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Filamentous fungi - a background Lecture 1 and 2 What are they? What are they doing? Slide 2 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 Slide 3 Slide 4 Fly agaric (flugsvamp) Slide 5 Ergot of rye Caused by Claviceps purpurea. Cause of ergotism: Holy Fire or St. Anthonys Fire. Sclerotia are dangerous. Witch hunts. Caused low fertility and death in 14th-18th century Europe. Slide 6 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 Slide 7 Medicines that come from fungi Penicillin. Penicillium chrysogenum. Alexander Fleming, 1928. Cephalosporin Cyclosporin Slide 8 Fungal diseases of humans - mycoses Trichophyton rubrum. Causal agent of athletes foot. Came from tropics. Candida albicans. Causes candidiasis = yeast infections. Around genitalia. Disease of mouth and throat. Blastomycosis, Cryptococcosis, Histoplasmosis, Aspergillosis are other diseases. Slide 9 Smut infection of a wheat field in Eastern Washington (1956) Slide 10 Ustilago maydis - the corn smut fungus Slide 11 Ustilago maydis is a popular food delicacy in Mexico Slide 12 Slide 13 Examples of symptoms caused by fungi: Cankers Storage rots of fruits and vegetables Rust, mildews Leaf spots Slide 14 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. Slide 15 Botrytis cinerea - a fungus -causes grey mold Slide 16 Grey mould of strawberries Slide 17 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. Slide 18 Botrytis cinerea causes rots on fruits and vegetables, blossom blights, damping off, stem cankers, leaf spots and bulb rots. scleriotia Slide 19 In the field, blossom blight often precede the fruit rots The fungus enters the fruit through the dead flower petals. Slide 20 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. Slide 21 Botrytis cinerea of tomato Slide 22 Spots on fruits are from spores that have landed Attack on fruit originated in the flower Slide 23 Grey mould - continued B. cinerea overwinters as mycelium in decaying plant debris or as sclerotia - black, hard resting structures.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.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. Slide 24 Life cycle of Botrytis cinerea Slide 25 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 Slide 26 Powdery mildew on Poinsettia Slide 27 Powdery mildew on squash Slide 28 Powdery mildew on cucumber Slide 29 Life cycle of powdery mildew Slide 30 Rust of roen (rnn) Slide 31 Rust of raspberry Slide 32 Rust of rose Slide 33 Four phyla of fungi oChytridiomycota - no sexual spore oZygomycota - zygospore oAscomycota - ascospore oBasidiomycota - basidiospore Slide 34 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. Slide 35 Fungal reproduction Asexually, by forming conidia Sexually (three steps): Plasmogami (dikaryon) Karyogami (zygote forms) Meiosis (sexual spore forms): ZygosporeZygospore AscosporeAscospore BasidiosporeBasidiospore Slide 36 Incompatibility systems Fungi (ascomycetes) have mating types. They are designated MATa and MAT (yeast), MATA and MAT (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. Slide 37 Chytridiomycota Slide 38 Zygomycota Slide 39 Gametangia fuse to produce a zygospore (Rhizopus stolonifer) Slide 40 Ascomycota Slide 41 Slide 42 Penicillium and Aspergillus Slide 43 Examples of conidiophores of other imperfect fungi or Deuteromycetes