Plant growth-promoting rhizobacteria (PGPR) are free-living, soil-borne bacteria that colonize the rhizosphere and, when applied to crops, enhance the growth of plants. Plant growth-promoting rhizobacteria may enhance plant growth either by direct or indirect mechanisms. The direct mechanisms of action include nitrogen fixation,production of phytohormones and lowering of ethylene concentrations. The objective of this study was to determine whether Pseudomonas putida strain 6-8 isolated from the rhizosphere of legume crops grown in Saskatchewan fields was able to promote the growth of canola cv. Smart and lentil cv. Milestone plants by direct mechanisms. Initial studies determined the effect of strain 6-8 and other known phytohormoneproducing PGPR strains on the growth of canola and lentil plants both in gnotobiotic and growth chamber conditions. Variations in the results were observed, as there were significant differences among trials. Strain 6-8 enhanced the growth of canola cv. Smart in growth pouches but not in pots in growth chamber studies. In the case of lentil cv.Milestone, strain 6-8 had no significant effect in growth pouches, but it significantly increased root dry weight, shoot dry weight and root surface area in pots in growth chamber studies. A similar effect was observed with wild-type strains GR12-2 and G20- 18. Strain GR12-2 was consistent in promoting the growth of lentil cv. Milestone both in growth pouches and in pots in growth chambers when compared to other strains and the control. The ability of the PGPR strains to produce auxin and cytokinin phytohomones in pure culture and in the canola rhizosphere was tested using the enzyme linked immunosorbent assay (ELISA). All the PGPR strains produced indole compounds and the concentration of the indoles produced increased with increasing concentrations of the precursor tryptophan. There were no significant differences among PGPR strains in production of indole-3-acetic acid (IAA) when assayed using ELISA. The concentrations of IAA secreted by PGPR strains were extremely low (0.19 µg/ml 9.80 µg/ml). Strain 6-8 produced the cytokinins, isopentenyl adenosine (IPA), zeatin riboside (ZR) and dihydroxyzeatin riboside (DHZR) in pure culture. Indole-3-acetic acid was detected in supernatants obtained from canola growth pouches inoculated with PGPR strains, but there were no significant differences in the concentrations of IAA secreted among PGPR strains. Significantly higher concentrations of IPA and ZR were observed in the rhizosphere of canola inoculated with strain 6-8 than in the non-inoculated control. Strain 6-8 produced siderophores, solubilized inorganic phosphate and used 1-aminocyclopropane-1-carboxylic acid (ACC), the precursor of ethylene, as sole nitrogen source. These traits are considered to be alternative mechanisms for direct plant growth promotion. A qualitative and quantitative study of root colonization by strain 6-8 was conducted by tagging the strain with green fluorescent protein in conjunction with confocal laser scanning microscopy and by conventional plating. The populations of strain 6-8 were higher on canola roots than on lentil roots by conventional plating. Similar results were also observed in confocal laser scanning microscopy (CLSM) studies after 5, 7 and 9 days for canola and 3, 6 and 9 days for lentil. Pseudomonas putida strain 6-8 produced cytokinins and also possessed other direct growth promoting characteristics. The ability of strain 6-8 to promote the growth of canola cv. Smart in growth pouches and lentil cv. Milestone in growth chamber studies may be related to these direct growth promoting characteristics. Strain 6-8 may have potential for development as a plant growth-promoting rhizobacterial inoculant.

<i>Pseudomonas fluorescens</i> BRG100 produces secondary metabolites with herbicidal activity to the grass weeds wild oat, Avena fatua, and green foxtail, Setaria viridis. The green fluorescence protein (gfp) gene was introduced into P. fluorescens BRG100 from Escherichia coli S17-1¥ë via a Tn5 mini transposon suicide vector system. Colony morphology, growth rate in liquid media, weed biocontrol efficacy (plant growth pouch), carbon utilization (Biolog GN) and root colonization of green foxtail by several P. fluorescens BRG100gfp transformants were determined to be the same as the wild type. <i>Pseudomonas fluorescens</i> BRGgfp-15 was found to be most similar to the wild-type in all of the above characteristics and was thus used in subsequent experiments. Note: all strains of Pseudomonas fluorescens will be referred to by only their strain throughout (ie. BRGgfp-15 and BRG100). <p>It was determined by population dynamics per section of root with spiral plating on culture medium, epi-fluorescence and confocal microscopy that BRGgfp-15 colonized all areas of the root, but showed a preference for the proximal 1/3 section and the seed. In the proximal section the mean number of viable cells per gram dry weight was log109.06 and log109.31, when applied as liquid inoculum and as the pesta granular formulation, respectively. With liquid inoculum there was only log107.53 viable cells/g in the middle 1/3 section and log107.01 viable cells/g in the distal 1/3 section. The number of viable cells/g with pesta granules was log107.61 and log107.34, for the middle and distal sections, respectively. The root hairs, root tip, and ventral portion of the seed were all areas of heavy colonization relative to the other areas of the root. <p>Survival of BRGgfp-15 in the pesta formulation was examined in 2 soil types, clay and clay loam, in a thermogradient plate apparatus by a factorial randomized design complete block experiment. The experiment included: 3-12 hour diurnal temperature regimes: 5-15¨¬C, 15-25¨¬C, and 25-35¨¬C and 3 moisture levels: 25, 50 and 75% of soil moisture holding capacity. Sampling was carried out after 0, 14, 28 and 42 days. The highest numbers of viable BRGgfp-15 cells/g were found in the pesta granules in soil subjected to the lowest diurnal temperature regime and moisture content. The lowest numbers of viable cells/g were found in the pesta granules incubated in the highest diurnal temperature and moisture. This suggests lower soil temperature and moisture enhances survival of BRGgfp-15 in pesta and/ or higher soil temperature and moisture enhances the release and dissemination of BRGgfp-15 from pesta granules. When subjected to a 5-15¨¬C-temperature regime the number of viable cells/g was log109.80. When subjected to 15-25¨¬C the viable cells/g was log108.96 and with 25-35¨¬C it was log107.33. The mean number of viable cells/g was log109.36, log108.86, and log107.87, for 25, 50, and 75% soil moisture holding capacity, respectively. There was also a significantly higher number of viable cells/g in the clay soil collected from Saskatoon, log109.00, as compared to the clay loam soil collected from Scott, which was log108.40. <p>These results suggest that Pseudomonas fluorescens BRG100 has considerable potential as a bioherbicide because of its successful root colonization of green foxtail and wheat. <i>Pseudomonas fluorescens</i> BRGgfp-15 survived well under various environmental conditions when formulated into pesta granules, proving the pesta formulation was an excellent formulation. In addition, gfp was shown to be an excellent conservative marker for monitoring the root colonization and survival of <i>P. fluorescens</i> BRG100.

Plant growth-promoting rhizobacteria (PGPR) are free-living, soil-borne bacteria that colonize the rhizosphere and, when applied to crops, enhance the growth of plants. Plant growth-promoting rhizobacteria may enhance plant growth either by direct or indirect mechanisms. The direct mechanisms of action include nitrogen fixation,production of phytohormones and lowering of ethylene concentrations. The objective of this study was to determine whether Pseudomonas putida strain 6-8 isolated from the rhizosphere of legume crops grown in Saskatchewan fields was able to promote the growth of canola cv. Smart and lentil cv. Milestone plants by direct mechanisms. Initial studies determined the effect of strain 6-8 and other known phytohormoneproducing PGPR strains on the growth of canola and lentil plants both in gnotobiotic and growth chamber conditions. Variations in the results were observed, as there were significant differences among trials. Strain 6-8 enhanced the growth of canola cv. Smart in growth pouches but not in pots in growth chamber studies. In the case of lentil cv.Milestone, strain 6-8 had no significant effect in growth pouches, but it significantly increased root dry weight, shoot dry weight and root surface area in pots in growth chamber studies. A similar effect was observed with wild-type strains GR12-2 and G20- 18. Strain GR12-2 was consistent in promoting the growth of lentil cv. Milestone both in growth pouches and in pots in growth chambers when compared to other strains and the control. The ability of the PGPR strains to produce auxin and cytokinin phytohomones in pure culture and in the canola rhizosphere was tested using the enzyme linked immunosorbent assay (ELISA). All the PGPR strains produced indole compounds and the concentration of the indoles produced increased with increasing concentrations of the precursor tryptophan. There were no significant differences among PGPR strains in production of indole-3-acetic acid (IAA) when assayed using ELISA. The concentrations of IAA secreted by PGPR strains were extremely low (0.19 µg/ml 9.80 µg/ml). Strain 6-8 produced the cytokinins, isopentenyl adenosine (IPA), zeatin riboside (ZR) and dihydroxyzeatin riboside (DHZR) in pure culture. Indole-3-acetic acid was detected in supernatants obtained from canola growth pouches inoculated with PGPR strains, but there were no significant differences in the concentrations of IAA secreted among PGPR strains. Significantly higher concentrations of IPA and ZR were observed in the rhizosphere of canola inoculated with strain 6-8 than in the non-inoculated control. Strain 6-8 produced siderophores, solubilized inorganic phosphate and used 1-aminocyclopropane-1-carboxylic acid (ACC), the precursor of ethylene, as sole nitrogen source. These traits are considered to be alternative mechanisms for direct plant growth promotion. A qualitative and quantitative study of root colonization by strain 6-8 was conducted by tagging the strain with green fluorescent protein in conjunction with confocal laser scanning microscopy and by conventional plating. The populations of strain 6-8 were higher on canola roots than on lentil roots by conventional plating. Similar results were also observed in confocal laser scanning microscopy (CLSM) studies after 5, 7 and 9 days for canola and 3, 6 and 9 days for lentil. Pseudomonas putida strain 6-8 produced cytokinins and also possessed other direct growth promoting characteristics. The ability of strain 6-8 to promote the growth of canola cv. Smart in growth pouches and lentil cv. Milestone in growth chamber studies may be related to these direct growth promoting characteristics. Strain 6-8 may have potential for development as a plant growth-promoting rhizobacterial inoculant.

<i>Pseudomonas fluorescens</i> BRG100 produces secondary metabolites with herbicidal activity to the grass weeds wild oat, Avena fatua, and green foxtail, Setaria viridis. The green fluorescence protein (gfp) gene was introduced into P. fluorescens BRG100 from Escherichia coli S17-1¥ë via a Tn5 mini transposon suicide vector system. Colony morphology, growth rate in liquid media, weed biocontrol efficacy (plant growth pouch), carbon utilization (Biolog GN) and root colonization of green foxtail by several P. fluorescens BRG100gfp transformants were determined to be the same as the wild type. <i>Pseudomonas fluorescens</i> BRGgfp-15 was found to be most similar to the wild-type in all of the above characteristics and was thus used in subsequent experiments. Note: all strains of Pseudomonas fluorescens will be referred to by only their strain throughout (ie. BRGgfp-15 and BRG100). <p>It was determined by population dynamics per section of root with spiral plating on culture medium, epi-fluorescence and confocal microscopy that BRGgfp-15 colonized all areas of the root, but showed a preference for the proximal 1/3 section and the seed. In the proximal section the mean number of viable cells per gram dry weight was log109.06 and log109.31, when applied as liquid inoculum and as the pesta granular formulation, respectively. With liquid inoculum there was only log107.53 viable cells/g in the middle 1/3 section and log107.01 viable cells/g in the distal 1/3 section. The number of viable cells/g with pesta granules was log107.61 and log107.34, for the middle and distal sections, respectively. The root hairs, root tip, and ventral portion of the seed were all areas of heavy colonization relative to the other areas of the root. <p>Survival of BRGgfp-15 in the pesta formulation was examined in 2 soil types, clay and clay loam, in a thermogradient plate apparatus by a factorial randomized design complete block experiment. The experiment included: 3-12 hour diurnal temperature regimes: 5-15¨¬C, 15-25¨¬C, and 25-35¨¬C and 3 moisture levels: 25, 50 and 75% of soil moisture holding capacity. Sampling was carried out after 0, 14, 28 and 42 days. The highest numbers of viable BRGgfp-15 cells/g were found in the pesta granules in soil subjected to the lowest diurnal temperature regime and moisture content. The lowest numbers of viable cells/g were found in the pesta granules incubated in the highest diurnal temperature and moisture. This suggests lower soil temperature and moisture enhances survival of BRGgfp-15 in pesta and/ or higher soil temperature and moisture enhances the release and dissemination of BRGgfp-15 from pesta granules. When subjected to a 5-15¨¬C-temperature regime the number of viable cells/g was log109.80. When subjected to 15-25¨¬C the viable cells/g was log108.96 and with 25-35¨¬C it was log107.33. The mean number of viable cells/g was log109.36, log108.86, and log107.87, for 25, 50, and 75% soil moisture holding capacity, respectively. There was also a significantly higher number of viable cells/g in the clay soil collected from Saskatoon, log109.00, as compared to the clay loam soil collected from Scott, which was log108.40. <p>These results suggest that Pseudomonas fluorescens BRG100 has considerable potential as a bioherbicide because of its successful root colonization of green foxtail and wheat. <i>Pseudomonas fluorescens</i> BRGgfp-15 survived well under various environmental conditions when formulated into pesta granules, proving the pesta formulation was an excellent formulation. In addition, gfp was shown to be an excellent conservative marker for monitoring the root colonization and survival of <i>P. fluorescens</i> BRG100.

Previous studies have shown that chemotaxis plays an important role in the colonization of the wheat roots surfaces by Azospirillum brasilense and a chemotaxis operon shown to control motility and chemotaxis in A. brasilense has been isolated. This study looked at the effects of mutations in individual genes coding for chemotaxis proteins from this operon on the ability of the cells to colonize the surface of sterile wheat roots. Using both quantitative and qualitative assays, the study shows differences in the colonization ability of the mutants relative to the wild type: the cheB, cheR, cheBR, and cheOp mutants were significantly impaired in wheat root colonization. Interestingly, the cheA mutant was not affected in its ability to colonize the wheat root surface relative to the wild type. Future studies will look for the factors that compensate for cheA impairment in the rhizosphere.

Previous studies have shown that chemotaxis plays an important role in the colonization of the wheat roots surfaces by Azospirillum brasilense and a chemotaxis operon shown to control motility and chemotaxis in A. brasilense has been isolated. This study looked at the effects of mutations in individual genes coding for chemotaxis proteins from this operon on the ability of the cells to colonize the surface of sterile wheat roots. Using both quantitative and qualitative assays, the study shows differences in the colonization ability of the mutants relative to the wild type: the cheB, cheR, cheBR, and cheOp mutants were significantly impaired in wheat root colonization. Interestingly, the cheA mutant was not affected in its ability to colonize the wheat root surface relative to the wild type. Future studies will look for the factors that compensate for cheA impairment in the rhizosphere.

Submitted by (lucia.rodrigues@ufrpe.br) on 2016-07-05T12:16:24Z No. of bitstreams: 1 Emmanuella Vila Nova da Silva.pdf: 1939037 bytes, checksum: f521d3bf721007766ec42ccf2f7454a6 (MD5) / Made available in DSpace on 2016-07-05T12:16:24Z (GMT). No. of bitstreams: 1 Emmanuella Vila Nova da Silva.pdf: 1939037 bytes, checksum: f521d3bf721007766ec42ccf2f7454a6 (MD5) Previous issue date: 2012-03-07 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The use of plants symbiotically associated with N2 fixing bacteria and mycorrhizal fungi (AMF) provides an efficient strategy to accelerate the recovery of impacted areas and reduces its costs considerably. The term "mycorrhiza helper bacteria” (MHB) has been introduced and discussed due to the synergistic effect that this dual combination promotes to plants. They are bacteria associated with roots and AMF that selectively promote the establishment of symbiosis with fungi. Thus, the objectives were to verify the AMF activity in the area with native vegetation in the Pernambucano semiarid, municipality of Sertânia; determine glomerospores number and the most probable number (MPN) of infective propagules; quantify the content of glomalin-related protein in the soil and determine the feasibility of bacteria (MHB) co-inoculation and AMF mixture in “sabiá” (Mimosa caesalpiniifolia Benth) aiming at obtaining combinations and compatibility of symbiotic pairs, as well as to evaluate the mycorrhizal efficiency and colonization. The experiments were conducted in greenhouse of the Agronomic Institute of Pernambuco (IPA). 10 composite soil samples were collected with points were defined at random. Samples were homogenized and analyzed for physical and chemical characteristics. Composite samples were used for direct count (DC) and propagation of AMF for indirect count (IC) of spores, using trap- cultures and sorghum (Sorghum bicolor L. Moench) and peanut (Arachis hypogea L.) as host plants (experiment I). To determine the MPN of infective propagules of AMF in the Haplic Luvisol was used a system of serial dilution: 0, 1:10, 1:100 and 1:1000 with five replicates each, with maize (Zea mays L.) as host plant (experiment II). In the experiment III were used pots with Haplic Luvisol soil (8 kg pot-1) at pH 6.0 and the plant used was the “sabiá”. On seeding, inoculation with Burkholderia sabiae (BR 3405) and co-inoculation with BR3405 + MHB were performed and each seed was inoculated with 2 mL of specific medium for each of MHB bacteria and for the BR3405 containing 108 CFU mL-1. In the inoculation with AMF mixture was used 4 g pot-1 in the form of propagule containing approximately 670 spores. Plants were harvested at 110 days after planting (DAP) and the following variables were evaluated: shoot dry mass (SDM), root (RDM), RDM/SDM ratio, plant height (PH) on periods of 45, 90 and 110 days, root length (RL), total N accumulated in SDM (Nat), strains efficiency (E) and mycorrhizal colonization. The experimental design was randomized blocks, with 9 x 2 factorial arrangement plus an absolute control (AC) - without inoculation; MHB strains and one control treatment inoculated only with Burkholderia sabiae with and without AMF (AMF mixture) with 3 blocks . The experimental results show that the MPN of AMF infective propagules found in the city of Sertânia was 23 propagules cm-3. Soil proteins related to easily extractable glomalin (PSRGFE) and soil proteins related to total glomalin (PSRGT) were approximately 0.46 and 0.26 mg g soil-1, respectively. The AMF colonization combined with the bacteria was positive, as in the case of RL, treatments with BR 3405 + Azospirillum amazonenses (Y2) and BR 3405 + Herbaspirillum seropedicae (Z67) showed significant difference by the Tukey test (p <0.05) compared to the factor with and without AMF. Thereby ensuring that, in the presence of MHB bacteria there was increase in root length of “sabiá” plants. Strains efficiency showed better results when bacteria were in the presence of AMF and the treatment BR 3405 + Paenibacillus brasilensis (24) + AMF showed the best response. The treatments that received AMF were higher compared to the others on the variables SDM, RDM, E, Nac, coming to present on average 84% of root colonization. / A utilização de plantas associadas simbioticamente, com bactérias fixadoras de N2 e fungos micorrízicos arbusculares (FMA), constitui uma estratégia eficiente para acelerar a recuperação de áreas impactadas além de reduzir consideravelmente os custos com a mesma. O conceito de “mycorrhiza helper bacteria (MHB)” tem sido introduzido e discutido devido ao efeito sinergístico que essa dupla associação promove às plantas. São bactérias associadas com raízes e FMA que, seletivamente, promovem o estabelecimento da simbiose com os fungos. Deste modo, os objetivos deste trabalho foram verificar a atividade de FMA em área com vegetação nativa do semiárido Pernambucano, no município de Sertânia; determinar o número de glomerosporos e o número mais provável (NMP) de propágulos infectivos; quantificar o teor de proteínas do solo relacionadas à glomalina; determinar a viabilidade da co-inoculação entre bactérias (MHB) e mistura de FMA em sabiá (Mimosa caesalpiniifolia Benth) visando obter combinações e compatibilidade de pares simbióticos, assim como avaliar a eficiência e colonização micorrízica. Os experimentos foram conduzidos em casa de vegetação na Sede do Instituto Agronômico de Pernambuco (IPA). Foram coletadas 10 amostras compostas de solo, sendo os pontos definidos aleatoriamente. As amostras foram homogeneizadas e analisadas quanto às características físicas e químicas. Amostras compostas foram utilizadas para contagem direta (CD) e multiplicação de FMA para contagem indireta (CI) de esporos, com o uso de culturas-armadilha, empregando sorgo granífero (Sorghum bicolor L. Moench) e amendoim (Arachis hypogea L.) como plantas hospedeiras (experimento I). Para a determinação do NMP de propágulos infectivos de FMA no Luvissolo Háplico foi utilizado um sistema de diluição em série: 0, 1:10, 1:100 e 1:1000, com 5 repetições cada e, tendo o milho (Zea mays L.) como planta hospedeira (experimento II). No experimento III foram utilizados vasos com o solo Luvissolo Háplico (8 kg vaso-1) com pH 6,0 e a planta utilizada foi a sabiá. Na semeadura, foi efetuada inoculação com Burkholderia sabiae (BR 3405) e co-inoculação com BR3405 + MHB contendo 108 UFC mL-1. Na inoculação com a mistura do FMA, foram utilizados 4 g vaso-1 em forma de propágulo, contendo aproximadamente 670 esporos. A colheita foi realizada 110 dias após plantio (DAP) e foram avaliadas as seguintes variáveis: massa seca da parte aérea (MSPA), raiz (MSR), relação MSR/MSPA, altura de planta (AP) nos períodos de 45, 90 e 110 dias, comprimento da raiz (CR), N total acumulado na MSPA (Nac), eficiência das estirpes (E%) e colonização micorrízica. O delineamento experimental adotado foi em blocos casualizados, com arranjo fatorial 9 x 2 mais uma testemunha absoluta (TA) – sem inoculação; estirpes de MHB e um tratamento controle inoculado apenas com Burkholderia sabiae com e sem FMA (mistura de FMA) com 3 blocos. Os resultados dos experimentos mostram que o NMP de propágulos infectivos de FMA encontrados no município de Sertânia foi de 23 propágulos cm-3. As proteínas do solo relacionadas à glomalina facilmente extraível (PSRGFE) e as proteínas do solo relacionadas à glomalina total (PSRGT) ficaram em torno de 0,46 e 0,26 mg g solo-1, respectivamente. A colonização dos FMA em conjunto com as bactérias foi positiva, como no caso do CR, os tratamentos com BR 3405 + Azospirillum amazonenses (Y2) e BR 3405 + Herbaspirillum seropedicae (Z67) apresentaram diferença significativa pelo teste de Tukey (p<0,05) em relação ao fator com e sem FMA. Confirmando deste modo que, na presença das bactérias MHB houve aumento no comprimento do sistema radicular das plantas de sabiá. A eficiência das estirpes obteve os melhores resultados quando as bactérias estavam em presença de FMA e o tratamento BR 3405 + Paenibacillus brasilensis (24) + FMA foi o que obteve melhor resposta. Os tratamentos que receberam os FMA foram superiores em relação aos demais nas variáveis MSPA, MSR, E, Nac, chegando a apresentar uma média em torno de 84% de colonização radicular.

Non-mycorrhizal fungal endophytes are able to colonize internally roots without causing visible disease symptoms establishing neutral or mutualistic associations with plants. These fungi known as non-clavicipitaceous endophytes have a broad host range of monocot and eudicot plants and are highly diverse. Some of them promote plant growth and confer increased abiotic-stress tolerance and disease resistance. According to such possible effects on host plants, it was aimed to isolate and to characterize native fungal root endophytes from tomato (Lycopersicon esculentum Mill.) and to analyze their effects on plant development, plant resistance and fruit yield and quality together with the model endophyte Piriformospora indica. Fifty one new fungal strains were isolated from desinfected tomato roots of four different crop sites in Colombia. These isolates were roughly characterized and fourteen potential endophytes were further analyzed concerning their taxonomy, their root colonization capacity and their impact on plant growth. Sequencing of the ITS region from the ribosomal RNA gene cluster and in-depth morphological characterisation revealed that they correspond to different phylogenetic groups among the phylum Ascomycota. Nine different morphotypes were described including six dark septate endophytes (DSE) that did not correspond to the Phialocephala group. Detailed confocal microscopy analysis showed various colonization patterns of the endophytes inside the roots ranging from epidermal penetration to hyphal growth through the cortex. Tomato pot experiments under glass house conditions showed that they differentially affect plant growth depending on colonization time and inoculum concentration. Three new isolates (two unknown fungal endophyte DSE48, DSE49 and one identified as Leptodontidium orchidicola) with neutral or positiv effects were selected and tested in several experiments for their influence on vegetative growth, fruit yield and quality and their ability to diminish the impact of the pathogen Verticillium dahliae on tomato plants. Although plant growth promotion by all three fungi was observed in young plants, vegetative growth parameters were not affected after 22 weeks of cultivation except a reproducible increase of root diameter by the endophyte DSE49. Additionally, L. orchidicola increased biomass and glucose content of tomato fruits, but only at an early date of harvest and at a certain level of root colonization. Concerning bioprotective effects, the endophytes DSE49 and L. orchidicola decreased significantly disease symptoms caused by the pathogen V. dahliae, but only at a low dosis of the pathogen. In order to analyze, if the model root endophytic fungus Piriformospora indica could be suitable for application in production systems, its impact on tomato was evaluated. Similarly to the new fungal isolates, significant differences for vegetative growth parameters were only observable in young plants and, but protection against V. dahliae could be seen in one experiment also at high dosage of the pathogen. As the DSE L. orchidicola, P. indica increased the number and biomass of marketable tomatoes only at the beginning of fruit setting, but this did not lead to a significant higher total yield. If the effects on growth are due to a better nutrition of the plant with mineral element was analyzed in barley in comparison to the arbuscular mycorrhizal fungus Glomus mosseae. While the mycorrhizal fungus increased nitrogen and phosphate uptake of the plant, no such effect was observed for P. indica. In summary this work shows that many different fungal endophytes can be also isolated from roots of crops and, that these isolates can have positive effects on early plant development. This does, however, not lead to an increase in total yield or in improvement of fruit quality of tomatoes under greenhouse conditions. / Endophyten, die nicht zu den Mykorrhizapilzen gehören, können das Innere von Wurzeln ohne sichtbare Krankheitssymptome besiedeln und bilden so mit der Pflanze neutrale oder mutualistische Wechselwirkungen. Diese Pilze, auch als nicht-clavicipetale Endophyten bekannt, haben ein breites Wirtsspektrum von mono- und dikotyledonen Pflanzen und weisen eine hohe Diversität auf. Einige von ihnen fördern Pflanzenwachstum und erhöhen Resistenz und Toleranz gegenüber biotischem und abiotischem Stress. Ausgehenden von diesen möglichen Effekten auf ihre Wirtspflanzen war das Ziel der vorliegenden Arbeit die Isolierung und Charakterisierung neuer pilzlicher Wurzelendophyten der Tomate (Lycopersicon esculentum Mill.) und die Analyse ihres Einflusses auf Pflanzenentwicklung und Pflanzenresistenz, sowie auf Ertrag und Fruchtqualität unter Einbeziehung des Modellendophyten Piriformospora indica. Aus vier verschiedenen Anbaugebieten in Kolumbien konnten 51 neue Pilzstämme von oberflächensterilisierten Tomatenwurzeln isoliert werden. Diese Isolate wurden vorcharakterisiert und 14 potentielle Endophyten bezüglich ihrer Taxonomie, ihrer Besiedlungsmuster und ihres Einfluss auf das Pflanzenwachstum näher untersucht. Sequenzierung der ITS Region des ribosomalen RNA Genclusters und genaue morphologische Charakterisierung zeigten, dass sie zu verschiedenen phylogenetischen Gruppen innerhalb der Ascomycota gehören. Neun Morphotypen ließen sich beschreiben, wobei sechs zu den ‚Dark Septate Endophytes’ (DSEs) gehören, aber nicht mit der bekannten Phialocephala Gruppe verwandt waren. Ausführliche konfokale mikroskopische Untersuchungen ergaben sehr verschiedene Besiedelungsmuster der Wurzelendophyten vom Endringen in die Epidermis bis zum Hyphenwachstum durch den Kortex. Topfexperimente unter Gewächshausbedingungen zeigten dass die Isolate in Abhängigkeit von der Inokulumkonzentration und der Zeit der Besiedlung das Wachstum der Tomaten sehr unterschiedlich beeinflussten. Drei neue Isolate (die beiden unbekannte pilzlichen Endophyten DSE48 und DSE49 und eines identifiziert als Leptodontidium orchidicola) mit neutralen oder positiven Effekten wurden für weitere Versuche ausgewählt. In mehreren Experimenten sollte ihr Einfluss auf das vegetative Wachstum, auf Ertrag und auf Fruchtqualität untersucht werden, sowie ihre Fähigkeit die Auswirkungen des Pathogens Verticillium dahliae auf Tomatenpflanzen zu vermindern. Obwohl wachstumsfördernde Effekte durch alle drei Pilze in jungen Pflanzen beobachtet wurden, waren vegetative Wachstumsparameter nach 22 Wochen der Besiedlung nicht mehr beeinflusst bis auf ein signifikante Erhöhung des Wurzeldurchmessers durch den Endophyten DSE49. L. orchidicola dagegen erhöhte die Biomasse und den Glukosegehalt der Früchte, aber nur zu frühen Ernteterminen und bei einer bestimmten Intensität der Wurzelbesiedelung. Hinsichtlich eines schützenden Effekts, konnten die Endophyten DSE49 und L. orchidicola die Krankheitssymptome, die durch V. dahliae verursacht wurden, vermindern, aber nur bei einem geringen Pathogendruck. Um zu überprüfen, ob der Modellendophyt P. indica in Produktionssytemen eingesetzt werden kann, wurde seine Auswirkungen auf Tomaten untersucht. Ähnlich wie die neuen pilzlichen Isolate, zeigte aber auch er seinen fördernden Einfluss nur auf das frühe vegetative Wachstum. Schützende Effekte gegen V. dahliae konnten ebenfalls nur bei niedrigem Pathogendruck konstant beobachtet werden. Wie L. orchidicola erhöhte P. indica die Biomasse an marktfähigen Tomaten am Anfang des Fruchtansatzes, was nicht zu einem insgesamt höheren Ertrag führte. Ob die beobachteten Effekte auf ein verbesserte Nährstoffversorgung der Pflanze zurückzuführen seien, wurde in Gerste im Vergleich mit dem arbuskulären Mykorrhizapilz Glomus mosseae untersucht. Während der Mykorrhizapilz sowohl Phosphat wie Stickstoffaufnehme der Pflanze erhöhte, konnte dies für P. indica nicht festgestellt werden. Zusammenfassend zeigt diese Arbeit, dass auch aus Wurzeln von Kulturpflanzen viele verschiedene pilzliche Endophyten isoliert werden können, und dass einige von diesen durchaus einen positiven Effekt auf die frühe Pflanzenentwicklung aufweisen. Zumindest für Tomate unter Gewächshausbedingungen führen diese Effekte aber nicht zu einer Erhöhung des Gesamtertrags oder einer nachhaltigen Verbesserung der Fruchtqualität.

La gestion efficace des champignons mycorhiziens arbusculaires (CMA) est largement considérée comme une stratégie prometteuse pour le développement de l’agriculture durable et de conservation. Or, la culture conventionnelle de Brassicaceae non-mycorhiziennes, un groupe qui comprend plusieurs cultures d’une grande importance économique en Amérique du Nord, telles que le chou régulier (Brassica oleracea var. capitata) et le brocoli (Brassica oleracea var. italica), peut réduire la densité des CMA dans les agroécosystèmes. Dans le but de réduire l’impact négatif des cultures de brocoli et de chou sur l’abondance des CMA au champ, nous proposons de cultiver ces plants en compagnonnage persistant avec du trèfle blanc (Trifolium repens L.), une plante dépendant largement des CMA. Nous avons testé l’impact de la culture intercalaire de B. oleracea, sur (1) la colonisation des racines de Brassicaceae par les CMA et le rendement de ces cultures, et (2) la vitesse et l’intensité de colonisation d’une culture subséquente associée aux CMA, le maïs sucré, et son rendement. Dans cette étude, nous avons observé que les CMA pouvaient coloniser et former des vésicules dans les racines de cultures de B. oleracea, même lorsque cultivées sans culture mycorhizienne d’entre-rang, probablement via d’autres sources de carbone. Néanmoins, plus de brocolis étaient colonisés lorsqu’ils étaient cultivés dans les parcelles avec trèfle, mais ils étaient colonisés à une plus basse intensité. Comme escompté, l’adoption d’une culture de couverture intercalaire de trèfle persistant à travers les deux rotations a réduit le délai de colonisation de la culture de maïs et en a augmenté le rendement. / Efficient management of arbuscular mycorrhizal fungi (AMF) holds much potential in conservation and sustainable agriculture. Growing non-mycorrhizal Brassicaceae crops, including crops of great economic importance in North America such as regular cabbage (Brassica oleracea var. capitata) and broccoli (B. oleracea var. italica), has been associated with reduced AMF density in agroecosystem. In the hope of reducing the negative impact of broccoli and cabbage culture on AMF abundance in fields, we cultivated these crops alongside mycorrhizal white clover (Trifolium repens L.) in a persistent intercropping system. We tested the impact of B. oleracea intercropping on (1) AMF root colonization levels and crop yield, and on (2) the AMF colonization speed and level, as well as the yield of a following mycorrhiza-dependent crop rotation, sweet maize (Zea mays L.) In this study, we found that AMF could colonize and produce vesicles in B. oleracea crop roots, even when grown without a mycorrhizal intercrop, probably through other carbon sources. Intercropping with clover still led to more broccolis being colonized by AMF, but at a lower intensity than in sole crop plots. As expected, use of a persistent clover intercrop reduced colonization delay and increased yield of the subsequent maize rotation.