Book : Microorganisms
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Posted by: CHELSEA
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Writer CHELSEA

Ascomycota

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Introduction

The Ascomycota are morphologically diverse. The group includes organisms from unicellular yeasts to complex cup fungi. There are 2000 identified genera and 30,000 species of Ascomycota. The unifying characteristic among these diverse groups is the presence of a reproductive structure known as the ascus, though in some cases it has a reduced role in the life cycle. As a group, they are economically important. Many are tree diseases, such as dutch elm disease and apple blights. The yeasts are used to produce alcoholic beverages and breads. The mold Penacillium is used to produce the anit-biotic penicillin.

Reproduction

 Like all fungi, Ascomycota can undergo both asexual and sexual reproduction.

 Asexual Reproduction

Asexual reproduction among the different groups of fungi are very similar. Like Basidiomycota, Ascomycota reproduce asexually through budding or the formation of conidia.

Sexual Reproduction

Sexual reproduction in the Ascomycota differs from that in the Basidiomycota and Zygomycota because Ascomycota have male and female gametangia in their haploid stage. Plasmogamy, or the transfer of cytoplasm and nuclei, takes place when a part of the ascogonium, the trichogyne, fuses with the antheridium. This produces a binucleate, dikaryotic condition in the ascogonium. This phase is prolonged and a series of dikaryotic cells called an ascogonius hypha is produced. At the tip of this hypha, karyogamy or nuclear fussion takes place, resulting in the formation of a diploid ascus. Within this structure, the diploid nucleus undergoes meiosis, producing four haploid nuclei. These nuclei then undergo mitosis to form eight haploid ascospores. Notice that this is twice as many spores as produced in the basidium.



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