Taxonomía de los hongos ascomicetos del suelo.

Identifier:  TDX:526

Handle: https://hdl.handle.net/20.500.11797/TDX526

Authors:  García Sánchez, Dania

Abstract:
In the last 20 years the compounds obtained from fungi were increased up to 77%, and main of these species of fungi which producing new metabolites were isolated from soil. The first step in the investigation of substances biologically active produced by fungi is collects a profuse diversity of these organisms, their isolation, classification and conservation. <br/>The soil is one of the major reservoir of fungal propagules; but soil ascomycetes may remain in dormant spores phase, so is necessary the disruptions of this stage to obtain pure cultures. Therefore one of our main objectives was to use different activation techniques of dormant ascospores. <br/><br/>In other hand, classification of the ascomycetes has been traditionally based on morphological criteria. However, numerous recent studies have demonstrated that a taxonomic classification based only on morphological characters frequently does not correlate with the phylogenetic relationships inferred from DNA sequences. In this way the mains aims of this study was to evaluate the morphological and genetic relationships between Gelasinospora and Neurospora and also to delimitate the relationships among the genera recognized in the family Coniochaetaceae.<br/><br/>In this work more than 1500 soil samples were analyzed. The methods selected for the activation of the dormant ascospores were those based on the action of acetic acid, ethanol and phenol.<br/><br/> <br/>Through the activation by the action of phenol and by ethanol five new taxa were isolated: <br/><br/>· Apiosordaria globosa, <br/>· Apiosordaria hispanica,<br/>· Neurospora nigeriensis, <br/>· Neurospora uniporata and<br/>· Poroconiochaeta tetraspora.<br/><br/>The application of soil bait technique (indirect isolation method) using a dry wood fragment like bait, allowed to us to described five new taxa; the new genus Coronatomyces and the new species: <br/><br/>· Coronatomyces cubensis, <br/>· Sphaerodes quadrangularis, <br/>· Sphaerodes tenuissima and <br/>· Syspastospora tropicalis. <br/><br/>In addition, three new combinations are proposed for the genus Sphaerodes, and a key to the accepted species of the genus is provided.<br/><br/>Neurospora and Gelasinospora are traditionally distinguished by the ornamentation pattern of their ascospores. However, a detailed examination of the morphology of numerous strains and the phylogenetic study based on partial sequences of the 28S rDNA gene from 27 species of both genera demonstrate:<br/><br/>1. that both genera form a monophyletic group, <br/>2. that the ornamentation pattern of the ascospores wall is not an useful criterion and <br/>3. that the morphology of the episporial-layer of the ascospores is a very informative character. <br/><br/>Consequently the names Neurospora and Gelasinospora were synonymized. Generic diagnosis of Neurospora is amended and 36 new combinations are proposed. A synopsis and a key to the 49 species of Neurospora now recognized in the genus are presented. Furthermore, the new genus Pseudoneurospora is described to accommodate P. amorphoporcata (syn. Gelasinospora amorphoporcata comb. nov.).<br/><br/>In order to clarify the phylogenetic relationships of genera in the Coniochaetaceae we performed a molecular study based on the analyses of the sequences of the partial 18S and 28S rADN genes. The phylogenetic trees obtained do not support the monophyly of the genera Coniochaeta, Coniochaetidium, Ephemeroascus and Poroconiochaeta. A morphological study confirmed that there were not enough differences to distinguish these genera, and the latter three are treated as synonyms of Coniochaeta. The circumscription of the genus Coniochaeta is revised and 9 new combinations are proposed. The genera Coniocessia, Pseudorosellinia, and Novaxylaria are proposed as new within the order Xylariales to accommodate Coniochaeta nodulisporioides, Coniochaeta emodensis, and Coniolaria murandii, respectively. The taxonomic positions of Synaptospora and Wallrothiella within Coniochaetales are also discussed.