Filamentous fungi - review and Oomycetes Lecture 3

Four phyla of fungi Chytridiomycota - no sexual spore Zygomycota - zygospore Ascomycota - ascospore Basidiomycota - basidiospore

Ascomycota

Botrytis cinerea - a fungus -causes grey mold

Powdery mildew of cucumber

Eye spot disease of strawberry Ramularia grevilleana, Mycosphaerella fragariae

Canker, Nectria galligena

Wilts caused by Fusarium oxysporum Darkened vascular tissue of cucumber caused by F. ox. f.sp. cucumerinum Wilt of field grown melon caused by F. ox. formae speciales melonis

Characteristics of Basidiomycota Mycelium is septate Septa are perforated - sometimes with dolipore (doughnut shaped)

Basidiomycetes have clamp connections

Fly agaric (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 anastomosis groups (AG) (fusion of hyphae only occur if same anastomosis group)

Corn smut

Corn smut

Corn smut

The disease cycle of corn smut

Oomycota They are very different from true fungi: Cell walls have cellulose and glucans. Hyphae have no cross walls (septae). Spore types: Oospore = resting spore, sexual spore Zoospores, zoosporangia = asexual spores Examples: Pythium -seed rot, damping off, root rot Bremia, Peronospora, Plasmopara - downy 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 sporangia

Alnus glutinosa attacked by Alder Phytophthora Brownish red discolouration Oogonia Oospore Amphigyne two-celled antheridia Alder stembase Photo: Christer Olsson

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 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