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1
Smith, S. E. « Studies on Mycorrhizal fungi ». Title page, contents and abstract only, 1990. http://web4.library.adelaide.edu.au/theses/09SD/09sds659.pdf.
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Kasiamdari, Rina Sri. « Interactions between arbuscular mycorrhizal fungi and other root-infecting fungi ». Title page, contents and abstract only, 2001. http://web4.library.adelaide.edu.au/theses/09PH/09phk1887.pdf.
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Antoniolli, Zaida Inês. « Arbuscular mycorrhizal community in a permanent pasture and development of species-specific primers for detection and quantification of two AM fungi / ». Title page, contents and summary only, 1999. http://web4.library.adelaide.edu.au/theses/09PH/09pha635.pdf.
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Stockinger, Herbert. « DNA barcoding of arbuscular mycorrhizal fungi ». Diss., lmu, 2010. http://nbn-resolving.de/urn:nbn:de:bvb:19-114870.
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Rewcastle, Joanne. « Plant protection using arbuscular mycorrhizal fungi ». Thesis, University of Edinburgh, 2005. http://hdl.handle.net/1842/27261.
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The interaction between several species of arbuscular mycorrhizal fungi, micropropagated strawberry plants and Phytophthora fragariae, the pathogen that causes red stele disease of strawberry plants, was investigated. The optimum temperature for germination of zoospore cysts of P. fragariae in vitro was found to be 15°C, and growth of the emerging germ tube was significantly orientated towards the strawberry root tip. Cyst germination was reduced in the presence of a mycorrhizal strawberry root. Elsanta was more susceptible to P. fragariae than the cultivar Rhapsody. A low level of colonisation of Elsanta with the arbuscular mycorrhizal fungi Glomus mosseae, Glomus intraradices or Glomus fistulosum resulted in a significantly greater amount of total phosphorus in plant shoots compared to non-mycorrhizal plants, although further increases in the percentage of root colonisation by the fungi had no effect on the plants. The presence of these mycorrhizal fungi had no effect on disease due to subsequent inoculation of the plants by P. fragariae. Increasing colonisation of Elsanta by Scutellospora nodosa was correlated with a significant increase in plant size and additional phosphorus uptake. However, these same plants exhibited greater levels of disease due to the following inoculation with P. fragariae. A low level of root colonisation of Elsanta by Acaulospora scrobiculata caused significant increases in plant size and phosphorus uptake up to a threshold level of root colonisation beyond which further increases had no affect on the plant. The results are discussed in relation to the utilisation of specific strains of arbuscular mycorrhizal fungi as inoculants of micropropagated strawberry plants of particular cultivars with the potential to increase plant growth and reduce the level of disease due to soil-borne plant pathogens.
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Monreal, Marcia Amelia. « Molecular identification of ericoid mycorrhizal fungi ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq25119.pdf.
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Stewart, Lynda Irene. « Phosphorus effects on arbuscular mycorrhizal fungi ». Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=102729.
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Two field studies were conducted to assess the potential benefit of arbuscular mycorrhizal (AM) inoculation of elite strawberry plants on plant multiplication, and fruit yield, under typical nursery conditions, in particular soils classified as excessively rich in P. To study plant productivity, five commercially in vitro propagated elite strawberry cultivars ('Chambly', 'Glooscap', 'Joliette', 'Kent', and 'Sweet Charlie') were not inoculated with AM fungi or were inoculated with either a single species (Glomus intraradices), or a mixture of species (G. intraradices, Glomus mosseae, and Glomus etunicatum). AM inoculation was found to impact strawberry plant productivity in a soil with excessive P levels. The AM fungi introduced into the field by inoculated mother plants established a mycelial network in the soil through colonization of the daughter plant roots, however, persistence of colonization was determined to below (<12% in inoculated plant roots). In soils excessively rich in P, individual crop inoculation may be the only option for management of the symbiosis, as the host and non-host rotation crops, planted prior to strawberry production, had no effect on plant productivity or soil mycorrhizal potential.To study the impact of AM inoculation on fruit production, three commercially grown strawberry cultivars (Glooscap, Joliette, and Kent) were not inoculated with AM fungi or were inoculated with either G. intraradices or G. mosseae. AM fungi impacted the fruit yield, with all inoculated cultivars producing more fruit than noninoculated cultivars during the first harvest year. The percentage of root colonization could not be used to explain the differences in total fruit yield during the first harvest year, or the increase in total fruit yield the second harvest year.
We wished to examine the effects of various P treatments on C metabolism within the intraradical mycelia (IRM) of the fungus. Specific primers were developed for the Glomus intraradices glucose-6-phosphate dehydrogenase (G6PDH) gene. Real-time quantitative reverse transcriptase polymerase chain reaction (QRT-PCR) was used to measure the gene expression of the G. intrarardices G6PDH gene in response to external P conditions of colonized transformed carrot roots. The results showed a significant down-regulation of G6PDH in the IRM of G. intraradices when cultures were grown in a high P (350 muM P) medium compared to those grown in the low P (35 muM P) medium. The down-regulation may suggest a reduction in the C flow from the host to the fungus. There was no effect on G6PDH expression following a two-hour incubation with additional P applications (No P, low P and high P).
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Mathieu, Stephanie. « The Genetics of Arbuscular Mycorrhizal Fungi ». Thesis, Université d'Ottawa / University of Ottawa, 2021. http://hdl.handle.net/10393/42770.
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Sexual reproduction is an important process amongst eukaryotic organisms, with one function being to maintain genetic variation. The idea that complex eukaryotic species can persist for millions of years in the absence of sex defies fundamental evolutionary dogma, yet a group of organisms known as ancient asexuals were thought to have evolved clonally under deep evolutionary time. Prominent among these are the arbuscular mycorrhizal fungi (AMF), which are obligate plant symbionts that colonize the root cells of plants and extend their hyphae into the soil assisting the plant in acquiring key nutrients. Unlike most eukaryotes, AMF cells are multinucleate with thousands of nuclei moving through a continuous cytoplasm. Genomic analyses have identified a putative mating-type (MAT) locus within the nuclear genomes of model AMF Rhizophagus irregularis, a region that in other fungi dictates the process of sexual reproduction. Additional findings demonstrated that AMF strains carry one of two nuclear organizations. They can be either homokaryotic (AMF homokaryons), where all nuclei within the cytoplasm are virtually identical, or heterokaryotic (AMF dikaryons), where two MAT-locus variants co-exist within the cytoplasm. Despite a lack of observable traits indicative of sex, this homo/heterokaryotic dichotomy is reminiscent of the nuclear organization of sexual fungi.
My research aims to build on these findings to investigate the actual role of the MAT-locus in driving AMF reproduction. To address this, I build my thesis into three main chapters. The first chapter reviews our current understanding of AMF genetics and what drives genome evolution in these organisms. The second chapter establishes a relatively easy, inexpensive, and reproducible approach to genotype known MAT variants of R. irregularis in natural and experimental conditions. The last chapter uses experimental crossings between strains to assess cytoplasmic compatibility and nuclear exchange. I demonstrate that dikaryotic spore progenies can be formed after co-culturing two distinct AMF homokaryotic strains. Further analyses of various genomic regions also reveal possible recombination in homokaryotic spore progenies from co-cultures. Overall, this research provides new experimental insights into the origin of genetic diversity in AMF. These findings open avenues to produce genetically new AMF strains in the lab using conventional crossing procedures and provide a glimpse of the mechanisms that generate AMF genetic diversity in the field.
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Ike-Izundu, Nnenna Esther. « Interaction between arbuscular mycorrhizal fungi and soil microbial populations in the rhizosphere ». Thesis, Rhodes University, 2008. http://hdl.handle.net/10962/d1004021.
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This study examined the rehabilitation potential of AM fungi with organic and inorganic fertilisers under pot and field trial conditions as well as their interaction with rhizospheric organisms and specific functional groups. In addition, the study highlighted the effects of land-use management on AM fungal populations in soil and the mycorrhizal status of some selected plants from one of the study sites. The study focussed on two sites that differ in operational activities and these included a mined area that was to be rehabilitated and a commercial farming site. A pot trial was conducted using an overburdened soil resulting from kaolin clay mining. Pots were seeded with Cynodon dactylon and treated with either Organic Tea or NPK (3:1:5) fertiliser, with or without AM fungal inoculum. The compatibility of these fertilisers with AM fungi was assessed by plant growth and percentage root colonisation. Maximum shoot height and plant biomass were observed at the 28th week with NPK (3:1:5) fertiliser supporting mycorrhizal colonisation by 80%. The result indicated the potential of AM fungi to be used in rehabilitation with minimal phosphate fertiliser. Similarly, a field trial was set-up using 17 x 17 m[superscript 2] plots in the mining site that were treated with the same organic and inorganic fertilisers as well as with AM fungal inoculum in different combinations. The interaction between AM fungi and soil microbial population was determined using culture dependent and culture independent techniques. The culture dependent technique involved the use of soil dilution and plating on general purpose and selective media. The result showed that there was no change in the total culturable bacterial number in the untreated and AM fungal treated plots, while a change in species composition was observed in the functional groups. Different functional groups identified included nitrogen fixing bacteria, pseudomonads, actinomycetes, phosphate solubilisers and the fungal counterparts. Gram-positive bacteria were observed as the predominant phenotypic type, while nitrogen fixers and actinomycetes were the predominant functional groups. Species identified from each functional group were Pseudomonas fulva, Bacillus megaterium, Streptomyces and actinomycetales bacteria. Meanwhile, fungi such as Ampelomyces, Fusarium, Penicillium, Aspergillus, Cephalosporium and Exserohilium were identified morphologically and molecularly. Furthermore, the mining site had a significantly higher bacterial number than the farming site thereby indicating the effects of land-use management on culturable bacterial numbers. The culture independent technique was carried out by cloning of the bacterial 16S rDNA and sequencing. Identified clones were Bradyrhizobium, Propionibacterium and Sporichthya. A cladogram constructed with the nucleotides sequences of identified functional species, clones and closely related nucleotide sequences from the Genbank indicated that nucleotide sequences differed in terms of the method used. The activity and establishment of the introduced AM fungal population was determined by spore enumeration, infectivity assay, percentage root colonisation and assessment of glomalin concentrations. The results indicated that the two land use types affected AM fungal populations. However, the establishment of AM fungi in the farming site was more successful than in the mining site as indicated by the higher infectivity pontential. Selected host plants, which were collected around the mine area, were observed to be mainly colonised by AM fungi and these were identified as Pentzia incana, Elytropappus rhinocerotis, Euphorbia meloformis, Selago corymbosa, Albuca canadensis and Helichrysum rosum. These plant species were able to thrive under harsh environmental conditions, thereby indicating their potential use as rehabilitation host plants. Generally, the findings of this study has provided an insight into the interaction between arbuscular mycorrhizal fungi and other soil microorganisms in two fields with differing land use management practices.
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Davidson, Kent. « Genetic studies of vesicular-arbuscular mycorrhizal fungi ». Thesis, University of Bristol, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.279742.
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Kang, Hyun-Joo. « The basic genetics of arbuscular mycorrhizal fungi ». [Bloomington, Ind.] : Indiana University, 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3358927.
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Thesis (Ph.D.)--Indiana University, Dept. of Biology, 2009.Title from PDF t.p. (viewed on Feb. 8, 2010). Source: Dissertation Abstracts International, Volume: 70-05, Section: B, page: 2653. Adviser: James D. Bever.
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Haller, Anjanette H. A. « The presence and role of arbuscular mycorrhizal fungi in coastal sand dune systems ». Thesis, Rhodes University, 2000. http://hdl.handle.net/10962/d1003765.
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Arbuscular mycorrhizas (AM) are mutually beneficial symbiotic associations between the roots of plants and certain Zygomycetous fungi. The role of AM fungi in coastal sand dunes has been explored in many parts of the world, though little work has been conducted in South African dune systems. This study aimed to investigate the presence and extent of mycorrhizal colonisation of a coastal sand dune in South Africa. The roots of five plant species (Scaevola plumieri, Arctotheca populifolia, Ipomoea pes-caprae, Ehrharta villosa and Chrysanthemoides monilifera) were sampled along a foredune profile at Old Woman's River in the Eastern Cape. These roots were assessed for the percentage mycorrhizal colonisation they supported. Spores extracted from the rhizosphere sand of each plant species were counted and identified to genus level. Results were related to seasonality and the position of the plants along the profile. All plant species were found to be mycorrhizal. Percentage colonisation ranged from 0-92%, depending on plant species and season. Mycorrhizal colonisation was generally highest in the winter months, and especially so in I pes-caprae and E. villosa. The extent of various mycorrhizal structures in root tissue varied between plant species. Spore numbers ranged from 0-48 spores 100g-1 sand with highest numbers occurring in winter. S. plumieri and A. populifolia were associated with greatest spore abundance. Four fungal genera (Glomus, Acaulospora, Scutellospora and Gigaspora) were identified. Distribution of these genera showed seasonal variations between plant species. A bioassay, using Sorghum, was conducted to test the inoculum potentials of sand from the Scaevola hummock and the IpomoealEhrharta dune. Highest percentage colonisation occurred in plants grown in the Scaevola sand, which also had the lowest root and shoot measurements. The bioassay confirmed that AM propagules are present and viable, even in the mobile sand of the foredune. This study showed that mycorrhizal colonisation and spore numbers varied seasonally, but that the extent of this was dependent on plant species. The position of plants along the foredune profile tended to be less important than plant species. It is thought that the growth cycle and rooting system of each plant species determines seasonal cycles and abundance of AM fungi. Variation within fungal populations probably also impacts on this. Knowledge of the presence and distribution of AM fungi in this system paves the way for more detailed studies which need to examine the role of these endophytes in South African sand dunes.
13
Leifheit, Eva [Verfasser]. « Soil sustainability and arbuscular mycorrhizal fungi / Eva Leifheit ». Berlin : Freie Universität Berlin, 2014. http://d-nb.info/1054636974/34.
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Toljander, Jonas. « Interactions between soil bacteria and arbuscular mycorrhizal fungi / ». Uppsala : Department of Forest Mycology and Pathology, Swedish University of Agricultural Sciences, 2006. http://epsilon.slu.se/200639.pdf.
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Shakeel, Muhammad. « Organization of genetic variation in arbuscular mycorrhizal fungi ». Thesis, University of York, 2011. http://etheses.whiterose.ac.uk/2776/.
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The arbuscular mycorrhizal (AM) symbiosis is a mutualistic association between plant roots and fungi that belong to the Phylum Glomeromycota. In this symbiosis, the plant provides the fungus with carbohydrate and gets phosphorus in return. Study of these fungi is fettered because of their obligatory symbiotic nature and lack of basic knowledge of their genetics. These fungi produce multinucleate spores and it is not clear whether nuclei within a spore are genetically similar or dissimilar. In this thesis, we discuss techniques that address some fundamental questions about the organization of genetic material in AM fungi. Sequence variants from coding and non-coding genes have been reported from single Glomus isolates but it is not known whether these arise from different nuclei or constitute multiple gene copies within each nucleus. Several alleles (variants) of Binding protein (Bip) gene were observed after cloning this gene from each of the four isolates of G. irregulare studied (Chapter-2). A Sanger sequencing trace of a sample with a mixture of allelic sequences shows two peaks at single nucleotide polymorphism (SNP) positions. A new approach of measuring peak heights was developed that can monitor changes in allelic frequency of selected genes without involving cloning and RFLP-screening, which are both expensive and time consuming. Using this technique addressed two important questions, first that spores are genetically different in a culture Petri plate within and among G. irregulare isolates (Chapter-3) and second, plant hosts have a significant effect in changing the allele frequency of selected fungal genes (Chapter-4). Single nuclei were isolated by Laser Capture Microdissection from spores and hyphae after optimising the experimental conditions to minimise autofluorescence. Sequences of two marker genes BiP and internal transcribed spacer-2 region (ITS2), were amplified from the whole genome amplified DNA of the catapulted single nuclei using multiplex PCR (Chapter-5). This study reports for first time the isolation of single nuclei from spores and hyphae using LCM. Isolation of single nuclei can provide useful information about the genome size, organization of genetic variation and genetic processes that are poorly understood in AM fungi.
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Whiffen, Leonie. « Arbuscular mycorrhizal fungi and carbon sequestration in soil ». Thesis, The University of Sydney, 2007. https://hdl.handle.net/2123/28114.
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Dickson, Sandra. « Phosphate transfer efficiency of two arbuscular mycorrhizal fungi ». Title page, contents and abstract only, 1999. http://web4.library.adelaide.edu.au/theses/09PH/09phd5541.pdf.
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Bibliography: leaves 169-193. This study investigated whether both S. Calospora and Glomus sp. "City Beach" WUM 16 both increase the rate of transfer of phosphate (P) to the plant Allium porrum, and whether the addition of P to the soil has any effect on the uptake rates. The main experiment compared the fungi under two P levels in soils. It was found that in soil with no added P, S. calospora depressed plant growth in the early stages, but was increased in later harvests. G. sp. "City Beach" increased plant growth throughout. In soil with added P, both sets of plants produced growth depressions at early stages. The effect on growth due to mycorrhizal symbiosis was greater in plants grown in soil with no phosphate added. There were no significant differences between the two fungi with reflexes of P across the interfaces. There were however temporal differences. The isolate of S. calospora did promote a positive plant growth response in A. porrum and transfer P to the plant. Mycorrhizal arbuscules were examined and visualised using Laser Scanning Confocal Microscope and 3D reconstructions performed. This allowed the surface area and volume of the arbuscules to be quantified in order to investigate differences between the fungi.
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Roberts, Karl J. Anderson Roger C. « An examination of the interactions between garlic mustard (Alliaria petiolata (Beib.) Cavara & ; Grande) and vesicular-arbuscular mycorrhizal (VAM) fungi ». Normal, Ill. Illinois State University, 1997. http://wwwlib.umi.com/cr/ilstu/fullcit?p9807487.
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Thesis (Ph. D.)--Illinois State University, 1997.Title from title page screen, viewed June 7, 2006. Dissertation Committee: Roger C. Anderson (chair), Anthony E. Liberta, Mathew J. Nadakavukaren, Derek A. McCracken, R. Michael Miller. Includes bibliographical references (leaves 68-77) and abstract. Also available in print.
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Skinner, Amy. « Investigating the effect of Glomus etunicatum colonization on structure and phloem transport in roots of Eragrostis curvula (Umgeni) ». Thesis, Rhodes University, 2007. http://hdl.handle.net/10962/d1003796.
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The symbiotic unit of an arbuscular mycorrhizal fungus and its host is able toachieve and maintain far higher inflow of nutrients than non-mycorrhizal roots. The colonization strategy of the mycobiont within the plant is intrinsic to the symbiosis with respect to both structural adaptations and nutrient exchange. An investigation into the effect of Glomus etunicatum colonization on the structure and phloem transport in Eragrostis curvula (Umgeni) allowed for greater insight into the dynamic of the symbiosis. The combined use of stains (such as Trypan Blue, Chlorazol Black, Safranin and Fast Green), and techniques, (such as freeze-microtome transverse sectioning and permanent slide preparations) contributed to a successful general observation of an intermediate colonization strategy using light microscopy methods. However, clarity into structural detail of mycorrhizal forms required electron microscopy studies. The SEM method used with freeze fracture was a relatively quick and simple method allowing for the observation of surface and internal features. The TEM method allowed for highresolution images providing insight into the variations in the apoplasmic compartmental form, and how this may relate to the function of the symbiosis with regard to fungal coils or arbuscules. The apoplasmic nature of mycorrhizas was substantiated and no symplasmic connections were found between symbionts. Fluorescence studies demonstrated that 5,6-carboxyfluorescein was transported through the phloem into the roots of E. curvula, but remained predominantly in the root phloem. Unloading only occurred in optimal nutrient exchange areas of meristimatic lateral or apical growth regions. It was not possible, using fluorescence techniques and related equipment available, to conclusively establish if there were symplasmic connections between the mycobiont and its host or if bidirectional transfer of nutrients occurred at the same interface.
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Eskdale, Jocelyn Wendy. « Management of arbuscular mycorrhizal fungi (AMF) in intensive vegetable production / ». St. Lucia, Qld, 2002. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16105.pdf.
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Haigh, Joanna Marie. « Dual mycorrhizal symbiosis in Salix : the role of arbuscular mycorrhizal fungi in an ectomycorrhizal genus ». Thesis, University of York, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341482.
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Krüger, Manuela. « Molecular phylogeny, taxonomy and evolution of arbuscular mycorrhizal fungi ». Diss., lmu, 2011. http://nbn-resolving.de/urn:nbn:de:bvb:19-140769.
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Currie, Amanda Felicity. « Interactions between root-feeding insects and arbuscular mycorrhizal fungi ». Thesis, Royal Holloway, University of London, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.555989.
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Piotrowski, Jeffrey Scott. « SUCCESSION OF ARBUSCULAR MYCORRHIZAL FUNGI : CAUSES, CONSEQUENCES, AND CONSIDERATIONS ». The University of Montana, 2008. http://etd.lib.umt.edu/theses/available/etd-05272008-134138/.
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Arbuscular mycorrhizal fungi (AMF) are soil fungi associations with the majority of terrestrial plants. These fungi may affect a wide range of ecosystem processes from primary productivity to soil stabilization. Understanding the patterns and controls of AMF abundance during succession soil will be critical to predicting and managing ecosystem development. The work presented in chapter 2 is the first to describe changes in the abundance of mycorrhizal types during development of an unregulated floodplain. These findings are important to floodplain regulation and management strategies as they suggest that flow regulation that limits early site formation will limit the ecosystem contributions of AMF on dammed rivers. Chapter 3 builds on the findings from chapter 2 to determine the mechanisms of how litter may affect the abundance of a native AMF community. We test the hypothesis that litter from cottonwoods (Populus sp.) is inhibitory to AMF colonization. Our works shows that even small amounts of litter and realistic concentrations of litter leachates can strongly inhibit AMF colonization of two plant species, and that this inhibition is not solely a result of changes in the soil nutrient status. Chapter 3 also demonstrates that common soluble phenolics found in cottonwood litter are inhibitory to AMF at ecologically realistic concentrations, whereas other root colonizing fungi are unaffected. These findings offer another explanatory mechanism for the shift we and others have observed between AMF and ECMF during succession. Chapter 4 addresses the potential consequences of a changing AMF community with respect to the key AMF mediated process of soil stabilization. This work is the first to document a significant interaction between co-occurring species of plants and AMF in soil aggregate formation. Chapter 5 synthesizes our findings with others to understand the potential consequences and management options to control AMF succession and species composition in agroecosystems. Chapter 6 is a product of my work with the ECOS program, and is a lesson on the importance of soil organic matter that is designed for the youngest of students. The significance of this body of work is discussed in chapter 7.
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Piotrowski, Jeffrey Scott. « Succession of arbuscular mycorrhizal fungi causes, consequences, and considerations / ». CONNECT TO THIS TITLE ONLINE, 2007. http://etd.lib.umt.edu/theses/available/etd-05272008-134138/.
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Bower, Erica. « Interactions between arbuscular-mycorrhizal fungi and foliar-feeding insects ». Thesis, Royal Holloway, University of London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266086.
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Craven-Griffiths, Amanda. « Ecology of arbuscular mycorrhizal fungi from a desertified ecosystem ». Thesis, University of Kent, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.300939.
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Amijee, F. « Colonization of root systems by vesicular-arbuscular mycorrhizal fungi ». Thesis, University of Leeds, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374170.
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Ridsdale, Carmen Jane. « Interactions of arbuscular mycorrhizal fungi and spore-associated bacteria ». Thesis, Rhodes University, 2013. http://hdl.handle.net/10962/d1018269.
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Arbuscular mycorrhizal (AM) fungi are naturally occurring in roots of terrestrial plants. AM fungi are capable of benefiting the host plant through various mechanisms such as enhanced nutrient supply, alleviation of environmental stress and inhibition of plant fungal pathogens. AM fungal spore-associated bacteria have been previously isolated and shown to have plant growthpromoting (PGP) abilities by several authors. Some bacterial isolates are able to promote AM fungal colonisation of host plants and are known to be mycorrhizal helper bacteria (MHB). This study focused on the isolation of AM fungal spore-associated bacteria, characterization of the isolates according to plant growth promoting abilities and evaluation of their potential to enhance plant growth and mycorrhizal colonisation. AM fungi were extracted from soils sampled from natural indigenous forest sources, raspberry (Rubus idaeus cv. Heritage) and strawberry (Fragaria ananassa) farms in South Africa and from a raspberry (Rubus idaeus cv. Autumn Bliss) plantation in Argentina. A total of 52 sporeassociated bacteria were isolated from the external and internal surfaces of AM fungal spore morphotypes from the two countries. The bacterial isolates were evaluated for their PGP abilities such as phosphate solubilisation, indole-3-acetic acid production, ammonia production and inhibition of the fungal pathogens Fusarium oxysporum and Phythophthora nicotianae through mechanisms such as siderophore and/ or hydrolytic enzyme production. A total of 23 bacterial isolates from both South Africa and Argentina showing the most potential to be PGP, were identified molecularly as belonging to the genera Acinetobacter, Alcaligenes, Bacillus, Microbacterium, Micrococcus, Serratia and Staphylococcus. The ability of ten selected bacterial isolates showing multiple PGP capacity were evaluated for their plant growth promotion and mycorrhizal colonisation enhancement ability on raspberry (Rubus idaeus cv. Meeker). Significant differences in increased shoot and root dry weights were shown by the treatments compared to the uninoculated control. The highest increase in shoot and root dry weights were shown by South African (Bacillus mycoides) and Argentinean (Alcaligenes faecalis) isolates. AM fungal colonisation was significantly enhanced by the South African (Bacillus mycoides) and Argentinean (Micrococcus luteus) isolates compared to the AM fungal singly inoculated control.
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Giannakis, Nikos. « Interactions between mycophagous nematodes, mycorrhizal and other soil fungi ». Thesis, University of Leeds, 1990. http://etheses.whiterose.ac.uk/778/.
Texte intégralRésumé :
The hypothesis that mycophagous nematodes feed on the mycelia of VAM fungi and consequently reduce the spread of vesicular-arbuscular mycorrhizal (VAM) infection in plant roots and the growth response of plants to this infection was investigated in experiments carried out under controlled environmental conditions. Preliminary experiments indicated that nematodes might be able to reduce VAM infection by Glomus clarum if they were added to soil at the same time as the fungal inoculum. However, nematodes did not affect the growth response of red clover to VAM infection even though there was an indication that nematodes may directly affect plant growth possibly by causing damage to root hairs which could facilitate the entry of pathogens. There seemed to be little effect of mycorrhizal status on the numbers of nematodes which could be recovered from the growth medium. The two standard methods used to extract nematodes in these preliminary experiments were found to give low and variable recoveries. A method which gave greater and less variable recoveries was developed and the conditions for its successful use were defined. The four species of nematodes used in this study differed in their ability to reduce the growth of a range of fungi and in their ability to increase in number as a result of feeding on these fungi. Both experimental data and a mathematical model, which was developed subsequently, showed that the suitability of a fungus as a source of nutrition could be measured by the increase in numbers of nematodes and the reduction in weight of mycelium as a result of grazing. The model therefore provided a rationale for ranking different fungi in terms of their suitability as hosts for a given species of nematode. Of the four species of nematodes, A phelenchus avenae was the most damaging to the growth of a range of fungi. However, when added at the same time as, or later than, the VAM inoculum, A. avenae had no effect on the spread of VAM infection or on the response of plants to VAM infection. The numbers of A. avenae recovered were similar in non-mycorrhizal and mycorrhizal treatments. A mathematical model was developed which simulated the spread of VAM infection and the change in numbers of nematodes with time. Close agreement between predictions of the model and experimental results was only achieved if it was assumed that the nematodes were not capable of feeding on the VAM fungus. Aphelencholdes composticola multiplied most when cultured in agar plates but grew poorly when cultured on its own in soil. When organic material (bran) colonized either by Agaricus bisporus (the nematodes preferred host) or by volunteer fungi was introduced into soil, the numbers of A. composticola increased by up to one hundred times. Neither VAM infection by G. clarum nor the mycorrhizal responses of the plant were affected by these high numbers of A. composticola, by the introduction of bran alone or by bran colonized by A. bisporus. In soil without added bran or saprotrophic fungi numbers of A. composticola were not affected by the presence of G. clarum, indicating that the available food sources in unamended soil were sparse. Mycorrhizal plants appeared to benefit more than non-mycorrhizal plants from the mineralization of phosphorus by the saprotrophic fungi. Factors which may determine the suitability of some fungi as food sources for mycophagous nematodes are discussed. The possibility that VAM fungi are immune to grazing by these nematodes is considered. Ways in which mycophagous nematodes may influence the growth of plants are also discussed.
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Asif, Mohammad. « Comparative study of production, infectivity, and effectiveness of arbuscular mycorrhizal fungi produced by soil-based and soil-less techniques / ». [Campbelltown, N.S.W. : The Author], 1997. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20030716.094919/index.html.
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Klugh, Katrina R. « Aluminum resistance of mycorrhizal plants ». Morgantown, W. Va. : [West Virginia University Libraries], 2006. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4793.
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Boulet, Frederic. « Mycorrhizal symbiosis as a strategy for survival in ultramafic soils ». University of Western Australia. Soil Science and Plant Nutrition Discipline Group, 2003. http://theses.library.uwa.edu.au/adt-WU2004.0051.
Texte intégralRésumé :
Ultramafic soils enriched in nickel, such as found in Australia and New Caledonia, are associated with unique, diverse and poorly known vegetation communities. Re-establishment of these highly specific ecosystems is still a challenge for Ni mining companies. Ultramafic vegetation communities are the outcome of a long evolution process resulting in their adaptation to the extreme soil conditions found on ultramafic outcrops. Mycorrhizal fungi, a very common plant symbiont, are generally thought to be beneficial to plants in other ecosystems, providing plants with phosphorus and even promoting metal tolerance in plants in some cases. We examined the hypothesis that mycorrhizal fungi may contribute to the survival of plants in ultramafic soil conditions. Bandalup Hill, an ultramafic outcrop enriched in Ni (South West of Western Australia) was selected to assess the contribution of mycorrhizal fungi to ultramafic plants. Soil constraints, in particular the degree of Ni toxicity, were assessed at two sites with ultramafic soils within the outcrop. Total metal, nutrient, DTPA extractable Ni and available P were measured in soil while Ni, Ca and Mg were tested in the soil solution. In addition, nutrients and metals were analyzed in shoots of some plant species occurring at each site: Eucalyptus flocktoniae, Melaleuca pomphostoma, Melaleuca coronicarpa and Hakea verucosa. Topsoils in Bandalup Hill and plant shoots had high levels of Ni, and very low levels of P, K and N. Variation in DTPA extractable Ni between sites reflected the variation in shoot Ni level of E. flocktoniae and M. pomphostoma. Variations in soil solution Ni levels reflected variations in shoot Ni levels of M. coronicarpa and H. verucosa between sites. The germination requirements of the plant species used to assess the soil constraints was assessed. Species selected included Eucalyptus flocktoniae, Melaleuca coronicarpa, and Hakea verucosa. Seeds of E. flocktoniae and M. coronicarpa had a higher germination rate if pre-treated with smoke water, while no pre-treatment was required to germinate H. verucosa seeds. The unusual germination requirement of E. flocktoniae and M. coronicarpa involve complex chemical signals that may be present in the soil when the conditions are more favorable for plant establishment. Such unusual germination requirement may represent an adaptation to the hostile conditions of the ultramafic soils of Bandalup Hill. The mycorrhizal association and root characteristics of the selected plant species was also assessed after 8 weeks of growth in undisturbed ultramafic topsoil cores from Bandalup Hill. Roots of these species (including H. verucosa from a previously designated non-mycorrhizal family, Proteaceae) were associated with mycorrhizal fungi. Roots of E. flocktoniae and M. coronicarpa were colonized by both arbuscular mycorrhizal fungi (AMF) and ectomycorrhizal fungi (ECM), while roots of H. verucosa only contained some AM fungal structures. All species had high shoot to root ratios and their root characteristics reflected their association with mycorrhizal fungi. Based on the previous observations, uninoculated and inoculated E. flocktoniae seedlings were grown for 10 to 16 weeks in sand amended with Ni at 0, 0.2, 1 and 2.3 mg/kg. Mycorrhizal inoculum consisted of spores of Pisolithus sp. (ECM) or a mix of AMF spores and colonized root fragments, both originating from Bandalup Hill. Another inoculum consisted in Pisolithus sp. spores from a site with ultramafic soils in New Caledonia. Inoculation with AM and ECM fungi from Bandalup Hill was beneficial to E. flocktoniae. Benefits consisted mainly of a reduction of Ni shoot translocation at the highest Ni soil level. At 1 mg/kg soil Ni, E. flocktoniae exhibited a certain degree of tolerance to Ni. A substantial increase in growth and nutrient uptake with Pisolithus sp. from Western Australia was also observed. The contribution of AM fungi from Bandalup Hill to E. flocktoniae, M. coronicarpa, H. verucosa, and Trifolium subterraneum (clover) was then examined in ultramafic soil from Bandalup Hill.Steaming of ultramafic soil increased the availability and plant uptake of P. Consequently, uninoculated seedlings grew better, and inoculation with AM fungi decreased the growth of native plant species but did not affect their shoot Ni concentration. The presence of AM fungi increased the concentration of P in shoots of native plants species. Inoculation had no effect on the growth and nutrient content of subterranean clover. As mining activities have the potential to reduce the infectivity of AM fungi in topsoils, the effect of disturbance and storage practices on the AM infectivity of ultramafic topsoils collected in summer or winter from Bandalup Hill was investigated. Disturbance consisted in passing topsoil through a 2mm seive and cutting roots into 1cm fragments. Disturbed topsoil was then stored at room temperature in pots that were either sealed from the atmosphere or left open, and pots were maintained at field capacity. E. flocktoniae seedlings were planted in undisturbed and disturbed topsoil just after topsoil collect and then after 3, 6 and 9 months of topsoil storage. AM fungi present in the topsoil collected in summer was less susceptible to initial disturbance than AM fungi present in topsoil collected during winter. Also, storage of topsoil in sealed pots watered to field capacity was more detrimental to its infectivity than storage of topsoil in dry conditions. Mycorrhizal fungi can contribute to the survival of some native plant species in the ultramafic soils of Bandalup Hill and they may represent another strategy to improve the success of Ni mine revegetation. However, such contribution may not be the unique avenue for native plants to survive in ultramafic soils of Bandalup Hill.
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Lansing, Jennifer Lyn. « Comparing arbuscular and ectomycorrhizal fungal communities in seven North American forests and their response to nitrogen fertilization / ». For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2003. http://uclibs.org/PID/11984.
Texte intégralRésumé :
Thesis (Ph. D.)--University of California, Davis and San Diego State University, 2003.Includes bibliographical references (leaves 142-144). Also available via the World Wide Web. (Restricted to UC campuses).
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Nichols, Kristine Ann. « Characterization of glomalin, a glycoprotein produced by arbuscular mycorrhizal fungi ». College Park, Md. : University of Maryland, 2003. http://hdl.handle.net/1903/86.
Texte intégralRésumé :
Thesis (Ph. D.) -- University of Maryland, College Park, 2003.Thesis research directed by: Natural Resource Sciences. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Egan, Cameron Patrick. « Community structure of arbuscular mycorrhizal fungi along an altitudinal gradient ». Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/62555.
Texte intégralRésumé :
A fundamental goal in ecology is to examine diversity patterns of naturally occurring communities and link these patterns to underlying structuring processes. Despite the importance of arbuscular mycorrhizal (AM) fungi in natural ecosystems, the majority of studies to date have focused on community structure in a restricted set of systems (mainly temperate grasslands, old fields, and agricultural ecosystems). This is highly limiting because it is well known that the functioning of mycorrhizal symbioses can be influenced by biotic and abiotic environmental factors, and thus our understanding of how mycorrhizas are structured and function across a wide variety of habitats is limited. Furthermore, with recent advances in next generation sequencing (NGS) technology, it is timely to begin a more thorough investigation of AM fungi across a wide variety of habitat types. The objectives of this thesis were to determine whether (1) modern NGS techniques accurately depict AM fungal communities using mock communities, (2) environmental filtering along an elevation gradient influences the phylogenetic structure of AM fungal communities in the soil, (3) habitat filtering or plant host selection is a stronger determinant of AM fungal communities along an elevation gradient, and (4) aerial dispersal of AM fungal spores varies among a wider variety of North American habitat types.
Examination of sequences generated from mock AM fungal communities revealed that taxonomic assignment of sequences within AM fungal families closely matched expected abundances, but accuracy decreased at lower taxonomic levels. However, analyses revealed that semi-quantitative metrics of sequence data still accurately inform on ecological patterns. Along elevation gradients AM fungal communities were observed to be more phylogenetically related than is expected by chance within all elevations sampled. In addition, AM fungal communities sampled from three co-occurring plant hosts revealed that communities are more strongly influenced by elevation sampled than host identity. Aerial dispersal also appears to be influenced by habitat type, where the highest proportion AM fungal spores in the air relative to in the soil was highest in more arid systems. Collectively, these studies indicate that local environmental conditions strongly influence assembly processes of AM fungal communities.Irving K. Barber School of Arts and Sciences (Okanagan)
Biology, Department of (Okanagan)
Graduate
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Raleigh, Ruth Elizabeth, et Ruth e. raleigh@dse vic gov au. « Propagation and biology of arachnorchis (orchidacae) and their mycorrhizal fungi ». RMIT University. Department of Biotechology and Environmental Biology, 2006. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20091007.144548.
Texte intégralRésumé :
Terrestrial orchids make up one of the most threatened groups of plants in Australia and the genus Arachnorchis is listed as the fourth most threatened. The process of propagation and re-introduction of terrestrial orchid plants to the wild has proven difficult, and so far, nearly impossible for some species. This may be partly because terrestrial orchids form complex relationships with mycorrhizal fungi and in genera like Arachnorchis the dependency on the fungus appears acute. Arachnorchis has long been considered by amateur growers of terrestrial orchids as one of the most difficult groups to propagate and maintain in cultivation. This lack of knowledge on how to grow Arachnorchis species hinders attempts made by conservation authorities to supplement threatened wild populations in order to achieve a more sustainable future for those species. Natural pollination was absent, but artificial pollination achieved 100% capsule production. Individuals were self-fertile, although seed viability was greater for cross-pollinated samples. This study attempted to track the fate of as many Arachnorchis species as possible from germination through to deflasking and re-emergence, and so destructive and potentially destructive measurements at earlier stages were avoided. This thesis examines germination and subsequent growth of up to eight species of Arachnorchis, but concentrated on A. phaeoclavia, A. tentaculata, A. fulva, A. robinsonii and A. venusta. Two of these are common species: A. pha eoclavia and A. tentaculata, and three carried a threatened classification of "rare" or " endangered": A. fulva, A. robinsonii and A. venusta. This study monitored the fate of individuals of the endangered A. fulva in the field and showed that large reproductive plants re-emerged and flowered each year, whereas smaller individuals might be absent in one or more years and were less likely to flower. Germination of all species concentrated on using symbiotic culture (using mycorrhizal fungi), since germination is known to be more rapid, resulting in healthier, more robust seedlings than when plants are grown asymbiotically. Tests using A. fulva and A. venusta, two threatened species, showed similar viability to A. tentaculata and A. phaeoclavia, more common species. Germination was maximised by examining the viability of seeds before and after treatment with surface-sterilising solutions required for aseptic culture. The highest levels of germination, with limited contamination, were achieved using 0.5% available chlorine for 3 minutes. The most effective fungal isolates (>65% germination) were obtained from common species like A. phaeoclavia and A. tentaculata, but there was no correlation between germination and time of year or life stage of the orchid. Collar collection was shown to be non-fatal to robust orchid plants, with large reproductive individuals (at the time of collar collection) re-emerging in the next year and producing a flower bud. Collar collection from small, weedy individuals could be fatal to the plant and isolation of an effective fungus was unlikely. Cross-inoculating seeds with fungi isolated from a different orchid species was not recommended, since the symbiosis failed in all experiments, as late as Stage 4 protocorm development. A range of substrates was used to produce strong seedlings capable of surviving the transfer to nursery conditions with minimal loss. More than 81% of seedlings survived deflasking from non-agar substrates, while the best result from agar was 55%. Some substrates reduced the time involved from seed to plants in the field to as little as 4 months, but aftercare became critical. Sucrose promoted tuberisation, but led to tuber deaths during dormancy. Potting mixes were tested in the nursery and a free-draining loam mix based on a mix used by the Australasian Native Orchid Society was the best medium for deflasking of seedlings. Watering during dormancy should be avoided. The choice of propagule for re-introduction was examined and the best survival to re-emergence was obtained by planting out actively growing seedlings in autumn. Identification of cultures using classical morphology grouped cultures as belonging to the form-genera Epulorhiza and Moniliopsis and suggested that most cultures contained more than one fungus. Identification of the most useful fungal cultures was attempted using molecular techniques such as sequencing the ITS region and mitochondrial DNA. One effective culture, CALAPHAER18 SHTX (cultured from a single monilioid cell) was identified as Serendipita vermifera (Oberwinkler) Roberts. All other cultures tested were mixtures of fungi. The use of specific primers designed to amplify a sequence present in the identified isolate (CALAPHAER18 SHTX) showed that nine mixed cultures also contained a fungus most closely related to Serendipita vermifera. Specific primers also showed that Rhizoctonia solani was not present in any of the 10 isolates from Arachnorchis plants. The molecular work showed that, although the sequenced endophytes from Arachnorchis were all most closely related to Serendipita vermifera, three dist inct groups of fungi were present and these associated with separate species of Arachnorchis. Future work with Arachnorchis species will require the isolation of single fungus cultures and further examination of the development of the orchid plant. In particular, the process of tuberisation and growth in vitro on various non-agar substrates should be investigated further.
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Lehmann, Anika [Verfasser]. « Interactions of crop plants and arbuscular mycorrhizal fungi / Anika Lehmann ». Berlin : Freie Universität Berlin, 2014. http://d-nb.info/1048047393/34.
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Siasou, Eleni. « Interactions among a soil-borne pathogen, mycorrhizal fungi and rhizobacteria ». Thesis, University of Aberdeen, 2010. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=159205.
Texte intégralRésumé :
Wheat crops are known to be devastated by infections of soil-borne pathogens, especially the fungus Gaeumannomyces graminis var. tritici (Ggt) that causes ‘take-all’. Plant growth promoting rhizobacteria (PGPR) such as Pseudomonas fluorescens have received much attention as biocontrol agents against Ggt, mainly due to their ability to produce antibiotics. The polycetide secondary antimicrobial metabolite 2,4-diacetylphloroglucinol (DAPG) is produced by a number of fluorescent pseudomonad strains and is known to suppress Ggt. Another soil microbial group which have been under investigation for their biocontrol potential against Ggt, are arbuscular mycorrhizal (AM) fungi which have the potential to out-compete Ggt and improve host plant nutrition and vigour. In this thesis, I report results from experiments that investigate interactions among AM fungi, Ggt, and DAPG-producing bacteria. A central hypothesis is that carbon flow from plants and AM fungi stimulates DAPG production. I therefore focus on interactions among AM fungi, Ggt and bacteria in vivo with wheat plants and in vitro with only fungal exudates. The synergistic co-operation of pseudomonads and AM fungi against Ggt was demonstrated and the fungal exudates (from AM and Ggt) produced both in vitro and in vivo increased DAPG production by P. fluorescens. The ecology and functioning of beneficial AM fungi was found not to be influenced by the presence of either Ggt or DAPG, highlighting the potential sustainable suppression of “take all” in wheat rhizosphere.
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Yap, H. L. « Is there signalling between Arabidopsis thaliana and arbuscular mycorrhizal fungi ? » Thesis, University of York, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.422529.
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Storer, Kate Elizabeth. « Interactions between arbuscular mycorrhizal fungi and soil greenhouse gas fluxes ». Thesis, University of York, 2013. http://etheses.whiterose.ac.uk/5022/.
Texte intégralRésumé :
Arbuscular mycorrhizal fungi (AMF) can form a mutualistic symbiosis with over two-thirds of all land plants, providing phosphorus and/or nitrogen in exchange for carbon. They can have a significant effect on the surrounding soil, altering pH, water content, structure, and drainage. Important greenhouse gases (GHG) including carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) can be influenced by these factors, yet to date the interactions between AMF and soil GHG fluxes are surprisingly understudied. A microcosm system was developed to study GHG fluxes in the presence and absence of AMF hyphae. A central compartment contained an AMF host plant (Zea mays L.), with two outer compartments, that either allowed (AMA) or prevented (NAMA) AMF hyphal access. Organic matter patches of dried, milled, Z. mays leaves mixed with soil were added to the outer compartments to encourage proliferation of AMF hyphae and GHG production. Soil-atmosphere fluxes of N2O, CO2 and CH4 from the outer compartments were quantified, and gas probes were developed to measure N2O concentrations within the organic matter patches. Data from a series of microcosm experiments provide evidence for AMF interactions with soil fluxes of N2O and CO2, but not CH4. Soil CO2 fluxes were found to be a useful non-invasive method for determining the presence of AMF in hyphal compartments. The N2O concentrations in organic patches decreased in AMA treatments, and a subsequent experiment demonstrated that N2O production by nitrifiers may be limited in the presence of AMF hyphae. In contrast, following harvesting, N2O fluxes from organic matter patches were higher in the AMA treatment; possibly because carbon release from severed AMF hyphae fuelled denitrification. These interactions have important implications for N cycling and sustainable agriculture. The evidence presented in this thesis suggests that AMF may play a previously unappreciated role in reducing soil-atmosphere losses of N2O.
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Ishaq, Lily. « The role of mycorrhizal fungi in Eucalyptus gomphocephala (Tuart) health ». Thesis, Ishaq, Lily (2014) The role of mycorrhizal fungi in Eucalyptus gomphocephala (Tuart) health. PhD thesis, Murdoch University, 2014. https://researchrepository.murdoch.edu.au/id/eprint/24799/.
Texte intégralRésumé :
Eucalyptus gomphocephala DC (tuart) is a woodland tree endemic to the Swan Coastal Plain of Western Australia. The species is of importance for ecological, economic and cultural values. However, E. gomphocephala is in severe decline and the cause of the decline is poorly understood. Due to their important role in ecosystem function, mycorrhizal fungi are hypothesized to play a role in the health status of E. gomphocephala. Recently a fungal pathogen, Phytophthora multivora has been implicated in tree decline.
In vitro and glasshouse trials were conducted to examine the impact of P. multivora on ectomycorrhizal (ECM) fungi and E. gomphocephala seedlings. Phytophthora multivora was negatively affected by Pisolithus albus (Cooke and Massee) Priest and a Pisolithus sp., and the ECM fungi were not/or only slightly impacted by P. multivora. The ECM fungal inoculation did not increase shoot growth of E. gomphocephala seedlings in the presence of P. multivora, however, root growth increased and shoots appeared healthy throughout the trial.
Intact soil cores for bioassay were collected from 12 sites with E. gomphocephala canopy condition ranging from healthy to declining. Sites were classified into three classes; healthy, moderately healthy and declining based on total crown health index. In each site, four trees were randomly selected and eight intact soil cores (0 - 20 cm depth) were collected. Soil samples for arbuscular mycorrhizal (AM) fungi spore assessment and chemical analysis were collected adjacent to the intact soil core. Sites differed for seventeen soil chemistry parameters, and nine variables measured were significantly related to the canopy condition of E. gomphocephala in the field. Although spore density of AM fungi differed between the sites there was no relationship between spores and canopy condition of E. gomphocephala.
A bioassay pot experiment with E. gomphocephala as the trap plant was set up using intact soil cores to evaluate inoculum potential of mycorrhizal fungi. Soil cores for AM fungi spore assessment were taken one month prior to harvest and plants were harvested at seven months. Roots were assessed for mycorrhizal colonization and the relationship between mycorrhizal colonization and crown health was evaluated. ECM fungi colonization dominated seedling roots produced in soils taken from under healthy canopies whereas AM fungi dominated seedling roots in soils taken from under trees with declining canopies. From the seventeen soil chemical properties measured, eight and ten variables were related to ECM and AM colonization, respectively.
Molecular analysis was undertaken to evaluate mycorrhizal communities associated with seedling roots from the bioassay trial. This confirmed observations on root colonization, namely there were more ECM fungi associated with seedling roots grown in soil collected from under healthy canopies, and more AM fungi were found in seedling roots grown in soil collected from under declining canopies. Also, there were more saprophytic fungi for seedling roots grown in soil collected from healthy canopies than for seedlings in declining canopy soil, but the reverse was the case for pathogenic and root rot fungi.
A second glasshouse trial was undertaken to assess mycorrhizal colonization over time using soils taken from contrasting sites. A similar trend in dominance of ECM in seedlings grown in soil collected from under a healthy canopy was observed even when the seedlings were still quite young. For example, at 5 weeks root tips of seedlings in a healthy site soil were 24% colonized by ECM fungi compared with 3% in the declining site soil.
This is the first study to investigate mycorrhizal formation in relation to the health status of E. gomphocephala. The low ECM fungal colonization of E. gomphocephala seedlings grown in declining sites soil might indicate reduced ECM inocula in the sites where the soil were collected. Reasons for the changes in populations of mycorrhizal fungi under declining trees are discussed. This research now needs to be extended to the field by investigating colonization patterns in seedlings and also the molecular analysis of mycorrhizal fungi populations in sites with a range of canopy conditions. An approach for managing health of E. gomphocephala, thus could be gained in the future.
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Sulistyowati, Emy. « Development of molecular probes to distinguish vesicular-arbuscular mycorrhizal fungi ». Title page, Summary and Contents only, 1995. http://web4.library.adelaide.edu.au/theses/09A/09as949.pdf.
Texte intégralRésumé :
Bibliography: leaves 71-79. Almost 80 percent of plant taxa develop vesicular-arbuscular mycorrhizae (VAM) which are symbiotic associations between plant roots and soil fungi. The fungi are biotropic-obligate symbionts. Identification of VAM fungi is currently based on spore characteristics. Molecular techniques provide tools for better and more accurate identification of species, as well as for the examination of genetic variability occuring between individual spores of a single species.
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Gibson, Fiona. « Establishment of ectomycorrhizal fungi on roots of birch (Betula spp.) ». Thesis, University of Edinburgh, 1987. http://hdl.handle.net/1842/14901.
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Smith, Lydia M. J. « The nature of mycorrhizal benefit in reclaimed ecosystems ». Thesis, University of East London, 1994. http://roar.uel.ac.uk/1265/.
Texte intégralRésumé :
The nature and importance of vesicular arbuscular mycorrhizae and ectomycorrhizae was determined for a range of different sites and mycotrophic plant species. Sites were chosen in the south-east, east and Midlands of England and South Wales so that different situations were represented in terms of historical management and biotic and edaphic parameters. Two major types of environmental disturbance were included; restored opencast coal mines and reclaimed landfill sites which had distinct reclamation problems associated with them. A number of undisturbed systems were also included in the survey including mature and ancient woodland on a number of different soil types, mature hedgerows and mature meadows. Several soil physico-chemical parameters were determined for each site and the relationship with the degree and type of mycotrophy for the flora were related to these features. Other edaphic factors were also taken into account including variations in the weather and the age of a given plant. The extent of mycotrophic development was found to be strongly linked to age of site and the preferred type of mycotrophy of the plant partner. Edaphic factors had a lesser, but significant, effect which was particularly important in reclaimed situations. Different methods were assessed on a small scale for the mycorrhizal inoculation of plant species commonly used for amenity purposes on reclaimed landfill sites. A simple scheme employing root fragments and certain soil components was selected on the basis of two required criteria: it was important that the scheme was not only effective but could be implemented within the financial and technical constraints imposed by a county council restoration programme. The chosen inoculation system was then implemented on a large scale in a field based experiment using lysimeters that were subject to a continuous input of landfill gas derived from a newly reclaimed landfill. The success of inoculation was related to both the plant species and the soil type. The importance of mycotrophy in terms of the success and sustainability of plant growth on a landfill reclamation was shown to be significant for certain species. Mycotrophy was more important to predominantly ectomycotrophic species than VA endomycotrophic species. A revision of current theories on the succession of ectomycorrhizal fungal species is suggested in the light of mycobionts identified during the course of the work.
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Bennett, Alison. « Mechanisms underlying complex interactions between plants, herbivores, and arbuscular mycorrhizal fungi ». [Bloomington, Ind.] : Indiana University, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:3204279.
Texte intégralRésumé :
Thesis (Ph.D.)--Indiana University, Dept. of Biology, 2006.Source: Dissertation Abstracts International, Volume: 67-01, Section: B, page: 0048. Adviser: James D. Bever. "Title from dissertation home page (viewed Feb. 9, 2007)."
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van, der Heyde Mieke Elisabeth. « The effect of grazing on arbuscular mycorrhizal fungi in temperate grasslands ». Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/59202.
Texte intégralRésumé :
Managed grazing, involving large animals destined for human consumption,
covers more than 25% of the land surface and has the capacity to alter ecosystems, often leading to desertification, woody encroachment, and deforestation (Asner et al 2014). Arbuscular Mycorrhizal (AM) fungi are ubiquitous root symbionts that colonize 80% of terrestrial plants and influence plant productivity and community composition. Despite the importance of AM fungi for plant communities, the effect of grazing on AM fungal communities is largely unknown. I used grazing exclosures of varying ages to compare AM fungal community and infectivity in grazed and ungrazed plots, as well as several environmental variables that may be affected by grazing. AM fungal community composition was not significantly different between grazed and ungrazed, but grazing increased spore density while decreasing soil hyphal length. This may be attributed to the plasticity of AM fungi in response to environmental conditions, flexibility allowed isolates to respond to grazing without shifting community composition. None of the environmental variables was related
to the change in AM fungi, indicating that variables not measured may be responsible. Time since the exclosure was established was the only variable related to community dissimilarity between grazed and ungrazed. As the age of the exclosure increased, the dissimilarity also increased, highlighting the importance of long-term studies in furthering our understanding of grazer-fungi interactions.Irving K. Barber School of Arts and Sciences (Okanagan)
Biology, Department of (Okanagan)
Graduate
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Pretorius, Travers. « Bioremediation of Contaminated Soils by Echinacea purpurea and Arbuscular Mycorrhizal Fungi ». Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/32500.
Texte intégralRésumé :
As a potential bioremediation system for contaminated soils, I evaluated the use of an arbuscular mycorrhizal (AM) fungus, Glomus intraradices on roots and shoots uptake of polycyclic aromatic hydrocarbons (PAHs), alkyl PAHs, and toxic metals in Echinacea purpurea, in using a controlled 20-week greenhouse study and a complimentary 2-year field study. E. purpurea seeds were either inoculated with the mycorrhizal fungus (AM) or not inoculated (non-AM) and grown in soil provided by the National Capital Commission (NCC) that have known contamination.
In the greenhouse study, AM inoculation increased the uptake of alkyl PAHs in the roots of E. purpurea. The AM inoculation showed no effect on root uptake of PAHs and toxic metals over the 20-week study period. However, when I calculated the uptake rates (k1) for PAHs between both treatments, the AM treated roots ha 10-fold higher k1 values than non-AM treated roots. The soil concentrations of PAHs were found to increase over time with AM inoculation, suggesting, that AM fungi are causing a solvent depletion through root uptake of minerals and carbon, which concentrates the more hydrophobic PAHs in soils. Alkyl PAHs and metals showed no change over time amongst any of the treatments.
Assessing the performance of AM fungi on the uptake of contaminants under field conditions, only PAHs showed increased bioaccumulation in the shoots of E. purpurea with AM inoculation. Alkyl PAHs and metals in plant material were unaffected by the AM inoculation, but increased significantly from year 1 to year 2. The uptake rates among treatments were similar, with non-AM roots having slightly greater uptake. Soil concentrations of PAHs and alkyl PAHs were unaffected over the course of the experiment. Our control soil, however, showed significant increases in concentration from year 1 to year 2 with alkyl PAHs.
These results quantified the influence of AM hyphae-mediated uptake of organic and inorganic contaminant transfer from soil to plants and the bioaccumulation kinetics for contaminants by E. purpurea that will be useful for environmental models and phytoremediation strategies.
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Lee, Jaikoo. « Investigations into the nuclear and mitochondrial genomes of arbuscular mycorrhizal fungi ». Thesis, University of York, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.516607.
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Setiadi, Yadi. « The practical application of arbuscular mycorrhizal fungi for reforestation in Indonesia ». Thesis, University of Kent, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282509.
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