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1
Eskdale, Jocelyn Wendy. "Management of arbuscular mycorrhizal fungi (AMF) in intensive vegetable production /." St. Lucia, Qld, 2002. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16105.pdf.
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Rozycka, Magdalena. "Use of biochemical and immunological methods to distinguish arbuscular mycorrhizal fungi (AMF)." Thesis, University of Kent, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387019.
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3
Bharadwaj, Dharam Parkash. "The plant - arbuscular mycorrhizal fungi - bacteria - pathogen system : multifunctional role of AMF spore-associated bacteria /." Uppsala : Dept, of Forest Mycology and Pathology, Swedish University of Agricultural Sciences, 2007. http://epsilon.slu.se/200790.pdf.
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Orfanoudakis, Michail. "Symbiotic relationships of Alnus glutinosa with arbuscular mycorrhizal fungi and with Frankia." Thesis, University of South Wales, 2003. https://pure.southwales.ac.uk/en/studentthesis/symbiotic-relationships-of-alnus-glutinosa-with-arbuscular-mycorrhizal-fungi-and-with-frankia(c70364aa-677c-4611-a733-ffd98314a733).html.
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The occurrence in Scotland of arbuscular mycorrhizal fungi (AMF) infective on Alnus glutinosa and the effects on early growth of inoculation of seedlings with AMF and Frankia were investigated. AMF characteristic of G/omiw-like fungi were detected microscopically in A. glutinosa roots from mineral and loam but not from highly organic soils. Both GJomus- and Gigaspora-like fungi were detected only in roots from sandy soils. Glasshouse experiments showed that Glomus and Gigaspora species gave higher colonisation of roots, and were of higher compatibility with the host plant, than Acutelospora or Scutettospora species. Colonisation by AMF increased nodulation by Frankia and vice versa. Inoculation with AMF alone and dual inoculation with Gigaspora rosea and Frankia inhibited growth of young A. glutinosa seedlings. Initially after inoculation, AMF colonisation was poor allowing the host to meet the requirements of both developing symbioses. Mycorrhizal plants inoculated with Frankia 15 days after AMF inoculation, were under significant stress and this delayed the beneficial effects of AMF and Frankia symbiosis. Seedlings compensated for the cost of symbiosis by developing a larger, leafy shoot in a period of 25-30 days after AMF inoculation, with or with out, Frankia nodulation. A significant increase in root length and branching detected after inoculation with AMF and Frankia must impose additional energy requirements. However, the stimulation of lateral root branching that follows AMF colonisation may facilitate nutrient uptake, thus helping the plant to overcome the disadvantages of early retardation of shoot growth. Competition with adjacent plant species for below ground space may also be enhanced thus facilitating competition for growing space with other plant species. These factors may be part of a strategy that assists the survival of very young seedlings in the field. The data obtained suggest that delaying Frankia inoculation for 3-4 weeks after inoculation with selected AMF should improve the production in Scottish nurseries of robust, well nodulated and mycorrhizal seedlings.
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Rodriguez, Alia. "Studies on the species concept in arbuscular mycorrhizal fungi (AMF) using morphological, biochemical and molecular analyses." Thesis, University of Kent, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369670.
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Els, Yolandi. "The implementation of selected technologies to enhance the restoration of indigenous tree species in the deforested riparian areas in the Mapungubwe National Park, South Africa : a case study / Yolandi Els." Thesis, North-West University, 2010. http://hdl.handle.net/10394/4571.
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Stretches of forest along the Limpopo and Shashe Rivers have been classified as a unique forest type
in the vegetation of South Africa and are considered as being "critically endangered" by the South
African Biodiversity Institute. Roughly 400 hectares of this riverine forest area inside the western
section of the Mapungubwe National Park (MNP), a UNESCO World Heritage site, were deforested
and therefore degraded due to previous agricultural cultivation practices. Given the extent of forest
degradation that has occurred, the restoration of this area by means of the re–vegetation of indigenous
trees to its former composition is one of the objectives of the MNP's management plan. The successful
establishment of tree seedlings, especially in semi–arid systems, is however presented with a wide
range of constraints and limiting conditions, which often result in very high mortality rates during
restoration projects. An experimental exclosure, as identified by South African National Parks
(SANParks), was therefore fenced off inside the degraded old lands to act as a demonstration site for
the restoration of indigenous trees.
A pilot study conducted in 2006, involved the transplantation of selected indigenous tree species with
the aim of evaluating suitable re–vegetation technologies. The research contained in this dissertation
was also conducted inside the experimental exclosure, where recommendations derived from the pilot
study were evaluated, including the assessment of new re–vegetation technologies to enhance the
establishment of the indigenous trees. This study was therefore a follow–up project which involved
both field– and greenhouse trials. Seedlings of the following species were either transplanted into the
experimental exclosure (field trial) or cultivated inside a controlled environment in the greenhouse at
the North–West University: Acacia xanthophloea Benth. (fever tree), Berchemia discolor (Klotzsch)
Hemsl. (brown–ivory), Combretum imberbe Wawra (leadwood), Faidherbia albida (Delile) A. Chev.
(ana tree), Philenoptera violacea (Klotzsch) Schrire (apple–leaf), Salvadora australis Schweick.
(narrow–leaved mustard tree) and Xanthocercis zambesiaca (Baker) Dumaz–le–Grand (nyala tree).
During the follow–up study the effects of various enhancement treatments were tested regarding the
survival, growth and physiological performance of seedlings in both the field– and greenhouse trials.
The enhancement treatments consisted of the addition of compost and indigenous arbuscular
mycorrhizal fungi (AMF). In addition, seedlings transplanted during the pilot study, which did not
include enhancement treatments, were also monitored for establishment and growth. The potential use
of established Acacia tortilis Hayne trees to facilitate growth and establishment and to act as "nursing
plants", was also assessed. In addition, various pre–sowing treatments were also applied to seeds of
selected tree species in the greenhouse to assess the germination rate.
The survivorship and growth of seedlings in both the field– and greenhouse trial were determined by
using three growth parameters, namely "stem diameter at the base", "stem diameter 30 cm from the base", and "height of the tree in its natural growth form". Chlorophyll fluorescence induction (JIP test)
was measured on seedlings in both trials, using the multi–parametric expression, namely performance
index (PIABS), as a measure of the overall vitality of the plants of each species–treatment combination.
Physical and chemical analyses were carried out on the soil inside the experimental exclosure. Basic
descriptive statistics were used to analyse seedling survival and germination rates, and a two–way
analysis of variance (ANOVA) was used to determine the statistical significant effects of the various
enhancement treatments on diameter growth in each species (p < 0.05). Fluorescence data were
processed using the Biolyzer software and significant effects in each species were determined using
the Student's t–test (p < 0.05). Multivariate data ordinations using the CANOCO package were used to
determine the differences in soil types inside the experimental exclosure.
Moisture stress due to transplantation shock, competition with dense grass cover and herbivory,
resulted in an overall 55.8% seedling survival rate and negative stem diameter growth for transplanted
seedlings in the field. In comparison, seedlings cultivated in the greenhouse had much higher survival
rates and showed positive stem diameter growth. Most species in the greenhouse showed higher
growth rates and significantly higher vitality values when planted with enhancement treatments. The
responses of transplanted seedlings to the enhancement treatments were very species–specific in the
field trials. Based on these results, it was concluded that the enhancement treatments were beneficial
with regard to the establishment and growth of most of the species. The beneficial effect was however
cancelled out by the various abiotic and biotic factors encountered in the natural environment.
Seedlings transplanted in the understory of established pioneer A. tortilis trees had much lower
survival rates as the extensive root system of A. tortilis most likely out–competed the transplanted
seedlings for moisture and nutrients. Many seedlings were also predated by insects or small mammals
which reduced the growing potential. The germination trials recorded the highest germination rates for
most species when germinated in the compost–containing treatments. These trials also indicated that
all of the investigated species showed higher survival rates when pre–sowing treatments, such as
soaking, mechanical scarification and removing the seed from fruit, were applied. Various
recommendations emphasising long–term monitoring, proper maintenance and after–care of future
restoration efforts are made. These include experimental layout of exclosure plots and pretransplantation
treatments of seedlings while cultivated in the nursery. During this study, the
experimental exclosure was also used as a demonstration site for training and capacity building for
SANParks personnel and students from academic institutions.<br>Thesis (M.Sc. (Environmental Science))--North-West University, Potchefstroom Campus, 2011.
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Li, Hui. "The role of arbuscular mycorrhizal fungi (AMF) on the tolerance and accumulation of arsenic in rice (Oryza sativa L.)." HKBU Institutional Repository, 2012. https://repository.hkbu.edu.hk/etd_ra/1409.
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Boddington, Claire L. "Studies on the ecological roles of arbuscular mycorrhizal fungi (AMF) from different genera in the growth and development of tropical plants." Thesis, University of Kent, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.264575.
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Russomanno, Olga Maria Ripinskas [UNESP]. "Influência de fungos micorrízicos arbusculares associa- dos ou não a Fusarium oxysporum Schecht. sobre plantas de alecrim (Rosmarinus officinalis L.) e manjericão (Ocimum basilicum L.)." Universidade Estadual Paulista (UNESP), 2006. http://hdl.handle.net/11449/105420.
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russomanno_omr_dr_botfca.pdf: 951502 bytes, checksum: 65ab95dd8d5f795650c7b83e6aa5b10f (MD5)<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)<br>Secretaria Agricultura<br>O objetivo do presente trabalho visou avaliar a influência dos FMA Glomus etunicatum Becker & Gerd. e Glomus clarum Nicol. & Schenck, no desenvolvimento de plantas de alecrim e manjericão, bem como verificar a capacidade destas plantas micorrizadas em superar os danos causados pelo fungo Fusarium oxysporum Schecht. Plantas de alecrim (Rosmarinus officinalis L.) e de manjericão (Ocimum basilicum L.) foram inoculadas, separadamente, com G. etunicatum e G. clarum, em casa de vegetação, com temperatura de 26 l 20C e luminosidade de 3000 Lux. Utilizou-se substrato autoclavado composto por uma parte de areia e uma de terra; o inóculo constou de esporos [500 esporos de G.etunicatum (50 mL-1) de solo e 700 esporos de G.clarum (50 mL-1) de solo] e ainda fragmentos de raízes infectadas e micélio. Em cada tipo de planta inoculada foram avaliadas as seguintes variáveis: altura das plantas (AP), peso da matéria seca da parte aérea (MSPA), peso da matéria fresca das raízes (MFR), esporulação (E), colonização radicular (CR) e teor de macro e micronutrientes no substrato e nas plantas (TMm). Foi avaliada também a influência de G. etunicatum e G. clarum no controle de F. oxysporum em plantas de alecrim e manjericão. A inoculação do patógeno (concentração de 5 x 103 esporos mL-1) foi realizada, separadamente, em plantas de alecrim e de manjericão com 90 dias de micorrização (5 vasos com G. etunicatum e 5 vasos com G. clarum) e ainda plantas testemunhas, não micorrizadas (5 vasos). No alecrim, G. clarum mostrou-se significativamente mais eficiente do que G. etunicatum em AP, MSPA e E; por outro lado, G. clarum apresentou CR menor do que G. etunicatum. Em relação às plantas testemunha, G. clarum diferiu significativamente destas em 2 todos as variáveis analisadas, porém G. etunicatum não diferiu estatisticamente das plantas testemunha em AP e MSPA. No manjericão, em relação... .<br>The purpose of the present work had the objective of evaluating the influence of AMF Glomus etunicatum Becker & Gerd. and Glomus clarum Nicol. & Schenck on the rosemary and basil plants development and also concerning the capacity of the mycorrhizal plants in resisting the wilt caused by Fusarium oxysporum Schecht. For that, rosemary (Rosmarinus officinalis L.) and basil (Ocimum basilicum L.) plants were previously inoculated with G. etunicatum and G. clarum in greenhouse under the temperature of 26 l 20C and luminosity of 3000 Lux. The soil was sterilized and composed by one part of sand and one part of earth. The inoculum was composed by the fungi spores [500 spores of G. etunicatum in (50 mL-1) soil and 700 spores of G. clarum in (50 mL-1) soil] and micelium and roots fragments infected by the AMF. In each plant inoculated the following variables were evaluated: plant height (PH), plant dry weigt (PDW), roots fresh weight (RFW), sporulation rate (SR), root mycorrhizal percentage (RMP) and macro and micronutrients level (MmL) present in the plants and in the soil. The G. clarum and G. etunicatum influence in the control of F. oxysporum wilt in both plants was also evaluated. The inoculation of the pathogen (5x103 spores mL-1) was separatety realized in the rosemary and basil plants after 90 days of the mycorrhization (5 pots of G. clarum and 5 pots of G. etunicatum); the control was also composed by 5 pots without mycorrhization. In the rosemary, G. clarum was significantely more efficient than G. etunicatum in the variables PH, RFW and SR; although G. clarum 4 presented RMP smaller than G. etunicatum. In relation to the control, G. clarum was significably better to the plants in all the variables, although G. etunicatum do not differed statistically for the control plants in PH and PDW. For basil in all the analised variables G. clarum differed statistically from G. etunicatum and was similar to the control treatment in all the variables.
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Sekoele, Mohlapa Junior. "The role of indigenously-associated abuscular mycorrhizal fungi as biofertilisers and biological disease-control agents in subsistence cultivation of morogo / Mohlapa Junior Sekoele." Thesis, North-West University, 2006. http://hdl.handle.net/10394/1263.
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The study examined interactions between morogo plants, arbuscular mycorrhizal fungi (AMF)
and Fusarium species. Morogo refers to traditional leafy vegetables that, together with maize
porridge, are dominant staple foods in rural areas of the Limpopo Province such as the Dikgale
Demographic Surveillance Site (DDSS). Morogo plants grow either as weeds (often among
maize), occur naturally in the field or are cultivated as subsistence crops by rural communities.
Botanical species of morogo plants consumed in the DDSS were determined. Colonisation of
morogo plant roots by AMF and Fusarium species composition in the immediate soil
environment were investigated in four of eight DDSS subsistence communities, Isolated AMF
were shown to belong to the genera Acaulospora and Glomus. Twelve Fusarium species were
isolated from soil among which Fusariurn verticilliodes and Fusarium proliferaturn occurred
predominantly.
Greenhouse pot trials were conducted to examine the effect of AMF on morogo plant growth
(cowpea; Mgna unguiculata) and Fusarium proliferatum levels in soil, Interaction between
plants and AMF, as well as tripartite interactions of cowpea plants, AMF and Fusarium
proliferatum were investigated. Non-inoculated cowpea plants served as controls for the
following inoculations of cowpea in pots: (i) Fusarium proliferatum; (ii) commercial AMF from
Mycoroot (PTY) Ltd. (a mixture of selected indigenous Glomus spp referred to commercial
AMF for the purpose of this study); (iii) indigenous AMF obtained from DDSS soil (referred to
iocal AMF for the purpose of this study); (iv) commercial AMF plus Fusarium proliferatum; (v)
local AMF plus Fusariurn proliferatum.
Results showed reduced root colonization by local as well as commercial AMF when Fusarium
proliferatum were present. Local AMF significantly enhanced cowpea growth while commercial
AMF apparently reduced the level of Fusarium proliferatum in the rhizosphere and surrounding
soil. Results suggest that AMF may have potential as biological growth enhancers and
bioprotective agents against Fusarium proliferatum.<br>Thesis (M. Environmental Science (Water Science))--North-West University, Potchefstroom Campus, 2007.
11
Russomanno, Olga Maria Ripinskas 1952. "Influência de fungos micorrízicos arbusculares associa- dos ou não a Fusarium oxysporum Schecht. sobre plantas de alecrim (Rosmarinus officinalis L.) e manjericão (Ocimum basilicum L.) /." Botucatu : [s.n.], 2006. http://hdl.handle.net/11449/105420.
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Orientador: Marli Teixeira de Almeida Minhoni<br>Banca: Nilton Luiz de Souza<br>Banca: Edson Luiz Furtado<br>Banca: Mario Barreto Figueiredo<br>Banca: Sandra Farto Botelho Turfem<br>Resumo: O objetivo do presente trabalho visou avaliar a influência dos FMA Glomus etunicatum Becker & Gerd. e Glomus clarum Nicol. & Schenck, no desenvolvimento de plantas de alecrim e manjericão, bem como verificar a capacidade destas plantas micorrizadas em superar os danos causados pelo fungo Fusarium oxysporum Schecht. Plantas de alecrim (Rosmarinus officinalis L.) e de manjericão (Ocimum basilicum L.) foram inoculadas, separadamente, com G. etunicatum e G. clarum, em casa de vegetação, com temperatura de 26 l 20C e luminosidade de 3000 Lux. Utilizou-se substrato autoclavado composto por uma parte de areia e uma de terra; o inóculo constou de esporos [500 esporos de G.etunicatum (50 mL-1) de solo e 700 esporos de G.clarum (50 mL-1) de solo] e ainda fragmentos de raízes infectadas e micélio. Em cada tipo de planta inoculada foram avaliadas as seguintes variáveis: altura das plantas (AP), peso da matéria seca da parte aérea (MSPA), peso da matéria fresca das raízes (MFR), esporulação (E), colonização radicular (CR) e teor de macro e micronutrientes no substrato e nas plantas (TMm). Foi avaliada também a influência de G. etunicatum e G. clarum no controle de F. oxysporum em plantas de alecrim e manjericão. A inoculação do patógeno (concentração de 5 x 103 esporos mL-1) foi realizada, separadamente, em plantas de alecrim e de manjericão com 90 dias de micorrização (5 vasos com G. etunicatum e 5 vasos com G. clarum) e ainda plantas testemunhas, não micorrizadas (5 vasos). No alecrim, G. clarum mostrou-se significativamente mais eficiente do que G. etunicatum em AP, MSPA e E; por outro lado, G. clarum apresentou CR menor do que G. etunicatum. Em relação às plantas testemunha, G. clarum diferiu significativamente destas em 2 todos as variáveis analisadas, porém G. etunicatum não diferiu estatisticamente das plantas testemunha em AP e MSPA. No manjericão, em relação... (Resumo completo, clicar acesso eletrônico abaixo).<br>Abstract: The purpose of the present work had the objective of evaluating the influence of AMF Glomus etunicatum Becker & Gerd. and Glomus clarum Nicol. & Schenck on the rosemary and basil plants development and also concerning the capacity of the mycorrhizal plants in resisting the wilt caused by Fusarium oxysporum Schecht. For that, rosemary (Rosmarinus officinalis L.) and basil (Ocimum basilicum L.) plants were previously inoculated with G. etunicatum and G. clarum in greenhouse under the temperature of 26 l 20C and luminosity of 3000 Lux. The soil was sterilized and composed by one part of sand and one part of earth. The inoculum was composed by the fungi spores [500 spores of G. etunicatum in (50 mL-1) soil and 700 spores of G. clarum in (50 mL-1) soil] and micelium and roots fragments infected by the AMF. In each plant inoculated the following variables were evaluated: plant height (PH), plant dry weigt (PDW), roots fresh weight (RFW), sporulation rate (SR), root mycorrhizal percentage (RMP) and macro and micronutrients level (MmL) present in the plants and in the soil. The G. clarum and G. etunicatum influence in the control of F. oxysporum wilt in both plants was also evaluated. The inoculation of the pathogen (5x103 spores mL-1) was separatety realized in the rosemary and basil plants after 90 days of the mycorrhization (5 pots of G. clarum and 5 pots of G. etunicatum); the control was also composed by 5 pots without mycorrhization. In the rosemary, G. clarum was significantely more efficient than G. etunicatum in the variables PH, RFW and SR; although G. clarum 4 presented RMP smaller than G. etunicatum. In relation to the control, G. clarum was significably better to the plants in all the variables, although G. etunicatum do not differed statistically for the control plants in PH and PDW. For basil in all the analised variables G. clarum differed statistically from G. etunicatum and was similar to the control treatment in all the variables.<br>Doutor
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Bragalini, Claudia. "Impact des changements globaux sur la diversité des champignons du sol : approche en génomique environnementale." Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10040/document.
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La thèse porte sur l'impact de changements globaux sur la diversité taxonomique et fonctionnelle des champignons du sol. L'impact de l'intensification agricole sur les champignons mycorhiziens à arbuscules a été évalué par comparaison des communautés fongiques présentes sur des sites Européens soumis à différents niveaux d'intensification dans l'usage des terres. La diversité taxonomique a été appréciée par « métabarcoding » sur l'ADN de sol. L'effet de l'intensification apparait lié au contexte local. L'adaptation aux conditions environnementales locales ainsi que des processus stochastiques semblent jouer un rôle important dans le modelage des communautés fongiques. L'effet des changements climatiques en zone Méditerranéenne a été évalué sur les sols d'un site expérimental où une réduction de la pluviométrie a été établie. Nous avons réalisé une approche de séquençage haut débit de 4 familles géniques, 3 d'entre elles codant des enzymes actives sur la biomasse végétale. La date d'échantillonnage, et non la réduction de pluviométrie, a un fort impact sur la diversité béta. Nous formulons l'hypothèse que les communautés fongiques présentes sur des sites soumis à de fortes et récurrentes variations climatiques ont développé des stratégies adaptatives leur conférant une résistance à des variations d'une plus forte intensité. Enfin, une technique indépendante de la PCR (« solution hybrid selection capture ») a été adaptée pour étudier la diversité fonctionnelle des communautés eucaryotes à partir d'ARN de sol. Cette approche, testée sur une famille génique codant des endoxylamases a permis l'isolement d'ADNc complets produisant des enzymes fonctionnelles dans la levure<br>In this thesis we assessed the impact of two drivers of global change on the taxonomic and functional diversity of soil fungi. The impact of changes in land use on symbiotic Arbuscular Mycorrhizal Fungi (AMF) was evaluated comparing AMF communities from European sites with different levels of land use intensification. AMF taxonomic diversity was assessed by metabarcoding using soil-extracted DNA. The effect of land use intensification was found to be context-dependent. Adaptation to local environmental conditions and stochastic processes may play important roles in shaping these communities. The effect of climate change in the Mediterranean area was assessed in soils collected from an experimental forest where a rainfall reduction experiment had been established. A parallel high-throughput metabarcoding on soil-extracted RNA was performed on four transcribed fungal genes, 3 of them encodind enzymes involved in plant biomass degradation. Analyses indicated that sampling time had a strong impact on beta-diversity indices, while rainfall reduction had not. We hypothesized that microbial communities present in environments which naturally experience strong and recurrent climatic variations have developed adaptive strategies to cope with these variations and may be to some extent resistant to further climate changes. Finally, an original PCR-independent technique (“solution hybrid selection capture”) was adapted to study the functional diversity of eukaryotic microbial communities using soil RNA. The approach, tested on an endoxylanase gene family, allowed the efficient recovery of full-length cDNA which could be expressed as functional proteins in yeast
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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.<br>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.<br>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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Kang, Hyun-Joo. "The basic genetics of arbuscular mycorrhizal fungi." [Bloomington, Ind.] : Indiana University, 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3358927.
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Thesis (Ph.D.)--Indiana University, Dept. of Biology, 2009.<br>Title from PDF t.p. (viewed on Feb. 8, 2010). Source: Dissertation Abstracts International, Volume: 70-05, Section: B, page: 2653. Adviser: James D. Bever.
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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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Roberts, Karl J. Anderson Roger C. "An examination of the interactions between garlic mustard (Alliaria petiolata (Beib.) Cavara & Grande) and vesicular-arbuscular mycorrhizal (VAM) fungi." Normal, Ill. Illinois State University, 1997. http://wwwlib.umi.com/cr/ilstu/fullcit?p9807487.
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Thesis (Ph. D.)--Illinois State University, 1997.<br>Title from title page screen, viewed June 7, 2006. Dissertation Committee: Roger C. Anderson (chair), Anthony E. Liberta, Mathew J. Nadakavukaren, Derek A. McCracken, R. Michael Miller. Includes bibliographical references (leaves 68-77) and abstract. Also available in print.
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Bennett, Alison. "Mechanisms underlying complex interactions between plants, herbivores, and arbuscular mycorrhizal fungi." [Bloomington, Ind.] : Indiana University, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:3204279.
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Thesis (Ph.D.)--Indiana University, Dept. of Biology, 2006.<br>Source: Dissertation Abstracts International, Volume: 67-01, Section: B, page: 0048. Adviser: James D. Bever. "Title from dissertation home page (viewed Feb. 9, 2007)."
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Mangan, Scott A. "Importance of the species composition of arbuscular mycorrhizal fungi to tropical tree seedlings." [Bloomington, Ind.] : Indiana University, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3243802.
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Thesis (Ph.D.)--Indiana University, Dept. of Biology, 2007.<br>Title from PDF t.p. (viewed Nov. 18, 2008). Source: Dissertation Abstracts International, Volume: 67-12, Section: B, page: 6842. Adviser: James D. Bever.
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Soti, Pushpa Gautam. "Influence of Soil Biogeochemical Properties on the Invasiveness of Old World Climbing Fern (Lygodium microphyllum)." FIU Digital Commons, 2013. http://digitalcommons.fiu.edu/etd/960.
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The state of Florida has one of the most severe exotic species invasion problems in the United States, but little is known about their influence on soil biogeochemistry. My dissertation research includes a cross-continental field study in Australia, Florida, and greenhouse and growth chamber experiments, focused on the soil-plant interactions of one of the most problematic weeds introduced in south Florida, Lygodium microphyllum (Old World climbing fern). Analysis of field samples from the ferns introduced and their native range indicate that L microphyllum is highly dependent on arbuscular mycorrhizal fungi (AMF) for phosphorus uptake and biomass accumulation. Relationship with AMF is stronger in relatively dry conditions, which are commonly found in some Florida sites, compared to more common wet sites where the fern is found in its native Australia. In the field, L. microphyllum is found to thrive in a wide range of soil pH, texture, and nutrient conditions, with strongly acidic soils in Australia and slightly acidic soils in Florida. Soils with pH 5.5 - 6.5 provide the most optimal growth conditions for L. microphyllum, and the growth declines significantly at soil pH 8.0, indicating that further reduction could happen in more alkaline soils. Comparison of invaded and uninvaded soil characteristics demonstrates that L. microphyllum can change the belowground soil environment, with more conspicuous impact on nutrient-poor sandy soils, to its own benefit by enhancing the soil nutrient status. Additionally, the nitrogen concentration in the leaves, which has a significant influence in the relative growth rate and photosynthesis, was significantly higher in Florida plants compared to Australian plants. Given that L. microphyllum allocates up to 40% of the total biomass to rhizomes, which aid in rapid regeneration after burning, cutting or chemical spray, hence management techniques targeting the rhizomes look promising. Over all, my results reveal for the first time that soil pH, texture, and AMF are major factors facilitating the invasive success of L. mcirophyllum. Finally, herbicide treatments targeting rhizomes will most likely become the widely used technique to control invasiveness of L. microphyllum in the future. However, a complete understanding of the soil ecosystem is necessary before adding any chemicals to the soil to achieve a successful long-term invasive species management strategy.
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Kelly, Charlene N. "The diversity of arbuscular mycorrhizal fungi functional and ecological responses to stressful soil conditions /." Morgantown, W. Va. : [West Virginia University Libraries], 2004. https://etd.wvu.edu/etd/controller.jsp?moduleName=documentdata&jsp%5FetdId=3374.
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Thesis (M.S.)--West Virginia University, 2004.<br>Title from document title page. Document formatted into pages; contains vii, 57 p. : ill. Vita. Includes abstract. Includes bibliographical references.
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Merryweather, James. "Function and diversity of the arbuscular mycorrhiza in Bluebell, Hyacinthoides non-scripta (L.) Chouard ex Rothm." Thesis, University of York, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387544.
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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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Gamper, Hannes. "Effects of elevated atmospheric CO₂ on arbuscular mycorrhizal fungi in an agricultural model grassland /." Zürich, 2004. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=15682.
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Clark, Naomi M. "Seasonal belowground plant responses to elevated CO₂ in the Mojave Desert root respiration and arbuscular mycorrhizal fungi dynamics /." abstract (free order & download UNR users only), 2007. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1447588.
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Krüger, Manuela [Verfasser]. "Molecular phylogeny, taxonomy & evolution of Glomeromycota : DNA-based characterization and identification of arbuscular mycorrhizal fungi / Manuela Krüger." Saarbrücken : Südwestdeutscher Verlag für Hochschulschriften, 2012. http://d-nb.info/1023426722/34.
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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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Viereck, Nanna. "In vivo 31P NMR spectroscopy for the study of P pools and their dynamics in arbuscular mycorrhizal fungi /." Roskilde : Roskilde University, Department of Life Sciences and Chemistry; Risø National Laboratory, Plant Research Department, 2002. http://rubdoc.ruc.dk/epublisher/document.asp?func=show&id=103&type=0&service=01.
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Scharnagl, Klara. "The Effects of Arbuscular Mycorrhizal Fungi on four Legume Hosts in South Florida Pine Rockland Soils." FIU Digital Commons, 2013. http://digitalcommons.fiu.edu/etd/922.
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This study addressed the effects of salinity and pot size on the interaction between leguminous plant hosts and arbuscular mycorrhizal fungi in four pine rockland soils using a shade house trap-plant experiment. Little is known about the belowground diversity of pine rocklands and the interactions between aboveground and belowground biota – an increased understanding of these interactions could lead to improved land management decisions, conservation and restoration efforts. Following twelve weeks of growth, plants were measured for root and shoot dry biomass and percent colonization by arbuscular mycorrhizal fungi. Overall, arbuscular mycorrhizal fungi had positive fitness effects on the four legume species (Cajanus cajan, Chamaecrista fasciculata, Tephrosia angustissima and Abrus precatorius), improving their growth rate, shoot and root biomass; pot size influenced plant-fungal interactions; and percent colonization by arbuscular mycorrhizal fungi was influenced by soil type as well as salinity.
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Pinto, José Tomás Madeira. "the role of arbuscular mycorrhiza in the biological control of Fusarium oxysporum in tomato." Master's thesis, Universidade de Évora, 2020. http://hdl.handle.net/10174/29043.
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The functional diversity amongst arbuscular mycorrhizal fungi (AMF) is scientifically
recognized, yet not practically exploited as the understanding of the interactions
between different crops and their rhizosphere microbiome is still very narrow.
Following the strategy developed by the team that guided this dissertation, this work
was aimed to test different plants (Lolium rigidum and Ornithopus compressus) as
hosts to develop AMF extraradical mycelium (ERM) for an early colonization of tomato
plants and to evaluate their role in the bioprotection against Fusarium oxysporum f. sp
radicis-lycopersici.
Although L. rigidum promoted a greater AM colonization of tomato plants, O.
compressus was most beneficial, resulting in a reduced disease incidence and a higher
dry weight in the tomato plants. The disease incidence was also lower in undisturbed
soil (intact ERM) conditions, confirming the importance of an early AM colonization,
accomplished through an intact ERM, in granting bioprotection to the tomato plants; O papel das micorrizas arbusculares no controlo biológico
de Fusarium oxysporum em tomate
Resumo:
Apesar da diversidade funcional entre fungos micorrízicos arbusculares (AMF) estar
cientificamente descrita, o conhecimento do microbioma rizosférico das culturas é
ainda bastante limitado e a sua utilização em termos práticos está ainda longe de ser
uma realidade.
Seguindo a estratégia desenvolvida pela equipa que acolheu esta dissertação, este
trabalho visou testar plantas (Lolium rigidum e Ornithopus compressus) como
hospedeiros para desenvolver micélio extraradicular (ERM) de AMF, para obter uma
colonização precoce nos tomateiros e avaliar o seu papel na bioprotecção contra
Fusarium oxysporum f. sp. radicis-lycopersici.
Apesar do L. rigidum ter promovido uma colonização micorrízica superior nos
tomateiros, o O. compressus foi mais benéfico, resultando numa redução de incidência
da doença e num aumento do peso seco dos tomateiros. A incidência da doença foi
menor em condições de solo não perturbado (ERM intacto), confirmando a importância
da colonização micorrízica precoce, obtida a partir de ERM intacto, no efeito
bioprotector a tomateiros.
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SCHAEFER, Holger Christian. "Production and decomposition dynamics of extraradical hyphae of arbuscular mycorrhizal fungi in warm-temperate forests of Chamaecyparis obtusa (hinoki cypress)." Kyoto University, 2019. http://hdl.handle.net/2433/243322.
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Kleikamp, Bernd. "Studies on arbuscular mycorrhiza (AM) in the Alentejo (Portugal) using pea mutants resistant to AM fungi as a control tool for field conditions." [S.l. : s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=968468055.
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Okiobe, Simon Thierry [Verfasser]. "Potential effects of arbuscular mycorrhiza fungi on denitrification potential activity and nitrous oxide (N2O) emissions from a fertile agricultural soil. / Simon Thierry Okiobe." Berlin : Freie Universität Berlin, 2019. http://d-nb.info/1205317724/34.
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Wen, Kui. "Down-regulation of defense gene transcripts of Rhizoctonia solani-infected bean seedlings in response to inoculation with non-pathogenic fungi." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=80895.
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In this study, we have demonstrated that inoculation of bean seeds with non-pathogenic binucleate Rhizoctonia (np-BNR) at sowing protected bean seedlings from infection of R. solani. Using quantitative real-time RT-PCR (QRT-PCR), transcript levels of defense genes encoding 1,3-beta-glucanase (GLUC), phenylalanine ammonia-lyase (PAL), chalcone synthase (CHS) in one-week old bean seedlings was monitored during np-BNR and R. solani interaction. The results revealed that protection effect of np-BNR correspond to a systemic suppression of these three defense genes' expression from significant higher level elicited by R. solani to the level of non-infected plants. This indicates that bio-protection by np-BNR isolates is not correlated to activation of these three defense genes' expression. Similar suppression was achieved for pre-colonization of bean seedlings with arbuscular mycorrhizal (AM) Glomus introradices on GLUC gene expression, although the AM fungus did not significantly reduce rot symptoms. Possible mechanisms implicated in down-regulation during plant-pathogen and np-BNR or AM interaction are discussed.
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Azevedo, Lucas Carvalho Basilio de. "Comunidades de fungos micorrízicos arbusculares no solo e raízes de cana-de-açúcar." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/11/11140/tde-11032009-084948/.
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Os fungos micorrízicos arbusculares (FMAs, filo Glomeromycota) formam associações simbióticas com a maioria das plantas vasculares. Normalmente, as hifas dos FMAs crescem no solo e colonizam o interior das raízes. No entanto, não se sabe se as espécies mais abundantes detectadas no solo, por meio da identificação com base na morfologia dos esporos assexuais, são também as mais abundantes no interior das raízes, devido às dificuldades para a identificação dos FMAs com base nas estruturas intrarradiculares. Assim, o objetivo do presente trabalho foi avaliar a estrutura da comunidade de FMAs em cana-de-açúcar sob dois manejos de colheita por meio da identificação das espécies que estão no solo na forma de esporos assexuais e aquelas que estão nas raízes usando o sequenciamento de clones do gene rRNA 18S. Amostras de solo e raízes de cana-de-açúcar de três variedades e dois manejos de colheita: SEM QUEIMA prévia e COM QUEIMA prévia à colheita, foram coletadas em um experimento localizado no município de Novo Horizonte, SP. Foram utilizadas três abordagens para a identificação dos FMAs no interior das raízes: emprego de (1) iniciador específico para fungos em geral, (2) iniciador específico para FMAs e (3) iniciadores específicos para grupos de FMAs. O número de esporos por 50 g de solo, a riqueza de espécies observada e estimada e a diversidade de esporos não diferiram significativamente entre os manejos SEM QUEIMA e COM QUEIMA. Efeitos significativos de variedades de cana-de-açúcar ou na interação dos fatores manejo e variedade não foram observados. A análise de ordenação com base nos esporos identificados também não indicou separação das amostras em função dos tratamentos. Entretanto, plantas do tratamento sob manejo SEM QUEIMA apresentaram as maiores taxas de colonização micorrízica arbuscular, quando comparadas às plantas do tratamento sob manejo COM QUEIMA. Esses dados indicam que a taxa de colonização micorrízica arbuscular é um indicador mais sensível à mudança de manejo de colheita da cana-de-açúcar do que os outros indicadores avaliados. Após a extração de DNA das raízes, o uso dos iniciadores específicos para fungos em geral, para FMAs e iniciadores específicos para grupo de FMAs não resultou em sequências de Glomeromycota. Mesmo assim, a comunidade de fungos associados às raízes detectada por sequenciamento do gene rRNA 18S foi avaliada. Os resultados indicam que a estrutra da comunidade fúngica associada às raízes de cana-de-açúcar diferiu significativamente entre os manejos de colheita SEM QUEIMA e COM QUEIMA prévia, apesar de não haver diferenças na riqueza e índices de diversidade de unidades taxonômicas operacionais observadas. Em geral, estudos adicionais devem ser feitos para otimizar as condições para amplificação do gene rRNA 18S de FMAs para melhor entender a ecologia dos mesmos.<br>Arbuscular mycorrhizal fungi (AMF, Glomeromycota) form mutualistic symbioses with most land plants. AMF hypha generally grow through the soil and colonize the cortical tissue of the plant roots. However, it is not known whether the most abundant species in the soil, determined based on the morphology of asexual spores are the most abundant inside the roots, due the difficulties in identifying AMF based on intraradical structures. Therefore, the aim of this study was to evaluate the AMF community structure in sugarcane rhizosphere and roots under two harvesting managements, based on spores in the soil and sequencing of 18S rRNA gene clones, respectively. Sugarcane rhizosphere soil and roots were sampled from three varieties, under two harvesting managements: without pre-harvesting burning and with pre-harvesting burning, at an experimental field located in Novo Horizonte (São Paulo, Brazil). Three approaches were used to identify AMF inside the roots: (1) using fungi-specific primers, (2) using AMF-specific primers and (3) using AMF group-specific primers. The number of spores in the soil, the observed and estimated species richness and the diversity of AMF spores in the treatments without and with pre-harvesting burning were not statistically different. Statistically significant effects of sugarcane varieties or the interaction of the factors Harvesting Management and Varieties were not observed. Ordination analysis based on the identified spores did not show clustering by treatments. However, intraradical root colonization rates were higher in the treatment without pre-harvesting burning, as compared to the treatment with pre-harvesting burning. These data indicate that intraradical colonization rate may be used as a more sensitive indicator of environmental changes due to harvesting management, as compared to the other indicators evaluated. The use of fungi-specific, AMF-specific and AMF group-specific primers did not allow the detection of Glomeromycota in the sugarcane roots sampled from the field experiment. Nonetheless, the fungal communities associated with sugarcane roots detected by 18S rRNA gene clone sequencing were evaluated. The results indicate that the fungal communities associated with sugarcane roots from the treatments without and with pre-harvesting burning were statistically different, even though no differences in operational taxonomic unit richness and diversity indices were observed. In general, additional studies are necessary to optimize AMF 18S rRNA gene amplification for a better understanding of their ecology.
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Detmann, Kelly da Silva Coutinho. "Fungos micorrízicos arbusculares e endofíticos do tipo Dark Septate em plantas nativas de Cerrado." Universidade Federal de Viçosa, 2007. http://locus.ufv.br/handle/123456789/4282.
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Previous issue date: 2007-08-03<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior<br>The high acidity, the intense intemperism, and high aluminum content are limiting factors to plant development in Brazilian Cerrado Upon abiotic stress conditions the association with mycorrhizal fungi can assist the host plant in absorbing nutrients and water from soil. The high availability of these elements to the host plant improved by arbusculares mycorrhizal fungi (AMF) is determinant in plant survival and structuring of plant ecosystems. The presence of dark septate entophytic fungi in plant roots is another type of symbiotic association related to abiotic conditions such as low humid and day length. The reduced number of publications about these associationsin cerrado species is mainly a function of edaphic conditions and root structural characteristics of native species which difficult the in loco studies of these characters. In this work, it was aimed to study the association between AMF and cerrado native species. It was evaluated and adapted methods for fungal structures observation in symbiosis with Annonaceae, Anacardiaceae, Leguminosae, Melastomataceae, Myrsinaceae, Myrtaceae and Rubiaceae families, which were collected during dry season on senso strictu Cerrado in Floresta Nacional (FLONA) in the municipal district of Paraopeba, Minas Gerais State. Root samples were submitted to three protocols for fungal structures observationg. All evaluated species were colonized by AMF and dark septate fungi, except Xylopia aromatica, which not presented dark septate strutctures. The best diaphanization procedure was obtained when the root samples were autoclaved at 121ºC by 20 minutes in a 2% KOH solution and transferred to a 2% KOH solution by 24 hours at room temperature. This procedure was repeated twice and, after that, the samples were submerged in a 2% KOH solution for 2 hours. The arbuscules were observed with more detail after been included in resin, sectioned and stained with toluidine blue. The non-specific characteristic of AMF observed in sensu stricto Cerrado species was confirmed
and suggested for dark septate associations. It indicates that these associations were important as adaptive strategies to cerrado conditions. Roupala montana Aubl. is a species from Proteaceae family which presents a large distribution on different phytophysiognomies of cerrado. Recent studies have been showed that several mycorrhizal fungi structures occurred in these species said to be typically non- mycorrhizal. The low pH and nutrients deficiency in cerrado soils propitiate good conditions for development and establishment of mycorrhizal association in R. montana, as observed in other Proteaceae species. Therefore, in this work it was also aimed to confirm the presence of AMF in R. montana specimens growing at natural cerrado conditions, and correlated the mycorrhizal frequency with nutritional status and edaphic conditions. Three individuals of R. montana were collected in FLONA on cerrado senso strictu, dense cerrado senso strictu, and cerradão during dry and rain seasons. The mycorrhizal occurrence was positively correlated with P, Al, and Mg contents in the soil, and P, K, and Ca in the leaves, and negatively correlated with Ca, Mn, and N contents in the soil. The cerrado soils are acid and have high Al contents which can inhibit the transport of Ca and K to the plants. In this way, the presence of mycorrhizal fungi in R. montana could be a adaptive mechanism for plant surviving under Brazilian cerrado conditions.<br>A elevada acidez, o intenso intemperismo e os altos teores de alumínio nos solos do Cerrado são fatores limitantes do desenvolvimento vegetal. Em condições de estresses abióticos a associação com fungos micorrízicos auxilia a planta hospedeira na absorção de nutrientes e água do solo. A maior disponibilidades desses elementos para a planta hospedeira pelos fungos micorrízicos arbusculares (FMAs) é determinante na sobrevivência das plantas e na estruturação de formações vegetais. A presença de fungo endofítico do tipo dark septate (DSEF) nas raízes das plantas é outro tipo de associação simbiótica relacionada às condições abióticas como baixa umidade e comprimento do dia. O reduzido número de trabalhos encontrados na literatura dessas associações em espécies de cerrado se deve em parte, pelas condições edáficas e características estruturais radiculares das espécies nativas que dificultam a realização de estudos in loco. Neste trabalho teve-se por objetivo estudar a associação de FMAs em espécies de plantas nativas do cerrado. Para isso, foram testados e adaptados métodos para observação das estruturas fúngicas em simbiose em espécies das famílias Annonaceae, Anacardiaceae, Leguminosae, Melastomataceae, Myrsinaceae, Myrtaceae e Rubiaceae coletadas durante a estação seca em cerrado senso strictu na Floresta Nacional (FLONA) do município de Paraopeba, Minas Gerais. Amostras radiculares foram submetidas a três tipos de protocolos para observação de estruturas fúngicas. Todas as espécies investigadas encontravam-se colonizadas por FMAs e DSEF, exceto DSEF em Xylopia aromática. O melhor método de diafanização foi observado quando as raízes foram autoclavadas a 121 °C em KOH 2 %, por 20 min e, subseqüentemente transferidas para solução nova de KOH 2 % por 24 horas à temperatura ambiente. Este procedimento foi repetido por duas vezes e, em seguida, essas amostras foram imersas em H2O2 2 % por 2 horas. Os arbúsculos foram observados com maiores detalhes após as raízes serem incluídas em resina, seccionadas e coradas com azul de toluidina. O caráter generalista dos FMAs observado nas espécies vegetais do cerrado sensu stricto foi confirmado e sugerido para DSEFs, indicando a importância destas simbioses como estratégia adaptativa às condições de cerrado. Roupala montana Aubl. é uma espécie da família Proteaceae com ampla distribuição nas diferentes fitofisionomias do cerrado. Estudos recentes têm relatado estruturas típicas de fungos micorrízicos em condições de estresses abióticos em espécies dessa família tipicamente não micorrizável. A acidez e deficiência dos solos de cerrado provem apropriadas condições para o desenvolvimento e formação de associações micorrízicas em R. montana, como observado em outros espécies da família Proteaceae. Assim, este trabalho também teve por objetivo confirmar a presença de fungos micorrízicos arbusculares em R. montana crescidas naturalmente em cerrado, correlacionando a freqüência de micorrização com o estado nutricional e condições edáficas. Em três repetições, indivíduos de R. montana foram coletados na FLONA em cerrado senso strictu, cerrado senso strictu denso e cerradão nas estações seca e chuvosa. A micorrização em R. montana foi correlacionada positivamente com o teor de P, Al, e Mg, no solo e de P, K e Ca nas folhas, e negativamente com Ca, Mn e N no solo. Os solos de Cerrado são ácidos com altas concentrações de Al, os quais podem inibir o transporte de Ca e K para as plantas, sugerindo que a presença de fungos micorrízicos em R. montana é um mecanismo adaptativo de sobrevivência as condições do cerrado brasileiro.
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Mustafa, Ghalia. "Protection du blé contre l'oïdium par des champignons mycorhiziens à arbuscules : mécanismes et optimisation." Thesis, Littoral, 2015. http://www.theses.fr/2015DUNK0388/document.
Full textAbstract:
L'utilisation des champignons mycorhiziens à arbuscules (CMA) pourrait constituer une alternative potentielle aux traitements fongicides conventionnels pour lutter contre les maladies cryptogamiques des plantes. Notre travail a consisté à étudier l'éventuel effet protecteur de la mycorhization arbusculaire chez le blé tendre (triticum aestivum L.) contre Blumeria graminis f. sp. tritici (Bgt), un champignon biotrophe responsable de l'oïdium, une maladie affectant les parties aériennes de la plante. L'inoculation mycorhizienne du blé avec le CMA Funneliformis mosseae (FM), en conditions controlées et optimisées, nous a permis d'obtenir parallèlement à un taux de mycorhization de 38% des plants de blé, une amélioration significative de la biomasse et un taux de protection contre Bgt estimé à 78%. Ces résultats suggèrent l'induction d'une résistance systémique des réactions de défense du blé par mycorhization (Mycorrhiza-Induced Resistance, MIR). Cette protection serait liée à une accumulation de composés phénoliques et de preoxyde d'hydrogène dans les cellules épidermiques des feuilles de blé mycorhizé, au niveau du site de pénétration de Bgt. Une surexpression des gènes POX, PAL, CH11 et NPR1 codant pour des marqueurs de défense a également été mise en évidence dans les feuilles en absence d'infection par Bgt. Enfin, nos travaux ont également souligné l'intégration de divers paramètres pour optimiser l'utilisation des CMA comme agents de biocontrôle chez le blé. La meilleure protection contre l'oïdium a été obtenue aec un apport en phosphore réduit de 5 fois par rapport à celui préconisé au champ et un inoculum mycorhizien à base de Fm, que ce soit chez un cultivar modérément sensible ou un cultivar plus résistant<br>The use of arbuscular mycorrhizal fungi (AMF) could be an innovative alternative to chemicals against fungal plant diseases. Our work aimed at studying the possible protective effect of arbuscular mycorrhization in the bread wheat (Triticum aestivum L.) against Blumeria graminis f. sp. tritici (Bgt), a biotrophic fungi responsible of wheat powdery mildew, a disease affecting the aerial plant organs. Wheat mycorrhizal inoculation by Funneliformis mosseae (Fm), under controlled and optimized conditions, allowed us to obtain concomitantly a micorrhizal rate of 38%, a significant increase of plant biomass and a protection level against Bgt estimated at 78%. These results suggest the induction of systemic wheat defense reactions resulting from mycorrhization (Mycorrhiza-Induced Resistance - MIR). This protection is linked to an accumulation of phenolic compounds and hydrogen peroxide at the Bgt penetration sites in epidermal leaf cells of mycorrhized wheat plants. Up-regulations of POX, PAL, NPR1 and CH11 genes encoding for defense markers were also pointed out in leaves of mycorrhizal wheat in the absence of Bgt infection. Moreover, our study highlighted the importance of taking into account various parameters to optimize the use of AMF as biocontrol agents. The highest protection against powdery mildew was obtained with a 5-fold reduced phosphorus input compared to that recommended in the field and with the mycorrhizal inoculum Fm, in both a moderately susceptible or a more resistant cultuva
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Jefwa, Joyce Mnyazi. "The Taxonomy and ecology of Arbuscular Mycorrhizal fungi (AMF) in agroforestry systems in Malawi." Thesis, 2004. http://hdl.handle.net/2263/27135.
Full text
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Poku, Emmanuel Adu. "Improving phosphorus uptake by cassava (Manihot esculanata Crantz) using Arbuscular Mycorrhizal Fungi (AMF)." Thesis, 2014. http://hdl.handle.net/10413/10855.
Full textAbstract:
Phosphorus uptake cassava (Manihot esculanta Crantz) were tested using on thirty-six plants per
plot under dryland conditions at four different sites selected Bioresource group 1 (BRG 1) of
northern KwaZulu-Natal of South Africa, which is described as Moist, Coastal Forest, Thorn and
Palm veld, exhibiting sub-tropical characteristics. Soils in this region are very low in Phosphorus (P)
due to high fixation by iron and aluminium oxides. With its high root yields coupled with efficient
nutrients miner, cassava removes large quantities of N, P, K and Mg. With the ever-increasing prices
of P fertilizer, which impact on the socio-economic livelihood of smallscale farmers, there is the
need to look into improving the P uptake by the crop by alternative means apart from using mineral
fertilizers. The objective of this study was to investigate the use of Arbuscular Mycorrhizal Fungi
(AMF) to improve P uptake by cassava in agricultural soils. Laboratory studies were conducted at
Soil Fertility and Analytical Services in Cedara (Pietermaritzburg). A Latin Square design (LSD)
was used. Four treatments used were Untreated (Control), P-fertilizer, AMF, and P + AMF.
Correlation and path-coefficient (probabilities) were computed. The P + AMF were significantly
(p<0.05) taller than those in P-fertilizer treatment plots but were significantly (p<0.05) similar to
those in Control and AMF-treated plots. Percent leaf P was statistically similar at the four sites with
grand mean of 0.4%. Adding AMF and P+AMF to the soil substantially increased leaf P
concentration to 0.5%. Tubers collected from P+AMF-treated plots were significantly (p<0.05) the
longest, while those from Control plots were the shortest. P, and AMF-treated plots increased tuber
length relative to the Control. All soil treatments significantly (p<0.05) increased tuber yields over
the Control-treatment plots. However, AMF and P+AMF treated plots were significantly higher than
P and control plots. This study suggests that using AMF or P+AMF can improve cassava yield as
compared P alone or control – untreated cassava plants. Cassava producers in northern KwaZulu-
Natal should consider using AMF or P+AMF to optimize tuber yield. A further study into the
economic implications of the use of AMF is recommended.<br>Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2014.
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Lewandowski, Thaddeus J. "The Effect of Arbuscular Mycorrhizal Fungal Diversity on Plant Pathogen Defense." Thesis, 2012. http://hdl.handle.net/10214/4045.
Full textAbstract:
Arbuscular mycorrhizal fungi (AMF) are widespread soil dwelling microorganisms that associate with plant hosts. AMF receive carbon from the host as a result of the mutualism, while the plant’s ability to acquire nutrients is enhanced by AMF. Additionally, AMF benefit their host in the form of pathogen protection. While it is known that increased AMF species richness positively correlates with aboveground plant productivity, the relationship between AMF diversity and pathogen protection is not well understood. In a growth chamber study, the plant host Leucanthemum vulgare, a non-native plant species in North America, was introduced to all combinations of three AMF species either in the presence or absence of the plant root pathogen Rhizoctonia solani. In the presence of the pathogen, the plant host increased its dependence on the AMF symbiosis. However, the richest AMF species assemblage did not provide the greatest pathogen protection. Understanding how diverse groups of AMF protect plants from pathogen attack provides insight into how plant communities are formed and structured.<br>NSERC
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Kong, Mengxuan. "Biodiversity of arbuscular mycorrhizal fungi from extreme petroleum hydrocarbon contaminated site." Thèse, 2016. http://hdl.handle.net/1866/19131.
Full textAbstract:
Les activités industrielles, la production d’énergie le transport et l’urbanisation ont engendré de sérieux problèmes environnementaux qui ont des effets néfastes non seulement pour les divers écosystèmes, mais aussi pour la santé des Humains. Il existe plusieurs méthodes de réhabilitation des sites contaminés. Les méthodes dites conventionnelles consistent le plus souvent à excaver, transporter et entreposer des sols dans des sites d’enfouissements, alors que d’autres technologies utilisent des traitements physico-chimiques ou l’incinération des polluants. Les inconvénients majeur de ces méthodes en sont le coût élevé, l’émission des gaz à effet de serre et la destruction des habitats. Cependant, plusieurs technologies ont émergé ces dernières décennies. Parmi ces technologies émergentes, la phytoremédiation est une méthode prometteuse et dont l’efficacité devienne de plus en plus reconnue. La phytoremédiation consiste à utiliser des plantes et les microbes qui leurs sont associés pour dégrader, extraire ou stabiliser les polluants du sol aussi bien organiques qu’inorganiques. Parmi les microbes associés aux racines des plantes, on trouve les champignons mycorhiziens arbusculaires (CMA) dont le rôle en phytoremédiation a été montré. Cependant, la diversité et les changements des structures des communautés de ces champignons dans des sites hautement contaminés et en association avec les populations des plantes qui poussent spontanément dans ces sites demeurent méconnues. L’objectif de mon projet de maitrise consiste à étudier la diversité et la structure des communautés des CMA dans les racines et les sols rhizosphériques de trois espèces de plantes Eleocharis elliptica, Populus tremuloides et Persicaria maculosa qui poussent spontanément dans des bassins d’une ancienne raffinerie pétro-chimique. J’ai échantillonné trois individus par espèce de plante dans trois bassins qui ont montré des concentrations différentes des polluants pétroliers. J’ai utilisé l’approche de la PCR conventionnelle, le clonage et le séquençage en ciblant le gène 18S de l’ARN ribosomique autant sur des échantillons de racines et des que sur ceux de sols rhizophériques. J’ai analysé au minimum 48 clones par échantillon. L’analyse de la diversité Beta a montré que la structure des communautés des CMA était significativement différente selon les biotopes (racines et sols rhizosphèriques) et les concentrations de contaminants pétroliers. Mes résultats ont montré que l'identité de la plante et la concentration de contaminants ont fortement influencé la structure des communautés de CMA. J’ai aussi observé qu’en plus de l’effet des facteurs biotiques et abiotiques mentionnés ci-dessus, plusieurs OTUs de CMA sont corrélés soit positivement ou négativement entre eux et aussi avec différents types de polluants d'hydrocarbures pétroliers. Cette étude a permis de comprendre les facteurs qui influencent les changements des structures des communautés des CMA et pourrait nous aider à améliorer l’efficacité de la phytoremédiation avec des plantes indigènes poussant spontanément sur des sites hautement contaminés par des hydrocarbures pétroliers.<br>Industrial activities, energy production, transportation, and urbanization have led to serious environmental problems that have negative effects not only for the natural ecosystems, but
also for the human health. Several methods of rehabilitation of contaminated sites such as conventional methods consisting on excavation, transportation and storage of contaminated soils in landfills (known as Dig and Dump), as well as other technologies that use physical and chemical treatments or incineration of polluted soil pollutants, have been largely utilized. However, these methods are very costly and not environmental-friendly because of greenhouse gas emission and destruction of habitats. Several green technologies have emerged in recent decades. Among these emerging technologies, phytoremediation is a promising method whose effectiveness becomes increasingly recognized worldwide.
Phytoremediation uses plant and their associated microbes to degrade, uptake or sequestrate organic and inorganic pollutants. Arbuscular mycorrhizal fungi (AMF) are among microbes that live intimately with plant root where they form a symbiosis known as arbuscular mycorrhiza. The objective of my master project was to study the diversity and changes of community structure of AMF in roots and rhizospheric soils of three native plant species Eleocharis elliptica, Populus tremuloides and Persicaria maculosa growing in petroleum-contaminated sedimentation basins of a former petro-chemical plant. I used conventional PCR, cloning and sequencing approach targeting 18S rRNA gene to investigate AMF community structure. I analyzed at minimum 48 clones for each sample. Beta diversity analyses showed that AMF community structure was significantly different across biotopes (roots and rhizospheric soils) and different concentrations of petroleum hydrocarbon contamination. Our results showed that plant identity and concentrations of petroleum hydrocarbon contaminations strongly influenced the AMF community structure as well as the inter-specific relationship among AMF taxa. Moreover, with consideration of both biotic and abiotic factors, we found that several AMF OTUs showed positive and negative correlations between each other and also with petroleum hydrocarbon pollutants. My study brings us in-valuable information to apply AMF for the phytoremediation in the future.
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Lin, Ying-Ling, and 林映綾. "Factors affecting germination of arbuscular mycorrhizal fungi, and interactions of AMF and root-knot nematode on sponge gourd." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/74324802932539243653.
Full textAbstract:
碩士<br>國立嘉義大學<br>農學研究所<br>95<br>This study focused on the influence of factors on spores germination of arbuscular mycorrhizal fungi (AMF) by membrane filter technique, and the application of AMF for enhancing the tolerance of sponge gourd to root-knot nematode. There were 7 species of AM fungi to be twsted; that was Acaulospora morrowiae (Am), A. scrobiculata (As), Entrophospora kentinensis (Ek), Glomus aggregatum (Ga), G. etunicatum (Ge), G. mosseae (Gm) and Scutellospora spp. (Scu. spp.). Spore viability and germination of Ge, Gm, Ga, and As were not significantly different in 64 weeks stored in 4 ℃and room temperature after gathering. Percentage of spore germination rate decreased following the storage time increased in 4 species except Ga, and membrane filter technique was not adequate for germination of As. The effected of sand, vermiculite #2, king gardening #3 and flora pleur #3 on spore germination of As, Ek, Ge and Gm stored 1- and 2.5- year were compared, results indicated germination rate of Ge, Gm was the highest in vermiculite independented on storage time, and germination rate was still not well for As and Ek, but spore germination of Am, Ek, Ga and Ge stored for 3 months were higher in vermiculite than in other media except As and Gm, the length and branch of germination tube were higher in vermiculite than in other media. Particle size of sand and embedded depth affected the spore germination of Ge; embedded in 1 cm depth, the germination rate was 28.3 % in 40 mesh sand, next was 26.7 % in 60 mesh sand; embedded in 6 cm depth, germination rate was the highest, up to 41.7 % in 20 mesh sand, and 20-21.7 % in the other 3 treatments; for spores of Gm embedded in 1 cm depth, the length of germination tube decreased but branch increased following the particle size of sand decreased, germination rate of spores embedded in 1 cm depth was higher than in 6 cm depth independented of the size of sand. Germination rate of 7 species of AM fungi embedded in 4 media were compared, resulted indicated germination rate was higher for Am, Ek, Ga and Ge in 40 mesh sand, for Gm in vermiculite, for Scu. spp. in king gardening #3, and there was no germination for As in 4 media. Sand, 20 mesh, 40 mesh, 60 mesh sand, and vermiculite #2 were used for the propagation of Ge, colonization was the highest in sand at 14 weeks after inoculation, next was vermiculite, but spores per 100 ml medium was the highest and up to 21,000 in vermiculite. Filtration of vermiculite #2, KG #3, FP #3 and peat moss were added in sand where spores of Ek embedded, germination rate was 58 and 50.2 % in sand added with filtration of KG #3 and vermiculite #2, respectively, check was 46.1 %, and 21.2, 30.5 % for FP #3 and Peat moss, but the branch of germination tube was up to 4.3 for check, next was 3.9 for vermiculite filtration. Germination rate of Gm obviously decreased in sand when the amount was over 0.467 g, 2.18 g and 0.5 g/kg for ammonia sulfate, urea and rock phosphate, respectively; inhibition of germination was more obviously followed by the amount of ammonia sulfate increased, there was no significantly different in germination of Gm between check and those amended with 0.25, 1 g/kg of calcium superphosphate. For Gm propagation in corn pot culture, nitrogen amendment such as ammonia sulfate could increased the sporulation of Gm, but phosphate amendment such as rock phosphate or calcium superphosphate had no obvious increased, nitrogen and phosphate amended single or mix had different effected for Gm propagation in pot culture with corn or grass, ammonia sulfate was better for sporulation than other treatments in corn pot culture, but osmocote #3 was better in bahia-grass pot culture.
Growth promotion of sponge gourd inoculated with Am, As, Ek, Ga, Ge and Gm were compared, and growth of seedlings were promoted at 2 and 3 weeks after inoculation. Length and dry weight of shoot, fresh and dry weight of roots and colonization of seedlings inoculated with As were better than other treatments at 6 weeks after inoculation. The minimal inoculum density of root-knot nematode inducing disease symptom were tested, inoculum density were 0, 200, 400, 600, 800 and 1000 of second stage larvae of root-knot nematode in each pot. Results showed that the growth of root was significantly different in treatments at 6 weeks after inoculation. Root knots were induced when seedlings inoculated with 200 larvae per seedling, whereas there were more than 30 root knots in treatment of 400 larvae, fresh weight of root was 36.2 g and significantly different to control (CK) 26.2 g. The growth and disease incidenced of seedlings pre-inoculated with AMF for 2 weeks and then inoculated with 400 larvae of M. incognita were tested. There were over 50 root knots in seedlings inoculated with nematodes, and root growth of those inoculated with nematodes was less than control (CK). Root growth of seedlings co-inoculated with AMF and nematode was better than those of nematode alone, and root knots were less than 30. The results showed that sponge gourd pre-inoculated with AMF cound reduced the infection of M. incognita. The number of larvae per 100 g soil in treatments inoculated with Am, As, Ge and Gm also decreased. In co-inoculation tested of As and roo-knot nematode, length and fresh weight of shoots in treatment of As was 201.5 cm and 58.7 g, respectively, next was 195.2 cm and 54.1 g in treatment of As and Mi. Fresh and dry weight of root in treatment of Mi was 8.28 g and 1.54 g, respectively. It was more than 50 root knots in roots of Mi, and root knot index was up to 4, but fresh and dry weight in roots of As and Mi was 7.41 g and 1.32 g, respectively, the number of root knots was under 30 and root knot index was between 2-3. Fresh and dry weight of roots in Mi was significantly different with the control (CK) which was 6.76 g and 1.19 g. The number of 2nd larvae per 100 g soil in treatment of Mi was 16, and higher than the treatment of As and Mi which was 9. In split-root experiment, result showed that root growth promotion of sponge gourd inoculated with AM fungi was systemic. Root knots and 2nd larvae were less in seedlings which separately inoculated with As and root knot nematode in both sides than those inoculated with nematode in one side. Results indicated that sponge gourd inoculated with AM fungi might reduced the number of M. incognita due to occupation of infecting site, and physiological biochemistry of plants might change as well, therefore, the number of root knots and the population of 2nd larva in soil decreased.
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Nadimi, Maryam. "Comparative mitochondrial genomics toward understanding genetics and evolution of arbuscular mycorrhizal fungi." Thèse, 2015. http://hdl.handle.net/1866/12376.
Full textAbstract:
Les champignons mycorhiziens arbusculaires (CMA) sont très répandus dans le sol où ils forment des associations symbiotiques avec la majorité des plantes appelées mycorhizes arbusculaires. Le développement des CMA dépend fortement de la plante hôte, de telle sorte qu'ils ne peuvent vivre à l'état saprotrophique, par conséquent ils sont considérés comme des biotrophes obligatoires. Les CMA forment une lignée évolutive basale des champignons et ils appartiennent au phylum Glomeromycota. Leurs mycélia sont formés d’un réseau d’hyphes cénocytiques dans lesquelles les noyaux et les organites cellulaires peuvent se déplacer librement d’un compartiment à l’autre. Les CMA permettent à la plante hôte de bénéficier d'une meilleure nutrition minérale, grâce au réseau d'hyphes extraradiculaires, qui s'étend au-delà de la zone du
sol explorée par les racines. Ces hyphes possèdent une grande capacité d'absorption d’éléments nutritifs qui vont être transportés par ceux-ci jusqu’aux racines. De ce fait, les CMA améliorent la croissance des plantes tout en les protégeant des stresses biotiques et abiotiques. Malgré l’importance des CMA, leurs génétique et évolution demeurent peu connues. Leurs études sont ardues à cause de leur mode de vie qui empêche leur culture en absence des plantes hôtes. En plus leur diversité génétique intra-isolat des génomes nucléaires, complique d’avantage ces études, en particulier le développement des marqueurs moléculaires pour des études biologiques, écologiques ainsi que les fonctions des CMA. C’est pour ces raisons que les génomes mitochondriaux offrent des opportunités et alternatives intéressantes pour étudier les CMA. En effet, les génomes mitochondriaux (mt) publiés à date, ne montrent pas de polymorphismes génétique intra-isolats. Cependant, des exceptions peuvent exister. Pour aller de l’avant avec la
génomique mitochondriale, nous avons besoin de générer beaucoup de données de séquençages de l’ADN mitochondrial (ADNmt) afin d’étudier les méchanismes évolutifs, la génétique des population, l’écologie des communautés et la fonction des CMA. Dans ce contexte, l’objectif de mon projet de doctorat consiste à: 1) étudier l’évolution des génomes mt en utilisant l’approche de la génomique comparative au niveau des espèces proches, des isolats ainsi que des espèces phylogénétiquement éloignées chez les CMA; 2) étudier l’hérédité génétique des génomes mt au sein des isolats de l’espèce modèle Rhizophagus irregularis par le biais des anastomoses ; 3) étudier l’organisation des ADNmt et les gènes mt pour le développement des marqueurs moléculaires pour des études phylogénétiques. Nous avons utilisé l’approche dite ‘whole genome shotgun’ en pyroséquençage 454 et Illumina HiSeq pour séquencer plusieurs taxons de CMA sélectionnés selon leur importance et leur disponibilité. Les assemblages de novo, le séquençage conventionnel Sanger, l’annotation et la génomique comparative ont été réalisés pour caractériser des ADNmt complets. Nous avons découvert plusieurs mécanismes évolutifs intéressant chez l’espèce Gigaspora rosea dans laquelle le génome mt est complètement remanié en comparaison avec Rhizophagus irregularis isolat DAOM 197198. En plus nous avons mis en évidence que deux gènes cox1 et rns sont fragmentés en deux morceaux. Nous avons démontré que les ARN transcrits les deux fragments de cox1 se relient entre eux par épissage en trans ‘Trans-splicing’ à l’aide de l’ARN du gene nad5 I3 qui met ensemble les deux ARN cox1.1 et cox1.2 en formant un ARN complet et fonctionnel. Nous avons aussi trouvé une organisation de l’ADNmt très particulière chez l’espèce Rhizophagus sp. Isolat DAOM 213198 dont le génome mt est constitué par deux chromosomes circulaires. En plus nous avons trouvé une quantité considérable des séquences apparentées aux plasmides ‘plasmid-related sequences’ chez les Glomeraceae par rapport aux Gigasporaceae, contribuant ainsi à une évolution rapide des ADNmt chez les Glomeromycota. Nous avons aussi séquencé plusieurs isolats de l’espèces R. irregularis et Rhizophagus sp. pour décortiquer leur position phylogénéque et inférer des relations évolutives entre celles-ci. La comparaison génomique mt nous montré l’existence de plusieurs éléments mobiles comme : des cadres de lecture ‘open reading frames (mORFs)’, des séquences courtes inversées ‘short inverted repeats (SIRs)’, et des séquences apparentées aux plasimdes ‘plasmid-related sequences (dpo)’ qui impactent l’ordre des gènes mt et permettent le remaniement chromosomiques des ADNmt. Tous ces divers mécanismes évolutifs observés au niveau des isolats, nous permettent de développer des marqueurs moléculaires spécifiques à chaque isolat ou espèce de CMA. Les données générées dans mon projet de doctorat ont permis d’avancer les connaissances fondamentales des génomes mitochondriaux non seulement chez les Glomeromycètes, mais aussi de chez le règne des Fungi et les eucaryotes en général. Les trousses moléculaires développées dans ce projet peuvent servir à des études de la génétique des populations, des échanges génétiques et l’écologie des CMA ce qui va contribuer à la compréhension du rôle primorial des
CMA en agriculture et environnement.<br>Arbuscular mycorrhizal fungi (AMF) are the most widespread eukaryotic symbionts,
forming mutualistic associations known as Arbuscular Mycorrhizae with the majority of plantroots. AMF are obligate biotrophs belonging to an ancient fungal lineage of phylum
Glomeromycota. Their mycelia are formed by a complex network made up of coenocytic hyphae, where nuclei and cell organelles can freely move from one compartment to another. AMF are commonly acknowledged to improve plant growth by enhancing mineral nutrient uptake, in particular phosphate and nitrate, and they confer tolerance to abiotic and biotic stressors for plants. Despite their significant roles in ecosystems, their genetics and evolution are not well understood. Studying AMF is challenging due to their obligate biotrophy, their slow growth, and their limited morphological criteria. In addition, intra-isolate genetic polymorphism of nuclear DNA brings another level of complexity to the investigation of the biology, ecology and function of AMF. Genetic polymorphism of nuclear DNA within a single isolate limits the development of efficient molecular markers mainly at lower taxonomic levels (i.e. the inter-isolate level). Instead, mitochondrial (mt) genomics have been used as an attractive alternative to study AMF. In AMF, mt genomes have been shown to be homogeneous, or at least much less polymorphic than nuclear
DNA. However, by generating large mt sequence datasets we can investigate the efficiency and usefulness of developing molecular marker toolkits in order to study the dynamic and evolutionary mechanisms of AMF. This approach also elucidates the population genetics, community ecology and functions of Glomeromycota. Therefore, the objectives of my Ph.D. project were: 1) To investigate mitochondrial genome evolution using comparative mitogenomic analyses of closely related species and isolates as well as phylogenetically distant taxa of AMF; 2) To explore mt genome inheritance among compatible isolates of the model AMF Rhizophagus irregularis through anastomosis formation; and 3) To assess mtDNA and mt genes for marker development and phylogenetic analyses. We used whole genome shotgun, 454 pyrosequencing and HiSeq Illimina to sequence AMF taxa selected according to their importance and availability in our lab collections. De novo assemblies, Sanger sequencing, annotation and comparative genomics were then performed to characterize complete mtDNAs. We discovered interesting evolutionary mechanisms in Gigaspora rosea: 1) we found a fully reshuffled mt genome synteny compared to Rhizaphagus irregularis DAOM 197198; and 2) we discovered the presence of fragmented cox1 and rns genes. We demonstrated that two cox1 transcripts are joined by trans-splicing. We also reported an unusual mtDNA organization in Rhizophagus sp. DAOM 213198, whose mt genome consisted of two circular mtDNAs. In addition, we observed a considerably higher number of mt plasmidrelated sequences in Glomeraceae compared with Gigasporaceae, contributing a mechanism for faster evolution of mtDNA in Glomeromycota. We also sequenced other isolates of R. irregularis and Rhizophagus sp. in order to unravel their evolutionary relationships and to develop molecular toolkits for their discrimination. Comparative mitogenomic analyses of these mtDNAs revealed the occurrence of many mobile elements such as mobile open reading frames (mORFs), short inverted repeats (SIRs), and plasmid-related sequences (dpo) that impact mt genome synteny and mtDNA alteration. All together, these evolutionary mechanisms among closely related AMF
isolates give us clues for designing reliable and efficient intra- and inter-specific markers to discriminate closely related AMF taxa and isolates.
Data generated in my Ph.D. project advances our knowledge of mitochondrial genomes
evolution not only in Glomeromycota, but also in the larger framework of the Fungal kingdom and Eukaryotes in general. Molecular toolkits developed in this project will offer new opportunities to study population genetics, genetic exchanges and ecology of AMF. In turn, this work will contribute to understanding the role of these fungi in nature, with potential applications in both agriculture and environmental protection.
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(5930507), Lisseth Zubieta. "Arbuscular mycorrhizal fungi: crop management systems alter community structure and affect soybean growth and tolerance to water stress." Thesis, 2019.
Find full textAbstract:
<p>Arbuscular mycorrhizal
fungi (AMF) are best known for their potential to help plants acquire
nutrients, especially phosphorous. These microbes improve soil health by
promoting soil aggregation and carbon sequestration, and further benefit plants
by helping them withstand biotic and abiotic stress. Currently, there are 200
recognized species of AMF within the phylum Glomeromycota. Recent studies
indicate that individual AMF species differ in the benefits they provide, with
some even acting as parasites. Moreover, AMF community composition can be
altered by soil and crop management practices, but the effect of these changes
on the benefits conferred by AMF are still not well understood. Consequently,
the goal of this study was to determine how two widely used crop management
systems can alter the composition of AMF species, and affect the potential for
these communities to promote the productivity and drought tolerance. To
accomplish this goal, we collected AMF inoculum from a long-term crop systems
trial comparing organic and conventional management for use in greenhouse
trials where we subjected plants to drought. We collected AMF inoculum during
mid-summer when differences between the two management systems were likely
cause larger effects on AMF communities, and again in autumn after harvest to
see if differences in AMF communities would persist. We determined AMF species
composition using next generation sequencing. Results of this study confirm
that soil-building practices commonly used in organic farming systems can
improve soil health and increase the productivity of food-grade soybeans. They
also demonstrate that AMF communities in Indiana croplands are highly diverse,
and some of these taxa can improve soybean growth and help plants tolerate
water stress. Although the overall diversity of AMF communities did not differ
between the organic and conventional management systems in mid-summer,
individual AMF taxa did differ between the systems, which were likely
responsible for the greater tolerance to water stress observed when plants were
amended with inoculum from the organic system. AMF communities present during
autumn were significantly different between the two crop management systems,
but did not result in differences in drought tolerance of soybeans, indicating
that the loss of key AMF taxa in the organic system from the first relative to
the second experiment was likely responsible. Finally, plants grown using
inoculum from both crop management systems in autumn had greater tolerance to
water stress than plants that received a AMF commercial inoculum. This provides
further evidence that individual AMF species vary in the benefits they provide,
and that the presence of a diverse consortium of AMF species is needed to
optimize plant health and productivity in agricultural systems. Agricultural
producers should consider incorporating soil-building practices that are
commonly used in organic farming systems such as planting winter cover crops,
to improve the health of their soil and enhance the productivity of their
crops. <b></b></p>
<br>
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Luna, Sara Patrícia Bettencourt. "Study of the arbuscular mycorrhizal fungi (AMF) associated to the Azorean endemic woody plant Picconia azorica (Tutin) Knobl. and their potential application on sustainable restoration programs." Doctoral thesis, 2018. http://hdl.handle.net/10400.3/5156.
Full textAbstract:
Tese de Doutoramento, Ciências Agrárias, especialidade em Biotecnologia, 07 de dezembro de 2018, Universidade dos Açores.<br>Os fungos micorrízicos arbusculares (FMA), simbiontes obrigatórios pertencentes ao filo Glomeromicota, formam relações mutualistas com cerca de 90% das espécies de plantas terrestres. Estes fungos fornecem água e minerais à planta e em troca a planta fornece produtos da fotossíntese. As comunidades de FMA presentes na rizosfera da planta endémica Picconia azorica, de duas ilhas do arquipélago dos Açores, foram estudadas com recurso a métodos morfológicos e moleculares. Os esporos de FMA isolados do solo foram morfologicamente classificados em 46 morfotipos. A caraterização molecular dos esporos foi efetuada por sequenciação de um fragmento de rADN com cerca de 1,5 kb (SSU-ITS-LSU) e resultou na obtenção de 125 sequências. Após análise filogenética estas sequências foram alocadas a 18 filotipos, as quais mostraram pertencer às famílias Acaulosporaceae, Archaeosporaceae, Claroideoglomeraceae, Gigasporaceae e Glomeraceae. Oito destas sequências não agruparam com nenhuma sequência previamente conhecida, o que sugere que correspondem a espécies que ainda não foram molecularmente identificadas ou que constituem novas espécies para a ciência. A análise da ecologia revelou que existem diferenças na comunidade de FMA entre as ilhas Terceira e São Miguel. A comunidade de FMA no solo da ilha Terceira é dominada por elementos das famílias Acaulosporaceae e Glomeraceae, enquanto, que em São Miguel é dominada pelas famílias Glomeraceae e Gigasporaceae. A análise microscópica das raízes de P. azorica revelou que as amostras se encontravam altamente colonizadas (89 – 99%) pelas diferentes estruturas do fungo (hifas, arbúsculos e vesículas), permitindo assim considerar a planta como sendo micotrófica e altamente dependente de FMA. A identificação dos fungos presentes nas raízes de P. azorica foi efetuada com base no fragmento de 1.5 kb do rADN e com recuso ao método de restrição terminal de fragmentos polimórficos (T-RFLP) conhecidos, no programa TRAMPR. A análise identificou 22 filotipos pertencentes às famílias Acaulosporaceae, Claroideoglomeraceae, Diversisporaceae, Gigasporaceae e Glomeraceae. Verificou-se que a espécie Acaulospora brasiliensis estava presente nas raízes de todas as plantas analisadas e que a família Glomeraceae foi a família mais representada com a identificação de 13 filotipos. Esta análise revelou ainda que em ambas as ilhas na colonização das raízes dominavam espécies da família Glomeraceae, sendo que nas raízes da ilha Terceira a presença de Acaulosporaceae foi mais frequente, enquanto, que nenhum membro da família Claroideoglomeraceae foi identificado em amostras de raízes de São Miguel. Os resultados destes estudos sugerem que as comunidades de FMA nas florestas nativas dos Açores são determinadas por fatores históricos e geográficos, bem como pelas propriedades químicas do solo e pelas condições ambientais. Para o estudo da capacidade de colonização de plantas micropropagadas pelas espécies Acaulospora laevis e Acaulospora koskei foram isolados e sequenciados segmentos de quatro genes de P. azorica homólogos a outros previamente relacionados à simbiose e foi analisada a expressão destes genes por qRT-PCR durante os estágios iniciais da simbiose com FMA. Nestes ensaios a indução da expressão por Ac. laevis revelou ser superior à obtida com Ac. koskei. A influência do FMA Funneliformis mosseae sobre o desenvolvimento de plantas de P. azorica micropropagadas foi estudada. Ao fim de 8 meses de tratamento as plantas inoculadas com o FMA revelaram-se maiores e mais robustas que as plantas não inoculadas. Esta é a primeira vez em que se estuda a condição de FMA presentes na rizosfera de P. azorica nas florestas nativas Açorianas. A P. azorica demonstrou elevada dependência pelos FMA o que revela sintonia com o facto de estes FMA terem revelado potencial para serem aplicados como promotores do sucesso na utilização de plantas micropropagadas em programas de conservação e restauração de florestas nativas no arquipélago dos Açores.<br>ABSTRACT: Arbuscular mycorrhizal fungi (AMF) are obligate symbionts, belonging to the phylum Glomeromycota that form mutualistic symbioses with about 90% of land plant species. They provide the host plant with mineral nutrients and water, in exchange for photosynthetic products. The communities of AMF present in the rhizosphere of endemic tree Picconia azorica from two Azorean islands, Terceira and São Miguel, were assessed by morphological and molecular methods. AMF spores isolated from the soil were morphologically classified in 46 distinguishable morphotypes. Molecular characterisation of a c. 1.5 kb rDNA fragment, comprising SSU-ITS-LSU, resulted in 125 AMF sequences. Phylogenetic analyses assigned the sequences to 18 phylotypes, belonging to the families Acaulosporaceae, Archaeosporaceae, Claroideoglomeraceae, Gigasporaceae and Glomeraceae. Also, 8 phylotypes did not cluster with sequences of any described species implying that they are either species that have not yet been identified or are new to science. Ecological analyses revealed differences in AMF community composition between islands. In Terceira, the rhizospheric soil was dominated by species belonging to Acaulosporaceae and Glomeraceae, while São Miguel was dominated by Glomeraceae and Gigasporaceae. Microscopic survey of P. azorica root samples showed that all studied samples were highly colonised (89 – 99%) by AMF structures (hyphae, arbuscules and vesicles) which allowed us to classify the endemic plant as mycotrophic and highly dependent on AMF. The identity and diversity of AMF colonising the roots of P. azorica were assessed by terminal restriction fragment length polymorphism (T-RFLP) of the c. 1.5 Kb rDNA fragment. Database terminal restriction fragment length polymorphism (T-RFLP) approach in conjunction with TRAMPR package was used to identify the AMF community present in the roots. By that were identified 22 phylotypes belonging to Acaulosporaceae, Claroideoglomeraceae, Diversisporaceae, Gigasporaceae and Glomeraceae. Acaulospora brasiliensis was present in all studied roots of all sampled plants and Glomeraceae showed to be the more diverse family with 13 phylotypes identified. It was also observed differences in AMF community composition between islands. Although in both islands root colonization was dominated by species belonging to Glomeraceae, in Terceira the presence of Acaulosporaceae was more frequent, while no Claroideoglomeraceae were identified in São Miguel root samples. All results suggest that AMF communities in native forest of Azores are determined by geographic and historical factors as well as soil chemical properties and environmental conditions. The ability of Acaulospora laevis and Acaulospora koskei to colonised micropropagated plants of P. azorica was tested by isolating and sequencing of partial sequences of four P. azorica symbiosis-related genes and analyses of gene expression by qRT-PCR during early stages of AMF symbiosis. This revealed that both AMF species varied in their capacity to induce the early stages of the plant symbiotic response, in which Ac. laevis showed superior to Ac. koskei. The influence of Funneliformis mosseae on the growth of micropropagated P. azorica was investigated. After eight months of growth, inoculated plants showed to be bigger and more robust than non-inoculated plants. This is the first time that AMF status in the rhizosphere of P. azorica in native forest of the Azores was investigated. P. azorica showed to be highly dependent on AMF which is in line with the showed potential of AMF application as promoters of plant establishment in conservation and restoration of native forests of the Azores archipelago.<br>Fundo Regional de Ciência e Tecnologia - FRCT (M2.1.2/F/041/2011)
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Lu, Fun-Chi, and 呂芳舉. "Study on Arbuscular Mycorrhizal Fungi (AMF) Inoculation on the Growth and Development, Tuber Weight, Allantoin Content and Antioxidant Ability in Yam (Dioscorea alata L.) Cultivated in Taiwan." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/98230614425969659146.
Full textAbstract:
博士<br>國立屏東科技大學<br>農園生產系所<br>104<br>The symbiotic association between arbuscular mycorrhizal fungi (AMF) and the roots of plants is widespread in the natural environment. AMF benefit their host plant principally by increasing the uptake of macronutrients and some micronutrients, resistance to soil pathogens, tolerance to salinity, heavy metals, and drought stress; maintenance of soil aggregate stability and influence the secondary metabolism levels of plants. The yam (Dioscorea spp.) tubers are edible, medicinal, and used as health foods, they have received considerable attention among the medicinal plants. Yam tubers can produce considerable amounts of antioxidant namely, polyphenols, flavonoids and anthocyanins. They also contained high levels of allantoin that is playing an important role in present skin inflammation and ulcers of the human body; thus, the secondary metabolites that exist in yam tubers have value for
development and utilization in medicine practice and health care.
In this study, five commercial species and line of yams (Dioscorea alata L.) were inoculated with six species of AMF, Glomus clarum, G. etunicatum, G. fasciculatum, Gigaspora sp., G. mosseae, and Acaulospora sp., in field cultivation conditions to investigate the influence of AMF inoculation on mycorrhizae formation rates, physiological components of leaves, nutrition analysis, tuber weights, secondary metabolite content and antioxidant ability in yam tubers. The results showed that all six AMF species were able to form mycorrhizae relationship with the host yams, and mycorrhizae formation rates ranged from 63.33% to 90%, indicating that these AMF present high compatibility with the host yams.
In this research, the majority of the yam plants with AMF inoculation had substantially higher chlorophyll content as well as soluble carbohydrate and protein compared with those non-inoculation control group. The amount of chlorophyll content in yam leaves inoculated with AMF the control group were 1.93/1.73, 2.30 /2.10, 2.12/1.86, 1.93/1.62 and 1.93 /1.66 mg/g for Tainung No. 1, Tainung No. 2, Zihyuxieshu , Ercih and Tainung No. 5 respectively; and the maximum increased amount of both the soluble protein and carbohydrate were 76.55/60.83, 98.99/73.70, 147.33/120.80, 74.06/51.37 and 92.91/ 59.41 mg/g; 140.75/105.75, 104.62/81.73, 129.88/103.54, 158.13/110.28 and 157.90/134.27 mg/g respectively. The root colonization by AMF enabled the leaves of host yam presented high concentrations of nitrogen and potassium than those of the controls. However, yams inoculated with six of AMF for six weeks did not increase the content of soluble phosphorus. Our study showed that AMF inoculation can improve the tuber weights of five yams. G. etunicatum inoculation treatment increased the yam tuber weights by 39%, 35%, 20%, 56%, and 40% for Tainung No. 1, Tainung No. 2, Ercih, Zihyuxieshu, and Tainung No. 5 compared with the control group, respectively.
The content of secondary metabolites, such as polyphenols, flavonoids, and anthocyanin, was significantly increased by the AMF treatment in tuber flesh and peel of the tested yam. Specifically, the maximums exchange of secondary metabolite contents increased to 40%, 42%, and 106% for polyphenols, flavonoids and anthocyanin respectively in the tuber fresh. Moreover, those ample functional ingredients, involving polyphenols, flavonoids and anthocyanins can be extracted from the peel of tuber, thereby increasing the potency and utilization of yam tubers. The AMF inoculation boost the secondary metabolites antioxidant compounds, thus enhancing the antioxidant ability of yams. The allantoin analysis experiments showed that the yam tuber peels was with higher allantoin content than the yam tuber flesh. The peels of per gram of tuber are 159%, 209%, 64%, 99% and 97% higher than those of the fresh of Tainung No. 1, Tainung No. 2, Ercih, Zihyuxieshu, and Tainung No. 5, respectively. Compared with the non-inoculated yams, the allantoin levels in tubers presented that in both the fresh and peels were 10.7%, 8.3%, 7.6%, 3.2% and 12.3%; 15.4%, 18.0%, 15.2%, 4.0% and 22.5% for Tainung No. 1, Tainung No. 2, Ercih, Zihyuxieshu, and Tainung No. 5 respectively.
In this study, the data showed that Tainung No. 1, Tainung No. 2 and Ercih three white flesh yams species treated with G. etunicatum and G. mosseae enhanced the yam tuber yield and polyphenols and flavonoids content. The two species of purple yams, Zihyuxieshu and Tainung No. 5, treated with G. etunicatum and Gigaspora sp. enhance the yam tuber yield and polyphenols, flavonoids and anthocyanins content. The inoculation of yams with AMF can expedite plant growth and increase the tuber weight, antioxidants, allantoin content of secondary metabolites in tubers. Therefore, AMF can be used as a microbial fertilizer and developed for yam cultivation and production.
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Lee, Soon-Jae. "The evolution of RNA interference system, blue light sensing mechanism and circadian clock in Rhizophagus irregularis give insight on Arbuscular mycorrhizal symbiosis." Thèse, 2018. http://hdl.handle.net/1866/21776.
Full text
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Iffis, Bachir. "Étude de la biodiversité microbienne associée aux champignons mycorhiziens arbusculaires dans des sites hautement contaminés par des hydrocarbures pétroliers." Thèse, 2016. http://hdl.handle.net/1866/18511.
Full textAbstract:
Les champignons mycorhiziens à arbuscules (CMA) forment un groupe de champignons qui appartient à l'embranchement des Gloméromycètes (Glomeromycota). Les CMA forment des associations symbiotiques, connus sous le nom des mycorhizes à arbuscules avec plus de 80 % des plantes vasculaires terrestres. Une fois que les CMA colonisent les racines de plantes, ils améliorent leurs apports nutritionnels, notamment le phosphore et l'azote, et protègent les plantes contre les différents pathogènes du sol. En contrepartie, les plantes offrent un habitat et les ressources de carbone nécessaires pour le développement et la reproduction des CMA. Des études plus récentes ont démontré que les CMA peuvent aussi jouer des rôles clés dans la phytoremédiation des sols contaminés par les hydrocarbures pétroliers (HP) et les éléments traces métaliques. Toutefois, dans les écosystèmes naturels, les CMA établissent des associations tripartites avec les plantes hôtes et les microorganismes (bactéries et champignons) qui vivent dans la rhizosphère, l'endosphère (à l'intérieur des racines) et la mycosphère (sur la surface des mycéliums des CMA), dont certains d'entre eux jouent un rôle dans la translocation, l’immobilisation et/ou la dégradation des polluants organiques et inorganiques présents dans le sol. Par conséquent, la diversité des CMA et celle des microorganismes qui leur sont associés sont influencées par la concentration et la composition des polluants présents dans le sol, et aussi par les différents exsudats sécrétés par les trois partenaires (CMA, bactéries et les racines de plantes). Cependant, la diversité des CMA et celle des microorganismes qui leur sont associés demeure très peu connue dans les sols contaminés. Les interactions entre les CMA et ces microorganismes sont aussi méconnus aussi bien dans les aires naturelles que contaminées.
Dans ce contexte, les objectifs de ma thèse sont: i) étudier la diversité des CMA et les microorganismes qui leur sont associés dans des sols contaminés par les HP, ii) étudier la variation de la diversité des CMA ainsi que celle des microorganismes qui leur sont associés par rapport au niveau de concentration en HP et aux espèces de plantes hôtes, iii) étudier les correlations (covariations) entre les CMA et les microorganismes qui leur sont associés et iv) comparer les communautés microbiennes trouvées dans les racines et sols contaminés par les HP avec celles trouvées en association avec les CMA.
Pour ce faire, des spores et/ou des propagules de CMA ont été extraites à partir des racines et des sols de l'environnement racinaire de trois espèces de plantes qui poussaient spontanément dans trois bassins de décantation d'une ancienne raffinerie de pétrole située dans la Rive-Sud du fleuve St-Laurent, près de Montréal. Les spores et les propagules collectées, ainsi que des échantillons du sol et des racines ont été soumis à des techniques de PCR (nous avons ciblés les genes 16S de l'ARNr pour bactéries, les genes 18S de l'ARNr pour CMA et les régions ITS pour les autres champignons), de clonage, de séquençage de Sanger ou de séquençage à haut débit. Ensuite, des analyses bio-informatiques et statistiques ont été réalisées afin d'évaluer les effets des paramètres biotiques et abiotiques sur les communautés des CMA et les microorganismes qui leur sont associés.
Mes résultats ont montré une diversité importante de bactéries et de champignons en association avec les spores et les propagules des CMA. De plus, la communauté microbienne associée aux spores des CMA a été significativement affectée par l'affiliation taxonomique des plantes hôtes et les niveaux de concentration en HP. D'autre part, les corrélations positives ou négatives qui ont été observées entre certaines espèces de CMA et microorganismes suggérèrent qu’en plus des effets de la concentration en HP et l'identité des plantes hôtes, les CMA peuvent aussi affecter la structure des communautés microbiennes qui vivent sur leurs spores et mycéliums. La comparaison entre les communautés microbiennes identifiées en association avec les spores et celles identifiées dans les racines montre que les communautés microbiennes recrutées par les CMA sont différentes de celles retrouvées dans les sols et les racines.
En conclusion, mon projet de doctorat apporte de nouvelles connaissances importantes sur la diversité des CMA dans un environnement extrêmement pollué par les HP, et démontre que les interactions entre les CMA et les microorganismes qui leur sont associés sont plus compliquées que ce qu’on croyait précédemment. Par conséquent, d'autres travaux de recherche sont recommandés, dans le futur, afin de comprendre les processus de recrutement des microorganismes par les CMA dans les différents environnements.<br>Arbuscular mycorrhizal fungi (AMF) are an important soil fungal group that belongs to the phylum Glomeromycota. AMF form symbiosic associations known as arbuscular mycorrhiza with more than 80% of vascular plants on earth. Once AMF colonize plant roots, they promote nutrient uptake, in particular phosphorus and nitrogen, and protect plants against soil-borne pathogens. In turn, plants provide AMF with carbon resources and habitat. Furthermore, more recent studies demonstrated that AMF may also play key roles in phytoremediation of soils contaminated with petroleum hydrocarbon pollutants (PHP) and trace elements. Though, in natural ecosystems, AMF undergo tripartite associations with host plants and micoorganisms (Bacteria and Fungi) living in rhizosphere (the narrow region of soil surounding the plant roots), endosphere (inside roots) and mycosphere (on the surface AMF mycelia), which some of them play a key role on translocation, immobilization and/or degradation of organic and inorganic pollutants. Consequently, the diversity and community structures of AMF and their associated microorganisms are influenced by the composition and concentration of pollutants and exudates released by the three partners (AMF, bacteria and plant roots). However, little is known about the diversity of AMF and their associated microorganisms in polluted soils and the interaction between AMF and these microorganisms remains poorly understood both in natural and contaminated areas.
In this context, the objectives of my thesis were to: i) study the diversity of AMF and their associated microorganisms in PHP contaminated soils, ii) study the variation in diversity and community structures of AMF and their associated microorganisms across plant species identity and PHP concentrations, iii) study the correlations (covariations) between AMF species and their associated microorganisms and iv) compare microbial community structures of PHP contaminated soils and roots with those associated with AMF spores in order to determine if the microbial communities shaped on the surface of AMF spores and mycelia are different from those identified in soil and roots.
To do so, AMF spores and/or their intraradical propagules were harvested from rhizospheric soil and roots of three plant species growing spontaneously in three distinct waste decantation basins of a former petrochemical plant located on the south shore of the St-Lawrence River, near Montreal. The harvested spores and propagules, as well as samples of soils and roots were subjected to PCR (we target 16S rRNA genes for bacteria, 18S rRNA genes for AMF and ITS regions for the other fungi), cloning, Sanger sequencing or 454 high throughput sequencing. Then, bioinformatics and statistics were performed to evaluate the effects of biotic and abiotic driving forces on AMF and their associated microbial communities.
My results showed high fungal and bacterial diversity associated with AMF spores and propagules in PHP contaminated soils. I also observed that the microbial community structures associated with AMF spores were significantly affected by plant species identity and PHP concentrations. Furthermore, I observed positive and negative correlations between some AMF species and some AMF-associated microorganisms, suggesting that in addition to PHP concentrations and plant species identity, AMF species may also play a key role in shaping the microbial community surrounding their spores. Comparisons between the AMF spore-associated microbiome and the whole microbiome found in rhizospheric soil and roots showed that AMF spores recruit a microbiome differing from those found in the surrounding soil and roots.
Overall, my PhD project brings a new level of knowledge on AMF diversity on extremely polluted environment and demonstrates that interaction of AMF and their associated microbes is much complex that we though previously. Further investigations are needed to better understand how AMF select and reward their associated microbes in different environments.
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John, Jesse. "Assessment of Arbuscular Mycorrhizal Fungi in a Green Roof System." 2013. http://hdl.handle.net/10222/36259.
Full textAbstract:
Green roof design has proceeded without integration of arbuscular mycorrhizal fungi (AMF). A literature survey was therefore conducted in order to determine which aspects of green roof functioning might be enhanced by AMF, and subsequently levels of AMF and endophyte colonization were determined for seven plant species used in green roofs. Plants were sampled from an experimental green roof and from the field. A commercial growing medium was also tested for AMF inoculum potential. Colonization was poor in both field and rooftop samples of the commercially popular succulent, Sedum acre, but significantly higher in Solidago bicolor, a proposed green roof species. The commercial growing medium was found to contain extremely low levels of viable AMF propagules. Although the apparent lack of mycorrhizal dependency of S. acre helps to explain its popularity as a green roof plant, its overuse precludes the important ecosystem services potentially provided by AMF symbioses.
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Natarajan, Mathimaran. "Communities and functions of arbuscular mycorrhizal fungi are affected by phosphorus fertilization and crop rotation /." 2005. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=16305.
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Kleinmann, Joachim Ulrich. "Plant-fungus interactions and their implications for nutrient cycling and biomass growth: Insights from modelling arbuscular mycorrhizal fungi in a heterogeneous environment." Doctoral thesis, 2017. https://repositorium.ub.uni-osnabrueck.de/handle/urn:nbn:de:gbv:700-2017051515904.
Full textAbstract:
A continuously growing world population with a projected size of more than 9 billion
inhabitants in the year 2040 requires huge efforts in food production while concurrently
avoiding adverse side effects such as the use of pesticides or fertilizers. Among them
phosphorous (P) is an important mineral fertilizer for which only few renewable sources
exist and which is becoming increasingly scarce. Therefore, methods to reduce P fertilization or enhance fertilization efficiency are urgently needed. One idea is to look how plants in natural ecosystems cope with the problem of nutrient limitation. A strategy, found in almost all plant species is interaction with mycorrhizal fungi. Plants usually deliver carbohydrates (C) to the fungi and get nutrients, like phosphorous (P), in exchange. In natural ecosystems, plants usually interact with multiple fungi which perform differently in their P delivery. However, in agro-ecosystems not all these fungi are helpful. Fungi which are carbon
demanding but deliver just few P, might even result in lower plant growth. Therefore a deep
knowledge of the mechanisms driving the P and C dynamics is necessary. This can be gained by a computer simulation model which is possible to examine the influence of different nutrient exchange strategies in detail and make prediction how they perform.
In this PhD thesis, a spatially explicit simulation model of arbuscular mycorrhizal fungi (AMF) was developed and specific laboratory experiments have been conducted and used for model calibration. This model has been used to evaluate the performance of different nutrient exchange strategies by the emerging maximum achievable fungal biomass, the C uptake rate from the plant and the P delivery rate to the plant. On this basis, three
functional types could be identified: parasitic type, intermediate type, mutualistic type.
In further steps these functional types have been used to investigate their performance to
smooth temporal P pulses (i.e., by transforming them into a continuous P flux delivered to the plant) and to take up spatially heterogeneously distributed P. In both cases, the
mutualistic type was found to perform worst and parasitic type best. Two key mechanisms
for efficient resource use in spatiotemporally heterogeneous environments could be
identified. By the ability of quick fungal biomass growth, AMF can efficiently explore space
and store P inside the fungal mycelium. By the creation of spores that do not need C for
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maintenance, AMF can use the saved C to grow new hypha for further spatial exploration.
Through these two mechanisms AMF are able to adapt their mycelium to the spatial and
temporal conditions of the P distribution and thus have the potential to largely enhance Puse
efficiency. This finally might reduce the application of P fertilizers.