Taxonomic systematics of dothideomycetes with brown muriform spores

Name: Wanasinghe, Dhanushka Nadeeshan

Organization : Mae Fah Luang University

keyword: Dothideomycetes

LCSH: Fungi -- Genetics

Classification :.LCCS: QK623.A1

LCSH: Phylogeny

LCSH: Ascomycetes

Abstract: Dothideomycetes is a class of bitunicate fungi which historically been called the Loculoascomycetes and is currently considered to be the largest and most phylogenetically diverse group within the Ascomycota. Dothideomycetes are ubiquitous but the majority are plant associated fungi and can exhibit a mix mode of life such as pathogenic, endophytic, saprobic, or epiphytic on a varied range of hosts, in terrestrial as well as aquatic habitats. Species are known to be economically important because of their pharmaceutical and biotechnological potential and agriculturally important as they cause major plant diseases worldwide. To date, there are 32 orders and 120 families within Dothideomycetes and over the last few decades there have been major taxonomic revisions culminating in an improved taxonomic scheme for a more appropriate classification and species nomenclature. Despite a growing taxonomic interest on many plant pathogens on these group, a number of families which harbour a high number of potential novel taxa are poorly understood and warrant further taxonomic investigations. There have only been a few taxonomic studies incorporating DNA based sequence data on a limited number of species and their intergeneric and interfamilial taxonomy is still obscure. Spore septation is a significant morphological character used in the identification and delineation of species in Dothideomycetes. There are only a few taxa that produce aseptate spores and those are mostly characterized by one transverse septum in the spore. The presence of a longitudinal septum in one or more cells of a transversely septate spore is termed "muriform" (multicellular spores appear as bricks in a wall). Muriform septate spores are characteristic of a considerable number of species that may be quite divergent in other characters. The arrangement in which longitudinal as well as transverse septa form and the extension or not of longitudinal septa into end cells are features to be evaluated further. Brown muriform ascospores can be found in either sexual morphs or asexual morphs (both hyphomycetes and coelomycetes) of Dothideomycetes’ species. The Dothideomycetes with brown muriform spores are not a monophyletic group and recent phylogenetic studies reported that muriform spored species are accommodated across a range of orders and families. A large number of genera bearing muriform spores, such as Barnettella, Camarosporellum, Camarosporiopsis, Endobotrya, Nagrajomyces, Orphanocoela, Phragmotrichum and Stigmella are poorly studied members and their classification needs to be revised. In early classifications, species having brown muriform spores were assigned to a few genera without support from DNA sequence data. If it was an asexual morph with brown muriform spores, was referred to as a Camarosporium species, while the sexual morph with brown muriform spores was identified as a Pleosporaceae species. In this study, the taxonomy of these Dothideomycetes are investigated using a dual taxonomic approach (morphological and molecular). Fungal specimens associated with various hosts in terrestrial habitats were collected from Italy, Russia, Thailand, UK and Uzbekistan. They were morphologically examined and their DNA sequence data from rDNA and protein genes (ITS, LSU, SSU, TEF, β-tub and RPB2) were analysed to verify their identity and phylogenetic affinities to better assess their natural placement. A backbone tree reflecting a more natural classification of the Amniculicolaceae is provided herein with a broader taxon sampling of taxa with muriform ascospores. In this family, muriform ascospores are only known in the genus Murispora. Six new species, M. fagicola (on dead branches of Fagus sylvatica), M. galii (on dead twigs of Galium sp.), M. cardui (on dead twigs of Carduus sp.), M. medicaginicola (on dead twigs of Medicago sp), M. cicognanii (on dead branches of Clematis sp.) and M. hawksworthii (on dead twigs of an unknown woody plant) are introduced in this study. Descriptions, illustrations and justifications for these novelties are provided for each taxon. Morphological character differences and analysis of combined LSU, SSU and TEF sequence datasets support the validity of the new species and their placement in Murispora within Amniculicolaceae. The asexual morph of M. hawksworthii was also established from single ascospore isolates. The phylogeny of the Didymosphaeriaceae is also revisited while introducing Laburnicola gen. nov., with four new species, Paramassariosphaeria gen. nov., with a new species and Montagnula saikhuensis sp. nov. with sequence analyses of a combined LSU, SSU and ITS sequence data. Phylogeny supports the transfer of Munkovalsaria appendiculata and M. donacina to the genus Montagnula. The taxonomy of the family Cucurbitariaceae and its allies, especially Fenestellaceae has received little attention despite its broad relevance. To further clarify phylogenetic relationships between the two families, new collections were made and samples examined morphologically. The families were also characterized based on rDNA sequence data analyses. Morphometric observations reveal two new Fenestella species that are different from other known species and are introduced as Fenestella ostryae sp. nov. and F. mackenziei sp. nov. The asexual morph of F. ostryae is also established from single spore cultures and described. Phylogeny inferred from a concatenated dataset of ITS, LSU and SSU rDNA sequence data also reveals a close association of the new taxa to F. fenestrata, but they are distinct. Ribosomal DNA sequence analyses also support our previous assumption that Fenestellaceae should be synonymized with Cucurbitariaceae. To better resolve intergeneric level relationships and improve taxonomic issues within Cucurbitariaceae, a new genus, Neocucurbitaria gen. nov. is introduced with Neocucurbitaria acerina as a new species. A concatenated dataset of LSU, SSU, ITS and tef1 DNA sequence data was analysed to investigate the taxonomic position and phylogenetic relationships of the genus Camarosporium in Pleosporineae (Dothideomycetes). Newly generated sequences from camarosporium-like taxa collected from Europe (Italy) and Russia form a well-supported monophyletic clade within Pleosporineae. A new genus Camarosporiella and a new family Camarosporiellaceae are established to accommodate these taxa. Four new species, Neocamarosporium korfii, N. lamiacearum, N. salicorniicola and N. salsolae, constitute a strongly supported clade with several known taxa for which the new family, Neocamarosporiaceae, is introduced. The genus Staurosphaeria based on S. lycii is resurrected and epitypified, and shown to accommodate the recently introduced genus Hazslinszkyomyces in Coniothyriaceae with significant statistical support. Camarosporium quaternatum, the type species of Camarosporium and Camarosporomyces flavigena cluster together in a monophyletic clade with significant statistical support and sister to the Leptosphaeriaceae. To better resolve interfamilial/intergeneric level relationships and improve taxonomic understanding within Pleosporineae, I validate Camarosporiaceae to accommodate Camarosporium and Camarosporomyces. The latter taxa along with other species are described in this study. In the pursuit of discovery more fungi, this study was extended to investigate the taxonomy and phylogeny of fungal taxa mostly from Rosaceae. This resulted in 73 taxa being accommodated in 13 families which are mainly described from Rosa (Rosaceae). Novel fungal taxa are described, including 14 new genera, 54 new species, four combinations, a sexual record for a species and new host records for four species. Bhatiellae, Cycasicola, Dactylidina, Embarria, Hawksworthiana, Italica, Melanocucurbitaria, Melanodiplodia, Monoseptella, Uzbekistanica, Neopaucispora, Pararoussoella, Marjia and Sporormurispora are introduced as new ascomycete genera. New host records are provided for Muriformistrickeria rubi, Neofusicoccum australe, Pleurophoma pleurospora and Teichospora rubriostiolata. The new combinations are Dactylidina dactylidis (=Allophaeosphaeria dactylidis), Embarria clematidis (=Allophaeosphaeria clematidis), Hawksworthiana alliariae (=Dematiopleospora alliariae) and Italica luzulae (=Dematiopleospora luzulae). This study also provides some insights into the diversity of fungi on Rosa species and especially those on Rosa spines. All data presented based on morphological examination of specimens, coupled with phylogenetic sequence data to better integrate taxa into appropriate taxonomic ranks and infer their evolutionary relationships. A saprobic ascomycete was isolated from Clematis vitalba which was collected in Italy. The species has unique characters and I introduced the taxon as a new genus and species within Lentitheciaceae. Phylogenetic inferences are drawn from LSU, SSU, EF1-α and RPB2 combined sequence analyses. It is distinguished from other genera of this family in having muriform ascospores whose central cells have longitudinal septa and light end cells. The new genus is compared with similar genera in the Lentitheciaceae and a comprehensive description, and micrographs are provided. The cultures were obtained via single ascospore isolation, and the asexual state was also established.

Mae Fah Luang University

Address: CHIANG RAI

Email: library@mfu.ac.th

Name: Kevin David Hyde

Role: Advisor

Created: 2017

Issued: 2561

Modified: 2020-01-21

Issued: 2018-09-11

วิทยานิพนธ์/Thesis

application/pdf

CallNumber: Thesis QK623.A1 W244t 2017

eng

DegreeName: Dotor of Philosophy

Level: Doctoral Degree

Descipline: Biosciences

Grantor: Mae Fah Luang University

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