Célèbres depuis l'accident de Seveso en 1976, les dioxines/furanes (PCCD/F) restent, malgré une forte baisse de leurs émissions, un sujet de préoccupation permanent en France et dans le monde. Le rémanence de ces composés organochlorés dans le sol et le risque toxique qu'ils représentent pour l'homme et l'environnement font que la gestion et la remédiation des sols contaminés par les PCDD/F sont devenues une priorité des industriels, législateurs et scientifiques. La phytoremédiation compte parmi les méthodes émergentes de dépollution des sols contaminés en raison de son adéquation avec le développement durable. Elle combine les capacités naturelles des plantes et de leur microbiote rhizosphérique à biodégrader les polluants organiques. Cependant, l'efficacité de cette phytotechnologie est encore souvent limitée, en particulier lorsqu'il s'agit de composés chlorés, à cause de leur récalcitrance, de leur phytotoxicité et leur faible biodisponibilité dans le sol. Ainsi, l'objectif de ce travail de thèse a consisté à étudier les performances de la phytoremédition assistée, en particulier par les champignons mycorhiziens arbusculaires, d'un sol agricole historiquement pollué par les PCDD/F prélevé sur une parcelle expérimentale située à proximité d'un ancien incinérateur. L'ensemble des résultats obtenus mettent en évidence, en particulier, le potentiel de deux espèces végétales, la luzerne et la fétuque, dans la rhizodégradation des PCCDD/F. La végétalisation du sol permet de moduler les communautés microbiennes du sol (bactéries, Archées et champignons) et notamment celles qui semblent impliquées dans la dissipation des PCCDD/F. En revanche, bien que la mycorhization agisse sur les communautés microbiennes du sol, celle-ci n'a pas eu d'impact, dans nos conditions expérimentales, sur la dissipation des PCCDD/F quelles que soit l'origine de l'inoculum utilisé et les espèces mycorhiziennes qui le compose. La dégradation de ces composés organochlorés est plus marquée dans un sol préalablement stérilisé, puis recolonisé par certaines communautés microbiennes spécifiques, impliquées dans la dissipation des PCCDD/F. L'utilisation combinée d'un mélange de rhamnolipides avec l'introduction dans le sol d'une bactérie Sphingomonas wittichii RWI, décrite pour ses capacités de dégradation des PCCDD/F, permet d'accroitre l'efficience de la rhizodégradation des PCDD/F qui se traduit par une baisse significative de la cytotoxicité du sol après phytoremédiation. / Famous since the Seveso accident in 1976, dioxins/furans (PCCD/F) remain, despite a sharp decline in emissions, a subject of permanent concern in France and in the world. The remanence of these organochlored compounds in soil and the toxic risk they represent for humans and the environment mean that the management and remediation of PCDD/F contaminated soil has become a priority for industrialists, legislators and scientists. Phytoremediation is one of the emerging depollution methods of contaminated soils due to Its suitability for sustainable development. It combines the natural capacities of plants and their rhizospheric microbiota to biodegrade organic pollutants. However, the effectiveness of this phytotechnology is still often limited, especially in the case of chlorinated compounds, due to their recalcitrance, phytotoxicity and low bioavailability in the soil. Thus, the thesis aims to study the performance of assisted phytoremission, in particular by mycorrhizal fungi, of an agricultural PCDD / F based-polluted soil from an experimental plot near an old incinerator. The results obtained show the potential of two plant species, alfalfa and tall fescue, in the rhizodegradation of PCCDD/F. Soil vegetation shows to modulate soil microbial communities (bacteria, archaea and fungi) includind those that appear to involved in the dissipation of the PCCDD/F. On the other hand, although mycorrhization affects soil microbial communities, it has not had any impact on the dissipation of PCCDD/F in our experimental conditions, whatever the inoculums origin and the mycorrhizal species which compose it. The degradation of these organochlorined compounds is more significant in a previously sterilized soil and then recolonized by specific microbial communities involved in the PCCDD/Fdissipation. The combined use of rhamnolipids mixture and Sphingomonas wittichii RWI bactrerium described for its degradation capabilities of PCCDD/F makes it possible to increase the efficiency of PCDD/F rhizodegradation which results in a significant decrease in soil cytotoxicity after phytoremediation.

The work in this thesis aimed to demonstrate the contribution of arbuscular mycorrhizal (AM) fungi to the yield and fruit quality of field-grown processing tomatoes, and the potential to increase the sustainability of tomato production through greater fertiliser use efficiency by inoculating tomato seedlings with beneficial AM fungi. Previously, the conclusion that tomato growth is unresponsive to AM colonisation, particularly in high-P soils, has often been based on only a part of the tomato life-cycle. However, there is increasing evidence that that positive AM yield responses can occur in soils with relatively high plant-available P, and that AM responsiveness of tomato during vegetative growth may be a poor predictor of reproductive growth. A preceding industry study found that AM colonisation of field-grown processing tomatoes was very low, mostly less than 5%. The reason for the low colonisation was unclear since previous studies have shown that tomato can become relatively highly colonised by AM fungi. It was not known if farm practices, such as soil cultivation and chemical sterilisation, which have been shown to decrease AM colonisation of tomato and other crops, could have contributed to the low colonisation. Furthermore, it was unclear what contribution AM fungi were making to the yield and fruit quality of tomato in commercial production, and what their potential contribution might be if greater AM colonisation could be achieved through inoculating seedlings. Yield and fruit quality are important to tomato growers as both are used to calculate payment when the fruits are sold. Large amounts of soluble fertilisers, particularly P, are applied during tomato production with the aim of increasing yield and quality. However, fertiliser use efficiency, particularly P, on tomato farms has been identified as being low, and needing to be improved in order to increase the economic and environmental sustainability of tomato farming. Increasing P, and also other nutrients, such as Zn and Ca, in tomatoes could also help to improve agricultural sustainability by alleviating human malnutrition in developing countries and, in the case of Ca, have the potential to reduce blossom end rot, which can severely reduce marketable yield. There is considerable potential for AM fungi to assist in the supply of these nutrients to field-grown tomatoes. AM fungi are widely accepted to increase plant uptake of P. This has mostly been demonstrated in low-P soils, as increases in plant-available P are generally known to be detrimental to AM colonisation and any subsequent growth effects. However, there is increasing evidence of the ability of AM fungi to increase P uptake and yield even in high P soils. There is also good evidence of increased Zn uptake by mycorrhizal supply to plants. Evidence for increased Ca uptake in mycorrhizal plants is in comparison limited and conflicting, but has been demonstrated in some cases. It is possible that AM fungi could allow applications of these nutrients, particularly P, to be reduced while maintaining or increasing fruit yield and quality. However, the ability of indigenous or inoculated AM fungi to do so in the relatively high-P farm soils used in this project was unknown. In order to address these uncertainties a series of pot studies and a field experiment were conducted using field soils from tomato farms and an adjacent nature reserve for comparison. Data on soil characteristics from five farms, collected during the previous industry study, was analysed in conjunction with data from another farm located nearby with contrasting soil properties. Two farm soils and an unfarmed comparison were selected on the basis of their having contrasting levels of P, Zn and Ca, and pH, with the constraint that they were located within 50 km of each other to minimise travel time in the study area. The two farmed soils had a relatively high concentration of plant-available P (103 and 58 mg/kg Colwell), while plant-available P in the unfarmed soil was probably marginal to that required for healthy tomato growth (27 mg/kg Colwell). Samples of the soils were taken soon after commencement of the work and used in pot studies. Firstly, a bioassay was conducted to establish the ability of tomato to become colonised in the three field soils. AM colonisation of tomato and medic, which is known to be highly susceptible to AM colonisation, was compared between three harvests over an approx. 16 week period. Vegetative growth was also measured. The total colonisation of tomato mostly did not differ from that of medic at each harvest in any soil. Furthermore, despite the large differences in plant-available P between the three soils, colonisation and vegetative growth of tomato did not differ between soils at any harvest. In a subsequent pot experiment, the effect of colonisation by AM fungi in the three field soils on the vegetative and reproductive growth, and nutrient status of tomato was determined using the tomato mutant rmc (reduced mycorrhizal colonisation) and its progenitor 76R. A number of non-destructive vegetative and reproductive growth measurements were repeatedly measured over an approx. 24 week period. Destructive measurements were carried out at two harvests, 39 and 164 days after planting. Tomato 76R was again well colonised in all soils. Tomato rmc remained uncolonised, and was therefore an effective non-mycorrhizal control. AM colonisation had little effect on plant growth or nutrient status in any soil at the first harvest, but significant growth and nutrient responses were recorded at the second harvest. In particular, AM colonisation markedly increased vegetative growth in the unfarmed soil. AM colonisation did not affect vegetative growth in either of the farmed soils. However, AM colonisation increased reproductive growth, particularly yield over time, in all soils. AM colonisation increased shoot P concentration and content, but effects on Zn were mixed and largely inconclusive. Shoot Ca concentration and content were mostly reduced by AM colonisation. Similar patterns were observed in fruit nutrient status. The potential of pre-inoculation with AM fungi to increase AM colonisation and/or AM growth and nutrient effects in the field was considered. A commercial AM fungal inoculum was initially proposed for use, but was found to be unreliable and laboratory cultures of Scutellospora calospora and Glomus mosseae were used instead. Tomato seedlings were inoculated by amending a commercial seed-raising medium with an equal mixture of S. calospora and G. mosseae inocula. Seeds of tomato rmc, 76R and the commercial processing tomato cultivar U941 were sown and raised according to the practices followed by a commercial seedling nursery. After 9 weeks a sub-sample of inoculated seedlings of 76R and U941 had become colonised by both AM fungi, although the total colonisation was relatively low (approx. 10%). There was no difference in the shoot or root dry weights between inoculated and non-inoculated seedlings. The remaining seedlings were then used in the field experiment. Seedlings were transplanted amongst a commercial processing tomato crop on two farms and grown to maturity. A substitute farm with soil of moderate P (66 mg/kg Colwell) was used as tomatoes were no longer being grown on the initial farm with moderate P. Two P treatments, ‘normal’ and ‘reduced’ P fertilisation, were imposed in order to investigate the effect of P fertilisation on colonisation by indigenous and inoculated AM fungi, and growth and nutrient status of tomato in the field. Non-destructive growth measurements and soil core samples to assess mycorrhizal colonisation were taken mid-season (approx. 10 weeks after transplanting). Destructive growth measurements and core samples to assess colonisation were taken at harvest (approx. 19 weeks after transplanting). Colonisation of rmc was insubstantial and it again served as an effective non-mycorrhizal control to 76R. Colonisation was insubstantial in all treatments on the farm where soil had moderate plant-available P. On the other farm, where soil had relatively high plant-available P, colonisation of all plants was low mid-season, but was mostly substantial (>20%) in 76R and U941 at harvest. Low colonisation on both farms was probably the result of farming practices, particularly soil cultivation. However, a combination of inoculation and reduced P fertilisation increased colonisation. Colonisation by indigenous AM fungi had no effect on the growth or nutrient status of field grown tomatoes. In contrast, pre-inoculation with AM fungi increased fruit yield by a mean of approx. 40% in 76R and U941. This was the result of an 18% increase in the fresh weight of individual fruits and, when inoculation was combined with reduced P fertilisation, a 21% increase in the number of fruits on each plant. The increase in the number of fruits on each plant was associated with an increase in the number of flowers at the most advanced growth stage. Inoculation also increased vegetative growth, and fruit P, Zn and Ca contents. A small (4%) decrease in fruit brix was more than offset by increased yield. This study has shown that while AM fungi indigenous to tomato farm soils have the ability to substantially colonise tomato, they appear to have little effect on tomato growth, yield or nutrition in the field. In contrast, inoculation of tomato seedlings with mutualistic AM fungi during nursery production can substantially increase the growth, yield and fruit nutrient contents of field-grown tomatoes under commercial conditions. This increase could also be enhanced by a reduction in P fertilisation. Increased yield and fruit nutrient contents, and decreased P fertilisation neatly address the aims of increased agricultural sustainability. Incorporating pre-inoculation of tomato into existing farming practices has a potential to increase the productivity and sustainability of processing tomato production worldwide. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1292847 / Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2007

Pulses are an important component in crop rotations in the semiarid Brown soil zone of southern Saskatchewan, Canada. Besides their capability to fix nitrogen, pulse crops establish a strong symbiotic relationship with arbuscular mycorrhizal fungi (AMF), which have been shown to increase nutrient and water uptake through hyphal extensions in the soil. Incorporating strongly mycorrhizal crops in a rotation may increase inoculum levels in the soil and benefit the growth of a subsequent crop. The objective of this study was to determine if AMF potential and colonization of a durum crop is significantly affected by cropping history and to assess the impact of pulses in crop rotations on the abundance and diversity of AMF communities in the soil. In 2004 and 2005, soil, plant, and root samples were taken on Triticum turgidum L. (durum) with preceding crops of Pisum sativum L. (pea), Lens culinaris Medik (lentil), Cicer arietinum L. (chickpea), Brassica napus L. (canola) or Triticum turgidum L. (durum). Although there were few differences in soil N and P levels, previous crop had a significant effect (p<0.05) on durum yields in both years. A previous crop of pea was associated with the highest yields, while the durum monocultures were lowest. Arbuscular mycorrhizal potential and colonization were significantly affected (p<0.05) by cropping history, but not consistently as a result of inclusion of a pulse crop. Phospholipid and neutralipid fatty acids (PLFA/NLFA) were completed to analyse the relative abundance of AMF (C16:1ù5), saprophytic fungi (C18:2ù6), and bacteria in the soil. The effect of treatment on the abundance of AMF, saprotrophic fungi and bacteria were not significant (p<0.05), but the changes over time were. These results demonstrate that although previous crop may play a role in microbial community structure, it is not the only influencing factor.

Pulses are an important component in crop rotations in the semiarid Brown soil zone of southern Saskatchewan, Canada. Besides their capability to fix nitrogen, pulse crops establish a strong symbiotic relationship with arbuscular mycorrhizal fungi (AMF), which have been shown to increase nutrient and water uptake through hyphal extensions in the soil. Incorporating strongly mycorrhizal crops in a rotation may increase inoculum levels in the soil and benefit the growth of a subsequent crop. The objective of this study was to determine if AMF potential and colonization of a durum crop is significantly affected by cropping history and to assess the impact of pulses in crop rotations on the abundance and diversity of AMF communities in the soil. In 2004 and 2005, soil, plant, and root samples were taken on Triticum turgidum L. (durum) with preceding crops of Pisum sativum L. (pea), Lens culinaris Medik (lentil), Cicer arietinum L. (chickpea), Brassica napus L. (canola) or Triticum turgidum L. (durum). Although there were few differences in soil N and P levels, previous crop had a significant effect (p<0.05) on durum yields in both years. A previous crop of pea was associated with the highest yields, while the durum monocultures were lowest. Arbuscular mycorrhizal potential and colonization were significantly affected (p<0.05) by cropping history, but not consistently as a result of inclusion of a pulse crop. Phospholipid and neutralipid fatty acids (PLFA/NLFA) were completed to analyse the relative abundance of AMF (C16:1ù5), saprophytic fungi (C18:2ù6), and bacteria in the soil. The effect of treatment on the abundance of AMF, saprotrophic fungi and bacteria were not significant (p<0.05), but the changes over time were. These results demonstrate that although previous crop may play a role in microbial community structure, it is not the only influencing factor.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

Certain crop plants are susceptible to pathogens or unable to develop efficient microbial symbioses. These crops adversely impact soil biological quality with consequences on plant health and productivity of cropping systems. Chickpea is a rotational pulse crop with two types: kabuli and desi, and several cultivars. Cultivation of chickpea has inconsistent effects on soil microbial communities and subsequent wheat crops. I conducted field studies and used high throughput molecular analyses to explore the variations among chickpeas to identify cultivars developing fungal communities that are conducive to plant health and productivity. I also carried out greenhouse studies and used biochemical analyses to investigate the response of chickpea cultivars to arbuscular mycorrhizal (AM) fungi and non-AM fungal endophytes and identify the influence of root and root metabolites on the endophytic and pathogenic fungi. Cultivars and types of chickpeas and environmental conditions promoted different fungal communities in the root endosphere. Funneliformis and Claroideoglomus were the dominant AM fungal genera and Fusarium and Alternaria were the dominant non-AM fungal genera in the roots of chickpea. The roots of cultivars CDC Corrine, CDC Cory and CDC Anna hosted the most diverse fungal communities in contrast to CDC Alma and CDC Xena roots which hosted the least diverse communities. Plant response to AM and non-AM fungal endophytes varied with genotype and type of chickpea. The root symbiosis effectively promoted plant growth in CDC Cory, CDC Anna and CDC Frontier and stimulated nitrogen fixation in CDC Corrine. Cultivars of chickpea responded differently to dual inoculation of the AM and non-AM fungal endophytes. Co-inoculation with AM and non-AM fungal endophytes had additive effects on CDC Corrine, CDC Anna and CDC Cory but non-AM fungal endophytes reduced the positive effect of AM fungi in Amit and CDC Vanguard. Desi chickpea appeared to form more efficient symbioses with soil fungal resources than kabuli chickpea. Protein(s) up-regulated in the mycorrhizal roots of the desi chickpea CDC Anna suppressed the growth of the fungal endophytes Trichoderma harzianum and Geomyces vinaceus and of the pathogens Fusarium oxysporum and Rhizoctonia sp. The formation of AM symbiosis decreased the production of root bioactive metabolites soluble in 25% methanol. Some of the root metabolites stimulated the growth of Trichoderma harzianum and Geomyces vinaceus, and a few inhibited Rhizoctonia sp. and Fusarium oxysporum. A few metabolites with contrasting effects on the different fungal species were detected. The non-protein phytochemicals had selective effects on the endophytes and pathogens whereas the antifungal proteins of mycorrhizal roots were non-selective. Overall the study reveals a "genotype effect" of chickpea on the soil microbiota suggesting the possibility to improve the performance of this crop through the selection of genotypes improving the communities of root associated fungi, by associating and responding to beneficial fungi and repressing the pathogens.

Made available in DSpace on 2014-06-11T19:35:00Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-05-25Bitstream added on 2014-06-13T19:05:01Z : No. of bitstreams: 1 russomanno_omr_dr_botfca.pdf: 951502 bytes, checksum: 65ab95dd8d5f795650c7b83e6aa5b10f (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Secretaria Agricultura / O objetivo do presente trabalho visou avaliar a influência dos FMA Glomus etunicatum Becker & Gerd. e Glomus clarum Nicol. & Schenck, no desenvolvimento de plantas de alecrim e manjericão, bem como verificar a capacidade destas plantas micorrizadas em superar os danos causados pelo fungo Fusarium oxysporum Schecht. Plantas de alecrim (Rosmarinus officinalis L.) e de manjericão (Ocimum basilicum L.) foram inoculadas, separadamente, com G. etunicatum e G. clarum, em casa de vegetação, com temperatura de 26 l 20C e luminosidade de 3000 Lux. Utilizou-se substrato autoclavado composto por uma parte de areia e uma de terra; o inóculo constou de esporos [500 esporos de G.etunicatum (50 mL-1) de solo e 700 esporos de G.clarum (50 mL-1) de solo] e ainda fragmentos de raízes infectadas e micélio. Em cada tipo de planta inoculada foram avaliadas as seguintes variáveis: altura das plantas (AP), peso da matéria seca da parte aérea (MSPA), peso da matéria fresca das raízes (MFR), esporulação (E), colonização radicular (CR) e teor de macro e micronutrientes no substrato e nas plantas (TMm). Foi avaliada também a influência de G. etunicatum e G. clarum no controle de F. oxysporum em plantas de alecrim e manjericão. A inoculação do patógeno (concentração de 5 x 103 esporos mL-1) foi realizada, separadamente, em plantas de alecrim e de manjericão com 90 dias de micorrização (5 vasos com G. etunicatum e 5 vasos com G. clarum) e ainda plantas testemunhas, não micorrizadas (5 vasos). No alecrim, G. clarum mostrou-se significativamente mais eficiente do que G. etunicatum em AP, MSPA e E; por outro lado, G. clarum apresentou CR menor do que G. etunicatum. Em relação às plantas testemunha, G. clarum diferiu significativamente destas em 2 todos as variáveis analisadas, porém G. etunicatum não diferiu estatisticamente das plantas testemunha em AP e MSPA. No manjericão, em relação... . / The purpose of the present work had the objective of evaluating the influence of AMF Glomus etunicatum Becker & Gerd. and Glomus clarum Nicol. & Schenck on the rosemary and basil plants development and also concerning the capacity of the mycorrhizal plants in resisting the wilt caused by Fusarium oxysporum Schecht. For that, rosemary (Rosmarinus officinalis L.) and basil (Ocimum basilicum L.) plants were previously inoculated with G. etunicatum and G. clarum in greenhouse under the temperature of 26 l 20C and luminosity of 3000 Lux. The soil was sterilized and composed by one part of sand and one part of earth. The inoculum was composed by the fungi spores [500 spores of G. etunicatum in (50 mL-1) soil and 700 spores of G. clarum in (50 mL-1) soil] and micelium and roots fragments infected by the AMF. In each plant inoculated the following variables were evaluated: plant height (PH), plant dry weigt (PDW), roots fresh weight (RFW), sporulation rate (SR), root mycorrhizal percentage (RMP) and macro and micronutrients level (MmL) present in the plants and in the soil. The G. clarum and G. etunicatum influence in the control of F. oxysporum wilt in both plants was also evaluated. The inoculation of the pathogen (5x103 spores mL-1) was separatety realized in the rosemary and basil plants after 90 days of the mycorrhization (5 pots of G. clarum and 5 pots of G. etunicatum); the control was also composed by 5 pots without mycorrhization. In the rosemary, G. clarum was significantely more efficient than G. etunicatum in the variables PH, RFW and SR; although G. clarum 4 presented RMP smaller than G. etunicatum. In relation to the control, G. clarum was significably better to the plants in all the variables, although G. etunicatum do not differed statistically for the control plants in PH and PDW. For basil in all the analised variables G. clarum differed statistically from G. etunicatum and was similar to the control treatment in all the variables.

Made available in DSpace on 2015-03-26T13:51:44Z (GMT). No. of bitstreams: 1 01 - capa_abstract.pdf: 58664 bytes, checksum: 66cb47131cc46bcd2d5d263065f54c20 (MD5) Previous issue date: 2008-07-29 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / The objective of this work was to evaluate the effects of the arbuscular mycorrhizal fungus (AMF), Glomus clarum, multiplied monoxenically in transformed carrot roots, on the growth, survival, mycorrhizal colonization and root development of micropropagated plantlets in different stages of rooting. Inoculation was performed in vitro and ex vitro conditions. Micropropagated plantlets with 0, 14 or 21 days maintained in rooting medium, supplemented or not with 1 mg L-1 of Indolbutiric acid (IBA), were transferred to a substrate composed by sand:soil:vermiculite (1:1/2:1). The in vitro system allowed the establishing mycorrhizal association, but no stimulatory effect on the development of shoot or root by mycorrhizal inoculation was observed. The period of time and addition of IBA did not affect plant growth. In ex vitro system, the stimulatory effects of arbuscular mycorrhizal association were evident in all evaluated characteristics, except to plant height. Plants that were not submitted to rooting showed growth similar or superior to those that were maintained in the rooting media, independent of IBA addition. Inoculated plants were shown to be more efficient at nutrient absorption, especially to phosphate. The arbuscular mycorrhizal association promotes beneficial effects when inoculation is performed ex vitro and the best period for inoculation of physic nut seedlings is in the beginning of acclimatization, without in vitro rooting phase. Inoculation of physic nut with arbuscular mycorrhizal fungi showed to be an important tool for micropropagated seedlings production. / O objetivo deste trabalho foi avaliar o efeito da inoculação do fungo micorrízico arbuscular (FMA), Glomus clarum, multiplicado monoxenicamente em raízes de cenoura transformadas, sobre o crescimento, a sobrevivência, a colonização micorrízica e o desenvolvimento radicular de plantas micropropagadas de pinhão-manso em diferentes estádios de enraizamento. A inoculação foi efetuada em condições in vitro e ex vitro. Plantas micropropagadas de pinhão-manso com 0, 14 ou 21 dias de permanência em meio de enraizamento, suplementado ou não com 1 mg L-1 de ácido indol-butírico (AIB), foram transferidas para substrato areia lavada:solo:vermiculita (1:1/2:1). O sistema in vitro utilizado permitiu o estabelecimento da associação micorrízica, mas não foi possível observar efeitos estimuladores da inoculação sobre o crescimento e desenvolvimento radicular das plantas. O tempo de permanência em meio de enraizamento e a adição de AIB também não afetaram o crescimento das plantas. No sistema ex vitro os efeitos estimuladores das micorrizas arbusculares foram evidenciados em todas as características relacionadas ao crescimento, com exceção da altura das plantas. As plantas que não foram submetidas à etapa de enraizamento mostraram crescimento semelhante ou superiores àquelas submetidas à etapa de enraizamento, independente da adição do AIB. As plantas inoculadas com G. clarum mostraram-se também eficientes na absorção de nutrientes, principalmente de fósforo. Pode-se concluir que os efeitos estimuladores das micorrizas arbusculares foram evidenciados quando foi realizada a inoculação ex vitro dessas plantas e que a melhor época de inoculação de J. curcas corresponde à fase de início da aclimatização, sem necessidade de passar pela fase de enraizamento in vitro. A inoculação com FMAs pode representar importante ferramenta para a produção de mudas micropropagadas de qualidade.

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

Les plantes vivent en association avec une grande diversité de microorganismes qui forment son microbiota. Ce microbiote fournit des fonctions clés qui influencent tous les aspects de la vie d'une plante, de l'établissement à la croissance jusqu'à la production. Cette thèse a pour intention de déterminer les règlent d'assemblage du microbiote et ses conséquences pour le phénotypel l'adaptation et l'évolution des plantes. Pour atteindre cet objectif nous avont utilisé différentes approches expérimentales comprenant des plantes clonales comme organismes modèles ainsi que des mésocosmes prairiaux pour analyses à l'échelle des communautés. Nos résultats ont démontré i) que les Champignons Mycohiziens à Arbuscules induisent d'important es variations phénotypiques pour les traits des plantes clonales impliqués dans l'exploration de l'espace et l'exploitation des ressources. Ces changements dépendent de l'identité des symbiontes et altèrent les capacités des plantes à développer des réponses plastiques à l'hétérogénéité environnementale. ii) Les plantes ont évolué un méchanisme permettant la transmission d'une partie de leur microbiote a leur descendance, assurant la qualité de leur habitat. iii) Le contexte spécifique des communautés de plantes est un facteur majeur structurant l'assemblage du microbiota des plantes à échelle locale. L'abondance de certaines espèces de plante dans le voisinage d'une plante cible augmente ou diminue la diversité de son microbiote, déterminant in fine ses performances. De manière générale, cette thèse démontre l'importance des organismes symbiotiques dans la compréhension de l'adaptation et de l'évolution des plantes. / Plants live in association with a wide diversity of microorganisms forming the microbiota. The plant microbiota provides a variety of key functions that influence many aspects of plant's life comprising establishment, growth and reproduction. The present thesis aims at determining the assembly rules of the plant microbiota and its consequences for plant phenotype, adaptation and evolution. To fulfill this objective, we used different experimental approaches using either clonal plants as model organisms or grassland mesocosms for community-wide analyses. Our results demonstrated i) that Arbuscular Mycorrhizal Fungi induce important phenotypic variations in clonal plants traits involved in space exploration and resources exploitation. These changes depended on the identity of the symbionts and altered the plants ability to produce plastic responses to environmental heterogeneity. ii) Plants have evolved a mechanism allowing the transmission of a part of their microbiota to their progeny, ensuring thus their habitat quality. iii) The plant community context is a major factor structuring local plant microbiota assembly. Particular plant species identity in the neighborhood increase or decrease the microbiota diversity and ultimately determine the focal plant performance. This thesis overall demonstrates the importance of symbiotic microorganisms in the understanding of the plant adaptation and evolution. From the knowledges acquired we developed a novel understanding of symbiotic interactions in clonal plants by extending the holobiont theory to the meta-holobiont theory.