3 - Copy - PP 315/590J Laboratory 3 Diseases Caused by...

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PP 315/590J   Laboratory 3  Diseases Caused by Fungi - II                   True Fungi  Introduction – Phyllum Ascomycota (Ascomycetes)  Class Hemiascomycetes: asci without an ascocarp  Class Plectomycetes: asci in a closed ascocarp - cleistothecium  Objectives of lab 3 1) To become familiar with vegetative and reproductive structures of the Hemiascomycete and  Plectomycete classes within Ascomycota, and their role in disease development. 2) To observe symptoms and signs of representative diseases caused by pathogens in the Ascomycota  phyllum. Description Ascomycetes, or sac fungi, make up the largest group of fungi, having 50,000 species including yeasts,  licens, and truffles. These fungi are about 75% of all known species. Ascomycetes are also responsible  for many plant diseases such as Dutch elm disease and powdery mildews.  Vegetative hyphae are septate The ascomycete sexual stage is characterized by the ascocarp fruiting body, which may be absent,  closed, disk-shaped, or flask shaped. 
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meiosis take place. Usually, one cell undergoes mitosis and then meiosis to produce eight new haploid  cells, eventually becoming ascospores. When released, these ascospores are very resistant to  environmental stresses, but eventually develop into a new haploid mycelial growth.  The asexual stage is characterized by the presence of conidia (asexual spores) produced terminally on  specialized branched hyphae, called conidiophores. Ascomycetes can be divided into various distinct classes, based primarily upon the ascocarp morphology.  This lab focus on the  Hemiascomycetes  (no ascocarp) and the  Plectomycetes  (closed ascocarp -  cleistothecium). Hemiascomycetes Characteristics 1. Hyphae absent; vegetative thallus is composed of 1 or 2 cells. Drawing of a leaf infected with Taphrina deformans 2. These fungi are unique in that the asci are not produced in an ascocarp, but rather on the surface of  the symptomatic area of the leaf.  Photomicrograph of a leaf infected with Taphrina deformans, an Hemiascomycetes, showing an  hymenium of asci containing ascospores (stained with a red dye).
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This note was uploaded on 03/22/2008 for the course PP 315 taught by Professor Shew during the Spring '08 term at N.C. State.

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3 - Copy - PP 315/590J Laboratory 3 Diseases Caused by...

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