: Clavicipitales

1. Claviceps purpurea Disease: Ergot

Host: Rye & barley

Produce toxin, harmful to humans & animals

2. Ustilaginoidea virens Disease: False smut

Host: Rice

Attack flowers/grainsSclerotia of ergot in grains of wheat.

Two ergot sclerotia producing stroma shaped like perithecia.

Claviceps purpurea



4. Discomycetes

Ascocarp: Apothecium

Saprophytes

E.g.: Peziza sp., Morchella sp.

Parasites

E.g.: Sclerotinia sclerotiorum (stem rot & white mold on vegetables & flowers), Diplocarpon sp. (black spots on rose)


4. Discomycetes (cont’)

Stem rot & white mold on potato (left) and pepper (right).

Sclerotinia sclerotiorum

Sclerotia in tomato stem.

Germinating sclerotia producing apothecia.



5. Loculoascomycetes

Ascus produced in ascostroma

Examples:1. Scabs: Elsinoe fawcetti (host: citrus), Venturia

inaequalis (host: apple)

2. Sooty molds: Capnodium sp., Limacinula sp., Tripospermum sp. (host: fruit trees)

3. Sigatoka of banana: Mycosphaerella musicola(teleomorph)/Cercospora musae (anamorph)

4. South American Leaf Blight (SALB) of rubber: Microcyclus ulei


5. Loculoascomycetes (cont’)

Elsinoe fawcetti: Citrus scab

Sooty molds: Tripospermum sp., Limacinula sp., Capnodium sp.

Mycosphaerella musicola: Sigatoka of banana

Mycrocyclus ulei: South American Leaf Blight (SALB) of rubber

Source: JPT


6. Deuteromycetes

Fungi imperfecti

Reproduction: Asexual

Conidia produced on conidiophores

Conidia production: Basipetal: youngest conidia nearest to

conidiophore

Acropetal: oldest conidia nearest to conidiophore

Conidiogenous cells: phialide, annelide


6. Deuteromycetes (cont’)Basipetal conidia

Youngest conidium Annelide

Phialide

Conidiogenous cells

Source: Agrios (2005); Webster (1988)


Order:

1. Moniliales

2. Melanconiales

3. Sphaeropsidales

4. Agonomycetales

6. Deuteromycetes (cont’)


1. Order: Moniliales

Produce micro- & macroconidia, no fruiting body

Examples:i. Fusarium sp.

ii. Drechslera sp. (previously known as Helminthosporium)

iii. Alternaria sp.

iv. Pyricularia sp.

v. Cercospora sp.

vi. Curvularia sp.


Fusarium sp.

Wilt diseases

F. oxysporum f. sp. cubensis: Panama wilt of banana

F. o. f. sp. elaidis: Wilt of oil palm (limited to West Africa)

F. o. f. sp. lycopersici: Wilt of tomato

Fusarium oxysporum f. sp. cubensis: Panama wilt of banana

Macroconidia Microconidia

Source: JPT; Agrios (2005)

1. Order: Moniliales


ii. Drechslera sp. D. oryzae: Brown spot

of rice

D. maydis: Leaf blight of corn

D. hevea: Bird eye spot of rubber

iii. Alternaria sp. Disease: Leaf spots

Host: wide host range, esp. ornamentals, vegetables (e.g., Brassica, potato, tomato), tobacco

Drechslera heveae: Bird eye spot of rubber.

Alternaria solani: Leaf spot of tobacco.

Source: JPT, Agrios (2005), Malloch (U. Toronto)

1. Order: Moniliales (cont’)

Dark brown conidia of Alternaria sp..


iv. Pyricularia oryzae Disease: Blast

Host: Rice

v. Cercospora sp. Disease: Leaf spots

a. C. arachidicola (Host: peanut)

b. C. capsici (Host: chilli)

c. C. albelmoschi (Host: okra)

d. C. oryzae (Host: rice, narrow brown spot)

Cercospora oryzae: Narrow brown spot of rice.

Pyricularia oryzae: Rice blast (left) and conidia (right).


Source: JPT, Agrios (2005)


vi. Curvularia sp.

Disease: Leaf spots

Host: palms (coconut, oil palm, ornamental palms), turf grass

Symptom: brown spot with yellow halo



2. Melanconiales

Produce conidia in fruiting body called acervulus (saucer-like shape)

Examples:

i. Colletotrichum sp.

ii. Pestalotiopsis sp.


i. Colletotrichum sp.

Disease: Anthracnose

C. gloeosporioides(Host: mango, conidia rod-shaped)

C. capsici (Host: chilli, conidia sickle-shaped)

ii. Pestalotiopsis sp.

Disease: Leaf spots

Host: palms

(A) Colletotrichum capsici: Anthracnose of chilli, (B) Conidia and setae (black pointed structure).

A) B)

Pestalotiopsis sp.: Leaf spot

Source: JPT, Agrios (2005)

2. Melanconiales (cont’)


3. Sphaeropsidales

Produce conidia in fruiting body called pycnidium

Examples:

Phoma sp.: Seedling rot

Septoria sp.: Leaf blight (Host: celery)



4. Agonomycetales

Sterile fungi

Produce sterile mycelia & sclerotia

Sexual reproduction & structures extremely rare, lacking or unkown

Examples:i. Rhizoctonia solaniii. Sclerotium rolfsii Teleomorphic stage of some species within

these 2 genera showed that they are Basidiomycetes


4. Agonomycetales (cont’)

i. Rhizoctonia solani Disease: sheath blight

Host: Rice, grasses (bermudagrass, centipedegrass)

Rhizoctonia solani: Sheath blight of rice.

Sclerotia

Source: JPT

Typical Rhizoctonia hyphae showing its branching at a right angle and septa close to the branching point.

Source: APSNet


4. Agonomycetales (cont’)

ii. Sclerotium rolfsii Disease: Foot rot, damping-off of seedlings,

etc.

Host: wide host range, most common hosts are legumes, crucifers & cucurbits (e.g., chilli, brinjal, peanut, tomato)

Sclerotia

Sclerotium rolfsii: Foot rot of chilli.

Source: JPT


Thank You


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