Arbuscular mycorrhizal fungi (AMF) play a crucial role in improving the growth of a vast majority of plants. Past researchers have discovered that agricultural practices have a significant negative effect on the diversity of AMF. Arbuscular mycorrhizal fungi are reported to enhance plant nutrient uptake, stress tolerance, and soil aggregate formation which are key aspects of productive low-input farming. The objective of this study was to investigate the effects of four pesticides on the ability of AMF to colonize the roots of okra plants (Abelmoschus esculentus). The pesticides being tested include two synthetic chemicals (glyphosate and carbaryl) and two organic chemicals (neem oil and citrus oil). The tested parameters included crop yield, plant biomass, leaf matter CNP, and the percentage of mycorrhizal colonization in roots. The results of this study show that the organic chemicals had no significant effect on AMF colonization while the synthetic chemicals did have somewhat of a negative effect on colonization.

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 / 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

Submitted by Ricardo Cedraz Duque Moliterno (ricardo.moliterno@uefs.br) on 2015-11-17T22:52:38Z No. of bitstreams: 1 DISSERTA??O CD EIRYANNE UEFS.pdf: 1137680 bytes, checksum: c8146db40e5cf5c055b38dd228bd86d9 (MD5) / Made available in DSpace on 2015-11-17T22:52:38Z (GMT). No. of bitstreams: 1 DISSERTA??O CD EIRYANNE UEFS.pdf: 1137680 bytes, checksum: c8146db40e5cf5c055b38dd228bd86d9 (MD5) Previous issue date: 2013-03-20 / The grapevine is one of the most important crops in the San Francisco Valley, to be an important generator of income and social development. It is noteworthy production for the domestic and foreign market, whose requirements demand the need for competitive development of new genetic material to the producer. In this case, the breeding program for cultivation in tropical conditions has employed the crossing of varieties of seedless grapes, using as support embryo rescue technique, which enables the acquisition of hybrid course. Moreover, the cytogenetic characterization of hybrids and parental emerges as a tool that can generate important data for the breeding programs of the grapevine. Counterpart, micropropagation, which is the wider applicability of the technique of tissue culture, has, as one of the many advantages, the large scale production of plants in less time than usual and pathogen-free. During the acclimatization phase of grapevine micropropagation significant losses occur. The various benefits they provide, mycorrhizal fungi are an alternative because they reduce losses, making the transition less stressful conditions in vitro to ex vitro. This study aimed to evaluate cytogenetically vine varieties and hybrids, as well as study the mycorrhizal association in ex vitro establishment of plantlets, trying to select isolates effective in promoting growth and nutrient uptake in apirenic hybrid grapesvines. / A videira representa uma das mais importantes culturas no Vale do S?o Francisco, por ser importante gerador de renda e desenvolvimento social. Destaca-se a produ??o para o mercado interno e externo, cujas exig?ncias em competitividade demandam a necessidade de desenvolvimento de novos materiais gen?ticos para o produtor. Nesse caso, os programas de melhoramento gen?tico para a cultura em condi??es tropicais tem empregado o cruzamento de variedades de uvas apir?nicas, utilizando como suporte a t?cnica de resgate de embri?es, que possibilita a obten??o de h?bridos. Por outro lado, a caracteriza??o citogen?tica de h?bridos e parentais surge como ferramenta que pode gerar dados importantes para os programas de melhoramento gen?tico da videira. Contraparte, a micropropaga??o, que ? a t?cnica de maior aplicabilidade da cultura de tecidos, tem, como uma das muitas vantagens, a produ??o em larga escala de plantas em tempo menor que o habitual, e com garantia fitossanit?ria. Por outro lado, durante a fase de aclimatiza??o da micropropaga??o da videira ocorrem perdas significativas. Nessa fase, pelos v?rios benef?cios que proporcionam, os fungos micorr?zicos arbusculares surgem como alternativa de uso, pois reduzem as perdas, tornando menos estressante a passagem das condi??es in vitro para ex vitro. Este estudo teve como objetivo avaliar citogeneticamente variedades e h?bridos de videira, bem como estudar a associa??o micorr?zica no estabelecimento ex vitro de mudas micropropagadas, buscando selecionar isolados eficientes em promover o crescimento e absor??o de nutrientes em h?brido apir?nico de videiras.

Algumas actinobactérias habitantes da rizosfera são produtoras de substâncias capazes de combater micro-organismos patogênicos às plantas, o que as torna potenciais agentes de controle biológico, passíveis de serem utilizadas como princípio ativo de inoculantes de sementes e mudas. O presente trabalho teve como objetivo isolar e avaliar o potencial de isolados de actinobactérias no controle de doenças causadas por fungos nas espécies arbóreas Araucaria angustifolia (Araucária) e Pinus elliottii (Pinus). Além disso, foi iniciado o estudo do processo de elaboração de inoculante a base de actinobactérias antagônicas. Foram isoladas 215 estirpes de actinobactérias do rizoplano da Araucária, das quais 13 apresentaram, em testes in vitro, potencial como antagonistas contra os fungos fitopatogênicos Fusarium oxysporum, Cylindrocladium candelabrum, C. pteridis e Armillaria sp., e apenas os isolados Ac136 e Ac202 apresentaram os maiores valores de inibição nos testes com os quatro patógenos. Na avaliação de produção de algumas substâncias antimicrobianas, apenas celulases, quitinases e sideróforos foram produzidas pelos isolados, sendo este último o mais frequente. Nos testes de interação com organismos foi verificado que, embora os isolados de actinobactéria tenham inibido a germinação de esporos do fungo micorrízico arbuscular (FMA) Gigaspora rosea em teste in vitro, no experimento in vivo, em que foi utilizado o milho como planta hospedeira para inoculação com o FMA e os isolados A43, Ac136 e Ac202, os isolados Ac136 e Ac202 estimularam a colonização das raízes pelo FMA. Estes mesmos isolados também estimularam a germinação de sementes e desenvolvimento inicial de plântulas de Pinus, porém prejudicaram a germinação e desenvolvimento inicial de Araucária. Estes mesmos isolados foram capazes de reduzir a mortalidade de plântulas de Pinus em cerca de 25%, e esta diminuição foi atribuída à inibição de Fusarium sp.. No teste de viabilidade dos isolados em diferentes veículos o isolado que mostrou maior sobrevivência foi o Ac202, mantendo um número de propágulos viáveis correspondente a 5,48 log UFC mL-1, enquanto que o veículo mais apropriado para a elaboração de inoculante com actinobactérias foi a glicerina. A análise molecular mostrou que os isolados mais promissores apresentaram maior similaridade com S. kasugaensis. Dentre todos isolados Ac202 (S. kasugaensis) foi o mais promissor obtido neste trabalho para o uso como agente de biocontrole de doenças causadas por fungos, apresentando forte antagonismo contra os quatro patógenos testados, promovendo a germinação e desenvolvimento inicial de Pinus e aumentando a sobrevivência de plântulas contaminadas com fungos fitopatogênicos. / Some actinobacteria that inhabits the rhizosphere are producers of substances that are capable of combating plant-pathogenic microorganisms, what makes them potential biological control agents, which can be used as the active ingredient of seeds and seedlings inoculants. This study aimed to isolate and evaluate the potential of actinobacteria isolates in controlling diseases caused by fungi in Araucaria angustifolia and Pinus elliottii. In addition, the study initiated the process of elaboration of an actinobacteria-based inoculant. 215 actinobacterial strains were isolated from the Araucarias rhizoplane, and 13 of them showed potential as antagonists against the phytopathogenic fungi Fusarium oxysporum, Cylindrocladium candelabrum, C. pteridis and Armillaria sp. in in vitro tests, and only the Ac136 and Ac202 strains showed the highest inhibition in the tests against the four pathogens. Among the antimicrobial substances tested, only cellulases, chitinases and siderophores were produced, with the latter being the most frequent. In the interaction tests with other organisms it was found that although the actinobacterial strains have inhibited the germination of the arbuscular mycorrhizal fungi (AMF) Gigaspora rosea spores on the in vitro test, the in vivo experiment, with maize as host plant, inoculated with the AMF and A43, Ac136 and Ac202 actinobacterial strains, Ac136 and Ac202 stimulated root colonization by AMF. These strains also stimulated Pinus seed germination and seedling early development, but hindered the germination and early development of Araucaria. In addition, the same strains were able to reduce the mortality of pine seedlings by about 25%, and this decrease was attributed to the inhibition of Fusarium sp.. In the viability test of the strains in different vehicles the strain that showed the greatest shelf-life was Ac202, with 5.48 log CFU mL-1, and the most appropriate vehicle for the actinobacteriabased inoculant development was glycerin. Molecular analysis showed that the most promising isolates showed the greatest similarity with S. kasugaensis. Among all strains Ac202 (S. kasugaensis) was the most promising one for the use as biocontrol agent of fungal diseases, exhibiting a strong antagonism against the four pathogens tested, promoting germination and early development of Pinus and increasing survival of seedlings infected with pathogenic fungi.

Symbiosis with endomycorrhiza is found in a majority of plant-fungal symbioses. The symbiosis helps with various stressors such as drought and malnutrition. This study looked at how four different field, meadow and brook plants - Centaurea cyanus, Galium verum, Viscaria vulgaris and Veronica beccabunga - are affected by mycorrhiza and fertilizer treatment. The hypotheses tested whether mycorrhiza occurrence and fertilizer treatment affected the total number and number of mature and open flowers in C. cyanus as well as whether mycorrhiza occurrence and fertilizer treatment affected the aboveground biomass and the underground biomass of the four plant species. The study looked at 160 plants and a total of 40 plants of each species were planted. Per species, there were 10 control plants, 10 pots with mycorrhiza and 10 pots with fertilizer as well as 10 pots with both mycorrhiza and fertilizer. The pot arrangement was randomized. Mycorrhizal fungi were collected together with plant roots from different grass and forest habitats. The fertilizer treatment was applied once a week and lasted for six weeks. Two-way ANOVA was used in the analyses of the number of flowers in C. cyanus and three-way ANOVA was used in the analyses of aboveground and underground biomass. Fertilizer treatment had statistically significant effects on both the total number of flowers and the number of mature and open flowers. Fertilizer treatment also increased the aboveground of the selected species as well as the underground biomass of C. cyanus. The underground biomass of the other species decreased. However, the study could not find any significant effect of mycorrhiza treatment nor any significant interaction between mycorrhiza treatment and fertilizer treatment. The study did not test whether or how much of the mycorrhiza colonization was successful and the nonsignificant result may be due to several reasons. More research is needed to confirm the results in this study. / Symbios med endomykorrhiza återfinns hos en majoritet av växt-svampsymbioser. Symbiosen hjälper vid olika typer av stress såsom torka och näringsbrist. Denna studie tittade på hur fyra olika åker-, ängs- och bäckväxter - Centaurea cyanus, Galium verum, Viscaria vulgaris och Veronica beccabunga - påverkas av mykorrhiza och gödsling. Hypoteserna testade om mykorrhizaförekomst och gödsling påverkar det totala antalet och antalet utslagna blommor hos C. cyanus samt ovanjordsbiomassan och underjordsbiomassan hos de fyra växterna. Undersökningen tittade på 160 plantor och totalt planterades 40 plantor av varje art. Per art fanns 10 kontrollplantor, 10 krukor med mykorrhiza och 10 krukor med gödsling samt 10 krukor med både mykorrhiza och gödsling. Krukorna planterades ut slumpmässigt. Mykorrhizasvampar samlades in tillsammans med växtrötter från olika gräs- och skogshabitat. Kvävebehandlingen skedde en gång i veckan och varade i sex veckor. Två-vägs-ANOVA användes vid analys av antal blommor hos C. cyanus och tre-vägs-ANOVA användes vid analys av ovanjords- och underjordsbiomassa. Kvävebehandling kunde signifikant visas öka både det totala antalet blommor och antalet utslagna blommor. Kvävebehandling ökade även ovanjordsbiomassan hos de utvalda arterna samt underjordsbiomassan hos C. cyanus. Underjordsbiomassan minskade hos de andra arterna. Studien kunde emellertid inte hitta någon signifikant effekt av mykorrhizabehandling och inte heller någon signifikant interaktion mellan mykorrhizabehandling och kvävebehandling. I studien testades inte om eller hur mycket av mykorrhizakoloniseringen var framgångsrik och det icke-signifikanta resultatet kan ha haft flera orsaker. Mer forskning behövs för att bekräfta resultaten i denna studie.

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Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / nÃo hà / Nas regiÃes Ãridas e semi-Ãridas à comum a acumulaÃÃo de sais no solo em quantidades prejudiciais ao crescimento e rendimento das plantas. Neste contexto, os fungos micorrÃzicos arbusculares (FMA) vÃm sendo estudados nos Ãltimos anos, havendo resultados que indicam que as associaÃÃes micorrÃzicas com as plantas minimizam alguns efeitos do estresse salino. O presente trabalho teve por objetivo avaliar, mediante parÃmetros fisiolÃgicos e bioquÃmicos, os efeitos da inoculaÃÃo dos fungos micorrÃzicos arbusculares na cultura do meloeiro sob estresse salino. Portanto foi instalado um experimento em casa-de-vegetaÃÃo do Departamento de CiÃncias do Solo da Universidade Federal do CearÃ, no Campus do Pici em Fortaleza. O delineamento experimental utilizado foi o inteiramente ao acaso, em arranjo fatorial 2 (plantas nÃo inoculadas e plantas inoculadas) x 4 (nÃveis de salinidade 0,5; 1,5; 3,0 e 4,5 dS m-1) com 4 repetiÃÃes, totalizando 32 unidades experimentais. No decorrer do experimento foram realizadas mediÃÃes de condutÃncia estomÃtica, taxa de transpiraÃÃo e taxa fotossÃntese. Ao fim de 37 dias apÃs a germinaÃÃo das plantas foi coletado o experimento, quando, entÃo, foram determinados os fatores de crescimento (matÃria seca e Ãrea foliar), as variÃveis microbiolÃgicas (dependÃncia micorrÃzica e colonizaÃÃo), os teores minerais (N, P, K, Ca, Mg, Na e Cl) e os solutos orgÃnicos (carboidratos solÃveis, NaminossolÃveis e prolina). A associaÃÃo com os FMA proporcionou um incremento no desenvolvimento da cultura do meloeiro, proporcionando um aumento na matÃria seca da parte aÃrea e na Ãrea foliar dessa cultura, principalmente no tratamento a 0,5 dS m-1; esse efeito benÃfico, entretanto, decresceu com o incremento da salinidade. A condutÃncia estomÃtica, taxa de transpiraÃÃo e taxa fotossintÃtica foram influenciadas de forma positiva pela associaÃÃo com os FMA, apresentando maiores valores nas plantas inoculadas em diferentes estÃdios de desenvolvimento dessa cultura. Os solutos orgÃnicos, prolina, N-aminossolÃveis e carboidratos solÃveis, nÃo contribuÃram diretamente para o ajuste osmÃtico dos tecidos foliares. A associaÃÃo simbiÃtica entre os FMA e as plantas de meloeiro nÃo proporcionou um aumento na tolerÃncia dessa cultura ao estresse salino, entretanto auxiliou na menor absorÃÃo dos Ãons potencialmente tÃxicos (Na e Cl) a partir da salinidade da Ãgua de irrigaÃÃo de 3 dS m-1. / Nas regiÃes Ãridas e semi-Ãridas à comum a acumulaÃÃo de sais no solo em quantidades prejudiciais ao crescimento e rendimento das plantas. Neste contexto, os fungos micorrÃzicos arbusculares (FMA) vÃm sendo estudados nos Ãltimos anos, havendo resultados que indicam que as associaÃÃes micorrÃzicas com as plantas minimizam alguns efeitos do estresse salino. O presente trabalho teve por objetivo avaliar, mediante parÃmetros fisiolÃgicos e bioquÃmicos, os efeitos da inoculaÃÃo dos fungos micorrÃzicos arbusculares na cultura do meloeiro sob estresse salino. Portanto foi instalado um experimento em casa-de-vegetaÃÃo do Departamento de CiÃncias do Solo da Universidade Federal do CearÃ, no Campus do Pici em Fortaleza. O delineamento experimental utilizado foi o inteiramente ao acaso, em arranjo fatorial 2 (plantas nÃo inoculadas e plantas inoculadas) x 4 (nÃveis de salinidade 0,5; 1,5; 3,0 e 4,5 dS m-1) com 4 repetiÃÃes, totalizando 32 unidades experimentais. No decorrer do experimento foram realizadas mediÃÃes de condutÃncia estomÃtica, taxa de transpiraÃÃo e taxa fotossÃntese. Ao fim de 37 dias apÃs a germinaÃÃo das plantas foi coletado o experimento, quando, entÃo, foram determinados os fatores de crescimento (matÃria seca e Ãrea foliar), as variÃveis microbiolÃgicas (dependÃncia micorrÃzica e colonizaÃÃo), os teores minerais (N, P, K, Ca, Mg, Na e Cl) e os solutos orgÃnicos (carboidratos solÃveis, NaminossolÃveis e prolina). A associaÃÃo com os FMA proporcionou um incremento no desenvolvimento da cultura do meloeiro, proporcionando um aumento na matÃria seca da parte aÃrea e na Ãrea foliar dessa cultura, principalmente no tratamento a 0,5 dS m-1; esse efeito benÃfico, entretanto, decresceu com o incremento da salinidade. A condutÃncia estomÃtica, taxa de transpiraÃÃo e taxa fotossintÃtica foram influenciadas de forma positiva pela associaÃÃo com os FMA, apresentando maiores valores nas plantas inoculadas em diferentes estÃdios de desenvolvimento dessa cultura. Os solutos orgÃnicos, prolina, N-aminossolÃveis e carboidratos solÃveis, nÃo contribuÃram diretamente para o ajuste osmÃtico dos tecidos foliares. A associaÃÃo simbiÃtica entre os FMA e as plantas de meloeiro nÃo proporcionou um aumento na tolerÃncia dessa cultura ao estresse salino, entretanto auxiliou na menor absorÃÃo dos Ãons potencialmente tÃxicos (Na e Cl) a partir da salinidade da Ãgua de irrigaÃÃo de 3 dS m-1. / Nas regiÃes Ãridas e semi-Ãridas à comum a acumulaÃÃo de sais no solo em quantidades prejudiciais ao crescimento e rendimento das plantas. Neste contexto, os fungos micorrÃzicos arbusculares (FMA) vÃm sendo estudados nos Ãltimos anos, havendo resultados que indicam que as associaÃÃes micorrÃzicas com as plantas minimizam alguns efeitos do estresse salino. O presente trabalho teve por objetivo avaliar, mediante parÃmetros fisiolÃgicos e bioquÃmicos, os efeitos da inoculaÃÃo dos fungos micorrÃzicos arbusculares na cultura do meloeiro sob estresse salino. Portanto foi instalado um experimento em casa-de-vegetaÃÃo do Departamento de CiÃncias do Solo da Universidade Federal do CearÃ, no Campus do Pici em Fortaleza. O delineamento experimental utilizado foi o inteiramente ao acaso, em arranjo fatorial 2 (plantas nÃo inoculadas e plantas inoculadas) x 4 (nÃveis de salinidade 0,5; 1,5; 3,0 e 4,5 dS m-1) com 4 repetiÃÃes, totalizando 32 unidades experimentais. No decorrer do experimento foram realizadas mediÃÃes de condutÃncia estomÃtica, taxa de transpiraÃÃo e taxa fotossÃntese. Ao fim de 37 dias apÃs a germinaÃÃo das plantas foi coletado o experimento, quando, entÃo, foram determinados os fatores de crescimento (matÃria seca e Ãrea foliar), as variÃveis microbiolÃgicas (dependÃncia micorrÃzica e colonizaÃÃo), os teores minerais (N, P, K, Ca, Mg, Na e Cl) e os solutos orgÃnicos (carboidratos solÃveis, NaminossolÃveis e prolina). A associaÃÃo com os FMA proporcionou um incremento no desenvolvimento da cultura do meloeiro, proporcionando um aumento na matÃria seca da parte aÃrea e na Ãrea foliar dessa cultura, principalmente no tratamento a 0,5 dS m-1; esse efeito benÃfico, entretanto, decresceu com o incremento da salinidade. A condutÃncia estomÃtica, taxa de transpiraÃÃo e taxa fotossintÃtica foram influenciadas de forma positiva pela associaÃÃo com os FMA, apresentando maiores valores nas plantas inoculadas em diferentes estÃdios de desenvolvimento dessa cultura. Os solutos orgÃnicos, prolina, N-aminossolÃveis e carboidratos solÃveis, nÃo contribuÃram diretamente para o ajuste osmÃtico dos tecidos foliares. A associaÃÃo simbiÃtica entre os FMA e as plantas de meloeiro nÃo proporcionou um aumento na tolerÃncia dessa cultura ao estresse salino, entretanto auxiliou na menor absorÃÃo dos Ãons potencialmente tÃxicos (Na e Cl) a partir da salinidade da Ãgua de irrigaÃÃo de 3 dS m-1. / The accumulation of salts in the soil is a common problems of arid and semi-arid regions, that cause reduction in plant growth and yield. In this context, the arbuscular mycorrhizal fungi (AMF) have been studied in recent years, with results indicating that their associations with the plants roots minimize some effects of salt stress. The objective of this work was to evaluate the influence of increasing levels of salinity of the irrigation water in the melon plants mycorrhized with AMF. The experiment was carried out at the greenhouse of the Departamento de CiÃncias dos Solo da Universidade Federal do CearÃ, in Fortlaeza, CearÃ. The experiment design was completely randomized with treatments outlined following a 2 x 4 factorial design, comprised of two mycorrhiza treatments (inoculated and not inoculated plants) x 4 levels of salinity (CEa = 0.5; 1.5; 3.0 and 4.5 dS m-1), with 4 repetitions. During the experiment were conducted measurements of stomatal conductance, transpiration and photosynthesis rates. The plants were collected thirty-seven days after germination, when growth (dry and leaf area), microbiological traits (dependency and mycorrhizal colonization), mineral content (N, P, K, Ca, Mg, Na, Cl) and the organic solutes concentrations (soluble carbohydrates, N-aminossolÃveis and proline) were measured. The mycorrhized plants showed higher production of shoot dry matter and leaf area, in relation to non-inoculated plants, mainly in the treatment of 0.5 dS m-1. However, this beneficial effect decreased in the higher levels of salinity. The stomatal conductance, transpiration rate and photosynthetic rate were influenced by AMF, being the values higher in mycorrhized plants. The organic solutes, proline, N-aminossolÃveis carbohydrates soluble, did not contribute directly to the osmotic adjustment of leaf tissue. The symbiotic association between the AMF, and the melon has not provided an increase in tolerance of this culture to salt stress, however helped in lower absorption of potentially toxic ions (Na, Cl) from the salinity of irrigation water 3.0 dS m - 1. / The accumulation of salts in the soil is a common problems of arid and semi-arid regions, that cause reduction in plant growth and yield. In this context, the arbuscular mycorrhizal fungi (AMF) have been studied in recent years, with results indicating that their associations with the plants roots minimize some effects of salt stress. The objective of this work was to evaluate the influence of increasing levels of salinity of the irrigation water in the melon plants mycorrhized with AMF. The experiment was carried out at the greenhouse of the Departamento de CiÃncias dos Solo da Universidade Federal do CearÃ, in Fortlaeza, CearÃ. The experiment design was completely randomized with treatments outlined following a 2 x 4 factorial design, comprised of two mycorrhiza treatments (inoculated and not inoculated plants) x 4 levels of salinity (CEa = 0.5; 1.5; 3.0 and 4.5 dS m-1), with 4 repetitions. During the experiment were conducted measurements of stomatal conductance, transpiration and photosynthesis rates. The plants were collected thirty-seven days after germination, when growth (dry and leaf area), microbiological traits (dependency and mycorrhizal colonization), mineral content (N, P, K, Ca, Mg, Na, Cl) and the organic solutes concentrations (soluble carbohydrates, N-aminossolÃveis and proline) were measured. The mycorrhized plants showed higher production of shoot dry matter and leaf area, in relation to non-inoculated plants, mainly in the treatment of 0.5 dS m-1. However, this beneficial effect decreased in the higher levels of salinity. The stomatal conductance, transpiration rate and photosynthetic rate were influenced by AMF, being the values higher in mycorrhized plants. The organic solutes, proline, N-aminossolÃveis carbohydrates soluble, did not contribute directly to the osmotic adjustment of leaf tissue. The symbiotic association between the AMF, and the melon has not provided an increase in tolerance of this culture to salt stress, however helped in lower absorption of potentially toxic ions (Na, Cl) from the salinity of irrigation water 3.0 dS m - 1. / The accumulation of salts in the soil is a common problems of arid and semi-arid regions, that cause reduction in plant growth and yield. In this context, the arbuscular mycorrhizal fungi (AMF) have been studied in recent years, with results indicating that their associations with the plants roots minimize some effects of salt stress. The objective of this work was to evaluate the influence of increasing levels of salinity of the irrigation water in the melon plants mycorrhized with AMF. The experiment was carried out at the greenhouse of the Departamento de CiÃncias dos Solo da Universidade Federal do CearÃ, in Fortlaeza, CearÃ. The experiment design was completely randomized with treatments outlined following a 2 x 4 factorial design, comprised of two mycorrhiza treatments (inoculated and not inoculated plants) x 4 levels of salinity (CEa = 0.5; 1.5; 3.0 and 4.5 dS m-1), with 4 repetitions. During the experiment were conducted measurements of stomatal conductance, transpiration and photosynthesis rates. The plants were collected thirty-seven days after germination, when growth (dry and leaf area), microbiological traits (dependency and mycorrhizal colonization), mineral content (N, P, K, Ca, Mg, Na, Cl) and the organic solutes concentrations (soluble carbohydrates, N-aminossolÃveis and proline) were measured. The mycorrhized plants showed higher production of shoot dry matter and leaf area, in relation to non-inoculated plants, mainly in the treatment of 0.5 dS m-1. However, this beneficial effect decreased in the higher levels of salinity. The stomatal conductance, transpiration rate and photosynthetic rate were influenced by AMF, being the values higher in mycorrhized plants. The organic solutes, proline, N-aminossolÃveis carbohydrates soluble, did not contribute directly to the osmotic adjustment of leaf tissue. The symbiotic association between the AMF, and the melon has not provided an increase in tolerance of this culture to salt stress, however helped in lower absorption of potentially toxic ions (Na, Cl) from the salinity of irrigation water 3.0 dS m - 1.

3 vidéos sont dans des fichiers complémentaires à ce mémoire / Les champignons mycorhiziens à arbuscules (CMA) ont une structure génétique très particulière et certains aspects de leur génétique sont encore incompris et peu documentés. Les CMA se reproduisent par voie asexuée à l’aide de spores multinucléées. Dans cette étude, j’ai cherché à comprendre les mécanismes de l’hérédité génétique des noyaux par la voie de la reproduction asexuée chez les CMA. La première étape était de déterminer le contenu en noyaux des spores matures, ainsi que celui des spores en formation. Des analyses statistiques ont été utilisées pour vérifier le type de relation entre le nombre de noyaux et le diamètre des spores. Quatre espèces du genre Glomus ont été observées au microscope confocal. Les résultats démontrent une hétérogénéité entre les spores dans leur contenu en noyau pour un même diamètre en plus d’une relation positive entre le nombre de noyau et le diamètre de la spore. Afin de vérifier le contenu en noyaux dans les phases extraracinaires, trois différentes structures du mycélium ont été observées au microscope confocal. Aucune structure n’a été retrouvée avec un seul noyau, ce qui permet de conclure que les CMA ne possèdent vraisemblablement pas de stade uninucléé dans leurs phases extraracinaires. Pour étudier l’hérédité des noyaux, deux différentes approches ont été utilisées: (i) Glomus irregulare a été mis sur milieu complémenté avec de l’aphidicoline pour inhiber la mitose. Des observations au microscope confocal ont permis de dénombrer les noyaux qui sont issus des hyphes et non des mitoses. Les résultats indiquent que la population de noyaux présents dans les spores matures provient d’une migration massive de noyaux à l’intérieur des spores en formation suivie d’un nombre faible de mitoses. (ii) La deuxième approche est l’observation microscopique en temps-réel de spores en formation de G. diaphanum qui a permis de confirmer cette affirmation, car il a été possible de voir plusieurs noyaux entrer dans la spore. Dans la dernière partie de cette étude, je me suis intéressée aux échanges génétiques horizontaux chez les CMA qui sont possibles grâce aux anastomoses. Quatre isolats de l’espèce G. irregulare ont été croisés en co-culture par couple de deux isolats (six croisements) pour permettre une proximité propice aux anastomoses et aux échanges génétiques. Ces croisements ont été maintenus pendant deux ans en culture par le repicage des racines colonisées. Des spores des deux différents isolats ont été confrontées sur eau gélifiée, afin d’observer la formation d’anastomose. Un pourcentage de 13% de formation de fusions d’hyphes pour une des confrontations suggère que l’échange des marqueurs parentaux a pu avoir lieu entre les deux isolats grâce aux anastomoses. Un marqueur moléculaire mitochondrial nommé Indel 5 a été développé et utilisé pour l’analyse des spores filles. Ce marqueur possède entre les isolats une délétion de 39 pb et la différence entre les isolats est facilement détectable sur gel d’électrophorèse après amplification PCR. Le génotypage par PCR des spores individuelles a montré que certaines des spores filles issues du croisement possèdent un des deux marqueurs parentaux alors que d’autres spores ont un génotype qui semble posséder les deux marqueurs. Même si la fusion d’hyphes entre spores en germination est possible, d’autres recherches devront être réalisées pour confirmer qu’un échange génétique est possible entre deux isolats très éloignés géographiquement. Le fait qu’il n’existe aucun stade uninucléé au cycle de vie des CMA et qu’il y ait une migration massive de noyaux lors de la formation des spores permet de limiter la dérive génique lors de la reproduction asexuée. Les anastomoses, quant à elles, permettent de rétablir la diversité génétique. Ces deux particularités de la génétique des CMA ont été fort importantes au cours de leur évolution pour permettre de maintenir une variabilité génétique élevée et permettre ainsi une grande adaptation à différents type d’habitats. / Arbuscular Mycorrhizal Fungi (AMF) have a particular and complex genetic structure. Yet, many aspects of their genetics are still misunderstood and poorly documented. These organisms reproduce by asexual multinucleate spores. In this study, I investigated the mechanisms of genetic inheritance of nuclei through asexual reproduction in AMF. First, I determined the number of nuclei in mature and juveniles spores; I used statistical analysis to determine the relationship between the number of nuclei and the spore diameter. Four species from the genus Glomus were observed with a confocal microscope. The results showed that the number of nuclei has a significant positive relationship with spore diameter and more importantly, surprising heterogeneity in the number of nuclei among sister spores was found. To determine the number of nuclei in extraradical phases, three different structures from the mycelia were carefully examined with a confocal microscope. All the structures possessed more than one nucleus and showed that AMF probably lack a single-nucleus stage during their extraradical phases. To study the nuclei’s heritance, two different approaches were used: (i) Glomus irregulare was grown on medium complemented with aphidicolin to inhibit the mitosis. Observations with a confocal microscope permit to count the nuclei that come from the hyphae and not from the mitosis. The results showed that massive nuclear migration and mitosis are the mechanisms by which AMF spores are formed. (ii) The second approach confirm these results because with time-laps live cellular imaging of young spores of Glomus diaphanum it was possible to see many nuclei to get in the spores. In a second part of this thesis, I studied horizontal gene exchanges among AMF isolates through anastomoses. Thus, four isolates of the species G. irregulare were used in in vitro crossing experiments, in total six combinations using two isolates per crossing experiment. These crossing co-cultures were maintained over two years by subculturing. Spores of two different isolates were confronted in vitro prior to observation of anastomoses. 13% of spores formed anastomoses suggesting the occurrence of genetic exchange between two isolates. A mitochondrial molecular marker referred as Indel 5, was used to genotype individual spores of crossing progenies. A 39 bp deletion occurs in the marker among different isolates and is clearly discriminated by PCR. PCR patterns showed that some spores seem to have both parental markers demonstrating that genetic exchange could occur between the two isolates used in crossing experiment. Even though hyphal fusions occur between germinating spores, subsequent research needs to be done to confirm genetic exchange among different isolates from different geographic areas. The finding that AMF lack a single nuclear stage in their extraradical phases and that mitosis and nuclear migration are the mechanisms by which AMF spores are formed reduce genetic drift that acts on these organisms during asexual reproduction. Anastomoses are likely a mechanism that maintains the genetic diversity in AMF. These genetic characteristics of AMF were very important during their evolution to maintain a high genetic variability that allows their adaptation to many different ecosystems.