Post on 26-Mar-2018
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.
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Higher Fungi
Source: Agrios (2005)
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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
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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)
Source: Agrios (2005)
Multilocular Monolocular
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Asexual Reproduction
Source: Agrios (2005)
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1. Hemiascomycetes
Saccharomyces cerevisiae (yeast)
Important in wine & bakery industries
Morphology: unicell
Asexual reproduction: budding
Sexual reproduction: ascospores
Source: Webster, 1988
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2. Plectomycetes
Filamentous ascomycetes (Agrios, 2005)
Ascocarp: cleistothecium
Examples:i. Aspergillus sp.
ii. Penicillium sp.
iii. Erysiphe sp.
iv. Oidium sp.
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2. Plectomycetes (cont’)
1. Aspergillus sp.
(anamorph/asexual stage)
Eurotium sp.
(teleomorph/sexual stage)
Aspergillus flavus: produces aflatoxins
Aspergillus niger:produces citric/gluconic acid
Source: Agrios (2005)
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2. Plectomycetes (cont’)
2. Penicillium sp. (anamorph)
Talaromyces sp. (teleomorph)
P. italicum (blue mold)
P. digitatum (green mold)
P. chrysogenum: produces penicillin
P. griseofulvum: producesgriseofulvin
Source: Agrios (2005)
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2. Plectomycetes (cont’)
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
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3. Pyrenomycetes
Ascocarp: Perithecium
Order:
1. Meliolales
2. Chaetomiales
3. Clavicipitales
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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
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3. Pyrenomycetes (cont’)
ii. Order: Chaetomiales Ascocarp: Perithecium with appendages
& ostioles
Saprophyte
E.g.: Chaetomium sp.
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3. Pyrenomycetes (cont’)
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
Source: Agrios (2005)
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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)
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4. Discomycetes (cont’)
Stem rot & white mold on potato (left) and pepper (right).
Sclerotinia sclerotiorum
Sclerotia in tomato stem.
Germinating sclerotia producing apothecia.
Source: Agrios (2005)
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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
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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
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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
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6. Deuteromycetes (cont’)Basipetal conidia
Youngest conidium Annelide
Phialide
Conidiogenous cells
Source: Agrios (2005); Webster (1988)
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Order:
1. Moniliales
2. Melanconiales
3. Sphaeropsidales
4. Agonomycetales
6. Deuteromycetes (cont’)
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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.
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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
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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..
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1. Order: Moniliales (cont’)
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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).
1. Order: Moniliales (cont’)
Source: JPT, Agrios (2005)
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vi. Curvularia sp.
Disease: Leaf spots
Host: palms (coconut, oil palm, ornamental palms), turf grass
Symptom: brown spot with yellow halo
1. Order: Moniliales (cont’)
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2. Melanconiales
Produce conidia in fruiting body called acervulus (saucer-like shape)
Examples:
i. Colletotrichum sp.
ii. Pestalotiopsis sp.
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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’)
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3. Sphaeropsidales
Produce conidia in fruiting body called pycnidium
Examples:
Phoma sp.: Seedling rot
Septoria sp.: Leaf blight (Host: celery)
Source: Agrios (2005)
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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
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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
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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
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Thank You
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