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. / NSERC

Empresa Brasileira de Pesquisa Agropecuária / The knowledge of the level of association that occurs between diazotrophic bacteria and fungi arbusculares mycorrhizae (AMF) in grassland ecosystems may be important for the understanding of the changes caused by the addition of fertilizers containing phosphorus (P) and nitrogen (N), in the production and botanical composition of natural pastures. The objective of this study was to evaluate. (a) the occurrence of three genera of diazotrophic bacterial in the root system under fertilization with N and P, and determine the contribution of N via BNF, and (b) evaluate the behavior of the association between AMF and native grasses. Four most abundant grasses in natural grasslands of the Southern Campos in Rio Grande do Sul , Axonopus affinis, Paspalum notatum, Andropogon lateralis and Aristida laevis were grown in pots of 5 kg, in a greenhouse, two studies being conducted (A e B ). In A, two treatments were applied: 50 mg kg-1 soil P and 100 mg kg-1 of soil N (NP) and a control, being evaluated, the number of diazotrophic bacteria of the genera Azotobacter, Azospirillum and Herbaspirillum, and the contribution of BNF was determined by the technique of natural 15N abundance. In B, the treatments consisted of applying 50 mg kg-1 soil P (P), application of 50 mg kg-1 soil P and 100 mg kg-1 of soil N (NP), and a control, in both treatments mycorrhizal colonization was determined. For A, A. laevis demonstrate to be more dependent on biological N fixation than the other species. The grass P. notatum compared with other species demonstrated to be more efficient to absorb available soil N. The dry matter accumulation in shoots of the native species was higher with the application of NP. In B the mycorrhizal colonization was similar between the control, P and NP to the roots of A. lateralis and A. laevis, thus presenting a greater dependence on the mycorrhizal association. Differently, in A. affinis and P. notatum, the mycorrhizal colonization was lower when subjected to fertilization with P and NP, thus presenting a lower dependence. It is concluded for A that fertilization with N and P reduces diazotrophic colonization, increasing the production of dry matter and N content of the tissue. A. laevis showed the highest contribution of biological nitrogen fixation, since P. notatum showed higher N accumulation in soil. In relation to B, A. laevis and A. lateralis have a higher dependence on the mycorrhizal than A. affinis and P. notatum. / O conhecimento do nível de associação que ocorre entre bactérias diazotróficas e fungos micorrízicos arbusculares (FMA) nos ecossistemas campestres, pode ser importante para a o entendimento das alterações provocadas pela adição de fertilizantes, contendo fósforo (P) e nitrogênio (N), na produção e na composição botânica das pastagens naturais. O objetivo do presente trabalho foi avaliar (a) a ocorrência de três gêneros de bactérias diazotróficas no sistema radicular sob fertilização com N e P, e determinar a contribuição de N via FBN, e (b) avaliar o comportamento da associação entre FMAs e gramíneas nativas. Foram utilizadas quatro gramíneas de maior abundância nas pastagens naturais dos Campos Sulinos no Rio Grande do Sul, Axonopus affinis, Paspalum notatum, Andropogon lateralis e Aristida laevis, cultivadas em casa de vegetação, sendo conduzidos dois estudos (A e B). Em A, foram aplicados dois tratamentos: 50 mg kg-1 de solo de P + 100 mg kg-1 de N solo (NP) e uma testemunha, sendo avaliados, o número de bactérias diazotróficas dos gêneros Azotobacter, Azospirillum e Herbaspirillum, e a contribuição da FBN através da técnica da abundância natural de 15N. Em B, os tratamentos consistiram na aplicação de 50 mg kg-1 de solo de P (P); aplicação de 50 mg kg-1 de solo de P + 100 mg kg-1 de N solo (NP), e uma testemunha, em ambos foi determinada a colonização micorrízica. A espécie A. laevis demonstrou ser mais dependente da fixação biológica de N que as demais espécies. A espécie P. notatum em comparação as demais espécies, demostrou ser mais hábil em absorver o N disponível no solo. A matéria seca acumulada da parte aérea das espécies nativas foi maior com a aplicação de NP. A colonização micorrízica foi semelhante entre a testemunha, P e NP para as raízes de A. lateralis e A. laevis, apresentando assim uma maior dependência da associação micorrízica. Diferentemente, nas espécies A. affinis e P. notatum, a colonização micorrízica foi menor quando submetidas a adubação com P e NP, apresentando assim uma menor dependência. Conclui-se assim, que a adubação com N e P reduz a colonização de bactérias diazotróficas, aumentando a produção de matéria seca e teor de N no tecido. A. laevis apresentou a maior contribuição da fixação biológica de nitrogênio, já P. notatum apresentou maior acúmulo de N do solo. As espécies A. laevis e A. lateralis apresentam maior dependência da micorrização que as espécies A. affinis e P. notatum.

Submitted by Sandra Pereira (srpereira@ufrrj.br) on 2017-01-09T10:11:25Z No. of bitstreams: 1 2014 - Joel Quintino de Oliveira Junior.pdf: 986333 bytes, checksum: 680ec4322bce52cb9979155c6978ea36 (MD5) / Made available in DSpace on 2017-01-09T10:11:25Z (GMT). No. of bitstreams: 1 2014 - Joel Quintino de Oliveira Junior.pdf: 986333 bytes, checksum: 680ec4322bce52cb9979155c6978ea36 (MD5) Previous issue date: 2014-02-28 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / Leguminosae comprises a wide variety of species that form symbiosis with mycorrhizal fungi (AMF), and mostly with nitrogen fixing bacteria. Within this frame fits the group Pitadenia encompassing genres: Mimosa , Piptadenia , Parapiptadenia , Anadenathera , Pseudopiptadenia , Microlobius , Stryphnodendron and Adenopia , comprising over 500 species, of which most are found in the New World , especially in Brazil . Their habits vary from tree and herbaceous species to thrive in flooded, dry, high altitude grasslands , savanna ecosystems among other areas . Are well known and used in the rehabilitation of degraded soils by their aggressiveness and ability to grow under adverse soil conditions. Results indicate that in some species of this group only nodulated with the presence of mycorrhizal fungi. Legumes use for the realization of these two symbioses very similar molecular mechanisms and some of leguminous species from the subfamily Mimosoideae show atypical and high potential exploration of evolutionary symbiosis between the two skills. The objective of this work is to investigate and confirm this dependence of the presence of arbuscular mycorrhizal fungi for nodulation and nitrogen fixation in species group Piptadenia nodulated by Burkholderia sp . under controlled conditions / A fam?lia Leguminosae compreende um imensa variedade de esp?cies que formam simbiose com fungos micorr?zicos arbusculares (FMAs) e, em sua grande maioria, com bact?rias fixadoras de nitrog?nio. Dentro desse quadro se encaixa o grupo de Pitadenia que engloba os g?neros: Mimosa, Piptadenia, Parapiptadenia, Anadenathera, Pseudopiptadenia, Microlobius, Stryphnodendron e Adenopia, compreendendo mais de 500 esp?cies, sendo que a maioria delas ? encontrada no novo mundo, em especial no Brasil. Seus h?bitos variam desde esp?cies herb?ceas at? arb?reas e se desenvolvem em ?reas alagadas, secas, campos de altitude, cerrado entre outros ecossistemas. S?o bem conhecidas e utilizadas na reabilita??o de solos degradados por sua agressividade e capacidade de se desenvolver nas mais adversas condi??es ed?ficas. Resultados indicam que em algumas esp?cies desse grupo s? nodulariam com a presen?a de fungos micorr?zicos. As leguminosas usam para a realiza??o dessas duas simbioses mecanismos moleculares muito similares e algumas dessas esp?cies de leguminosas nativas da subfam?lia Mimosoideae mostram habilidades at?picas e com alto potencial de explora??o evolucion?ria entre as duas simbioses. O objetivo deste trabalho ? investigar e confirmar essa depend?ncia da presen?a de fungos micorr?zicos arbusculares para a nodula??o e fixa??o biol?gica de nitrog?nio em esp?cies do grupo de Piptadenia noduladas por Burkholderia sp. sob condi??es controladas

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.

Commercial AM fungi isolates, Rhizophagus clarus, Gigaspora gigantea, Funneliformis mosseae, Claroideoglomus etunicatum and Paraglomus occulum were tested on four seasonal ornamentals, Dianthus chinensis x barbatus, Impatiens wallerana, Petunia x hybrid and Viola x wittrockiana planted in peat-base medium. The experiment was conducted in a glasshouse with three replicates in a completely randomised design. Various vegetative (height, width, length, number of leaves, leaf area and dry biomass) and reproductive (number of flowers and buds) plant parts were measured in the course of three months. AM fungi was found to increase seedling growth and reduced seedling mortality rate of all the plants studied. Inoculated plants produced more leaves (16-33%) and grew taller (12-28%). Dry biomass of inoculated Dianthus, Impatiens and Viola plants were significantly increased by 25-53%. All plants under low colonisation rates displayed mycotrophic qualities and net growth output thereof were found to be similar to plants with equal or higher colonisation rate. Mortality were less frequent in inoculated plants and they were also less susceptible to transplant shock. / Agriculture, Animal Health and Human Ecology / M. Sc. (Ornamental Horticulture)