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Feb 18 2009 Ascomyetes Review of sexual reproduction strategies Asexual reproduction Representative disease cycles ** Images and lecture material were.

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Presentation on theme: "Feb 18 2009 Ascomyetes Review of sexual reproduction strategies Asexual reproduction Representative disease cycles ** Images and lecture material were."— Presentation transcript:

1 Feb Ascomyetes Review of sexual reproduction strategies Asexual reproduction Representative disease cycles ** Images and lecture material were not entirely created by J. Bond. Some of this material was created by others.**

2 ASCOMYCETES Characteristics cont. 6. Asexual spores - conidia, chlamydospores. These fungi produce both sexual and asexual spores. The sexual stage produced by a fungus is termed the "perfect stage". Ascomycete fungi also produce asexual spores (conidia). This termed the "imperfect stage". Conidia can be produced in several different sporocarps (aka arrangements), and each fungus generally (but not always) produces conidia in only one arrangement:

3 Conidia Arrangement a. Free and independent (aka naked) - one conidium or chain of conidia at end of conidiophore. Ex: Taphrina deformans - peach leaf curl Ex: Sphaerotheca pannosa - powdery mildew of rose

4 Conidia Arrangement b. Synnema - upright bundle of conidiophores, all cemented together. Ex: Ophiostoma ulmi - Dutch elm disease

5 Conidia Arrangement c. Acervulus - a depressed mat of hyphae with short conidiophores. Ex: Venturia inaequalis - apple scab

6 Acervulus

7 Conidia Arrangement d. Sporodochium - conidiophores are produced on a pin cushion-shaped stroma. Ex: Monilinia fructicola - brown rot of stone fruits Ex: Claviceps purpurea - ergot of grains

8 Conidia Arrangement e. Pycnidium - a structure, round or flask-shaped, with conidia and conidiophores within. Ex: Guignardia bidwellii - black rot of grape Ex: Cryphonectria parasitica - chestnut blight

9 Leaf Curl Diseases Peach leaf curl – Taphrina deformans Leaf blister on oaks – Taphrina caerulescens

10 Plant Pathology, G.N. Agrios

11 Powdery Mildews Obligate biotrophsObligate biotrophs Anamorph: conidiaAnamorph: conidia Teleomorph: asci in cleistotheciaTeleomorph: asci in cleistothecia Host specificHost specific

12 Plant Pathology, G.N. Agrios

13 Ergot of Cereals and Grasses Most common on rye and pearl millet Grain susceptible only when flowering Sclerotia mature as seed in grain head mature Sclerotia contain many toxic alkaloids including LSD Rye susceptible when deficient of copper

14 Ergot of Rye Sclerotium (pl. sclerotia) – a mass of hyphae that is so compacted that hyphae have lost their individuality. Can survive adverse conditions – overseasoning structures. Germinate by producing stalked stroma (closely woven somatic hypha)

15 Plant Pathology, G.N. Agrios


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