Deuteromycota Phylum: Deuteromycota Commonly referred to as the Fungi Imperfecti or imperfect fungi. Classification based on asexual stage because: Sexual reproduction rare, occurs only in narrow environmental parameters. Sexual phase of life cycle no longer exist. Phylum: Deuteromycota Phylum: Deuteromycota Only asexual reproduction occurs, typically conidia borne on When mycelial septate. conidiophores. Thallus also may be yeast or dimorphic. Classified according to conidia color, When sexual reproduction discovered, shape, size and number of septa. usually an Ascomycota or less often Form taxon: An artificial classification Basidiomycota. scheme. When sexual reproduction discovered, usually an Ascomycota or less often Basidiomycota. Purpose of Deuteromycota Purpose of Deuteromycota Division was erected to accommodate Instead, recall example of Emericella conidia producing fungi with unknown variecolor (=Aspergillus variecolor). sexual cycle. When sexual stage discovered, Emericella variecolor, the sexual species would be reclassified stage is the telomorph. according to sexual stage. Aspergillus variecolor, the asexual In practice this concept did not work. stage is the anamorph. Thus, sexual stage is often present. 1 Defining Taxa in Deuteromycota Taxonomy of Deuteromycota based mostly on spore morphology Saccardoan System of spore Saccardoan System of classification. Oldest system of defining taxa in Spore Classification. fungi. Artificial means of classification. No longer used in other taxa. Amerosporae: Conidia one celled, Didymosporae: Conidia Ovoid sphaerical, ovoid to elongate or to oblong, one septate short cylindric. Allantosporae: Conidia bean- Hyalodidymospore: shaped, hyaline Conidia Hyaline. to dark. Phaeodidymospore: Hyalosporae: Conidia dark. Conidia hyaline Phaeosporae: Conidia dark. Phragmosporae: Conidia oblong, Dictyosporae: Conidia ovoid to two to many transverse septa oblong, transversely and longitudinally septate. Hyalophramospore: Conidia hyaline. Hyalodictyospore: Phaeophramospore: Conidia hyaline. Conidia dark. Phaeodictyospore: Conidia dark. 2 Scolecosporae: Conidia threadlike to wormlike, septate or not, Staurosporae: Conidia stellate, hyaline or dark septate or not, hyaline or dark Helicosporae: Conidia helical, Classification of Deuteromycota septate or not, hyaline or dark We will recognize a single class: Deuteromycetes, with four orders: Moniliales Sphaeropsidales Melanconiales Mycelia Sterilis Moniliales Moniliales Order: Moniliales (Alternaria tenuis) Conidia and conidiophores borne on mycelium. Yeast or dimorphic. Not produce in pynidium or acervulus. conidium conidiophore 3 Moniliales Moniliales Order: Moniliales (Alternaria tenuis) Order: Moniliales (Sporobolomyces) Example of an asexual yeast. Moniliales Sphaeropsidales Order: Moniliales (Aureobasidium) An example of a Conidia produced in a pycnidium dimorphic genus. (pl.=pycnidia). Conidia bud An asexual fruiting body. Variable in directly from shape: globose, flask-shaped, cup- hyphal cells, and shaped, irregular or stromatic. With bud off other ostiole or not. conidia, i.e. Variation like that of ascocarps, but yeast cells. produce conidia and conidiophore. Sphaeropsidales Melanconiales Pycnidia of Phoma on agar. Two genera of acervulus producing fungi: Ostiole Conidia Pycnidium Flattened stroma Pycnidium as seen through microscope. 4 Mycelia Sterilia Mycelia Sterilia Order in which conidia and Sclerotium rolfsii conidiophores are not produced. Other characteristics are utilized to classify genera. Sclerotium Often sclerotium stage is present and its morphology is utilized to classify these fungi. Mycelia Sterilia Genetic Recombination Rhizoctonia solani Many species are thought to have evolved away sexual reproduction. How is this possible? Shouldn’t Deuteromycota become extinct? A means of genetic recombination occurs: The Parasexual Cycle. Mycelia characteristic used to define genus Genetic Recombination Parasexual Cycle Essential features of process: Parasexual Cycle: Mechanism discovered by Pontecorvo and Roper Heterokaryon formation (1952) in septate, mycelial fungi by Diploidization which genetic recombination is not Mitotic Crossing-over based on sexual reproduction. Haploidization 5 Parasexual Cycle Parasexual Cycle Summary of Parasexual. Two hyphae of the same species of fungi that are genetically different come into contact. Parasexual Cycle Parasexual Cycle Diploidization: Heterokaryon Formation of Formation: diploids from Plasmogamy of karyogamy of hyphal cells from nuclei. genetically, Heterozygous different diploid nuclei individuals. provide genetic recombination. Parasexual Cycle Parasexual Cycle Mitotic crossing Haploidization:The over: Can be seen as a more gradual reduction vigorous growth in of chromosome mycelium colony: number to the Sectoring. haploid state. Many aneuploids from non- disjunctive mitosis Sectoring also generated. 6 Parasexual Cycle The frequency of genetically, recombined, haploid nuclei formed was very low. Many mycologist feel that this is merely a laboratory phenomenon and does not play an important role in nature. How else can we explain the success of the Deuteromycota in nature? 7.