Filamentous fungi -review and Oomycetes

Lecture 3

Four phyla of fungiFour phyla of fungi

o Chytridiomycota - no sexual sporeo Zygomycota - zygosporeo Ascomycota - ascosporeo Basidiomycota - basidiospore

AscomycotaAscomycota

Botrytis cinereaBotrytis cinerea - a fungus -causes - a fungus -causes grey moldgrey mold

Powdery mildew of cucumber

Eye spot disease of strawberryRamularia grevilleana,

Mycosphaerella fragariae

Canker, Nectria galligena

Wilts caused by Fusarium oxysporum

Wilt of field grown melon Wilt of field grown melon caused by caused by F. ox.F. ox. formae formae speciales speciales melonismelonis

Darkened vascular Darkened vascular tissue of cucumber tissue of cucumber caused by caused by F. ox.F. ox. f.sp. f.sp. cucumerinumcucumerinum

Characteristics of Basidiomycota• Mycelium is septate• Septa are perforated - sometimes with

dolipore (doughnut shaped)

Basidiomycetes have clamp Basidiomycetes have clamp connectionsconnections

Fly agaricFly agaric(flugsvamp)(flugsvamp)

Stem rust of wheat

Aecia on barberry

Rust of raspberry

Rust of rose

Rhizoctonia solani• It is a basidiomycete;

teliomorph (Thanatephorus cucumeris) is rare.

• Has very characteristic mycelium; typical of basidiomycete.

• Differentiated into anastomosisanastomosis groups (AGAG) (fusion of hyphae only occur if same anastomosis group)

Corn smutCorn smut

Corn smut

Corn smut

The disease cycle of corn smut

OomycotaThey are very different from true fungi:They are very different from true fungi:•Cell walls have cellulose and glucans.Cell walls have cellulose and glucans.•Hyphae have no cross walls (septae).Hyphae have no cross walls (septae).Spore types:Spore types:

•Oospore Oospore = resting spore, sexual spore= resting spore, sexual spore•Zoospores, zoosporangiaZoospores, zoosporangia = asexual spores = asexual spores

Examples:Examples:PythiumPythium -seed rot, damping off, root rot -seed rot, damping off, root rot

BremiaBremia, , PeronosporaPeronospora, , PlasmoparaPlasmopara - - downy mildewsdowny mildews

Oomycetes belong to Chromista

Different types of diseases caused by Oomycetes

Late blight of potato, caused by Phytophthora infestans

The disease cycle of potato late blight (Phytophthora infestans)

Mature sporangium

There are 8-10 zoospores per sporangium

Zoospores are released

One zoospore left…

Zoospores germinate

See movie of zoospore release

Grass lawn attacked by Pythium ultimum (damping off)

Life cycle of Pythium ultimum

Downy mildew of grape

Attack of grape berries

Symptoms of grape downy mildew (Plasmopara viticola)

Disease cycle of Plasmopara viticola, downy mildew of grape

Zoospores of downy mildew of hop, landing on leaf and infecting

Downy mildew of onion (Peronospora destructor)

Downy mildew of cabbage (Peronospora parasitica)

Tree and strawberry diseases caused by Phytophthora species

Strawberry crown rot, caused by Phytophthora cactorum

Oospore and sporangiaOospore and sporangia

Alnus glutinosa attacked by Alder Phytophthora

Brownish red discolouration

Oogonia

Amphigyne two-celled antheridia

Oospore

Photo: Christer OlssonAlder stembase

Symptoms of Phytophthora alni ssp. uniformis on alder (Alnus glutinosa)

•The pathogen infects through wounds at the stembase or through the roots.•The tree tops die•The tree dies later

Phytophthora ramorum, chlamydospores. (Diameter 20 – 90 µm, 52.5 – 75 µm on this slide). Often germinating with a sporangiophore.

Isolat CH 180, (CBS 101328; P1357), The Netherlands, Rhododendron.Heterothallic (A1).

Christer Olsson, 1/7 2002, DIA bilder