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1
Bisot, Corentin. "Bridging scales in the Arbsucular Mycorhizal Symbiosis". Electronic Thesis or Diss., Lyon, École normale supérieure, 2024. http://www.theses.fr/2024ENSL0057.
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La vie microscopique des sols est responsable de large flux macroscopique de matière à l’échelle planétaire. Mais la complexité des écosystèmes et des organismes qui les constituent rend difficile le passage d’une échelle à l’autre. La thèse intitulée "Relier les échelles dans la symbiose mycorhizienne arbusculaire" tisse des liens entre des objets allant de la taille de la gouttelette de lipide (~500nm) à la longueur totale d’hyphe de champignons à l’échelleplanétaire (~10^20 m).Le premier chapitre introduit un cadre d'analyse des colonies fongiques par des "ondes de propagation", reliant l'échelle microscopique du comportement individuel des hyphes à des variables macroscopiques telles que la densité et la vitesse de propagation. Ces résultats constituent la première analyse de données expérimentales avec un degré de résolution spatiotemporel élevé d’une dynamique de morphogénèse d’un organisme ramifié.Le chapitre 2 décrit en détail les conséquences écologiques de cette propagation macroscopique en quantifiant l’échange de ressources qu’elle implique. Ce résultat jette un éclairage nouveau sur la science des mycorhizes en permettant de relier des traits phénotypiques de colonies de champignon à leur conséquence sur la croissance des plantes dans différents environnements. Le troisième chapitre se concentre sur le lien entre les flux de matière dans la colonie de champignons, l'allongement et l'épaississement des hyphes, mettant en lumière l'importance du transport de lipides dans ces champignons, responsables de flux significatifs de carbone à l'échelle planétaire. Enfin, dans un chapitre annexe les résultats sont projetés à l’échelle d’écosystèmes. Le travail sur le rayon des hyphes permet en particulier de réduire l’incertitude de calcul sur la biomasse totale de champignon mycorhiziens dans un écosystème et à Arbuscule à l’échelle planétaireThe microscopic life of soils is responsible for large macroscopic flows of matter at a planetary scale. However, the complexity of ecosystems and the organisms that comprise them makes it difficult to scale from one level to another. The thesis titled "Linking Scales in Arbuscular Mycorrhizal Symbiosis" establishes connections between objects ranging from the size of a lipid droplet (~500nm) to the total length of fungal hyphae at a planetary scale (~10^20m).The first chapter introduces a framework for analyzing fungal colonies through 'travelling waves', connecting the microscopic scale of individual hyphal behavior to macroscopic variables such as density and propagation speed. These results constitute the first analysis of experimental data with high degree of spatiotemporal resolution of a branching organism's morphogenesis dynamics.The second details the ecological consequences of this macroscopic propagation by quantifying the resource exchange it entails. This result sheds new light on mycorrhizal science by linking phenotypic traits of fungal colonies to their impact on trade with plants in different environments.The third chapter focuses on the microscopic underpinning of bidirectional resource trade within the Arbuscular Mycorhizhal (AM) fungal colonies. It aims at characterizing the robust physical mechanisms that allow the directed transport of carbon and phosphorous over the centimeter wide colony.In an annex chapter, the results are projected at the scale of ecosystems. The work on the radius of the hyphae particularly helps to reduce the calculation uncertainty on the total biomass of mycorrhizal fungi in an ecosystem and at a planetary scale
2
Ruotsalainen, Anna Liisa. "Mycorrhizal colonization and plant performance in arcto-alpine conditions /". Oulu [Finland] : Oulun Yliopisto, 2003. http://herkules.oulu.fi/isbn9514269888/html/index.html.
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3
Gao, Lingling. "Control of arbuscular mycorrhizal colonisation : studies of a mycorrhiza-defective tomato mutant". Title page, contents and summary only, 2002. http://web4.library.adelaide.edu.au/theses/09PH/09phg2117.pdf.
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Bibliography: leaves 161-178. This thesis characterises a mycorrhiza-defective tomato (Lycopersicon esculentum Mill.) mutant, rmc, with respect to fungal colonisation patterns and plant defence reactions during interactions with different species of arbuscular mycorrhizal (AM) fungi, root fungal pathogen Rhizoctonia solani and binucleate Rhizoctonia (a fungal parasite that colonises roots without causing disease). The results suggest that the mutated gene in rmc is involved in the regulation of recognition and plant defence responses in the establishment of AM symbioses.
4
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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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.
6
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.
7
Dhillion, Shivcharn S. Anderson Roger C. "Mycorrhizas and mycorrhizal little bluestem grass (Schizachyrium scoparium) on burned and unburned sand prairies". Normal, Ill. Illinois State University, 1991. http://wwwlib.umi.com/cr/ilstu/fullcit?p9203026.
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Thesis (Ph. D.)--Illinois State University, 1991.Title from title page screen, viewed December 6, 2005. Dissertation Committee: Roger C. Anderson (chair), Anthony E. Liberta, R. Michael Miller, Tsan Iang Chuang, Jerome R. Cain. Includes bibliographical references (leaves 104-113) and abstract. Also available in print.
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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.
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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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Scherpenisse, Dara S. "Mycorrhizae In Sagebrush-Steppe Community Restoration: Mycorrhizal Dependency Of Invasive And Native Grasses With Intraspecific And Interspecific Competition". DigitalCommons@USU, 2009. https://digitalcommons.usu.edu/etd/394.
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Mycorrhizae have been used in restoration for decades. However, studies assessing the use of mycorrhizae in Bromus tectorum-invaded areas of the Great Basin are limited. Two greenhouse pot experiments were conducted to assess the role of mycorrhizae in sagebrush restoration. The first objective (Chapter 2) was to determine the response of Pseudoroegneria spicatum, Elymus elymoides, and B. tectorum to mycorrhizal symbiosis by altering
phosphorus, density, species, presence of mycorrhizae and water levels in a 5 factor design. To assess the mycorrhizal response, a variety of morphological and physiological traits were measured, such as tissue P concentration, specific root length, specific leaf area, carbon isotope discrimination, etc. The effects of the different treatment combinations were analyzed using ANOVA. The second objective (Chapter 3) was to determine the role of different inocula in competition between the three grasses. Species, density, and inoculum type were altered in a 3 factor design. Inoculum was cultured on Allium plants. The effect of locally cultured inoculum on the species was compared to the effect of commercial inoculum. The response of each species to mycorrhizae with different species compositions and densities was assessed. Morphological measurements were used to determine each species response to the different factor combinations. The effects of the different treatment combinations were analyzed using ANOVA. This research provides land managers with information regarding the efficacy of using local versus commercial inocula and whether they should use mycorrhizae in restoring their systems.
10
Boling, Blake C. "Leaf elemental analysis and growth characteristics of mycorrhizal treated post oak seedlings via particle induced X-ray emission spectroscopy". Thesis, University of North Texas, 2006. https://digital.library.unt.edu/ark:/67531/metadc5295/.
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Growth and element assimilation was investigated in post oak seedlings exposed to four different treatment combinations of fertilization and ectomycorrhizal inoculation. Element concentration in excised leaves was analyzed via particle induced X-ray emission spectrometry with a 1.8 MeV proton macrobeam. Mean growth was significantly different across the treatment groups as well as mean concentration of Mg, Al, S, K, Ca, Fe, Cu, and Zn. The data suggest that fertilization rather than mycorrhizal inoculation had a stronger influence on plant growth and nutrient uptake. A follow up study was conducted with a 3 MeV microbeam. A 850 μm2 scanned area of a post oak leaf produced topographical maps of 11 elements.
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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.
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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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Rains, Kai Coshow. "Ericoid mycorrhizas in organic substrates : distribution of ericoid mycorrhizas among epiphytes in a Costa Rican cloud forest and uptake of organic nitrogen by ericoid, ecto-, and arbuscular mycorrhizal pygmy forest plants /". For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2004. http://uclibs.org/PID/11984.
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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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Cavagnaro, Timothy R. "Structure and physiology of Paris-type arbuscular mycorrhizas". Title page, contents and abstract only, 2001. http://web4.library.adelaide.edu.au/theses/09PH/09phc376.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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Asif, Mohammad. "Comparative study of production, infectivity, and effectiveness of arbuscular mycorrhizal fungi produced by soil-based and soil-less techniques". Thesis, [Campbelltown, N.S.W. : The Author], 1997. http://handle.uws.edu.au:8081/1959.7/510.
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The present study was firstly aimed at producing the AM fungal inocula by using soil-based and soil-less culture techniques, including the in-vitro axenic technique, and secondly to assess the infectivity and effectiveness of the inocula so produced in glasshouse and field conditions. Indigenous AM fungi from 5 different sites of New South Wales were successfully propagated and multiplied using the pot-culture and atomizing disc aeroponic culture techniques, and their infectivity was measured using the MPN bioassay method. The coarse and fine sand mix was proven to be very effective for the production of AM fungal inocula. The findings indicated that aeroponic culture technique is far superior to that of conventional pot-culture technique, and could possibly substitute the most commonly used pot-culture technique of AM fungal inoculum production. The ultra-sonic nebulizer technology could possibly be an alternative to conventional aeroponic systems for producing AM fungal isolates in commercial quantities. The introduction of the sheared-root inoculum of Glomus intraradices, produced by the ultra-sonic nebulizer technique, into agricultural soils can substantially reduce the intake of P-fertilizers as much as 50% of the recommended level. The study also indicated that soil phosphorus is a critical factor in limiting mycorrhizal colonization, possibly limiting mycorrhizal responses.The research suggests that various commercially produced single or 'cocktail' inocula may work on mycorrhiza dependent plants in soils where the indigenous AM flora is either not abundant and/or efficient. Furthermore, ecophysiology of the same AM species have different effects on plant growth.
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Williams, Alwyn. "On the Ecology and Restoration of Podocarpus cunninghamii in the Eastern South Island High Country". Thesis, University of Canterbury. Forestry, 2010. http://hdl.handle.net/10092/5141.
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Podocarpus cunninghamii is an endemic New Zealand conifer that, in pre-human times, formed extensive forest communities across the eastern South Island high country. Anthropogenic disturbances have reduced the distribution of Podocarpus cunninghamii communities such that they now exist mainly as small and isolated remnants within a highly modified, predominantly pastoral landscape. Very little is known of the ecology of high country Podocarpus cunninghamii communities, and without this information it is not possible to develop an ecological basis for their restoration. This thesis explores the ecology of Podocarpus cunninghamii in the eastern South Island high country, investigating factors that potentially affect the restoration of Podocarpus cunninghamii within this environment, with special attention paid to the role of arbuscular mycorrhizal fungi (AMF).
Field investigations of Podocarpus cunninghamii communities showed that they contain a high degree of floristic and structural variation determined by soil and climatic variables. Analysis of age and size class distributions suggest that Podocarpus cunninghamii has more than one regeneration strategy, and can regenerate within intact forest following the opening of small canopy gaps or can undergo large-scale recruitment following catastrophic disturbance. Field and glasshouse experiments investigating growth and nutrient responses of Podocarpus cunninghamii to different AMF inoculants found that Podocarpus cunninghamii responses are dependent on both AMF type and grass competition. Finally, investigation of Podocarpus cunninghamii carbon stocks showed that they are less than that of other New Zealand forest types, but are greater than that of grazed pastures.
Successful restoration of high country Podocarpus cunninghamii communities will require the incorporation of associated species based on local environmental conditions, and will also need to allow for disturbance processes. AMF may have an important role to play in restoration by reducing seedling production times and by increasing the competitiveness of Podocarpus cunninghamii when in competition with exotic grasses.
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Zhang, Haoqiang. "Arbuscular mycorrhiza in Medicago truncatula". Doctoral thesis, Humboldt-Universität zu Berlin, Landwirtschaftlich-Gärtnerische Fakultät, 2014. http://dx.doi.org/10.18452/16925.
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Die arbuskuläre Mykorrhiza (AM) ist eine mutualistische Symbiose, die die Phosphataufnahme und Pathogenresistenz von Pflanzen verbessern kann. In der vorliegenden Doktorarbeit wurde die Rolle der Protonen-pumpenden ATPase MtHA1 für die AM Symbiose in Medicago truncatula untersucht. In MtHA1 Mutanten konnten AM Pilze nur noch verkürzte Arbuskel ohne typische Verzweigungen ausbilden. Dies zeigte sich auch in Expressionsmustern von Genen, die für Proteine in verschiedenen Bereichen der periarbuskulären Membran kodieren. Außerdem waren AM Pilzbesiedelung, die verbesserte Nährstoffaufnahme und die Wachstumsförderung in MtHA1 mutierten Pflanzen reduziert. Die Mykorrhiza-induzierte Resistenz (MIR) wurde näher in M. truncatula Pflanzen untersucht, die von Aphanomyces euteiches infiziert waren, dem Erreger einer Wurzelfäule in Leguminosen. In einem geteilten Wurzelsystem, das eine hohe Expression von Verteidigungsgenen aufwies, unterdrückte ein AM Pilz diese Expression und erhöhte in Folge die Empfindlichkeit für das Pathogen. In Wurzeln von Topfkulturen dagegen konnte eine typische MIR beobachtet werden, die wahrscheinlich auf erhöhter Aktivität der Jasmonat/Ethylen-regulierten Verteidigungsantwort beruht, verursacht durch eine Unterdrückung der Salizylsäuresynthese. Im Ergebnis zeigt diese Arbeit die bedeutende Rolle des Gens MtHA1 für die Bildung und Funktion der arbuskelhaltigen Zellen. Die Mutation des Gens führt zur verminderten Arbuskelverzweigung, reduzierter Phosphataufnahme und Wachstumsförderung in der Mykorrhiza und schließlich zu einer geringeren Gesamtbesiedelung durch den AM Pilz. Genexpressionsanalysen weisen darauf hin, dass unterschiedliche Mechanismen den lokalen und systemischen Wechselwirkungen zwischen AM Pilzen und Pathogenen in der Wurzel zu Grunde liegen. Verschieden physiologische Zustände von geteilten Wurzelsystemen und Wurzeln in Topfkulturen erschweren allerdings einen direkten Vergleich der beiden experimentellen Ansätze.Arbuscular mycorrhiza (AM) is a wide spread mutualistic symbiosis, which can improve phosphate acquisition and pathogen resistance of plants. In the current Ph.D. thesis the role of a proton pumping ATPase (MtHA1) for the AM symbiosis in Medicago truncatula was investigated. In MtHA1 mutant plants, different AM fungi only developed truncated arbuscules without forming typical hyphal branches, and this phenotype was mirrored by expression patterns of genes for proteins located in different areas of the periarbuscular membrane. AM fungal colonization, improved phosphate uptake and plant growth promotion were reduced in MtHA1 mutant plants. Mycorrhiza-induced resistance (MIR) and the nodule symbiosis were, however, not affected. MIR was further analyzed in the M. truncatula infected with Aphanomyces euteiches which causes a root-rot disease in legumes. In a split root system showing high levels of defense-gene expression, colonization of an AM fungus reduced this expression and in consequence increased susceptibility of the roots for the pathogen. In roots of pot cultures, however, a typical MIR was observed and could be based on the higher activity of jasmonate/ethylene-regulated defense responses due to suppression of salicylic acid biosynthesis. In conclusion, this work shows that the gene MtHA1 encoding a proton pumping-ATPase plays a critical role in the formation and function of arbuscule-containing cells. Expression of the mutated gene results in reduced formation of arbuscule branches. This in turn negatively influences mycorrhizal phosphate uptake, plant growth promotion and overall mycorrhizal colonization of the roots. Gene expression analyses indicate that different mechanisms underlay local and systemic interactions between the mycorrhizal fungus and the root pathogen. The different physiological stages of pot culture and split root system make a comparison of the two experimental approaches, however, difficult.
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Joubert, Angelique. "Investigation on selected biotic and abiotic factors in the maintenance of the "fairy circles" (barren patches) of southern Africa". Diss., Electronic thesis, 2008. http://upetd.up.ac.za/thesis/available/etd-01172008-125625/.
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Sommerville, David W. "Phosphorus fertilization : effects on asparagus yield, and soil microbial parameters". Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=80876.
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Asparagus (Asparagus officinalis) is a perennial crop well suited to grow in Quebec. Despite high demand for this crop, asparagus production is declining because of asparagus root rot disease that is caused by Fusarium spp. Phosphorus is one of the most important nutrients for the production of healthy asparagus roots that may resist infection by Fusarium. The objective of this study was to determine the effects of phosphorus (P) applications on asparagus yield and soil microbial parameters. Plots receiving 0 to 200% of the P recommendation, based on the Centre de reference en agriculture et agroalimentaire du Quebec (CRAAQ) guidelines, did not differ significantly (p < 0.05) in first year yield or plant tissue concentrations. However, asparagus receiving no fertilizer had 2 to 3 times higher arbuscular mycorrhizal colonisation of roots than other treatments in May 2003. Fresh marketable yield was negatively correlated to Fusarium incidence (p = 0.0091 r = -0.51) suggesting that plants with higher yields are less susceptible to Fusarium symptoms and that producers should avoid over-harvesting low yielding plants to reduce Fusarium spread in the field. Soil microbial activity was not affected consistently by P fertilizers because of high variability in the field.
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Wilkinson, Melinda M. "Changes in growth and survival by three co-occurring grass species in response to mycorrhizae, fire, and drought". Thesis, University of Hawaii at Manoa, 2003. http://proquest.umi.com/pqdweb?index=0&did=765961171&SrchMode=2&sid=6&Fmt=2&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1209417332&clientId=23440.
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Pivato, Barbara. "Ecology of arbuscular mycorrhizas : interactions plant - fungal genotypes and mycorrhizas - bacteria". Dijon, 2008. http://www.theses.fr/2008DIJOS006.
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La première étape de la thèse a consisté à comparer la diversité et la structure génétique des populations de champignons mycorhiziens à arbuscules (MA) associées à quatre espèces de médiques annuelles. Les résultats obtenus montrent que l’abondance des champignons MA différait, indiquant que la structure génétique de la communauté fongique a été influencée par l’espèce végétale. La deuxième étape de ce travail visait à tester l’hypothèse selon laquelle la longue histoire évolutive entre champignons MA et plantes ne se serait pas faite de façon indépendante des bactéries. La structure génétique des populations bactériennes associées aux racines mycorhizées et non de M. Truncatula a été comparée. Les communautés bactériennes différaient de façon significative, ces différences étant expliquées par des marqueurs moléculaires associés aux familles des Oxalobacteraceae et Comamonadaceae. Six isolats représentatifs des populations associées aux racines mycorhizées et deux souches de référence (Collimonas fungivorans Ter331 et Pseudomonas fluorescens C7R12) ont été testées afin de déterminer leur effet sur la mycorhization. Une souche appartenant aux Oxalobacteraceae (Collimonas sp. J5B4) et P. Fluorescens C7R12 ont amélioré la croissance du champignon AM et sa colonisation racinaire, confirmant partiellement l’hypothèse que les bactéries associées aux racines mycorhizées auraient un effet favorable sur la mycorhization. Enfin, la caractérisation de l’effet promoteur de P. Fluorescens C7R12 sur la mycorhization a montré que cet effet était spécifique du champignon MA et que la colonisation des cellules bactériennes différait sur les racines mycorhizées et non-mycorhizéesIn the first part of the thesis, possible effect of the plant genotype on the genetic diversity and structure of the arbuscular mycorrhizal (AM) fungal community was assessed. Results indicated a similar diversity of AM fungi in the four Medicago species used. However, the abundance of AM fungi differed significantly upon the plant species, indicating preferential associations between AM fungal and plant genotypes. The second part of the thesis was based on the hypothesis that the long joint evolution of AM fungi and plants did not occur independently of the associated bacteria. To test this hypothesis, the genetic structure of bacterial communities associated with mycorrhizal and non mycorrhizal roots of M. Truncatula was compared. The bacterial communities differed significantly between mycorrhizal and non mycorrhizal roots, these differences being explained by sequences belonging to Oxalobacteraceae and Comamonadaceae families. Six bacterial isolates representative of the populations belonging to Oxalobacteraceae and Comamonadaceae were tested together with two reference strains (Collimonas fungivorans Ter331 and Pseudomonas fluorescens C7R12) for their effect on mycorrhization. One strain belonging to Oxalobacteraceae (Collimonas sp. J5B4) and P. Fluorescens C7R12 promoted both AM fungal growth and mycorrhization, partially confirming our hypothesis that bacteria preferentially associated with mycorrhizal roots would be beneficial to the symbiosis. Finally, the characterization of the promoting effect of P. Fluorescens C7R12 showed that it was fungal specific and that the pattern of colonization of bacterial cells on mycorrhizal and non mycorrhizal roots differed
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Mukasa-Mugerwa, Thomas Tendo. "The role of arbuscular mycorrhizal fungi in the biotransformation of coal and application in dump rehabilitation". Thesis, Rhodes University, 2007. http://hdl.handle.net/10962/d1004059.
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Fundamental processes underpinning the biotransformation of coal by fungal biocatalysts have been intensively investigated, however, limited large-scale industrial applications using such systems have been reported. The un-anticipated sporadic growth of Cynodon dactylon on the surface of un-rehabilitated discard coal dumps has been noted and this was found to be coupled with the breakdown of coal into a humic soil-like material in the top 1.5 metres of the dumps. Extensive fungal growth was observed to be associated with the Cynodon dactylon root system and examination of plant roots indicated the presence of mycorrhizal fungi. Analysis of the Cynodon dactylon plant roots around which coal biotransformation was occurring confirmed the presence of arbuscular mycorrhizal colonisation with the species Glomus clarum, Paraglomus occultum, Gigaspora gigantea and Glomus mosseae identified to be associated with the plants. Further molecular characterisation of non-mycorrhizal rhizospheric fungi showed the presence of fungal species with coal-degrading capabilities that most likely played a role in the coal biotransformation observed. The discard coal dump environment was simulated in pot and column studies and coal biotransformation was reproduced, with this process enhanced by the addition of mycorrhizal and non-mycorrhizal rhizospheric fungal inocula to the environment. Mycorrhizal and non-mycorrhizal species in the inoculum were re-isolated from the simulated environment fulfilling a number of Koch’s postulates and indicating a causal role in the biotransformation of coal. An inversion of conventional mycorrhizal colonisation was demonstrated in this system with reduction in extraradicular presence and an increase in intracellular colonisation compared to soil controls. A descriptive model was formulated suggesting a two-part fungal system involving organic carbon and nutrient exchange between the plant, mycorrhizal fungi and non-mycorrhizal coal-degrading rhizospheric fungi ultimately resulting in the biotransformation of coal. The biotransformation observed was comparable to reports of “rock-eating fungi”. Results suggest that the biological degradation of coal in situ with the production of a soil-like substrate could provide a feasible method of discard coal dump rehabilitation as well as provide a humic-rich substrate that can be utilised in further industrial applications.
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Facelli, Evelina. "The role of mycorrhizal symbiosis in plant intraspecific competition and population structure". Title page, Contents and Abstract only, 1998. http://hdl.handle.net/2440/37773.
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The overall objective of this project was to investigate the effects of the symbiotic association of plants with vesicular - arbuscular mycorrhizal fungi on the intensity of intraspecific competition and its consequences on population structure I performed four main glasshouse experiments using a non - cultivated species, Rhodanthe chlorocephala ssp rosea, or a cultivated species, Trifolium subterraneum. I grew the plants at different plant densities, under different levels of resources ( phosphorus and / or light ), in environments with homogeneous and / or patchy distribution of phosphorus ( P ). In pots with homogeneous distribution of P, the addition of P to R. chlorocephala and mycorrhizal infection in T. subterraneum increased plant biomass of single plants. However, these beneficial effects were reduced by increasing plant density. Shading of plants of T. subterraneum did not generally alter these effects. Mycorrhizal symbiosis and the addition of P always increased the intensity of plant intraspecific competition. In trays with patchy or homogeneous distribution of P, mycorrhizal infection and patchy distribution of P increased the total biomass and size inequality of populations of plants of T. subterraneum. Individual biomass was determined by the local soil P concentration in patchy environments and by mycorrhizal infection in low density treatments. Mycorrhizal infection, but not patchy P distribution, increased relative competition intensity. Asymmetric or symmetric distribution of resources between plants will change these size hierarchies. The distinction between these two types of distributions has lead to two different models explaining the interaction between competition and size inequality ( degree to which the biomass is concentrated within a small fraction of the population &# 40 Weiner and Thomas 1986 ) ) the resource depletion and resource pre - emption models ( Weiner and Thomas 1986, Weiner 1988b ). In the first model ( resource depletion ) competition reduces the relative growth rate of all the individuals by the same proportion, reduces variance of growth rates and reduces variation in sizes. Thus, in this model resource acquisition is proportional to plant size ( Weiner 1990 ). This model is also called symmetric or two - sided competition and applies when competition for nutrients predominates. It predicts that at high density, plants will be smaller but the population will have less inequality than at low density ( Weiner and Thomas 1986 ). In the second model ( resource pre - emption ), competition increases the variation in relative growth rates and increases variation in sizes. Large plants obtain a more than proportional share of the resources ( relative to sizes ) ( Weiner 1990 ) and this increases their competitive ability which results in a positive feedback on plant size. This phenomenon is also called snowball cumulation, asymmetric or one - sided competition and it was observed only when competition for light was predominant ( Wilson 1988a ). This second model predicts that at high density plant populations will have more inequality than at low density ( Weiner and Thomas 1986 ). Although these two models are generally accepted, alternative analyses and recent experiments show that the degree of asymmetry of the interaction depends on the spatial and temporal distribution of the resource, the spatial distribution of the individuals in the population, neighbourhood competition and the mobility of the resource ( Huston 1986 ; Miller and Weiner 1989, Weiner 1990, Bonan 1991 ). Weiner ( 1990 ) suggested that if nutrients are distributed homogeneously and the uptake is proportional to root size, the competitive interaction will be more symmetric, whereas if patches with more nutrients can be reached by large individuals, asymmetric competition will predominate. This hypothesis has not been tested yet. Turner and Rabinowitz ( 1983 ) found that populations with an initial random spatial distribution of individuals had an unexpected increase in size inequality. My results emphasise that the main effects of mycorrhizas at the individual level cannot be expected to be apparent at the population level, because of the influence of density - dependent processes. However, infected individuals with a strong response to the symbiosis would have an advantage in situations of competition. This scenario can explain the maintenance of the symbiotic ability even under conditions such as dense populations, where there is no obvious advantage of the symbiosis at the population level.Thesis (Ph.D.)--Department of Soil and Water, 1998.
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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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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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Lux, Heidi B. "The effects of aluminum and nitrogen on mycorrhizal and non-mycorrhizal tulip poplar". Morgantown, W. Va. : [West Virginia University Libraries], 1999. http://etd.wvu.edu/templates/showETD.cfm?recnum=1050.
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Thesis (M.S.)--West Virginia University, 1999.Title from document title page. Document formatted into pages; contains ix, 111 p. : ill. Vita. Includes abstract. Includes bibliographical references.
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Tam, Chee-fai Paul. "Mycorrhizal associations in members of Hong Kong's fagaceae /". [Hong Kong : University of Hong Kong], 1993. http://sunzi.lib.hku.hk/hkuto/record.jsp?B13465132.
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Ditschar, Bernd. "C, P and water dynamics in Mycorrhiza". Doctoral thesis, [S.l.] : [s.n.], 2005. http://webdoc.sub.gwdg.de/diss/2005/ditschar.
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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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Reed, L. E. "Mycorrhizal effects in arable crops". Thesis, University of Leeds, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.371057.
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Harso, Wahyu. "The mycorrhizal plant root system". Doctoral thesis, Humboldt-Universität zu Berlin, Lebenswissenschaftliche Fakultät, 2016. http://dx.doi.org/10.18452/17574.
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Der Beitrag der arbuskulären Mykorrhizapilze zur Nährstoffaufnahme und zum Wachstum von Pflanzen ist vom Genotyp des Pilzes und der Pflanze abhängig, sowie von den Umweltbedingungen. In der vorliegenden Arbeit wurden Mykorrhizapilze unterschiedlicher Herkunft verwendet. Im Mittelpunkt der Arbeit stand die Untersuchung der Rolle der Mykorrhiza bei der Reaktion der Pflanze auf räumlich unterschiedliches Nährstoffangebot im Boden. Als Versuchspflanzen wurden Süßkartoffel und Tagetes verwendet. Für die Arbeit wurden verschiedene Modellexperimente durchgeführt. In speziell für diese Arbeit konstruierten Gefäßen wurden nicht-mykorrhizierte und mykorrhizierte Süßkartoffelpflanzen mit organischer Substanz versorgt, die entweder gleichmäßig oder heterogen im Substrat verteilt war. In weiteren Experimenten wurde mit Hilfe von "split-root" Systemen die Wirkung arbuskulärer Mykorrhizapilze auf ein lokales Angebot von mineralischem Phosphor und Stickstoff im Boden untersucht. Darüber hinaus wurde in Versuchen Kompost räumlich konzentriert im Substrat angeboten. Die Messungen umfassten den Mykorrhizierungsgrad der Wurzel, die Entwicklung des extraradikalen Myzels, die Trockenmasse der Pflanze sowie die Konzentrationen an Phosphor und Stickstoff in der Pflanze. Eine Besiedlung der Wurzeln mit arbuskulären Mykorrhizapilzen führte in den meisten Versuchsansätzenzu einer erhöhten Nährstoffaufnahme der Pflanze und zu einem verbesserten Wachstum. Ein besonders starkes Hyphenwachstum in Bodenzonen mit viel organischer Substanz wurde jedoch nicht beobachtet. Zugabe von Kompost führte teilweise zu einem Rückgang des Mykorrhizierungsgrades. Die Verwendung von organischem Material oder Kompost im Gartenbau kann sinnvoll sein und zur Verminderung von Mineraldüngung beitragen. Optimales Pflanzenwachstum und Mykorrhizawirkung erfordern jedoch eine gute Balance zwischen Art und Menge des organischen Stoffes bzw. Komposts, den Substrateigenschaften und den Pflanzen- und Pilzgenotypen.The actual contribution of arbuscular mycorrhizal (AM) fungi to plant nutrient uptake depends on the fungal and plant genomes, and on environmental conditions. In the present study, AM fungi of different origin, for example isolated from plots with different long-term fertilizer application history, were used to quantify their contribution to plant nutrient uptake under situations of spatially heterogeneous soil nutrient distribution. Test plants for this study were sweet potato and marigold. Several model experiments were carried out. In specifically constructed growth containers, non-mycorrhizal and mycorrhizal sweet potato plants were supplied with organic matter either homogeneously or heterogeneously distributed in the substrate. Bacteria from a long-term organically fertilized soil were also added as a treatment. In other experiments using a split-root approach, the influence of AM fungi on the plant response to localized mineral phosphorus and nitrogen supply was studied. In a further experiment, the effects of localized compost supply on marigold plants inoculated with Glomus mosseae were investigated. Arbuscular mycorrhizal fungi increased nutrient uptake and growth of plants under most conditions, also when nutrients were heterogeneously distributed in soil. However, there was no indication of increased hyphal proliferation or activity in soil spots with high organic matter. Plant phosphorus status regulated the extent of AM root colonization. The extent of AM root colonization was partly decreased by application of organic matter and of compost to the substrate. Application of organic matter and/or compost can be beneficial in horticulture and can replace mineral fertilizer use. However, optimum plant growth and mycorrhizal function require a good balance between type and amount of organic matter or compost, growth substrate properties and plant and AM fungal genotype.
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Chan, Wing-kuen. "Studies of mycorrhizal associations of some trees grown in Hong Kong /". [Hong Kong : University of Hong Kong], 1991. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12971856.
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Bonello, Pierluigi. "Defence responses of non-mycorrhizal and mycorrhizal seedlings of Pinus sylvestris L. to fungal pathogens". Thesis, University of Oxford, 1991. http://ora.ox.ac.uk/objects/uuid:83f17126-ed81-4060-9e5f-714814faada1.
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The defence mechanisms expressed in roots of Pinus sylvestris seedlings challenged with fungal pathogens were investigated, and a comparison was made between the expression of defences in non-mycorrhizal and mycorrhizal seedlings. Papillae were formed by cortical cells of non-mycorrhizal seedlings infected with Cylindrocarpon destructans. Histochemical evidence was obtained for pectic materials comprising an important polysaccharide component of these structures, and for the deposition of polyphenolic compounds also. Proton induced X-ray emission (PIXE) microanalysis indicated that insoluble calcium levels were elevated in papillae relative to normal cell walls. Although papillae appeared important in protecting cortical cells against penetration by fungal hyphae, a primary role for the wall appositions in the resistance of seedlings of Scots pine against root pathogens could not be proven. Although phytoalexins were not detected in the roots of Scots pine seedlings following infection with C. destructans, the mean content of an abietic acid fraction (comprising six compounds, of which only dehydroabietic acid could be positively identified), increased from 5.2 to 9.7mg g-1 dry weight. This fraction exhibited some antifungal activity. -related proteins induced de novo by infection could not be detected, but several constitutive apoplastic proteins, including some with chitinase activity, appeared to increase in the needles of root-infected seedlings. The formation of ectomycorrhizae with Pisolithus tinctorius, Suillus bovinus and Hebeloma crustuliniforme did not itself induce papilla formation in the roots of P. sylvestris. Evidence was obtained to suggest that the response was suppressed when mycorrhizal seedlings were challenged with C. destructans. Results highly suggestive of the induction of systemic resistance in P. sylvestris seedlings, consequent upon mycorrhizal infection, were obtained. In seedlings grown in vitro the survival rate of mycorrhizal seedlings challenged aerially with Botrytis cinerea was 37.5% compared with 7.1 in seedlings grown gnotobiotically. However, the physiological mechanisms by which this protection was imparted remain to be determined.
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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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Wahl, Anne-Lena. "Importance des interactions entre plantes et mycorhizes dans le maintien de la productivité des écosystèmes pastoraux montagnards soumis à des forçages climatiques". Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAS038/document.
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Bien que les champignons mycorhiziens arbusculaires (AMF) soient présents des habitats collinaires aux habitats alpins, les recherches sur leur rôle dans l’écosystème montagnard sont encore incomplètes. Les objectifs de cette thèse sont d’analyser l’écologie et le fonctionnement des AMF ainsi que leur réponse au changement global dans les écosystèmes montagnards. Nous tentons de répondre aux questions de recherche suivantes : quels sont les effets de l’altitude sur les AMF indépendamment des effets des autres gradients et de la relation AMF-plante hôte ? Quelles relations de facilitation se développent dans les écosystèmes montagnards et quels bénéfices les plantes tirent-elles des AMF ?Avec l’augmentation d’un stress environnemental la symbiose AMF-plante doit théoriquement devenir plus mutualiste. Nous émettons l’hypothèse d’une modification du fonctionnement des interactions AMF-plante selon un gradient altitudinal dans les conditions environnementales actuelles, puis dans les conditions futures. Afin de vérifier ces hypothèses, une expérimentation in situ a été mise en place dans les Alpes Centrales d’Italie pour évaluer les variations des taux de mycorhization et leur abondance dans la communauté microbienne du sol, étudier la nature des relations entre plantes et mycorhizes ainsi que la productivité végétale le long d’un gradient altitudinal. De plus, les influences d’une augmentation de la température et d’une réduction des précipitations sont analysées séparément dans une chambre de croissance sous conditions contrôlées, ce qui permet de distinguer leurs effets respectifs sur la productivité des plantes et sur les interactions plantes – mycorhizes.Cette thèse montre que les AMF sont omniprésents dans les écosystèmes de montagne et qu’une diminution de leur abondance avec l'altitude dépend du contexte climatique global. D'autre part, la relation des AMF avec les plantes est fortement dépendante de la plante-hôte, ainsi que du contexte biotique et abiotique. Troisièmement, un changement des interactions AMF-plante avec l'altitude est suggéré par des indices indirects, mais est également très probablement dépendant de l'identité de la plante hôte. Cette thèse propose aussi une nouvelle orientation de recherche pour bien évaluer les hypothèses présentées. Il est nécessaire de réaliser des études sur le terrain où la présence des AMF est contrôlée et les interactions AMF-plante peuvent être évaluées. Afin de généraliser les résultats, ces expérimentations doivent être menées à différentes échelles spatiales et représenter différentes aires géographiques.Il est particulièrement important de comprendre et de qualifier ces processus en zone montagnarde pour prévoir leur évolution possible dans un contexte de changement global. Nos expérimentations montrent en effet que le réchauffement est un facteur important car il aggrave les conditions de sécheresse en basse altitude et entraine une baisse de la productivité des plantes. Nous démontrons que la présence de mycorhizes atténue l’impact du changement climatique sur la productivité des plantes mais que le niveau de cette atténuation varie selon les espèces de plantes.Les connaissances actuelles concernant les AMF en milieu montagnard sont peu développées sur les processus en jeu dans les interactions AMF-plantes. Grâce aux hypothèses présentées et à leur approche expérimentale cette thèse offre de nouvelles perspectives sur l’analyse de ces processusEven though arbuscular mycorrhizal fungi (AMF) are present from foothills to all alpine habitats, research on their role in mountain ecosystems remains incomplete. The main objective of this dissertation was to investigate interactions between AMF and plants along altitudinal gradients under both, natural conditions and simulated future climate change conditions.A novel framework is suggested for the functioning of the AMF-plant relationship along altitudinal gradients based on the stress gradient hypothesis. The first hypothesis expects the AMF-relationship to shift along the mutualism–parasitism continuum following changing environmental stress along the altitudinal gradient. The relationship might be most mutualistic at the subalpine zone. In a second hypothesis, this shift along the mutualism-parasitism continuum is predicted to be different under climate change conditions, and the most mutualistic expression of the AMF-plant relationship expected in the montane and alpine zone. Studies to validate the presented hypotheses will help to identify important mechanisms underlying plant-AMF interaction and with that the mediation of plant-plant interactions by AMF. In the scope of this thesis, the framework was addressed in field experiment as well as under controlled conditions in a climate chamber experiment.From a literature review and from a field experiment along a dry inner-alpine altitudinal gradient this thesis proposes the following conclusions: First, AMF are also ubiquitous in mountain ecosystems, but a decrease in their abundance with increasing altitude is dependent on the overall climatic context. Second, their relationship to plants is however strongly dependent on the host plant species as well as the biotic and abiotic context. Third, a shift of the AMF-relationship along with altitude is expected but will quite possibly also depend on the plant species identity. Fourth, to fully assess the suggested working hypotheses for AMF-plant interactions field studies must be conducted at different spatial scales and covering different mountain systems.It is particularly important to understand and investigate the drivers of AMF plant relationship in mountain ecosystems to be able to make sound predictions for AMF-plant interactions under future climate change conditions. The presented field and climate chamber experiments on climate change show that temperature is an important factor because it aggravates the conditions of drought in lowland and a threshold is surpassed. It becomes also clear that whether AMF mitigate climate change effects for plants or not is dependent on the plant species. Altogether this thesis contributes to current research questions in ecology, climate change mitigation and plant–soil interactions, because it addresses the role of AMF in mountain grassland ecosystem, investigates the effects of climate change and provides a new framework concerning the functioning of the AMF-plant relationship ranging from parasitism to mutualism
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Abualghaith, Abdulaziz. "Carbon and nitrogen metabolisn in orchid-mycorrhiza associations". Thesis, University of Sheffield, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.604555.
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Members of the Orchidales produce dust seeds so lacking in nutrient and carbon reserves that they are dependent upon appropriate fungal partners to supply the essential additional carbon and nutrients required for successful establishment in nature. These plants are thus initially mycoheterotrophic before they normally go on to develop green leaves and become autotrophic as adults. However, at least 210 species of orchid remain fully mycoheterotrophic into adulthood. The metabolic pathways involved in the nitrogen and carbon fluxes from fungus-to -plant in mycoheteratrophic are still poorly understood, but result in characteristic enrichment in 13C and 13N. In this thesis in vitro studies on agar are employed to investigate the effects of different N sources, with and without sugar or cellulose carbon sources on the heterotrophic growth of mycorrhizal orchid seedlings and metabolite pools in the plants and their fungal partners. It is hypothesised that glutamine, a central metabolite in assimilation of mineral by basidiomycete fungi, passes from fungus-to -plant as in traditional models of N assimilation by ectomycorrhizal plants. A range of nitrogen and carbon sources including isotopically labelled 14C and 13C-glucose together with 15N labelled N sources including nitrate, ammonium, ammonium nitrate, glutamine, glycine and arginine were supplied to orchid mycorrhizal fungi in pure culture and to mycorrhizal seedlings of Goodyera repens or Dactylorhiza fuchsii. In three compartment Petri dishes in which the seedlings were grown with their fungal partners colonising the two other compartments, simultaneous additions of DC and 15N tracers provided compelling evidence of fungal assimilatory pathways providing co-transport of C and N into heterotrophic seedlings of G. repens. Nitrate was a better N source than ammonium or amino acids for the plants, and metabolomic analysis showed strong up-regulation of relative abundance of glutamine in the fastest growing plants. The findings presented in this thesis provides strong circumstantial evidence that glutamine serves as a major combined N and C source transported from fungus-to-plant in heterotrophic orchid seedlings.
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Liu, Yi. "Calcium-related fungal genes implicated in arbuscular mycorrhiza". Phd thesis, Université de Bourgogne, 2012. http://tel.archives-ouvertes.fr/tel-00985826.
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Fluctuations in intracellular (Ca2+) calcium levels generate signaling events and regulate different cellular processes. Whilst the implication of Ca2+ in plant cell responses during arbuscular mycorrhiza (AM) interactions is well documented, nothing is known about the regulation or role of this secondary meesenger in the fungal symbiont. The molecular basis of fungal calcium homeostasis in the AM symbiosis was analyzed by investigating the expression of Ca2+-related fungal genes. In a first study, G. mosseae genes putatively encoding a MAP3k-like protein kinase (Gm2) and a P-type ATPase (Gm152) were investigated. Both Ca2+-related genes were up-regulated by A. sinicum root exudates, suggesting a role in early interactions prior to symbiosis establishment. The full-length cDNA sequence of Gm152 obtained from germinating spores of G. mosseae confirmed its identity. The role of Ca2+ in fungal processes leading to establishment of an AM symbiosis was investigated in more detail in G. intraradices-M. truncatula interactions. Enhanced expression of genes encoding six membrane transport proteins and one nuclear protein kinase, selected from the G. intraradices transcriptome database, was related to colonization of wild-type M. truncatula (line J5) roots and not observed with the mycorrhiza-resistant mutant dmi3/Mtsym13. Laser microdissection mapping of transcripts indicated that the Ca2+-related G. intraradices genes were differentially up-regulated in arbuscules and/or in intercellular hyphae. The tempo-spatial variations in fungal gene expression suggest different roles in the development or functioning of the AM symbiosis. Full-length cDNA of three G. intraradices genes putatively encoding a PMR-like endoplasmic reticulum P-type ATPase, a VCX1-like vacuolar Ca2+ ion transporter and a nuclear CCaMK were obtained for functional analyses in yeast mutants to gain insight into their role in the mycorrhizal symbiosis. Possible mechanisms are discussed in which Ca2+-related proteins of G. intraradices may play a role in the mobilization and perception of the intracellular messenger by the AM fungus during symbiotic interactions with host roots
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Guillotin, Bruno. "Spatiotemporal regulation of the arbuscular mycorrhiza symbiosis establishment". Thesis, Toulouse 3, 2016. http://www.theses.fr/2016TOU30156/document.
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La symbiose mycorhizienne à arbuscule est une interaction bénéfique entre les champignons du phylum Glomeromycota et près de 80% des espèces de plantes terrestres. Elle est caractérisée par un échange réciproque de nutriments dans lequel le champignon fournit des sels minéraux à la plante en échange de sucres issus de la photosynthèse. Cependant, cette "alimentation" du champignon au cours de la symbiose représente un coût carbone important pour la plante. Ainsi, les plantes doivent strictement maitriser le développement des champignons symbiotiques dans les racines. Ce contrôle est appelé autorégulation. Plusieurs protéines ont été démontrées comme étant importantes pour la régulation des différentes étapes de la colonisation : la stimulation de la croissance fongique dans la rhizosphère par les strigolactones, l'entrée dans les racines, la prolifération des hyphes au sein des racines et la formation des arbuscules. Dans ce travail, nous avons examiné plus en détail le rôle de deux de ces protéines connues pour être impliquées dans le processus de mycorhization, les facteurs de transcription NSP1 et NSP2 (Nodulation Signaling Pathway). Nous avons d'abord pu confirmer dans les racines de M. truncatula en conditions non-symbiotiques, l'implication directe de NSP1 dans la régulation de deux gènes de biosynthèse des strigolactones, DWARF27 (D27) et MORE AXILLARY GROWTH (MAX1). Ensuite, nous avons montré que NSP1, contrairement à NSP2, favorise l'entrée du champignon dans la racine, sans doute due à l'induction de la synthèse des strigolactones stimulant le champignon, via l'activation de D27 et de MAX1. Ensuite, au cours des étapes ultérieures de la mycorhization, nous avons montré que dans les tissus colonisés, NSP1 est absent et que l'induction de D27 et de MAX1 n'était plus NSP1 dépendante. À cette étape, l'expression de la protéine NSP1 est localisée dans les cellules justes en amont du front de colonisation fongique. Là, elle contrôle négativement la propagation des hyphes dans la racine et positivement la formation des arbuscules. En revanche, NSP2 est présente dans le tissu colonisé où elle favorise la propagation des hyphes et le développement des arbuscules, peut-être en interaction avec d'autres facteurs. Nous avons également montré chez M. truncatula que si les protéines NSP1 sont absentes des tissus colonisés, les transcrits de NSP1 sont présents. De façon inattendue, nous avons mis en évidence que l'ARN messager de NSP1 avait la capacité de protéger l'ARN messager de NSP2 contre sa dégradation par le microARN (miR171h), par une action de piégeage du miR171h, appelé effet mimicry. Ceci est la première démonstration qu'une molécule d'ARN codante peut être la cible mimétique d'un microARN. Dans notre contexte d'étude cette constatation révèle que les transcrits de NSP1 permettent une régulation positive de l'expression de NSP2, et met en lumière un niveau de complexité supplémentaire dans le rôle de ces deux facteurs de transcription dans la symbiose mycorhizienne. Enfin, dans la tomate, nous avons montré que Sl-NSP1 pourrait être directement ou indirectement régulée par une protéine AUX / IAA impliquée dans la réponse précoce à l'auxine, Sl-IAA27. Ce lien avec l'auxine nous fait présumer que cette AUX/AAI est un nouveau composant de la voie de signalisation du contrôle de la colonisation fongique dans la tomate, et nous proposons qu'il puisse avoir un rôle dans le contrôle de la biosynthèse des strigolactones via la régulation de Sl-NSP1. L'ensemble de ce travail fournit de nouvelles pièces du puzzle constituant la symbiose mycorhizienne et montre l'importance de l'analyse des régulations spatiotemporelles pour une meilleure compréhension de ces processus biologiques extrêmement complexesThe arbuscular mycorrhiza (AM), a symbiosis between fungi from the phylum Glomeromycota and nearly 80% of terrestrial plant species. It is characterized by a two-way exchange in which the fungus provides mineral nutrients to the plant in exchange for carbohydrates. However this "feeding" of the fungus during the symbiotic process represents a significant carbon cost for the plant. To maintain a mutualistic interaction the two symbiotic partners have to strictly control the extent of fungal development in the roots. This control is called autoregulation. Several proteins have been found to be important for the regulation of the different mycorrhizal steps: the stimulation of fungal growth in the rhizosphere by the strigolactones, the fungal entrance in the roots, the hyphal proliferation in the roots and the arbuscule formation. In this work we examine in more detail the role of two of these proteins known to be involved in the mycorrhization process, the transcriptional factors NSP1 and NSP2 (Nodulation Signaling Pathway). We first confirm in M. truncatula roots the direct implication of NSP1 in the regulation of two strigolactone biosynthesis genes, DWARF27 (D27) and MAX1, during the asymbiotic conditions. Then, we show that NSP1, unlike NSP2, is a factor that promotes the fungal entries in the root, presumably due to its activation of D27 and MAX1 resulting in a stimulation of strigolactone synthesis and presymbiotic fungal growth. Next, during the later stages of mycorrhization, we highlight that in the colonized tissues NSP1 is absent and the induction of both D27 and MAX1 is not anymore NSP1 dependent. NSP1 protein is then localized in cells which are not yet colonized but are close to a colonization zone. There, it controls negatively the hyphal propagation in the root and positively the formation of arbuscules. In contrast, NSP2 is present in the colonized tissue where it promotes hyphal propagation and arbuscule development, perhaps by interacting with other proteins. We also show that if NSP1 proteins are absent of the colonized tissues, NSP1 transcripts are present. Unexpectedly, we unveil that in those colonized cells, NSP1 mRNA can protect, by a micro RNA (miR171h) decoy action called target mimicry, NSP2 mRNA against miR171h-mediated degradation. This is the first demonstration that a coding RNA molecule can be a target mimic for a microRNA. In our context this finding reveals a positive regulation of NSP2 expression by NSP1 transcripts and brings to light an additional layer of complexity in the mycorrhizal dual role of these two transcription factors. Finally, in tomato, we highlight that SlNSP1 could be directly or indirectly regulated by the AUX/IAA protein, SlIAA27. As a link with auxin we presume that this AUX/IAA protein is a new component of the signaling pathway controlling AM fungal colonization in tomato, and we propose that it controls strigolactone biosynthesis via the regulation of SlNSP1. Overall our work provides new pieces of the mycorrhizal puzzle and shows how important it is to perform spatiotemporal investigations for a better understanding of highly integrated and complex biological processes
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França, Soraya de Carvalho. "Comunidades de fungos micorrízicos arbusculares nos manejos convencional e orgânico de citros e suas interações com Phytophthora parasitica". Universidade de São Paulo, 2004. http://www.teses.usp.br/teses/disponiveis/11/11138/tde-14072004-152254/.
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Agricultores e técnicos envolvidos na citricultura orgânica procuram desenvolver sistemas de produção com maior atividade microbiana no solo. Dessa maneira, esperam obter benefícios dos processos que ocorrem no solo, entre eles, o controle natural de pragas e doenças. Porém, são poucos os estudos sobre a influência desse tipo de manejo sobre a microbiota do solo, em especial sobre os fungos micorrízicos arbusculares (FMAs) e o patógeno Phytophthora parasitica. Os objetivos dessa tese foram: avaliar a colonização micorrízica e conhecer a diversidade de FMAs nos sistemas de produção convencional e orgânico de citros; avaliar a aplicação de benomyl e da radiação γ na obtenção de testemunhas não micorrizadas para estudo de interação de comunidade de FMAs nativos e P. parasitica; verificar a capacidade indutora de resistência local e sistêmica dos FMAs nativos a P. parasitica; estudar atividade da quitinase no sistema radicular de limão 'Cravo' colonizado por fungos micorrízicos nativos. Foram realizadas amostragens em dois sistemas de produção de citros em São Paulo, um convencional e um orgânico. A riqueza e a diversidade de espécies de FMAs foram maiores no manejo orgânico. No entanto, a porcentagem de colonização micorrízica nas plantas no campo não variou com o tipo de manejo. Em casa de vegetação, experimentos com plantas de limão 'Cravo' (Citrus limonia) mostraram que a radiação γ foi mais adequada que a aplicação de benomyl na obtenção de testemunhas não micorrizadas para estudo de interação P. parasitica- FMAs nativos de agroecossistemas de produção de laranja. Também em casa de vegetação, foi realizado um experimento com raiz dividida de plantas de limão 'Cravo'. Não foi possível avaliar a capacidade indutora de resistência dos fungos micorrízicos arbusculares nativos porque não houve desenvolvimento da podridão de raízes nas plantas de limão 'Cravo' após a infestação com P. parasitica. Discute-se a interação de patógenos de raiz do solo natural e os FMAs nativos porque o solo natural dos sistemas de produção convencional e orgânico promoveram diferentes respostas de crescimento local e sistêmico das raízes das plantas micorrizadas. A atividade de quitinase foi igual nas raízes de plantas micorrizadas e não micorrrizadas cultivadas em solos dos sistemas de produção convencional e orgânico. Porém, a associação micorrízica aumentou localmente a proteína total nas raízes das plantas.Farmers and technicians involved with organic citriculture try to develop systems with high microbial activity in soil. In this way, they expect to obtain benefits from processes that occur in soil, as natural control of pests and diseases. However, there are few studies about the influence of this type of management on soil microbiota, specially on the arbuscular mycorrhizal fungi (AMF) and the pathogen Phytophthora parasitica. The objectives of this thesis were: to evaluate mycorrhizal colonization and diversity of AMF in citrus conventional and organic farming; to evaluate benomyl application and γ radiation to obtain non-mycorrhizal controls for study of interaction between indigenous AMF and P. parasitica; to verify local and systemic capacity of indigenous AMF to induce resistance against P. parasitica; to study chitinase activity in roots of 'Rangpur' lime colonized by indigenous AMF. Samplings were carried out in two citrus systems in São Paulo, one conventional and one organic farming. The richness and the diversity of AMF species were higher in the organic farming. In greenhouse, experiments with 'Rangpur' lime (Citrus limonia) showed that γ radiation was better than benomyl to obtain non-mycorrhizal control for studies of interaction between P. parasitica-indigenous AMF from orange agroecosystems. In greenhouse also, a split root experiment with 'Rangpur' lime was carried out. It was not possible to evaluate the indigenous AMF capacity to induce resistance because no root rot developed in 'Rangpur' lime plants after inoculation with P. parasitica. We discuss the interaction between root pathogens in natural soil and indigenous AMF because natural soil from conventional e organic farming promoted different local and systemic root growth responses in mycorrhizal plants. Chitinase activity was similar in roots of mycorrhizal and non-mycorrhizal plants grown in conventional and organic farming soils. However, mycorhizal association increased local protein content in roots.
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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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Misbahuzzaman, Khaled. "Mycorrhizal associations of Eucalyptus camaldulensis Dehnh". Thesis, University of Edinburgh, 1999. http://hdl.handle.net/1842/15403.
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The species Eucalyptus camaldulensis Dehnh. is of great importance in Mediterranean, sub-tropical and tropical countries for the production of domestic products, such as poles, posts timber and fuelwood. Some members of the genus Eucalyptus are reported to form both arbuscular- (AM) and ecto-mycorrhizas (EM). The main objectives of this study were to look at the host-symbiont interactions between E. Camaldulensis and AM and EM fungi, and interactions between the two mycorrhizal types. The initial aim of the project was to determine suitable experimental conditions for the formation of both types of mycorrhizas on E. camaldulensis seedlings. Two experiments, the first with AM fungi and the second with EM fungi, were set up successively using vermiculite-peat (VP) and sand-perlite (SP) as growth media, and 10 mg 1-1 and 30 mg l-1 phosphorus (P) Ingestad's nutrient solution in each case. Glomus intraradices Schenck and Smith. isolate UT 143-2 and Pisolithus tinctorius (Pers.) Coker and Crouch isolate PTE were used as the test AM and EM fungus respectively. Results showed that both AM and EM colonisation were very low (1-6%) but even so AM inoculation had a significantly depressive growth effect on seedlings of E. camaldulensis. In both experiments VP was found to be the best medium for both the growth of seedlings and the formation of mycorrhizas. A subsequent experiment using one nutrient concentration (5 mg 1-1 P) and three AM and six EM isolates with VP as the growth medium resulted in colonisation of up to 20% by two AM fungi (Glomus clarum Nicolson and Schenck. isolate BR148-1 and Gigaspora rosea Nicholson and Schenck isolate FL105-5) but none of the EM fungi used in that experiment formed any mycorrhizas. The fourth experiment using three AM inocula (including two from the previous experiment and one from a trap culture of Bangladeshi soil) and four nutrient regimes (Ingestad's 2.5,5.0,10 and 20 mg 1-1P) resulted in 30-50% colonisation; most colonisation was by G clarum BR148-1 and was greater at 10 mg 1-1P (>50%). AM colonisation again resulted in a negative growth response of E. camaldulensis seedlings. In a similar experiment using five isolates of P. tinctorius, only isolate K55 resulted in colonisation >15% most of which occurred at 2.5 mg 1-1 (>25%) while the other isolates resulted in <1% colonisation.
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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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Monteiro, Giselle Gomes. "Desenvolvimento de micorrizas arbusculares em mutantes hormonais de tomateiro (Lycopersicon esculentum cv Micro-Tom)". Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/11/11138/tde-17032011-104351/.
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Os hormônios vegetais etileno e ABA são possíveis reguladores chave do desenvolvimento das micorrizas arbusculares (MAs). O primeiro objetivo deste trabalho foi avaliar o desenvolvimento da MA em mutantes superprodutores e insensíveis ao etileno (epinastic e Never ripe, respectivamente) e verificar se enzimas relacionadas ao sistema de defesa vegetal são reguladas diferencialmente pelo etileno durante o desenvolvimento da simbiose A colonização de raízes de epinastic (epi) por G. clarum foi significativamente reduzida quando comparada com Micro-Tom (MT), além disso, a funcionalidade da simbiose, demonstrada pelo acúmulo de transcritos de LePT4, foi fortemente reduzida quando comparada com MT. Por outro lado, o padrão de colonização e funcionalidade da simbiose no mutante Nr não diferiu de MT. Indução no acúmulo de transcritos de genes que codificam quitinases e enzimas relacionadas ao estresse oxidativo foi observada no mutante epi, enquanto o acúmulo de transcritos de uma -1,3-glucanase foi fortemente induzido no mutante Nr. O segundo objetivo foi verificar se a colonização reduzida observada em mutantes deficientes em ABA é dependente da produção do etileno. Para tanto, mutantes que diferem na deficiência de ABA e produzem diferentes quantidades de etileno (notabilis e sitiens) e o mutante epi foram inoculados com G. clarum e tratados com aminoethoxivinilglicina (AVG), um inibidor de etileno. A colonização intrarradicular de G. clarum nos mutantes epi e notabilis (not) foi significativamente reduzida quando comparada com MT, sendo que o mutante sitiens (sit) foi o menos susceptível à colonização em relação aos demais genótipos. A aplicação de AVG a 10 µM restaurou completamente a colonização em epi, mas não nos mutantes deficientes em ABA. O acúmulo de transcritos de LePT4 confirmou os resultados de colonização. Os genes que codificam enzimas chave na biossíntese do etileno, LeACS2 e LeACO4, foram regulados positivamente pela inoculação com G. clarum, e a restauração do desenvolvimento da MA observada em epi que recebeu AVG, provavelmente envolveu ACC oxidase (LeACO4). O acúmulo de transcritos dos genes que codificam ACC oxidase (LeACO1 e LeACO4) foi induzido significativamente em sit, mostrando que a superprodução de etileno observada neste mutante pode envolver a regulação da ACC oxidase. Por fim, indução no acúmulo de transcritos do gene LeNCED foi observada em todos os genótipos micorrizados e em raízes de epi que receberam AVG, demonstrando que LeNCED é regulado positivamente pela inoculação com G. clarum e que o etileno regula a expressão deste gene. Os resultados demonstram que etileno e ABA estão envolvidos na regulação do desenvolvimento de MA e que etileno modula a expressão de genes relacionados ao sistema de defesa vegetal permitindo o estabelecimento de uma simbiose funcional.The plant hormones ethylene and ABA are probably key developmental regulators of arbuscular mycorrhizae (AM). The first objective of this work was to evaluate the development of MA in overproducing and insensitive mutants to ethylene (epinastic and Never ripe, respectively) and verify if enzymes related to plant defense system are differentially regulated by ethylene during the symbiosis development. The colonization of epinastic (epi) roots by G. clarum was significantly reduced when compared with Micro-Tom (MT), moreover, the functionality of the symbiosis as demonstrated by transcripts accumulation of LePT4, was strongly reduced when compared with MT. Still, the pattern of colonization and functionality of the symbiosis in the Nr mutant did not differ from MT. Induction in the transcripts accumulation of genes encoding chitinase and enzymes related to oxidative stress was observed in epi mutant, whereas transcripts accumulation of -1, 3-glucanase was strongly induced in the Nr mutant. The second objective was to determine whether the reduced colonization observed in mutants deficient in ABA is dependent on ethylene production. For this purpose, mutants that differ in ABA deficiency and produce different amounts of ethylene (notabilis and sitiens) and the epi mutant were inoculated with G. clarum and treated with an ethylene inhibitor called aminoethoxivinilglicin (AVG). The intraradical colonization of G. clarum in epi and notabilis (not) mutants was significantly reduced when compared with MT and sitiens mutant was less susceptible to colonization in comparison with other genotypes. The application of AVG to 10 µM completely restored the colonization in the epi but not in mutants deficient in ABA. The transcripts accumulation of LePT4 confirmed the results of colonization. The genes that encode key enzymes in the biosynthesis of ethylene, LeACS2 and LeACO4, were positively regulated by inoculation with G. clarum and the restoration in the development of MA observed in epi which received AVG probably involved ACC oxidase (LeACO4). Transcripts accumulation of genes that encode ACC oxidase (LeACO1 and LeACO4) were induced significantly in sit showing that overproduction of ethylene in this mutant can involve ACC oxidase. Finally, the induction in the accumulation of gene transcripts LeNCED was observed in all genotypes and mycorrhizal roots of epi which received AVG demonstrating that LeNCED is regulated positively by the inoculation with G. clarum and that ethylene regulates the expression of this gene. Results show that ethylene and ABA are involved in regulating of MA development and ethylene modulates the expression of genes related to the plant defense system allowing the establishment and functionality of the symbiosis.
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Groth, Martin. "Genetic Analysis of Arbuscular Mycorrhiza Development in Lotus japonicus". Diss., lmu, 2010. http://nbn-resolving.de/urn:nbn:de:bvb:19-133396.
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