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Among abiotic stresses, salinity is considered the main limiting stress that negatively affects plant growth and reduces productivity worldwide. To overcome this challenge, a sustainable solution such as plant growth-promoting bacteria (PGPB) can be used to meet the increasing demand for food. The desert microbe Enterobacter sp SA187, an endophytic PGPB, induces salt tolerance in both model plant and crops. The interaction between SA187 and the host plant triggers the sulfur pathway in the bacteria which then provides multiple sulfur-containing compounds to its host plant. However, the molecular sensor of these compounds in the host plant is not known. Here, we show that SA187 activates the plant target of rapamycin (TOR) pathway. The beneficial effect of SA187 was lost in TOR mutants like raptor, and by the application of TOR inhibitor AZD8055. Next, we show that SA187 modulates the one- carbon (1C) metabolism of the host plant consisting of methionine and folate cycles. The beneficial effect of SA187 was compromised by using chemical inhibitors of folate cycle like Methotrexate (MTX) and Sulfadiazine (SDZ). The intermediates of the 1C metabolism like Homocysteine and S-adenosyl methionine (SAM) showed similar beneficial effects as SA187 colonized plants. Finally, we showed that SA187 enhances 1C metabolism activity by increasing methylation index (SAM/SAH ratio) in the plants. Taken together, we could show that host TOR-1C axis is essential for plant salt tolerance by SA187.

Thesis (M. Tech. (Agriculture)) -- Central University of Technology, Free State, 2013 / ntroduction: Good quality Eucalyptus is of importance to South Africa’s pulp and paper industry. Limited land is available for forestry, therefore Eucalyptus with genotypes for good pulp and paper qualities, particularly hybrids, are bred and cloned via cuttings. Although these Eucalyptus clones keep the favourable genotypes in the population, many have difficulty with rooting. Research has shown that rhizobacteria can improve rooting. Thus, one strategy to enhance the rooting of cuttings is to use rhizobacterial preparations. The aim of this study was to characterise rhizobacterial communities of Eucalyptus hybrid and species and identify possible plant-growth promoting rhizobacteria (PGPR). Materials and methods: Rhizospheric samples were collected from Eucalyptus hybrids and species. The rhizobacterial communities were characterised using fatty acid methyl esters (FAME) analysis and denaturing gradient gel electrophoresis (DGGE). DGGE fragments were further sequenced to identify rhizobacteria. Results and discussion: FAME analysis successfully achieved a broad characterisation of the Eucalyptus hybrid and species rhizobacterial communities based on their fatty acid composition. Myristic acid (C14:0) was the most abundant fatty acid. DGGE profiles gave a molecular profile of the Eucalyptus hybrid and species rhizobacterial communities based on their DNA composition. Nitrosomona eutropha was present in all samples which illustrates a nitrogen-rich environment. Adhaenbacter aquaticus was unique to the better rooting Eucalyptus hybrid GU111. Conclusion: This study provided some insight into the diversity of rhizobacterial communities of Eucalyptus hybrids and species. Possible PGPR were identified and the observation made that the nature of the soil environment changes with the aging of the associated host. These findings allow further investigation into the formulation of potential rhizobacterial preparations for rooting enhancement of Eucalyptus cuttings.

Inoculation with diazotrophic bacteria is well documented as a means to enhance growth and increase yields of various crops, especially when used as an alternative or a supplement to the use of nitrogenous fertilizers and agrochemicals for sustainable agriculture. Nitrogen is the most limiting nutrient for increasing crop productivity, and the use of chemical sources of N fertilizers is expensive, and may contribute to environmental pollution. Therefore, there is a need to identify diazotrophic inoculants as an alternative or supplement to N-fertilizers for sustainable agriculture. The search for effective diazotrophic bacterial strains for formulation as biofertilizers has been going on for over 40 years and a number of inoculant biofertilizers have been developed and are commercially available. In the current study, 195 free-living diazotrophic bacteria were isolated from soils collected from the rhizosphere and leaves of different crops in different areas within the KwaZulu-Natal Province, Republic of South Africa. Ninety five of the isolates were selected for further screening because they were able to grow on N-free media using different carbon sources. Isolates that were very slow to grow on N-free media were discarded. Of these, 95 isolates were screened in vitro for growth promotion traits tests including tests for ammonia production and acetylene reduction. The best 20 isolates that were also able to reduce acetylene into ethylene were selected for growth-promotion trials on maize under greenhouse conditions. Of the 20 isolates, ten isolates enhanced (P = 0.001) growth of maize above the Un-inoculated Control. Molecular tests were conducted to identify the ten most promising isolates selected in the in vitro study. In the greenhouse study, these diazotrophic isolates were screened for their ability to enhance various growth parameters of maize (Zea mays L.), following various inoculation techniques (drenching, seed treatment, foliar spray and combination of these). Inoculations with the five best diazotrophic isolates by various methods of application increased dry weight and leaf chlorophyll content (P < 0.001, P = 0.001), respectively, compared to the Untreated Control. Although, all methods of application of diazotrophic inoculants used in this study resulted in increased dry weight and leaf chlorophyll content, combined methods of application (seed treatment + drenching) and sole application (seed treatment) were significantly more (P < 0.05) efficient. The best five most promising isolates were identified for growth promotion of maize under greenhouse conditions. They were also assessed for their effects on germination of wheat in vitro and were further tested in combination with various levels of nitrogenous fertilizer for growth-promotion of wheat (Triticum aestivum L.). These five isolates were also investigated for their potential to enhance growth and yields of maize and wheat crops in field trials, when combined with a low dose of nitrogenous fertilizer. These isolates were further studied for their contribution for enhancing plant growth through nitrogen fixation by predicting N content in leaves using a chlorophyll content meter (CCM-200) and correlated to extractable chlorophyll level at R2 = 0.96. In this study, relative to the Un-inoculated Control, the best five isolates enhanced growth of maize and wheat when combined with a 33% N-fertilizer levels for a number of growth parameters: increased chlorophyll levels and heights of maize, shoot dry weight of maize and wheat; and enhanced root and shoot development of these crops in both greenhouse and field conditions. The best contributions of diazotrophic bacteria was achieved by Isolate LB5 + 0% NPK (41%), V9 + 65% NPK (28.9%), Isolate L1 + 50% NPK (25%), Isolate L1 + 25%NPK (22%) and LB5 + 75% NPK (15%) undergreenhouse conditions. At 30 or 60 DAP, isolates with 33%N-fertilizer caused relatively higher dry weight than the 100%NPK. Inoculation of Isolate StB5 without 33N% fertilizer cuased significant (P<0.005) increases in stover dry weight. In field studies, inoculation of diazotrophic bacteria alone or with 33%N-fertilizer resulted in relatively greater increases of dry weight, stover dry weight, number of spikes and yield at different growth stages higher than the Un-inoculated or Unfertilized Control. However, the increases were not statistically significant. The use of microbial inoculants in combination with low doses of nitrogenous fertilizers can enhance crop production without compromising yields. The isolates obtained in this study can effectively fix nitrogen and enhance plant growth. The use of microbial inoculants can contribute to the integrated production of cereal crops with reduced nitrogenous fertilizer inputs, as a key component of sustainable agriculture. / Ph.D. University of KwaZulu-Natal, Pietermaritzburg 2013.

Der Einfluss der Rhizosphärenbakterien Bacillus subtilis FZB 24, FZB 37, FZB 42, Bacillus pumilus RK 13 und Streptomyces graminofaciens und des Algenpräparates Goemar Fruton Spezial® (Ascophyllum nodosum) auf Wachstum, Ertrag und Toleranz gegenüber Fusarium spp. bei Spargel wurde untersucht. Es wurden mehrjährige Parzellenfeldversuche und Modellversuche unter kontrollierten Bedingungen mit natürlich Fusarium spp. belasteten Böden und mit speziellen Fusarium Erregern inokulierten Substraten durchgeführt. Die Analyse des verwendeten Nachbaubodens ergab eine wesentlich höhere Kontamination mit Fusarium spp. (56%) in Relation zum Fruchtfolgeboden (14%). F. oxysporum war die dominante Fusariumart. Desweiteren wurde eine ganze Reihe anderer Arten, wie z.B. F. acuminatum, F. culmorum, F. proliferatum und F. culmorum bestimmt, was die Komplexität der Wurzel- und Stängelfäuleerkrankung belegt. Analog zu diesem Ergebnis konnten im Vergleich zur Fruchtfolgevariante von den in dem Nachbauboden kultivierten Spargelpflanzen signifikant mehr Fusarium spp. (80%) isoliert werden. Das Wurzelwachstum war hier extrem reduziert. Unter diesen konduktiven Bedingungen gelang es durch Rhizombakterisierung (107 cfu/ml) mit B. subtilis FZB 42, eine signifikante Förderung des Wurzelwachstums relativ zur unbehandelten Kontrolle und zur B. subtilis FZB 37 Variante zu erzielen. In Pathogenitätstests konnten F. culmorum, F. oxysporum und F. proliferatum als bedeutende Spargelpathogene mit signifikant reduzierter Trieb- und Wurzelmasse nachgewiesen werden, während F. acuminatum nur geringe Symptome verursachte. Eine bakterielle Saatgutbeizung (108 cfu/ml) und zusätzliche präinfektionelle Gießapplikation (107 cfu/ml) konnte eine Infektion mit F. oxysporum f.sp. asparagi nicht verhindern. Dennoch waren die negativen Effekte im Vergleich mit der nicht bakterisierten Kontrolle in den B. subtilis Varianten FZB 24 und vor allem bei FZB 42 deutlich kompensiert. Diese Ergebnisse lassen vermuten, dass eine Resistenz- bzw. Toleranzinduktion ein potentieller Wirkmechanismus der Bakterien ist. In den Feldversuchen erbrachte eine Bakterisierung einjähriger Rhizome (107 cfu/ml) zur Pflanzung und ergänzende Gießbehandlungen (108 cfu/ml/1l/m) in den folgenden 2 Jahren eine tendenzielle Reduzierung der Trieblänge und des Triebdurchmessers, insbesondere in Kombination mit dem Algenpräparat. Einen eindeutigen Einfluss auf das Sortierungsergebnis konnte nicht nachgewiesen werden. Im Gegensatz hierzu resultierte eine Saatgutbakterisierung mit B. subtilis FZB 24 in einem generell geförderten Triebwachstum und einer signifikant gesteigerten Wurzelentwicklung. Auch die anderen Mikroorganismen erbrachten eine tendenzielle Wuchsförderung. Es konnte eine gesicherte Korrelation zwischen Wurzelmasse und Knospenanzahl ermittelt werden. Blattapplikationen mit Goemar Fruton Spezial® während der Hauptvegetationsphase hatten keinen Einfluss auf das Pflanzenwachstum. / The effects of the rhizobacteria Bacillus subtilis, Strain FZB 24, FZB 37and FZB 42, Bacillus pumilus RK 13, Streptomyces graminofaciens N6 and the alga Ascophyllum nodosum (Goemar Fruton Spezial®) on plant growth, yield and Fusarium spp. tolerance of Asparagus officinalis (L.) were investigated. The trials were carried out under field conditions over sev-eral years by sawing and planting and as pot trials in the greenhouse and climate chamber with soil naturally infested with Fusarium spp. and with steamed substrates inoculated with particularly Fusarium species. Asparagus replant soil was considerable higher infested with Fusarium spp. (56 %) than fresh soil without asparagus history (14 %). F. oxysporum was the most determined Fusarium species followed by F. redolens, F. acuminatum, F. culmorum, F. proliferatum, F. solani a.o.. That indicates the complex character of root and crown rot of asparagus. From asparagus plants cultivated in replant soil a significant higher rate of Fusarium isolations (80 %) could be worked out compared to the fresh soil treatment. The root growth in the contaminated soil was extremely reduced. In these conductive situation bacterial treatments with B. subtilis FZB 42 done as rhizom soaking (107cfu/ml) resulted in significantly increased root growth up to 32, 9 % related to the non treated control. B. subtilis FZB 37 was ineffective. F. oxysporum, F. culmorum and F. proliferatum showed a high pathogenicity to asparagus seedlings, manifested in significantly reduced fresh and dry weights of shoots and roots, while F. acuminatum caused only slight symptoms. None of the tested microorganisms applicated as seed coating (108 cfu/ml) and substrate drenching before pathogen inoculation (107 cfu/ml) could prevent seedlings from being infected by F. oxysporum f. sp. asparagi. The negative effects of infection are significantly compensated by Bacillus subtilis FZB 42 and FZB 24. The results support the conclusion, that induced tolerance is a potential mechanism of bacterial mode of action. Under field conditions rhizom bacterization of one year old asparagus plants (107 cfu/ml) before planting and additional soil drenching (108 cfu/ml/1,5l/m) during the following two years reduced shoot length, shoot diameter and yield, especially in combination with Goemar Fruton Spezial®. There was no remarkable influence on spear quality. Seed coating with B. subtilis FZB 24 (108 cfu/ml) and a soil drenching (108 cfu/ml/1l/m) in summer however re-sulted in higher shoots and significantly increased fresh weight and dry substance of roots. But also the other tested microorganisms showed a plant growth promoting trend. There was a significant positive correlation between root fresh weight and number of buds. By spraying the phylloclads four times during the main vegetation season the alga application only gave a slight improvement of plant growth in the field trials.

Submitted by Sandra Pereira (srpereira@ufrrj.br) on 2016-08-09T11:45:20Z No. of bitstreams: 1 2011 - Anelise Dias.pdf: 15332435 bytes, checksum: 2029d6acb53e3ead830aa60dc2c29a5a (MD5) / Made available in DSpace on 2016-08-09T11:45:20Z (GMT). No. of bitstreams: 1 2011 - Anelise Dias.pdf: 15332435 bytes, checksum: 2029d6acb53e3ead830aa60dc2c29a5a (MD5) Previous issue date: 2011-09-23 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / A collection of 189 bacterial isolates, obtained from organic system of vegetable production, was characterized aiming to selection of cabbage growth promoting strains. Isolatings were performed from rhizosphere of vegetables and soil after harvest of cultivated species. The vast majority of the strains showed biochemical profiles identical to Pseudomonas (fluorescent group). While profiles identical to Burkholderia, Stenotrophomonas and Acinetobacter constituted other groups of representatives. Characterization of isolates took into account the capacity for synthesis of compounds possibly involved in mechanisms to stimulate plant growth, namely: biofilms, siderophores, acyl homoserine lactones (AHLs), indole-3-acetic acid (IAA) and indole related compounds, as well as solubilization of calcium phosphate. A total of 94 isolates were evaluated in the greenhouse for their ability to promote the growth of cabbage (Brassica oleracea var. acephala) in pots containing unsterilized loam soil. In addition, consortia were evaluated between components of the collection and rhizobia for the same purpose. In addition, it compared the effects of application of certain producing IAA isolates and the application of synthetic IAA on the growth of cabbage. Laboratory experiments showed that in vitro, 100% of the isolates formed biofilm, 71% synthesized siderophores, 31% produced AHLs, 95% produced IAA and 74% solubilized P. However, bioassays in the greenhouse showed that only 12% of the isolates induced significant responses to promote the growth of cabbage. Of these, a subgroup composed of 10 strains of rhizobacteria given increments in growth parameters of both the biomass and the root system of vegetables. Biofilms, siderophores, IAA and solubilization of P were common characteristics of the subgroup. No synergistic effect was observed among isolates in consortia, although it was found that the two strains of rhizobia consortium promoted the growth of inoculated plants. The isolates R1132 and S311 were higher than the application of synthetic IAA. The results suggested the potential of 12 bacteria to promote plant growth and increase production of cabbage / Uma cole??o de 189 isolados bacterianos, provenientes de sistema org?nico de produ??o de hortali?as, foi caracterizada com vistas ? sele??o de estirpes promotoras do crescimento de couve. Os isolamentos foram realizados a partir da rizosfera de hortali?as e do solo ap?s colheita das esp?cies cultivadas. A grande maioria das estirpes apresentou perfil bioqu?mico id?ntico a Pseudomonas (grupo fluorescente). Enquanto perfis id?nticos a Burkholderia, Acinetobacter e Stenotrophomonas constitu?ram outros grupos de representantes. A caracteriza??o dos isolados levou em conta a capacidade de s?ntese de compostos possivelmente envolvidos em mecanismos de est?mulo ao crescimento de plantas, a saber: biofilmes, sider?foros, acil-lactonas homoserinas (ALHs), ?cido indol-3-ac?tico (AIA) e compostos ind?licos relacionados, al?m da solubiliza??o de fosfato de c?lcio. Um total de 94 isolados foi testado na casa de vegeta??o quanto ? capacidade de promover o crescimento de couve (Brassica oleraceae var. acephala) em vasos contendo solo distr?fico n?o esterilizado. Paralelamente, foram avaliados cons?rcios entre componentes da cole??o e riz?bios para igual finalidade. Em adendo, foram comparados os efeitos da aplica??o de determinados isolados produtores de AIA e da aplica??o de AIA sint?tico sobre o crescimento da couve. Os experimentos de laborat?rio indicaram que, in vitro, 100% dos isolados formaram biofilme, 71% sintetizaram sider?foros, 31% produziram AHLs, 95% produziram AIA e 74% solubilizaram P. No entanto, os bioensaios na casa de vegeta??o evidenciaram que apenas 11% dos isolados bacterianos induziam respostas significativas de promo??o do crescimento da couve. Desses, um subgrupo formado por 10 estirpes de rizobact?rias conferiu incrementos nos par?metros de crescimento, tanto da biomassa a?rea quanto do sistema radicular da hortali?a. Biofilmes, sider?foros, AIA e solubiliza??o do P foram caracter?sticas comuns do subgrupo. N?o foi observado efeito sin?rgico entre os isolados em cons?rcios, embora tenha sido verificado que as duas estirpes de riz?bios consorciadas promoveram o crescimento das plantas inoculadas. Os isolados R1132 e S311 foram superiores ? aplica??o do AIA sint?tico. Os resultados obtidos sinalizaram o potencial de 12 bact?rias que promover o crescimento das plantas e incrementar a produ??o de couve.

Submitted by Sandra Pereira (srpereira@ufrrj.br) on 2016-08-17T14:23:26Z No. of bitstreams: 1 2011- German Andres Estrada Bonilla.pdf: 1652819 bytes, checksum: 24a4d4664a65dfad88ccdfe17b4a0c02 (MD5) / Made available in DSpace on 2016-08-17T14:23:26Z (GMT). No. of bitstreams: 1 2011- German Andres Estrada Bonilla.pdf: 1652819 bytes, checksum: 24a4d4664a65dfad88ccdfe17b4a0c02 (MD5) Previous issue date: 2011-06-09 / Rice (Oryza sativa L.) is one of the major world crops, being widely consumed among people from five continents. In recent years research have increased in relation to the use of plant growth promoting diazotrophic bacteria (PGPB) as a possible solution to reduce the use of chemical nitrogen and phosphate fertilizers. Thus, this study aimed to evaluate the physiological potential and inorganic phosphate (IP) solubilization capacity of different diazotrophic strains isolated from rice plants grown in different regions of Brazil as well as to evaluate their role in the development of rice plants. Firstly, the culture media employed to test the phosphate solubilization in petri dishes were standardized. In this study 49 strains were tested for their capability of solibilizing tricalcium phosphate in NBRIP and GL solid media. Afterwards, the soluble P, pH, population and the index of solubilization (IS) were quantified for 7 IP solubilizing strains grown in the NBRIP liquid medium. The IP solubilizing isolates were also tested for the production of indolic compounds (IAA) and the nitrogen fixation capacity through the acetylene reduction activity (ARA). The isolates were taxonomical identified through the amplification and partial sequencing of 16S RNAr and nifH genes. Three of these strains and the controls H. seropedicae ZAE94, G diazotrophicus PAL5 and A.chroochoccum AC1 were tested in greenhouse conditions in association with rice plants. All strains that solubilized IP in NBRIP liquid medium decreased the medium pH while the bacterial population remained around 108 cfu ml-1 for up to 15 days. All strains were capable to produce indole compounds and reduced acetylene. The partial analysis of 16S RNAr and nifH gene indicated the identification of the species Herbaspirillum seropedicae, Burkholderia vietnamiensis and B. kururiensis species. All strains showed an increase in the range of 33 and 47% in grain yield when tricalcium phosphate (PTC) was applied and between 18 and 44% when PSS (simple superphosphate) was used. In general, all of the strains stimulated an increase of total P in the grain and a greater harvest index. The use of these strains as bioinculant is promising and therefore it is necessary to test in the field conditions / O arroz (Oryza sativa L.) ? uma das principais culturas cultivadas, sendo amplamente consumida nos cinco continentes. Nos ?ltimos anos as pesquisas t?m aumentado em rela??o ao uso de bact?rias diazotr?ficas e promotoras de crescimento vegetal (BPCV), como uma poss?vel solu??o para diminuir o uso de fertilizantes qu?micos nitrogenados e fosfatados. Desta forma, este trabalho teve por objetivo avaliar o potencial fisiol?gico e a capacidade de solubiliza??o de fosfato inorg?nico (PI) de diferentes estirpes de bact?rias diazotr?ficas oriundas de plantas de arroz cultivadas em diferentes regi?es do Brasil e seu papel no desenvolvimento de plantas de arroz. Primeiramente foi padronizado o meio de cultura a ser empregado nos ensaios de solubiliza??o de fosfato inorg?nico em placas de petri. Neste estudo foram testadas 49 estirpes em quanto sua capacidade de solubilizar fosfato tric?lcico (PTC) nos meios s?lidos NBRIP e GL. Em seguida foi quantificado o P sol?vel, pH, a popula??o de bact?rias e ?ndice de solubiliza??o (IS) das 7 estirpes solubilizadoras de PI em meio l?quido NBRIP. As estirpes solubilizadoras de PI tamb?m foram testadas quanto ? produ??o de compostos ind?licos (AIA) e capacidade de fixar nitrog?nio atrav?s da atividade de redu??o e acetileno (ARA). As estirpes foram identificadas atrav?s da amplifica??o e do sequenciamento parcial dos genes 16S RNAr e gene nifH. Tr?s destas estirpes foram testadas em condi??es de casa de vegeta??o junto com os controles Herbaspirillum seropedicae BR11417 (ZAE94), Gluconacetobacter diazotophicus BR11281 (PAL5) e Azotobacter Chroochoccum AC1 quanto ? capacidade de aumentar o desenvolvimento e produ??o de plantas de arroz. Todas as estirpes que solubilizaram PI no meio de cultura NBRIP l?quido influenciaram na diminui??o do pH do meio enquanto que a popula??o se manteve em torno de 108 ufc.ml-1 por at? 15 dias. Todas as estirpes apresentaram capacidade de produzir compostos ind?licos e foram capazes de reduzir acetileno. A an?lise parcial do gene 16S RNAr e do gene nifH das sete estirpes possibilitou a identifica??o das esp?cies Herbaspirillum seropedicae, Burkholderia vietnamiensis e B. kururiensis. Todas as estirpes promoveram um aumento na produ??o de massa seca nos gr?os entre 33 e 47% quando foi utilizado o PTC e de 18 a 44% quando foi utilizado o fosfato super simples (PSS). Em geral, todas as estirpes estimularam um maior acumulo de N e P total no gr?o e um maior ?ndice de colheita. O uso dessas estirpes como bioinoculante ? bastante promissor e portanto torna-se necess?rio test?-las em condi??es de campo.

Made available in DSpace on 2017-07-10T17:37:02Z (GMT). No. of bitstreams: 1 Luiz_Claudio_Offemann.pdf: 946925 bytes, checksum: 6e708b213cd6fa0ed040f9f73a3bc05e (MD5) Previous issue date: 2015-02-24 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The objective of this study was to evaluate the combined use of Azospirillum brasilense inoculation by seed and foliar application, associated to nitrogen fertilization on the agronomic characteristics of wheat. The experiment was installed in greenhouse on May 24th 2014, for this purpose, vases were used with capacity 15 dm3, in which were conducted 4 plants. The harvest proceeded on September 12th 2014, to 111 after emergence. The experimental design was a randomized block factorial 2 x 2 x 3, with four repetitions. The first factor was formed by the absence or presence of seed inoculation with A. brasilense. The second by nitrogen fertilization at doses of 70 and 140 Kg ha-1 (50 and 100% respectively). The third factor by application by foliar spraying of A. brasilense in the stages of tillering, booting and two applications, the first in the tillering and the second in booting. Were evaluated the biometric parameters of the culture at the end of the silking stage, the production components at the end of crop cycle. Were also evaluated gas exchange rates in the flag leaf and contents of macronutrients N, P and K in leaves and grains. It can be concluded that the use of A. brasilense, applied by foliar spraying, promotes increases in average internode length, average length of ears, dry leaves mass, ears and root, root volume and nitrogen content in leaves, besides maximize the effect of nitrogen fertilization. Gas exchange measurements and leaf nutrient content, were affected positively only by the higher nitrogen dose / Objetivou-se com este estudo avaliar o uso combinado de inoculação de Azospirillum brasilense, via semente e pulverização foliar, associada à adubação nitrogenada, nas características agronômicas da cultura do trigo. O experimento foi instalado em casa de vegetação no dia 24 de maio de 2014. Foram utilizados vasos com capacidade de 15 dm3, nos quais foram conduzidas 4 plantas. A colheita foi realizada no dia 12 de setembro de 2014, aos 111 dias após a emergência. O delineamento experimental adotado foi de blocos ao acaso em esquema fatorial 2 x 2 x 3, com quatro repetições. O primeiro fator foi formado pela ausência ou presença de inoculação das sementes com A. brasilense. O segundo pela fertilização nitrogenada nas doses de 70 e 140 kg ha-1 (50 e 100% respectivamente). O terceiro fator pela aplicação via pulverização foliar de A. brasilense nos estádios de perfilhamento, espigamento e duas aplicações, sendo a primeira no perfilhamento e a segunda no espigamento. Foram avaliados os parâmetros morfométricos ao final do estádio de espigamento, os componentes da produção ao final do ciclo. Também foram avaliadas as taxas de trocas gasosas na folha bandeira e teores dos macronutrientes N, P e K em folhas e grãos. Pode-se concluir que A. brasilense, aplicado via pulverização foliar, promove incrementos em comprimento médio de entrenós, comprimento médio de espigas, massa da matéria seca de folhas, espigas e raízes, volume de raízes e teor de nitrogênio nas folhas. As medidas de trocas gasosas e teor de nutrientes nas folhas foram influenciadas positivamente apenas pela maior dose de nitrogênio

En raison de leur capacité à former une symbiose avec des bactéries du sol appelées Rhizobium, ces bactéries fixent l’azote atmosphérique et leurs plantes-hôtes n’ont donc pas besoin de fertilisant azoté, les légumineuses jouent un rôle important dans l'agriculture. En outre, certaines souches de Rhizobium ont la capacité de solubiliser le phosphate, fournissant ainsi du phosphore assimilable aux plantes hôtes. Une aptitude à lutter contre certains agents pathogènes a aussi été démontrée dans plusieurs études. La présente étude évalue l’efficacité symbiotique de rhizobiums tunisiens, leur capacité à solubiliser le phosphate, et leur aptitude à lutter contre la verticilliose ainsi que d’autres champignons pathogènes chez Medicago truncatula. Trente-six isolats de rhizobiums prélevés sur des nodules racinaires de M. truncatula provenant de différentes régions de Tunisie ont été obtenus pour ce travail. Environ 60% de ces isolats étaient capables de solubiliser le phosphate in vitro. Dans une seconde étape, trois rhizobiums solubilisant le phosphate et un isolat incapable de solubiliser le phosphate in vitro ont été utilisés pour des essais en phytotron afin de voir l’effet de la présence des rhizobiums sur les paramètres de croissance des plantes en présence de phosphate inorganique sous forme de CaHPO4 et rocheux sous forme brute. Les résultats de l’essai montrent que les plantes de la lignée A17 traitées au CaHPO4, ont tendance à produire plus de nodules et de biomasse aérienne que la lignée F83005.5 et que la forme du phosphate utilisé, soluble ou non soluble, affecte les paramètres étudiés. L'inoculation de quatre lignées de M. truncatula avec 16 isolats de rhizobium sélectionnés auparavant a montré une interaction significative entre les isolats et les lignées pour la symbiose visible par la formation de nodules. Tous les isolats de rhizobium testés ont augmenté la biomasse aérienne des plantes, réduit la biomasse racinaire et entraîné une teneur plus élevée en azote mais l’effet dépendait de l’isolat de rhizobium et de la lignée de M. truncatula utilisés. Enfin, ces isolats ont été testés pour leur capacité à protéger des plantes de M. truncatula contre une maladie racinaire, la verticilliose. Des activités antagonistes in vitro contre divers champignons pathogènes dont Verticillium et Fusarium ont également été recherchées permettant d’identifier un isolat efficace pour la lutte biologique. Les résultats de cette étude suggèrent que des isolats de rhizobium sélectionnés pourraient être utilisés comme biofertilisants dans les sols pauvres pour réduire l'utilisation d'engrais chimiques azotés et phosphorés mais pas pour lutter contre la verticilliose. / Because of their ability to form a symbiosis with soil bacteria called Rhizobium, legumes play an important role in agriculture. These bacteria fix atmospheric nitrogen; hence their host plants do not need nitrogen fertilizers. In addition, some strains of Rhizobium have the ability to solubilize phosphate, thus providing phosphorus to host plants. An ability to control certain pathogens has also been demonstrated in several studies. The present study evaluates the symbiotic efficiency of Tunisian rhizobia, their ability to solubilize phosphate, and their ability to control Verticillium wilt and other pathogenic fungi in Medicago truncatula. Thirty-six rhizobial isolates were obtained from root nodules of M. truncatula from different parts of Tunisia were used in this work. About 60% of these isolates were able to solubilize phosphate in vitro. In a second step, three phosphate solubilizing rhizobia and one isolate unable to solubilize phosphate in vitro were used for phytotron assays to see the effect of the presence of rhizobia on plant growth parameters in the presence of soluble and insoluble forms of phosphate. The results of the experiment show that A17 plants treated with CaHPO4, tend to produce more nodules and shoot biomass than F83005.5 and that the phosphate form used, soluble or non-soluble, affects parameters studied. Inoculation of four M. truncatula lines with 16 previously selected rhizobial isolates showed significant interaction between isolates and lines for symbiotic abilities as visualised by nodule formation. All rhizobial isolates tested increased above-ground biomass, reduced root biomass, and increased nitrogen content with strains effects of plant genotype and bacterial isolate. Finallly, these isolates were tested for their ability to protect M. truncatula plants against Verticillium wilt, and to inhibit the growth of pathogenic fungi such as Verticillium and Fusarium in vitro. However, no isolate could be identified as effective for biological control. The results of this study suggest that selected rhizobial isolates could be used as biofertilizers in poor soils to reduce the use of nitrogen and phosphorus fertilizers but not to control Verticillium wilt.

Resumo: O cultivo intensivo agrícola, apesar de altamente produtivo, possui diversos pontos questionáveis, como suplementação acentuada de insumos sintéticos, além da aplicação de defensivos para o controle de pragas que muitas vezes são danosos ao meio ambiente. Como alternativa, a agricultura orgânica propõe uma forma de manejo menos agressiva, que promove o uso sustentável dos recursos naturais renováveis, como o aproveitamento de resíduos orgânicos, além de possuir um maior valor agregado no produto final. No presente estudo, investigamos por meio de uma abordagem metagenômica os efeitos do manejo (orgânico ou convencional) na microbiota da rizosfera de cana-de-açúcar, região da planta que notoriamente causa um grande impacto no seu desenvolvimento e produtividade. Identificamos a abundância maior na rizosfera com manejo orgânico de porções genômicas que codificam enzimas associadas ao metabolismo do nitrogênio e enxofre, sendo que estes são nutrientes fundamentais para o sucesso da planta e assim, seu desenvolvimento e produtividade em campo. Contraditoriamente, encontramos também que os genomas da microbiota orgânica possuem conteúdo ligado a um potencial mais acentuado para a degradação de compostos xenobióticos, que são ativamente aplicados no manejo convencional. De acordo com nossa predição, os microrganismos dessa microbiota poderiam realizar sua completa mineralização, o que é muito favorável na remoção desses resíduos no ambiente. Esses achados indicam que há um potencia... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Modern industrialized agriculture although highly productive, has several sustainability problems such as the for intense supplementation of synthetic inputs, beyond the application of pesticides for pest control. Which are often harmful to environment. As an alternative to this system, organic agriculture is considered more environmentally progressive, having several characteristics favorable to the crop producer, promotes sustainable use of renewable natural resources, such as the use of organic waste, besides that a higher aggregated value in the final product. This study investigates the changes that an organic system brings when compared to conventional management for the sugarcane rhizosphere microbiome, a plant region known to be determinant of plant development and associated with net productivity, using a metagenomic approach. We identified a higher abundance of genomic portions which encode enzymes associated with nitrogen and sulphur metabolism, which are fundamental nutrients for plant success and subsequently, crop productivity. Conversely, we also found that genomes of the organic microbiome contain higher portions linked to xenobiotic degradation, compounds that are actively applied in conventional management. Microorganisms from this sequenced microbiome could perform complete mineralization of these damaging compounds, which is desirable in their removal from the environment. These findings indicate that there is a unique potential for exploitation of organic... (Complete abstract click electronic access below) / Mestre