Depuis 1960, la grande majorité des variétés de blé sont des variétés naines, présentant de nombreuses différences par rapport aux variétés plus anciennes. Elles sont capables de mieux utiliser les apports d’engrais synthétiques et présentent des rendements supérieurs. Cependant, peu d’intérêt a été porté au système racinaire et aux impacts sur les interactions avec les bactéries du sol. Pourtant, la main de l’Homme pourrait avoir rendu caduque les effets bénéfiques apportés par les PGPR (Plant Growth-Promoting Rhizobacteria) aux plantes, et les traits génétiques permettant les interactions entre plante et PGPR pourraient ne pas avoir été sélectionnés chez les génotypes de variétés modernes. L’hypothèse dans cette thèse est que les PGPR intéragiraient mieux avec des variétés anciennes qu’avec des variétés modernes. Nous avions à disposition 199 accessions de blé tendre représentatif des variétés de blés sélectionnées depuis le milieu du 19ème siècle. Par une approche de criblage, nous avons évalué in vitro la capacité de deux PGPR, Pseudomonas kilonensis F113 et Azospirillum brasilense Sp245, à coloniser les racines de ces génotypes de blé, et a y exprimer des gènes impliqués dans des fonctions bénéfiques pour la croissance de la plante. Par la suite nous avons testé si les résultats obtenus in vitro se traduisaient en une amélioration de la croissance du blé par une approche d’inoculation réalisée en sol. Enfin, une étude aux champs a été menée pour analyser l’impact des génotypes de blé sur les bactéries indigènes du sol. Ces travaux ont montré (1) une meilleure aptitude de F113 et Sp245 à interagir avec les génotypes anciens in vitro, (2) de meilleurs effets phytostimulateurs suite à l’inoculation de PGPR chez les génotypes de blés ayant présenté de bons résultats lors du criblage et (3) un impact du génotype de blé sur les bactéries indigènes associées à ses racines, notamment entre génotypes anciens et génotypes modernes / Since 1960, the great majority of wheat modern varieties are dwarf varieties (because of Rht genes), showing multiple differences compared to ancient varieties. Thus, they are more able to use synthetic fertilizers used in huge quantities since the mid-20th and show higher yield. However, few studies have been made regarding the impact of modern breeding on root systems and on interactions of crops with soil bacteria. Yet, these evolutions in agricultural practises could have reduced the beneficial effects brought by PGPR (Plant Growth-Promoting Rhizobacteria), and the genetic traits involved in these interactions between plant and PGPR may have not been selected in modern genotypes. Our work hypothesis in this thesis is that PGPR are more able to interact with ancient genotypes than modern ones. To test this hypothesis, we had 199 bread wheat accessions representative of the wheat varieties selected since the mid-19th. Using an in vitro screening approach, we assessed the abilities of two PGPR model strains, Pseudomonas kilonensis F113 and Azospirillum brasilense Sp245, to colonize the roots of these genotypes and to express genes involved in plant-beneficial functions. Then, we assessed whether the results obtained in vitro had a biological significance by measuring the amelioration of growth performance of wheat genotypes using a soil pot inoculation experiment under greenhouse. Finally, an in-field study was performed to analyse the impact of wheat genotypes on the indigenous bacterial communities. This work showed (1) a better ability of F113 and Sp245 to interact with ancient wheat genotypes than modern ones, (2) better growth performance improvements in wheat genotypes that showed good results during screening experiments and (3) an impact of wheat genotypes on indigenous bacterial communities, notably between ancient and modern genotypes

La rhizosphère est le siège de multiples interactions biotiques, contrôlées au moins en partie par l’échange de molécules signal entre les racines des plantes et les microorganismes qui leur sont associés. Dans le contexte des symbioses associatives entre les PGPR (Plant-Growth Promoting Rhizobacteria) et les plantes, le rôle et l’importance de ces molécules restent encore largement méconnus. Ainsi, l’influence de différents signaux rhizosphériques sur l’expression génique et les propriétés phytobénéfiques des PGPR a été étudiée par, (i) la caractérisation chimique d’une nouvelle molécule phytobénéfique d’Azospirillum et de son impact sur l’architecture du système racinaire, (ii) une approche ciblée portant sur l’analyse de l’expression in situ du gène phytobénéfique acdS de PGPR, et (iii) une approche globale permettant d’identifier la réponse du transcriptome d’Azospirillum à un métabolite secondaire bactérien. Ces travaux ont permis d’identifier des signaux rhizosphériques impliqués dans le contrôle de la colonisation racinaire et/ou des propriétés de phytostimulation des PGPR sur leur plante hôte / In rhizosphere, numerous biotic interactions are controlled by molecular signals exchanged between plant roots and microorganisms. In the case of the associative symbiosis between PGPR (Plant-Growth Promoting Rhizobacteria) and plants, the role and importance of these molecules are largely unknown. The impact of several rhizospheric signals on PGPR gene expression and plant beneficial properties was thus studied by performing (i) the chemical characterization of a new Azospirillum plant-stimulatory molecule whose positive impact on root development was revealed, (ii) an approach targeting the in situ expression of the acdS plant beneficial gene in PGPR, and (iii) a global approach to identify the Azospirillum transcriptomic response to a bacterial secondary metabolite. This works allowed the identification of rhizospheric signals controlling PGPR root colonization and/or plant growth promotion

La spécificité d'hôte est un concept fondamental pour comprendre les mécanismes évolutifs ayant abouti aux interactions étroites entre les bactéries et les plantes. Les études réalisées sur la coopération entre les bactéries rhizosphériques phytostimulatrices (PGPR) et les plantes suggèrent que la spécificité serait régie soit par une adaptation souchespécifique de la bactérie à des caractères aspécifiques de la plante, soit par une adaptation aspécifique de la bactérie à des propriétés spécifiques d'un génotype de plante. Ainsi, nous formulons l'hypothèse que ces adaptations se traduisent par la régulation de nombreux gènes indépendamment de leur implication directe dans l'effet phytobénéfique. Ces régulations pourraient dépendre de la combinaison souche bactérienne/génotype de plante considérée. L'objectif de ce travail est de mettre en évidence les gènes impliqués dans l'adaptation des partenaires l'un à l'autre et ceux impliqués dans la spécificité, au cours de la coopération PGPR-plantes. Pour cela, nous avons choisi comme modèle d'étude l'interaction entre Azospirillum lipoferum 4B et les céréales (blé, maïs, riz cultivars Cigalon et Nipponbare) avec un accent porté sur l'expression des gènes des deux partenaires de la coopération A. lipoferum 4B-riz. Les résultats de transcriptomique sur puce soulignent l'importance des mécanismes de réponse au stress oxydatif au cours de l'adaptation des partenaires l'un à l'autre ainsi que la mise en place de réseaux de régulation complexes. De nombreux gènes présentent un profil d'expression qui dépend de la combinaison souche/cultivar, suggérant que des mécanismes évolutifs ont conduit à une interaction préférentielle entre une souche et son cultivar d'origine / Host specificity is a fundamental concept in understanding evolutionary processes leading to intimate interactions between bacteria and plants. In the case of Plant Growth- Promoting Rhizobacteria (PGPR) specificity appears to be controlled either by a strainspecific bacterial adaptation to non-specific traits of the host plant or by non-specific bacterial adaptation to genotype-specific properties of the host plant. Thus, we hypothesize that these adaptations result in the regulation of a large number of genes, independently of their direct involvement in phytostimulation. These regulations may depend on the bacterial strain / plant genotype combination. This work aims at identifying genes involved in reciprocal adaptation of partners and those involved in host specificity in PGPR-plant cooperation. As a model, we studied the interaction between Azospirillum lipoferum 4B and cereals (wheat, corn, rice cultivars Nipponbare and Cigalon), with an emphasis on gene expression of both partners during A. lipoferum 4B-rice cooperation. Microarray transcriptomic results highlight the importance of mechanisms implicated in response to oxidative stress as well as a tight adjustment of regulatory networks during the adaptation of both partners to each other. Many genes display expression profile that depends on the strain/cultivar combination, suggesting that evolutionary processes have led to a preferential interaction between a strain and its original cultivar

Made available in DSpace on 2015-03-26T13:39:57Z (GMT). No. of bitstreams: 1 texto completo.pdf: 1003598 bytes, checksum: 93179899aa202add23f6db8cad322351 (MD5) Previous issue date: 2013-03-01 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / Picloram is used for weed control in pastures, it has long toxic residual properties in the soil and can be toxic for successive plantings of susceptible species. The phytoremediation associated with microbial activity in rhizosphere of the plants, is an alternative to reduce the herbicides residue in the soil. This study is aimed to evaluate the microbial activity associated with the rhizosphere of the plants phytoremediator, the inoculation with fungi in phytoremediation potential of species, the growth biomass accumulation of Piriformospora indica and viability of spores of Glomus clarum under the effect of picloram. In the first experiment the microbial activity in the rhizosphere and non-rhizosphere soils contaminated with picloram were evaluated. The treatments were arranged in a factorial scheme 5 x 2, the first factor, rhizosphere soils cultivated with Urochloa Brizantha, Panicum maximum, Zea mays and rhizosphere soil uncultivated and autoclaved and non-autoclaved, and the second factor consisted of the absence and presence of picloram (0 and 240 g ha-1) in a completely randomized design with three replications. The species were grown for 60 days, after this period, the rhizosphere soil was collected and the herbicide applied. The C-CO2 that evolved from the soil at 4, 8, 12, 16, 20 and 24 days of incubation was assessed. At 24 days the microbial carbon biomass (CBM) was assessed and the metabolic quotient (qCO2) was calculated. The second experiment evaluated the growth and biomass accumulation of the endophytic fungus P. indicates and the viability of spores of G. clarum in the presence of five levels of picloram: 0, 30, 120, 240 and 480 g ha-1. The radial growth of the colony in a Petri dish was assessed every six days for 24 days and the dry matter mycelium was determined. The viability of the spores of G. clarum was evaluated 15 days after inoculation with a solution containing the herbicide dose. In the third experiment, we evaluated the species U. Brizantha, P. maximum and Z. mays and the absence and presence of picloram (0 and 240 g ha-1) applied at pre-emergence, with associated or not to the inoculation of the fungus G. etunicatum or P.indica. The shoot dry matter, root dry matter and root volume of the species were evaluated after 60 days of cultivation. After the removal of soil ensiformis a bioassay with Phaseolus vulgaris was established after 35 days of cultivation to determine the intoxication. In the first experiment, the picloram changed the evolved CO2 and didn t affect the CBM and qCO2 for rhizosphere soils of the species. The rhizosphere soil cultivated with Z. mays showed higher microbial activity in the presence of picloram, and the microbial activity in the rhizosphere of P. maximum and U. Brizantha soils were lower in presence of the herbicide than in the non-contaminated soils with herbicide, suggesting a lower contribution of these species in the rhizospheric degradation of picloram. In the second experiment, levels of picloram tested did not affect mycelial growth up to 24 days after inoculation. However, levels above 240 g ha-1 negatively influenced the biomass accumulation of P. indicate, increasing the levels of the herbicide reduced the viability of spores. The inoculation with the fungi P. indica and G. etunicatum helped in phytoremediation of picloram by the species Z. mays and P. maximum and when inoculation was made by a herbicide application it did not reduce the root volume and root dry matter production of P. maximum. / O picloram é utilizado para o controle de plantas daninhas em pastagens, apresentando longo período residual no solo, podendo intoxicar plantios sucessivos de espécies sensíveis. A fitorremediação associada à atividade microbiana na rizosfera das plantas é uma alternativa para redução de resíduos deste herbicida no solo. Objetivou-se avaliar a atividade microbiana associada à rizosfera das plantas fitorremediadoras, a inoculação com fungos no potencial fitorremediador das espécies, o crescimento e acúmulo de biomassa de Piriformospora indica e a viabilidade de esporos de Glomus clarum sob efeito do picloram. No primeiro experimento foi avaliada a atividade microbiana de solos não rizosféricos e rizosféricos contaminados com picloram. Os tratamentos foram organizados em esquema fatorial 5 x 2, sendo o primeiro fator, solos rizosféricos cultivados com Urochloa brizantha, Panicum maximum, Zea mays e solos sem cultivo não rizosféricos autoclavado e não autoclavado, e o segundo fator constou-se da ausência e presença do picloram (0 e 240 g ha-1) em delineamento inteiramente casualizado, com três repetições. As espécies foram cultivadas por 60 dias, após esse período, o solo rizosférico foi coletado e aplicado o herbicida. Foi estimado o C-CO2 evoluído do solo aos 4, 8, 12, 16, 20 e 24 dias de incubação. Aos 24 dias foi determinado o carbono da biomassa microbiana (CBM) e calculado o quociente metabólico (qCO2). No segundo experimento, foram avaliados o crescimento e acúmulo de biomassa do fungo endófito P. indica e a viabilidade de esporos de G. clarum na presença de cinco doses de picloram, 0, 30, 120, 240 e 480 g ha-1. O crescimento radial da colônia em placa de Petri foi avaliado a cada seis dias, durante 24 dias, quando foi determinada a matéria seca micelial. A viabilidade dos esporos de G. clarum foi avaliada aos 15 dias após a inoculação em solução contendo as doses do herbicida. No terceiro experimento, foram avaliadas espécies U. brizantha, P. maximum e Z. mays e ausência e presença de picloram (0 e 240 g ha-1), aplicado em pré-emergência e associadas ou não à inoculação dos fungos G. etunicatum ou P.indica. Foram avaliados a matéria seca da parte aérea e volume e matéria seca radicular das espécies, após 60 dias de cultivo. Após a retirada da espécie fitorremediadora do solo, foi feito o bioensaio com Phaseolus vulgaris, foi determinada após 35 dias de cultivo, a intoxicação. No primeiro experimento, o picloram alterou o CO2 evoluído e não se observou efeito sobre o CBM e qCO2 para os solos rizosféricos das espécies. O solo rizosférico cultivado com Z. mays apresentou maior atividade microbiana na presença do picloram e a atividade microbiana na rizosfera de P. maximum e U. brizantha foi menor na presença do herbicida que em solos não contaminados com herbicida, sugerindo uma menor contribuição rizosférica dessas espécie na degradação do picloram. No segundo experimento, as doses de picloram testadas não influenciaram o crescimento micelial até 24 dias após a inoculação. Entretanto, doses acima de 240 g ha-1 influenciaram negativamente o acúmulo de biomassa de P. indica. O aumento das doses do herbicida reduziu a viabilidade dos esporos. A inoculação com os fungos P. indica e G. etunicatum contribui na fitorremediação do picloram pelas espécies Z. mays e P. maximum e que quando feita inoculação a aplicação do herbicida não reduz o volume radicular e a produção de matéria seca radicular de P. maximum.

Det här arbetet ger en orientering i växters olika förmågor att rehabilitera miljöskador och belyser möjligheten att använda växternas essentiella och varierande förmågor i miljöarbetet. De ämnen som har skadlig inverkan på miljön kallas för miljögifter. Både globalt och i Sverige har omloppet av många miljögifter ökat markant de senaste århundradet. Växter kan användas för att rena förorenad mark. De olika processerna när växter renar mark, vatten och luft från föroreningar samlas under begreppet fytoremediering. Det finns olika metoder och reningsprocesser inom fytoremediering. Växter kan dels ta upp och lagra föroreningar, bryta ned dem till ofarliga beståndsdelar samt förhindra så att de inte sprider sig ut i ekosystemet. I det här examensarbetet har föroreningssituation vid järnvägsstationen i Ockelbo använts som exempel för att konkretisera fytoremediering till en specifik plats. En beskrivning av de till platsen relaterade föroreningarna arsenik, bly, kadmium, kvicksilver, koppar, zink, PAH (polycykliska aromatiska kolväten) och olja presenteras tillsammans med aktuella fytoremedieringsmetoder och grödor för respektive förorening. Som slutsats bedöms fytoremediering vara möjligt för järnvägsstationen i Ockelbo. Fördelar och nackdelar med fytoremediering på stationen lyfts fram och möjliga parallella användningsområden medan fytoremedieringen pågår diskuteras. Vidare diskussion förs kring fytoremediering, miljöfrågor och rådande regelverk och logistik i Sverige. Arbetet innefattar ett förslag till utformning av fytoremediering på stationsområdet. Förslaget inkluderar ett växtval av olika fytoremedieringsgrödor lämpliga för platsen.