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Ascomycete: Structure
- Unicellular
- Filamentous
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- Hyphae have perforated septa
- The hyphal cells of the vegetative mycelium may be either uninucleate or multinucleate
- Some are homothallic and others are heterothallic
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Ascomycete: Reproduction
Asexual: forming conidia that are multinucleate; formed from onidiogenous cells, which are borne at the tips of modified hyphae called conidiophores (externally as conidia)
Sexual: formation of ascus that prodces ascosporesMeiosis occurs within the ascus
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Ascomycete: Relevance
- Serious plant diseases (ergot of rye, dutch elm, chestnut blight, dogwood anthracase)
- Yeasts are these
- Edible (morels and truffles)
- Saccharomyces species: baking and brewing industry; research in genetics and metabolism; used industrially to make hep vaccine, ethanol for biofuel
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Glomeromycetes: Structure
mostly coenocytic hyphae
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Glomeromycetes: Reproduction
Reproduce only asexually by means of a large multinucleate spore
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Glomeromycetes: Location
Grow in association with roots
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Glomeromycetes: Relevance
- Form mycorrhizas
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- Occurs in about 80% of vascular plants
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Asexual Cycle of Ascomycetes
- a. Mycelium grows out from a germinating ascospore on a suitable substrate
- b. Then, the mycelium reproduces asexually by forming conidia
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Sexual Cycle of Ascomycetes
- a. Occurs on the same mycelium that forms conidia
- b. Formation of multinucleate gametangia called antheridia and ascogonia precedes sexual reproduction
- c. The male nuclei of the antheridium pass into the ascogonium via the trichogyne
- d. Plasmogamyà in the ascogonium, the male nuclei pair with the genetically different female nuclei within the common cytoplasm, but they don’t fuse with them
- e. Ascogenous hyphae now begin to grow out of the ascogonium and compatible pairs of nuclei migrate into them
- f. Cell divisionà dikaryotic cells , where the asci form at the tips of the hyphae
- i. Sometimes a crozier is formed, allowing paired nuclei to divide simultaneously
- g. Subsequent cell division occurs where the immature ascus contains a compatible pair of nuclei, whci fuse--? Diploid zygoteà elongationà meiosisà mitosisà formation of ascus with eight nucleià cut off in segments to form ascosporesà release of ascosporesà formation of gametangium
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