Fungal Lecture 1 PowerPoint file 12MB

Filamentous fungi a background Lecture 1 and 2 What are they? What are they doing?

Fungi are important in nature As decomposers As pathogens of plants, animals and humans, and in food spoilage As producers of secondary metabolites, e. g. penicillin In cheese, bread and wine making

Fly agaric (flugsvamp)

Ergot of rye • Caused by Claviceps purpurea. • Cause of ergotism: “Holy Fire” or “St. Anthony’s Fire”. • Sclerotia are dangerous. • Witch hunts. • Caused low fertility and death in 14th-18th century Europe.

Other toxins made by fungi • Endophytic fungi (Acremonium) in grasses can be toxic to cattle (fescue toxicosis) • Other mycotoxins: – Ochratoxins – Aflatoxins - carcinogenic – Fumonosins - blind stagger of horses – Patulin - bleeding in lungs and brain, kidney damage, cancer

Medicines that come from fungi • Penicillin. Penicillium chrysogenum. Alexander Fleming, 1928. • Cephalosporin • Cyclosporin

Fungal diseases of humans - mycoses • Trichophyton rubrum. Causal agent of athlete’s foot. Came from tropics. • Candida albicans. Causes candidiasis = yeast infections. – Around genitalia. – Disease of mouth and throat. • Blastomycosis, Cryptococcosis, Histoplasmosis, Aspergillosis are other diseases.

Smut infection of a wheat field in Eastern Washington (1956)

Ustilago maydis - the corn smut fungus

Ustilago maydis

is a popular food delicacy in Mexico

Examples of symptoms caused by fungi: Cankers Storage rots of fruits and vegetables Rust, mildews Leaf spots

Pathogen life styles Necrotrophs - kill host cells with toxins and hydrolytic enzymes. Ex: Botrytis cinerea.

Biotrophs - specialize on a living host. Ex. Powdery mildews and rusts.

Hemibiotrophs - start out biotrophic. Then, they kill the host cells. Ex. Phytophthora infestans.

Botrytis cinerea - a fungus -causes grey mold

Grey mould of strawberries

Characteristics of grey mold

• B. cinerea is a necrotroph, entering the plant through dead or dying tissue. • It is a pathogen that attacks almost any known plant species. It invades healthy tissue through dead petals or leaves or dying wood.

Botrytis cinerea causes rots on fruits and vegetables, blossom blights, damping off, stem cankers, leaf spots and bulb rots. scleriotia

In the field, blossom blight often precede the fruit rots

The fungus enters the fruit through the dead flower petals.

The fungus Botrytis cinerea Develops grey mycelium with long, branched conidiophores with clusters of one-celled, ovoid conidia. The conidiophores and conidia resemble a grapelike cluster.

Botrytis cinerea of tomato

Botrytis cinerea of tomato Spots on fruits are from spores that have landed

Attack on fruit originated in the flower

Grey mould - continued •B. cinerea overwinters as mycelium in decaying plant debris or as sclerotia black, hard resting structures. •It also attacks fruit and vegetables during storage. The fruits rot internally (often from the flower end) and a soft mycelial mat develops on the surface. The fungus does most damage when it is very humid and damp.

Life cycle of Botrytis cinerea

Powdery mildew on rose • Sphaerotheca pannosa is the causal agent of powdery mildew on roses. It is an example of a biotroph: It grows only in living plant tissue. • The white, powdery appearance is due to conidiophores/conidia

Powdery mildew on Poinsettia

Powdery mildew on squash

Powdery mildew on cucumber

Life cycle of powdery mildew

Rust of roen (rönn)

Rust of raspberry

Rust of rose

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

Characteristics of fungi Fungi have hyphae. A mass of hyphae is a mycelium. The hyphae may be septate or aseptate. Specialized hyphae, haustoria are feeding structures.

Fungal reproduction Asexually, by forming conidia Sexually (three steps): •Plasmogami (dikaryon) •Karyogami (zygote forms) •Meiosis (sexual spore forms): •Zygospore •Ascospore •Basidiospore

Incompatibility systems Fungi (ascomycetes) have mating types. They are designated MATa and MATa (yeast), MATA and MATa (Neurospora) or MAT1-1 and MAT1-2. Sexual reproduction in a heterothallic ascomycete requires the participation of different mating types. In a homothallic strain the fusing individuals are of the same mating type. The inability of two individuals of the same mating type to fuse is called vegetative incompatibility.

Chytridiomycota

Zygomycota

Gametangia fuse to produce a zygospore (Rhizopus stolonifer)

Ascomycota

Penicillium and Aspergillus

Examples of conidiophores of other imperfect fungi or Deuteromycetes