fungal pathogens

8/19/2019 Fungal Pathogens

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Postharvest diseases – fungal pathogens

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Postharvest diseases

Fungal pathogens


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Classification of living organisms

http://www.ucmp.berkeley.edu/archaea/archaea.htmlhttp://www.ucmp.berkeley.edu/bacteria/bacteria.htmlhttp://www.ucmp.berkeley.edu/alllife/eukaryota.html


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Eukaryota

http://www.ucmp.berkeley.edu/alllife/eukaryota.maphttp://www.ucmp.berkeley.edu/alllife/eukaryota.map


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• “Fungi” that can cause postharvestdiseases are found in 2 kingdoms– Fungi or Eumycota

– Chromista

•

About 300 000 species of fungi have beendescribed

• About 10 000 species are pathogenic forplants

• No consensus about the taxonomy of fungi:here we use the taxonomy according toAinsworth


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downy mildew on grape Phytophthora palmivora on papaya

Pythium myriotylum on cocoyam


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Phytopthora disease cycle


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A. sporangium, B. zoospore, C. chlamydospore, D. oospore


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Phytophthora infestans – disease cycle


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Phytophthora infestans


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Oomycota – postharvest pathogens

• Phytophthora palmivora– papaya, cocoa, durian, tomato

• Phytophthora nicotianae– bananas, citrus, guavas, mangoes, passion fruit,

beans, eggplants, watermelons

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Pythium myriotylum– cocoyam, watermelon, melon, beans, eggplant,

ginger, groundnut


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Phytophthora palmivora - distribution


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black pod disease on cacao

Phytophthora palmivora


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Eumycota (Fungi)

• Chytridiomycota

about 800 species• Zygomycota

(+ Glomeromycota)

about 1000 species• Ascomycota

about 32300 species• Basidiomycota

about 22240 species


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Zygomycota• Zygomycota

– Class: Zygomycetes• Order: Mucorales: postharvest pathogens such as

Mucor and Rhizopus


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Mucor


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Rhizopus


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Rhizopus soft rot

on sweetpotato


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Disease cycle of Rhizopus


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Zygomycota – postharvest pathogens

• Rhizopus spp.– on sweet potato, beans, cabbages, cassava,

garlic, peppers, potato, tomato, okra, cocoyam,guavas, litchis, mangos, melons, pineapple, apple,banana, citrus, guavas, ...

• Mucor spp.– on tomato, cassava, melon, sweetpotato, guavas,

apples, pears


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Ascomycota

• Sexual spores are ascospores (usually 8ascospores in one ascus)

• Asci can be exposed or are formed in a sexualfruiting body (apothecium, perithecium,pseudothecium, cleistothecium)

• Asexual spores are conidia• Conidia and conidiophores are produced on the

surface or in an asexual fruiting body (acervulus or

pycnidium)• Cell wall consists of chitin• Great many important plant pathogens


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Ascomycota• Sexual stage = teleomorf

• Asexual stage = anamorf

• Asexual stages used to be grouped inDeuteromycota or Fungi Imperfecti


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Ascomycota56 orders including:

• Order Eurotiales (Penicillium, Aspergillus)

• Order: Hypocreales (Claviceps, Fusarium)

• Order: Microascales (Ceratocystis)• Order: Pleosporales (Alternaria)

• Order: Dothideales (Lasiodiplodia)

• Order: Helotiales (Botrytis, Sclerotinia, Monilia)

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Order uncertain: Glomerella (Colletotrichum spp.)


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Penicillium


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Penicillium


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life cycle of Penicillium


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Aspergillus


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Postharvest diseases – fungal pathogens 29

Aspergillus


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life cycle of Aspergillus


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Penicilllium and Aspergillus -

postharvest pathogens

• Penicillium spp.– On stored grains, citrus, grapes, melons,

mangoes, avocados, passion fruit, pineapple,kiwifruit, papaya, yam, tomato, sweetpotato,cocoyam

• Aspergillus spp.– On stored grains,groundnut, cassava, pepper,

tomato, melon, onion, cocoyam, guavas, citrus,litchis, mangoes, papayas, passion fruit


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Fusarium rot


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Fusarium – postharvest pathogens

• On cereals, potato, tomato, ginger, melon,peppers, cocoyam, yam, sweetpotato,

cabbages, beans, peas, cassava


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Ceratocystis - biology

• Fungus persists in soil and crop debris

• can produce thick-walled chlamydospores

• sexual state: perithecia that produceascospores

• asexual state: conidia produced in chains

• spore dispersal by wind, animals, rain


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Ceratocystis – postharvest pathogens

• Ceratocystis fimbriata (Thielaviopsis,Chalara)

– on sweetpotato, taro, carrot, citrus

• Ceratocystis paradoxa– on melon, banana, guava, pineapple


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Ceratocystis fimbriata on taro


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Ceratocystis paradoxa - distribution

Gl ll i l t


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Glomerella cingulata


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Glomerella cingulata - distribution


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anthracnose

on papaya

on apple

http://www.fito-info.bf.uni-lj.si/cirsium/images/Skodljivci/FC00291.jpg


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Colletotrichum – postharvest pathogens

• Glomerella cingulata (Colletotrichumgloeosporoides)

– On avocada, mango, papaya, banana, citrus,grapes, guavas, apples, melon, pepper, tomato

• Colletotrichum musae– on banana

Alternaria


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Postharvest diseases – fungal

pathogens

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Alternaria – postharvest pathogens

• On apple, citrus, grapes, mangoes, melons,papayas, passion fruit, avocados, beans,

eggplants, peppers, tomato, potato,cabbages, garlic, onion


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pathogens

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Alternaria on various crops


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pathogens

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Lasiodiplodia - biology

• Fungus survives in soil and crop debris asthick-walled chlamydospores

• asexual stage: pycnidia that give rise toconidia

• spores are spread by rain

•infection occurs via wounds during harvestand handling


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pathogens

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Lasiodiplodia theobromae - distribution


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pathogens

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Lasiodiplodia – postharvest pathogens

• Lasiodiplodia theobromae (= Botryodiplodiatheobromae)

– on apple, avocado, banana, citrus, grapes, guava,litchis, mangoes, mangosteens, melon, papaya,pineapple, rambutan, watermelon, cassava,eggplant, ginger, melon, onion, peppers,

sweetpotato, cocoyam, tomato, yam


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pathogens

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Lasiodiplodia


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pathogens

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Sclerotinia – postharvest pathogens

• widespread in temperate growing areas andin subtropical regions with a cool wet

season• on all kinds of vegetables,

• cause a soft and watery rot

•pure white mycelium with black sclerotia


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pathogens

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Sclerotinia on carrot


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pathogens

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pathogens

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Sclerotinia sclerotiorum


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pathogens

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Sclerotinia sclerotiorum


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pathogens

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pathogens

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Monilia

Botrytis cinerea – life cycle


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pathogens

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y y

Botrytis - ajuin


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pathogens

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pathogens

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Basidiomycota• Sexually produced spores are

basidiospores produced on a basidium

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Cell wall consists of chitin• Saprophytic and parasitic mushrooms, and

important plant pathogens such as rusts,smuts, Rhizoctonia spp., Sclerotium spp.

corn smut


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pathogens

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Armillariacorn smut

rust on cereals Rhizoctonia


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pathogens

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Basidiomycota

• Phylum: Agaromycotina– Rhizoctonia

– Sclerotium rolfsii

• Class: Pucciniomycotina– rusts

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Class: Ustilaginomycotina– smuts


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pathogens

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Sclerotium rolfsii - biology

• Sexual stage: Athelia rolfsii (Corticiumrolfsii) (not commonly seen in nature)

• causes Southern blight, very wide hostrange

• The fungus overwinters as sclerotia

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Sclerotia germinate in warm and humidconditions


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pathogens

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distribution map – Sclerotium rolfsii


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pathogens

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Sclerotium – postharvest pathogen

• On bean, carrot, cassava, cabbages,eggplants, garlic, ginger, melon, onion,

pepper, potato, sweetpotato, tannia, taro,tomato, yam, guava, ...


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pathogens

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Sclerotium on tomato and damp filter paper


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pathogens

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Rhizoctonia solani - biology• Sexual stage: Thanatephorus cucumeris

(not common in nature)

• Common inhabitant of most soils;extremely widespread, probably occursthroughout the world

Rhizoctonia solani disease cycle


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pathogens

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Rhizoctonia solani – disease cycle


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pathogens

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Rhizoctonia – postharvest pathogen• On beans, cabbages, carrots, eggplants,

lettuce, melon, peppers, tomato,

sweetpotato, tannia, taro, yam, peanut, ...

Rhizoctonia on various hosts


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http://upload.wikimedia.org/wikipedia/commons/b/b9/Thanatephorus_cucumeris_infected_peanuts.jpg

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