Submitted by JORGE MARTINELLI MARTELLO (jorgemartinelli@hotmail.com) on 2016-02-29T20:47:16Z No. of bitstreams: 1 DISSERTAÇÃO- JORGE MARTINELLI.pdf: 16363477 bytes, checksum: e325bf527b7f461e3d998472d2084c38 (MD5) / Approved for entry into archive by Ana Paula Grisoto (grisotoana@reitoria.unesp.br) on 2016-03-01T13:47:45Z (GMT) No. of bitstreams: 1 martello_jm_me_bot.pdf: 16363477 bytes, checksum: e325bf527b7f461e3d998472d2084c38 (MD5) / Made available in DSpace on 2016-03-01T13:47:45Z (GMT). No. of bitstreams: 1 martello_jm_me_bot.pdf: 16363477 bytes, checksum: e325bf527b7f461e3d998472d2084c38 (MD5) Previous issue date: 2016-01-29 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Recentemente no Brasil, a deficiência de boro têm sido constatada tanto em regiões tradicionais mas, principalmente, em regiões de expansão da cultura da cana-de-açúcar para solos arenosos e de baixa fertilidade. Relacionado a isso, doenças como estria vermelha (Bactéria - Acidovorax avenae), além de redução qualitativa e quantitativa da produtividade dos canaviais, têm sido observados. Portanto, estudos mais detalhados que revelem com maior clareza as particularidades deste micronutriente para a cultura se fazem necessários. Assim, objetivou-se com o presente trabalho avaliar o efeito da disponibilidade de boro em solução nutritiva sobre o desenvolvimento radicular e da parte aérea e, também, sobre a eficiência na absorção e concentração de nutrientes em duas variedades de cana-de-açúcar de ciclos semelhantes e recomendadas para o mesmo ambiente de produção. O experimento foi realizado em casa de vegetação, na Faculdade de Ciências Agronômicas /UNESP, em Botucatu-SP, Brasil. O delineamento experimental foi inteiramente casualizado com esquema fatorial composto por duas variedades (1- RB867515 e 2- RB92579) e, duas concentrações de B na solução nutritiva (1-Deficiente: 4,5 μmol L-1 e 2-Adequado: 45 μmol L-1 de B), totalizando quatro tratamentos com quatro repetições. Foram avaliados os parâmetros biométricos das plantas e morfológicos das raízes, a produção de matéria seca, a concentração e o acúmulo de nutrientes na parte aérea, e a quantidade de nutrientes absorvidos por metro de raiz. Os dados foram submetidos à análise de variância e aplicação do teste LSD a 5% de significância para as médias obtidas. O desenvolvimento e o comprimento radicular e dos entrenós das plantas de cana-de-açúcar foram restringidos pela deficiência de boro e, a concentração de nutrientes na parte aérea também foi reduzida. A variedade RB92579 apresentou maior produção de MSRA, MSC, MSF, menor diâmetro radicular e maior AP em relação a variedade RB867515, sob baixa concentração de B. As variedades de cana-de-açúcar estudadas comportam-se de maneira diferente frente a baixa disponibilidade de boro na solução nutritiva, sendo a variedade RB92579 mais tolerante e a variedade RB867515 mais suscetível a deficiência de boro. / Recently in Brazil, boron deficiency has been verified both in traditional, but mainly in expanding regions of the sugarcane crop to areas with sandy and low fertility soils. Associated with that, diseases like red stripe (Bacteria - Acidovorax avenae), as well as, qualitative and quantitative reduction in the productivity of sugarcane plants, have been observed. Therefore, more detailed studies, in order to further clarify special features of this micronutrient for the crop, become necessary. Thus, the aim of the present study was to evaluate the effect of boron availability in nutrient solution, on the root and shoot growth, and also on the nutrient uptake efficiency and concentration in two sugarcane varieties with similar growth cycles, that are recommended for the same growth environment. The experiment was conducted in a greenhouse at the College of Agricultural Sciences – Department of Crop Science/UNESP, in Botucatu-SP, Brazil. The experimental design was completely randomized in a factorial composed of two varieties (1- RB867515 and 2- RB92579) and two boron concentrations in the nutrient solution (1-Deficient: 4,5 μmol L-1 and 2-Adequate: 45 μmol L-1 B), four treatments with four repetitions in total. Were evaluated, the biometric parameters of plants, root morphology, dry matter yield, nutrient concentration and uptake in shoots and the uptake of nutrients by root length unit. Data were subjected to the variance analysis and means compared by the LSD test at 5 % significance. The root length and internodes development of sugarcane plants were restricted by boron deficiency and the concentration of nutrients in shoots was also reduced. The variety RB92579 showed higher production of MSRA, MSC, MSF, smaller root diameter and larger AP regarding RB867515 variety, under low boron concentration. The varieties of sugarcane studied, behave in a different way across the low availability of boron in the nutrient solution, being variety RB92579 more tolerant, and variety RB867515 more susceptible to boron deficiency. / CAPES: 3300406-4

La Vigne est cultivée en système greffé, combinant les qualités de production fruitière des Vignes Européennes (Vitis vinifera) et la tolérance phylloxérique des Vignes Américaines (Vitis spp.). Cependant l’utilisation de porte-greffes américains modifie le développement, la physiologie, et l’alimentation hydrique et minérale du greffon. Plus particulièrement, le fond génétique des porte-greffes de la Vigne semble impliqué dans la régulation de la nutrition en phosphore (P) du greffon. Le phosphore est un élément nutritif essentiel pour la croissance des plantes, impliqué dans la composition de nombreux composants cellulaires, ainsi que dans le contrôle des voies métaboliques via son apport énergétique et la régulation de l’activité enzymatique. Malgré son importance, P un est des éléments minéraux les plus limitants pour la croissance des plantes en raison de sa faible disponibilité assimilable dans le sol. L’objectif de ce travail est de déterminer les mécanismes impliqués dans le contrôle de la nutrition en P de la Vigne, en comparant deux porte-greffes V. riparia cv. Riparia Gloire de Montpellier (RGM) et V. rupestris x V. berlandieri cv. 1103 Paulsen (1103P) connus pour conférer respectivement de faibles ou fortes concentrations en P à leur greffon. Les résultats montrent que 1103P est plus adapté à acquérir le P que RGM, en partie grâce à un système racinaire plus développé permettant une meilleure exploration du sol ainsi qu’une meilleure efficience d’acquisition du P disponible. Ce porte-greffe montre également meilleure utilisation de ses réserves en P dans les parties pérennes afin d’optimiser la croissance des parties aériennes. En revanche la capacité des génotypes à augmenter le P assimilable dans la rhizosphère ne semble pas être différente. Enfin l’effet du greffage et plus particulièrement du greffon a été étudié, révélant le rôle de V. vinifera sur le développement et le fonctionnement racinaire du porte-greffe. Ces résultats contribuent à la compréhension des mécanismes régulant l’alimentation minérale de la Vigne, mettant ainsi en évidence le rôle du fond génétique du porte-greffe sélectionné, ainsi que la régulation de ce dernier par son greffon. / Grapevine is grown in a grafted system, combining the fruit production qualities of the European species (Vitis vinifera) and the phylloxera tolerance of American species (Vitis spp.). However, the use of American rootstocks affects the development, the physiology, and the water and mineral status of the scion. Particularly, the genetic background of grapevine rootstocks appears to be involved in the regulation of phosphorus (P) content of the scion. Phosphorus is an essential nutrient for plant growth, involved in the composition of many cellular components, as well as in the control of metabolic pathways via its role in energy transfer and the regulation of enzymatic activity. Despite its importance, P is one of the most limiting mineral elements for plant growth because of its poor availability in the soil. The objective of this work is to determine mechanisms involved in the control of P nutrition in grapevine, by comparing two rootstocks V. riparia cv. Riparia Gloire de Montpellier (RGM) and V. rupestris x V. berlandieri cv. 1103 Paulsen (1103P) known to confer low and high concentrations of P to their scion respectively. The results show that 1103P is more efficient at acquiring P than RGM, with a higher developed root system allowing greater soil exploration as well as a higher efficiency of P acquisition. In addition, this rootstock shows better use of its reserves of P in perennial parts to optimize the growth of the shoot. However, the ability of genotypes to increase the assimilable P in the rhizosphere does not seem to be different. Finally, the effect of grafting, and more particularly of the scion genotype, has been studied, demonstrating the capacity of V. vinifera to alter the development and root functioning of the rootstock. These results contribute to our understanding of the mechanisms regulating the mineral nutrition in grapevine and highlight the role of the genetic background of the rootstock, as well as its regulation by the scion.

L'adaptation des plantes face au stress thermique est cruciale pour leur survie et implique des réponses spécifiques telles que l’induction de protéines chaperonnes et la production d'espèces réactives de l'oxygène (ROS). Les glutaredoxines (GRX), une famille de protéines thiol anti- oxydantes, jouent un rôle important dans la régulation redox et la réponse au stress oxydatif. Mes études se concentrent sur GRXS17, une protéine multi-domaine à cœur fer-soufre. Malgré un phénotype de développement sévère du mutant grxs17 à des températures normales et plus élevées, peu est connu sur les fonctions biochimiques et les rôles intracellulaires précis de GRXS17. J’ai montré au cours de ma thèse que GRXS17 fonctionne comme une chaperonnedépendante de l’oxydation de la cellule. Elle présente à la fois une activité de type foldase mais également holdase. L'exposition aux stress oxydatif et thermique provoque le passage d'une forme dimérique à des complexes à poids moléculaires élevés ce qui est consistant avec une activité holdase. J’ai également montré que GRXS17 est requis pour la tolérance à des hausses de température de manière dépendante de ses cystéines catalytiques. Des approches de transcriptomique, métabolomique et protéomique montrent une réponse au stress thermique retardée dans le mutant grxs17, des défauts dans l’accumulation de certains métabolites clés, et ont permis d'identifier de potentiels nouveaux interactants de GRXS17 dans des conditions de stress thermique. Ces éléments soutiennent la fonction chaperonne de GRXS17 dans desconditions normales et de stress thermiques. / Adaption of plants to heat stress is crucial for their survival and involves dedicated response such as chaperones proteins induction and production of reactive oxygen species (ROS). Glutaredoxins (GRX), a family of thiol redox proteins, play an important role in redox regulation and response to oxidative stress. The focus of our studies is on GRXS17 which is a multi-subunit iron-sulfur glutaredoxin. Despite the severe developmental phenotype of the grxs17 mutant at normal and elevated temperatures, relatively little is known about the biochemical functions and precise intracellular roles of GRXS17. I show during my thesis that GRXS17 function as a foldase and holdase redox-dependent chaperone. Oxidative and heat stress exposure cause a shift from a dimeric form to high MW complexes which is concordant with a holdase activity. I show that GRXS17 is required for the tolerance to moderated heatstress in a Cys-dependent manner. Transcriptomic, metabolomic and proteomic approaches show heat stress response delayed in grxs17, key-metabolites defects and allowed to identifynew potential GRXS17-interactor under heat stress conditions, supporting a potential protecting function of GRXS17 against stress damage.

A cana-de-açúcar é uma das mais importantes cadeias do agronegócio brasileiro, além do seu elevado destaque no contexto internacional como fonte de energia renovável e sustentável. Com a competitividade que as Usinas vem passando e pelas perspectivas de crescimento, este trabalho teve como hipóteses: i) o preparo profundo em cana-de-açúcar proporciona um maior volume de solo explorado pelas raízes; ii) o trafégo controlado de máquinas aliado ao espaçamento em fileiras duplas irá trazer uma maior população de plantas, traduzindo isso em incrementos de produtividade e redução de custos para o produtor. O objetivo geral, portanto, foi avaliar métodos de preparo do solo e desenvolver o tráfego contrololado na área, propondo assim que o produtor tenha redução nos custos com o manejo da cultura e também aumente a produtividade e longevidade do canavial. Portanto, pode-se concluir que na análise do comprimento de raízes, em todas as profundidades estudadas, o Preparo Profundo obteve comprimento, área e volume de raízes maiores estatisticamente. A Resistência do solo a penetração no tratamento Preparo Profundo, para as profundidades de 20-40 e 40-60 cm foi de 0,29 MPa e 0,45 MPa, respectivamente. Nas avaliações biométricas da parte área, o Preparo Profundo se destacou com um IAF de 7,1. Os custos das operações no momento do plantio foram bem inferiores no Preparo Profundo, sendo 33% e 58% inferiores aos Mínimo duplo e Convencional duplo, respectivamente. A movimentação do solo causada pelo sistema Preparo Profundo no preparo do solo, foi de até 80% inferior ao tratamento Convencional duplo. O tráfego controlado que o Preparo Profundo proporciona, diminui em até 70% o tráfego de máquinas na lavoura; menor consumo de combustível; redução no tempo das operações agrícolas; redução do parque de máquinas; e menor custo operacional. / Sugarcane is one of the most important crops in the Brazilian agribusiness chain, besides its great branch in the international context as a renewable and sustainable energy source. Through the competitiveness that sugar mills experience and through the growth perspectives of the sector, this study focuses the deep soil preparation for sugarcane crop renewal, since it provides a larger soil volume to be explored by the root system. Furthermore, the machinery traffic controlled by a smaller number of soil preparation operations, reduces farmer´s production costs. The general objective was, therefore, evaluate soil preparation methods and develop a controlled traffic system in the area, in order to propose to the farmer a cost reduction in the farm soil management along with yield increase and extension of the longevity of the crop. As a result of the imposed treatments it was possible to conclude that by the root length analysis in all depths of the Deep Soil Preparation, root length, area and volume were greater. Soil resistance to penetration in the Deep Soil Preparation system was much less in relation to the other treatments, assuming values of 0.29 MPa and 0.45 Mpa in the 20-40 and 40-60 cm layers, respectively. The above ground evaluations showed leaf area index of 7.1 for the Deep Soil Preparation, much higher in relation to the other treatments. Operation costs at planting time were much less for the Deep Soil Preparation, 33% and 58% smaller than for the Double Minimum Tillage and Double conventional, respectively. Soil movement caused by Deep Preparation was up to 80% less in relation to the Double conventional. The controlled machinery traffic that the Deep Soil Preparation provides, reduced up to 70% the farming operations, therefore presenting a lower fuel consumption, a reduction of the time used in farming operations, reduction of the machinery park, and a lower operational cost.

Le riz est l'une des céréales les plus importantes au monde. Au Vietnam, le riz est également considéré comme un produit agronomique clé pour l'exportation. Cependant, le stress dû à la sécheresse menace la production de riz de plus en plus fréquemment et sur de plus longues périodes. Les racines coronaires constituent une partie importante du système racinaire du riz et jouent un rôle crucial dans le maintien du rendement en cas de sécheresse. Le nombre de racines coronaires affecte la biomasse de racines et détermine la capacité de la plante à extraire les ressources du sol. Un QTL de NRC, qNCR11, localisé sur le chromosome 11, avait été détecté dans une étude d’association précédente utilisant un panel de riz vietnamiens. Dans notre étude, son effet sur le NCR, léger, a été validé par cartographie de QTL en utilisant une population biparentale . Afin de déterminer les gènes sous-jacents à qNCR11 et régissant l'initiation et le développement des racines coronaires, une étude de séquençage du génome entier et une étude d'expression ont été réalisées. Deux gènes candidats, NCR2 (NBS-LRR) et NCR3 (OsbHLH014) ont été identifiés. NCR2 portait un SNP non synonyme dans son ORF, provoquant un codon stop prématuré corrélé avec un NCR élevé; NCR3 était moins exprimé dans les bases de la tige des plantes à haplotype NCR élevé que chez les plantes à haplotype NCR faible. Des mutations dans ces gènes ont été obtenues à l'aide du système CRISPR / Cas9 et le phénotypage des lignées obtenues est en cours. Le QTL qNCR11 à effet mineur pourrait être utile aux sélectionneurs pour produire des variétés de riz avec un NCR augmenté ou diminué pour les différents écosystèmes-cibles, afin de favoriser l'extraction de l'eau dans des conditions de sécheresse. / Rice is one of the most important cereals worldwide. In Vietnam, rice is also known as a key agronomic product for exportation. However, drought stresses threaten rice production with an increasing frequency and for longer periods. Crown roots are a major component of rice root system and play a crucial role in maintaining yield under drought. The number of crown roots (NCR) impacts on root biomass and determines the ability of a plant to acquire soil resources. qNCR11, a QTL for NCR located on chromosome 11, was detected in a previous genome-wide association study using a Vietnamese rice panel. qNCR11 was validated to have a slight effect on NCR by QTL mapping using a biparental population in this study. To determine the genes underlying qNCR11 and governing crown root initiation and development, whole genome sequencing and expression study were performed. Two candidate genes, NCR2 (NBS-LRR) and NCR3 (OsbHLH014) were identified. NCR2 carried a non-synonymous SNP inside its ORF, causing a premature stop-codon that correlates with the high NCR trait; NCR3 was less expressed in stem bases of the high NCR haplotype plants relative to the low NCR haplotype plants. Mutations in these genes were obtained using the CRISPR/Cas9 system and the phenotyping of the obtained lines is on-going. The minor-effect qNCR11 could be useful for breeders to generate rice varieties with increased or decreased NCR for different target agro-systems, in order to enhance water extraction under drought stress.

A cana-de-açúcar é uma das mais importantes cadeias do agronegócio brasileiro, além do seu elevado destaque no contexto internacional como fonte de energia renovável e sustentável. Com a competitividade que as Usinas vem passando e pelas perspectivas de crescimento, este trabalho teve como hipóteses: i) o preparo profundo em cana-de-açúcar proporciona um maior volume de solo explorado pelas raízes; ii) o trafégo controlado de máquinas aliado ao espaçamento em fileiras duplas irá trazer uma maior população de plantas, traduzindo isso em incrementos de produtividade e redução de custos para o produtor. O objetivo geral, portanto, foi avaliar métodos de preparo do solo e desenvolver o tráfego contrololado na área, propondo assim que o produtor tenha redução nos custos com o manejo da cultura e também aumente a produtividade e longevidade do canavial. Portanto, pode-se concluir que na análise do comprimento de raízes, em todas as profundidades estudadas, o Preparo Profundo obteve comprimento, área e volume de raízes maiores estatisticamente. A Resistência do solo a penetração no tratamento Preparo Profundo, para as profundidades de 20-40 e 40-60 cm foi de 0,29 MPa e 0,45 MPa, respectivamente. Nas avaliações biométricas da parte área, o Preparo Profundo se destacou com um IAF de 7,1. Os custos das operações no momento do plantio foram bem inferiores no Preparo Profundo, sendo 33% e 58% inferiores aos Mínimo duplo e Convencional duplo, respectivamente. A movimentação do solo causada pelo sistema Preparo Profundo no preparo do solo, foi de até 80% inferior ao tratamento Convencional duplo. O tráfego controlado que o Preparo Profundo proporciona, diminui em até 70% o tráfego de máquinas na lavoura; menor consumo de combustível; redução no tempo das operações agrícolas; redução do parque de máquinas; e menor custo operacional. / Sugarcane is one of the most important crops in the Brazilian agribusiness chain, besides its great branch in the international context as a renewable and sustainable energy source. Through the competitiveness that sugar mills experience and through the growth perspectives of the sector, this study focuses the deep soil preparation for sugarcane crop renewal, since it provides a larger soil volume to be explored by the root system. Furthermore, the machinery traffic controlled by a smaller number of soil preparation operations, reduces farmer´s production costs. The general objective was, therefore, evaluate soil preparation methods and develop a controlled traffic system in the area, in order to propose to the farmer a cost reduction in the farm soil management along with yield increase and extension of the longevity of the crop. As a result of the imposed treatments it was possible to conclude that by the root length analysis in all depths of the Deep Soil Preparation, root length, area and volume were greater. Soil resistance to penetration in the Deep Soil Preparation system was much less in relation to the other treatments, assuming values of 0.29 MPa and 0.45 Mpa in the 20-40 and 40-60 cm layers, respectively. The above ground evaluations showed leaf area index of 7.1 for the Deep Soil Preparation, much higher in relation to the other treatments. Operation costs at planting time were much less for the Deep Soil Preparation, 33% and 58% smaller than for the Double Minimum Tillage and Double conventional, respectively. Soil movement caused by Deep Preparation was up to 80% less in relation to the Double conventional. The controlled machinery traffic that the Deep Soil Preparation provides, reduced up to 70% the farming operations, therefore presenting a lower fuel consumption, a reduction of the time used in farming operations, reduction of the machinery park, and a lower operational cost.

Impacts d’agropolymères sur la germination, le développement racinaire, et les interactions plantes-microorganismes. Les travaux réalisés au cours de la thèse sont de nature exploratoire et visent à déterminer les effets physiologiques de la gomme de guar (Cyamopsis tetragonoloba) et trois de ses dérivés fonctionnalisés, sur la germination des semences, le développement racinaire des plantes et leur capacité à interagir avec un microorganisme symbiotique.Arabidopsis thaliana a été choisie comme plante modèle pour déterminer si le développement des plantes est modifié lorsqu’elles sont soumises à ces molécules, et explorer les mécanismes impliqués. Une analyse fine des modifications architecturales a été menée, via des études de microscopie et l’utilisation de plantes transgéniques. Des développements racinaires contrastés ont été mis en évidence pour deux des agropolymères fonctionnalisés, avec un raccourcissement de la racine primaire et des modifications du nombre de racines latérales. Les plantes traitées par ces deux agropolymères présentent une augmentation de la production d’espèces réactives de l’oxygène (ROS) qui traduisent un état de stress des plantes. Ces macromolécules polysaccharidiques ne semblent pas avoir d’impact sur les nutritions carbonée et azotée des plantes.Parallèlement aux recherches entreprises avec A. thaliana, des travaux ont été menés sur l’arbre tropical actinorhizien Casuarina glauca. Cette espèce d’intérêt pour certains pays du Sud peut se développer dans les sols pauvres en raison de son association symbiotique avec l’actinobactérie fixatrice d’azote Frankia. Les résultats obtenus mettent en évidence que les polymères induisent sur C. glauca des phénotypes racinaires identiques à ceux observés avec A. thaliana. Pour ce qui concerne l’interaction symbiotique, selon l’agropolymère testé et les concentrations choisies, des impacts positifs ou négatifs ont été observés sur le processus de nodulation résultant de l’interaction avec Frankia. L’ensemble de ces travaux fournit des éléments préliminaires qui devraient permettre de promouvoir, dans le futur, ces agropolymères dans le milieu agricole comme biostimulant, afin de tendre vers une agriculture plus durable et responsable.Mots clefs : Agropolymères – germination – développement racinaire – interactions plantes / microorganismes – Arabidopsis thaliana – Casuarina glauca / Impact of agropolymers on seed germination, root development, and plant-microorganism interactionsThe work performed during this thesis is of an exploratory nature and aims at providing insight to the physiological effects of guar (Cyamopsis tetragonoloba) gum polymer and three functionalized derivatives on seed germination, root development and a symbiotic plant-microorganism interaction.Arabidopsis thaliana was chosen as model plant to determine whether plant development was modified by the presence of these polymers and to explore the mechanisms involved. A detailed microscopic analysis of the root architecture was carried out using transgenic plants. Contrasted root development was evident for two of the functionalized agropolymers. Primary roots were shorter and lateral roots distribution was modified. Biochemical analyses revealed that the plants treated by these two agropolymers exibited an increase of reactive oxygen species (ROS) production in root tissues indicating that plants are in stress conditions. Such polysaccharides did not seem to have any effects on carbon and nitrogen plant nutrition.In parallel, studies were performed on the tropical actinorhizal tree Casuarina glauca. This species is of great environmental value in mitigating desertification since is able to grow in poor tropical soils because of its symbiotic interaction with the nitrogen-fixing actinobacteria Frankia. Treatment of C. glauca with the polymers induced root phenotypes that were very similar to those observed with A. thaliana. Treatment with agropolymers resulted in positive or negative effects on the nodulation process during the symbiotic interaction between C. glauca and FrankiaTaken together this work provides preliminary evidence supporting the value of the use agropolymers as agricultural biostimulants, facilitating the development of sustainable agriculture.Key words: Agropolymers – germination – root development – plants-microormanisms interactions – Arabidopsis thaliana – Casuarina glauca

Nitrogen (N) is a central nutrient in cropping systems. However, a considerable N fraction is lost through runoffs and leaching with detrimental consequences for environment and controversial effects on human health. Increasing the plant N uptake by optimizing the degree of root branching for exploring a larger soil volume in search of the mobile nitrate resource may contribute to limit soil leaching and subsequently to rely more efficiently on the soil mineralization and fertilizer inputs. Rapeseed (Brassica napus L.) is a major oil crop that highly depends on N fertilization. This doctoral thesis aims at exploring the diversity of root morphology in recently selected cultivars and in a large set of rapeseed inbred lines, and at understanding the genetic control on root morphology and how it is impacted by N nutrition.Firstly, a panel of twenty-eight European recently selected cultivars of winter oilseed rape were tested in laboratory and field conditions. Upon hydroponic culture, these hybrids showed a great diversity for biomass production and root morphological traits. Differences in root and shoot dry biomasses and lateral root length were mainly explained by the genotype, while differences in primary root length by the nutrition. The cultivars were tested in a pluriannual field trial. The observed variation for yield and seed quality traits attributed to the genotype was more important than the year or the genotype x year interaction effects. The total root length measured in laboratory could predict the proportion of nitrogen taken-up from the field and reallocated to the seeds. The genetic interrelationship between cultivars, established with polymorphic markers, indicated a very narrow genetic base. Positive correlations were found between the genetic distance measures, root morphological trait distances during nitrogen depletion conditions, and agronomic performance. Secondly, three cultivars previously selected from a root morphology screen at a young developmental stage were field tested with two nitrogen applications. The purpose was to examine the relationship between root morphology and Nitrogen Uptake Efficiency (NUpE) and to test the predictiveness of canopy optical indices for seed quality and yield. A tube-rhizotron system was used to incorporate below-ground root growth information. One-meter length clear tubes were installed in soil at an angle of 45°. The root development was followed with a camera at key growth stages in autumn (leaf development) and spring (stem elongation and flowering). Autumn was a critical time window to observe the root development and exploration in deeper horizons (36-48 cm) was faster without any fertilization treatment. Analysis of the rhizotron images was challenging and it was not possible to clearly discriminate between cultivars. Canopy reflectance and leaf optical indices were measured with proximal sensors. The Normalized Difference Vegetation Index (NDVI) was a positive indicator of biomass and seed yield while the Nitrogen Balance Index (NBI) was a positive indicator of above-ground biomass N concentration at flowering and seed N concentration at harvest.Thirdly, the natural variability offered by a diversity set of 392 inbred lines was screened to apprehend the genetic control of root morphology in rapeseed and how it is impacted by nitrogen nutrition. Seedlings grew hydroponically with low (0.2 mM) or elevated (5 mM) nitrate supplies. Low nitrate supply triggered the primary root and lateral root growth, while elevated supply promoted shoot biomass production. A considerable variation degree in the root morphological traits was observed across the diversity set, and there was no trade-off between abundant lateral root branching and shoot biomass production. Root traits were mainly dependent on the genotype and highly heritable. A genome wide association study identified some genomic regions associated with biomass production and root morphological traits. A total of fifty-nine QTLs were identified and thirty of them were integrated into seven clusters on chromosomes A01 and C07. Some candidate genes were identified with Arabidopsis orthologs related to root growth and development, nitrogen nutrition or hormone regulation.This study provides promising routes for redesigning the root system architecture by uncovering nitrogen-interactive genomic regions shaping root morphology. A perspective is to develop genetic markers associated with root morphological traits that could be used for assisted breeding. / Doctorat en Sciences agronomiques et ingénierie biologique / info:eu-repo/semantics/nonPublished

Early planting is one technique to avoid or reduce heat and drought problems that negatively affecting grain crop production. If producers adopt early planting, cold temperatures may negatively affect corn yield. It is important to select hybrids that are suited for planting earlier in the southern United States. Experiments were conducted by imposing low temperatures during seed germination. Twenty commercially available corn hybrids were evaluated for seed germination and root elongation. The first objective was: 1) To determine if some hybrids germinate better at cooler temperatures than others; and 2) Determine variation in root elongation at cold temperatures among commercially available hybrids. Corn hybrids varied significantly for seed germination and root traits under cold temperatures. Some hybrids have significantly surpassed others in seed germination traits, and they germinated earlier as well having longer radicle length. Also, there were significant differences across temperatures for all traits measured. A second objective was: 1) To quantify the effects of cold temperature on seed germination rate; 2) To evaluate the effects of different cold temperatures on seed germination behavior of corn hybrids under laboratory conditions to determine how fast they germinated; and 3) To classify hybrids for response to cold temperature using cumulative seed germination. The results showed that standard germination performance occurred at 10ºC for all hybrids, but these hybrids performed well under other cold treatments (7.2°C and 8.6° C). There were no big differences between early hybrids 93 to 105 RM (Relative Maturity) and full season 115 to 120 RM in germination % and rate in both experiments, so that means that it pretty much depends on the hybrid. Therefore, the temperature had a major influence on seed germination parameters. These findings are useful for hybrid selection with respect to cool soil temperature conditions during early planting.

Le lien qui existe entre la diversité et la productivité des écosystèmes constitue un sujet central en écologie. De nombreuses études ont montré une relation positive entre la diversité et la productivité des forêts, ainsi que leur résistance à différents stress comme à la sécheresse. En revanche, peu de travaux ont permis de comprendre les mécanismes à l'origine des avantages observés dans les forêts à plusieurs espèces comparés aux forêts monospécifiques. En particulier, en raison de la difficulté d'accès aux racines, le rôle du compartiment souterrain dans les interactions entre espèces est particulièrement méconnu. L'objectif de ma thèse a été d'étudier l’influence des interactions entre espèces d’arbres sur le système racinaire du hêtre (Fagus sylvatica) sous différents niveaux de contrainte hydrique. Ces travaux ont montré que, au stade jeune plant, la compétition souterraine entre hêtre, chêne et pin était forte et que mélanger les espèces à ce stade pouvait influencer la croissance du hêtre. La disponibilité en eau a un fort impact sur la croissance des plantules de hêtre mais la présence d’autres espèces à proximité des jeunes plants de hêtre n’a pas amélioré leur réponse à la sécheresse. Au stade adulte, dans une plantation forestière, nous avons montré que la présence de l’érable n’influençait que légèrement la profondeur d’extraction de l’eau du hêtre ou la distribution verticale de ses racines. Nous concluons (i) à une absence de séparation des niches souterraines entre ces deux espèces, tant au niveau spatial que fonctionnel (vis à vis de l'acquisition de l’eau), et (ii) que les mécanismes d’interaction souterraine ne semblent pas expliquer l’origine de la productivité plus forte dans la zone de mélange que dans les zones de monocultures. Enfin, j'ai montré que les peuplements mélangés hébergent une communauté fongique plus riche par rapport aux peuplements purs. Cette plus forte richesse de la communauté fongique dans le mélange pourrait contribuer à une meilleure acquisition des ressources hydriques et minérales dans le mélange. Mon travail suggère que les interactions souterraines entre le hêtre et d’autres espèces forestières ne sont probablement pas le mécanisme principal expliquant les effets positifs des mélanges sur la productivité / The link between species diversity and ecosystem productivity is a central issue in ecology. Numerous studies have shown a positive relationship between forest diversity and productivity, as well as a greater resistance to various stresses such as droughts. On the other hand, few studies demonstrated the mechanisms behind the benefits observed in multi-species forests compared to monospecific ones. In particular, the role of belowground interactions among species in explaining the origin of positive effects of species diversity on ecosystem functioning is unknown. The aim of my PhD work was to study the influence of tree species interactions on the root development of beech (Fagus sylvatica) under different levels of water conditions. We showed that at the seedling stage, underground competition between beech, oak and pine was strong and that mixing these species could influence the growth of the beech. Water availability had a strong impact on the growth of beech seedlings, but the presence of seedlings of other species competing with beech did not particularly improve its response to drought. At the adult stage, in a forest plantation, we showed that maple trees competing with beech did not strongly modify the mean depth of soil water extraction of beech trees or the vertical distribution of beech roots. We conclude that (i) there was no separation of the underground ecological niches of these two species, both spatially and functionally (with respect to water acquisition), and (ii) that the mechanisms of belowground interaction between these two species do not seem to explain the origin of the higher productivity in the mixture than in the monoculture zone. Finally, the richest fungal communities were found in the mixed species zone: we hypothesize that greater fungal community richness in the mixture may improve water and nutrient acquisition and then contribute to higher productivity in the mixed species zone. My work suggests that underground interactions between beech and other forest species are probably not the main mechanism explaining beneficial effects of mixtures on productivity