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See detailJupiter’s magnetopause: A search for wave and reconnection signatures
Bonfond, Bertrand ULg; Kivelson, M. G.; Khurana, K. K. et al

Conference (2014, September 12)

Surface waves and magnetic reconnection are two key processes taking place at the planetary magnetopause. They allow the coupling, through energy (and particle) transfer, of the interplanetary medium and ... [more ▼]

Surface waves and magnetic reconnection are two key processes taking place at the planetary magnetopause. They allow the coupling, through energy (and particle) transfer, of the interplanetary medium and the magnetosphere. The relative importance of large scale Dungey reconnection and viscous interaction (including small-scale intermittent reconnection associated with Kelvin-Helmholtz vortices) are expected to be different at Jupiter compared to the Earth’s case. Such differences would be due to the combination of a) a weaker solar wind pressure and Alfvén velocity as the distance to the Sun increases, b) a high-β plasma sheet, originating from Io’s outgassing, which inflates the Jovian magnetosphere, c) the rapid rotation of the planet relative to its size (e.g. Desroche et al. 2012). Here we analyse the signatures of wave activity and reconnection on the magnetopause of Jupiter, based on magnetic field and energetic particle measurements from the successive spacecraft that explored the Jovian system. Up to now, 7 spacecraft equipped with a magnetometer have crossed the Jovian magnetopause: Pioneer 10, Pioneer 11, Voyager 1, Voyager 2, Ulysses, Galileo and Cassini. We make use of several normal direction finding techniques, such as the Minimum Variance Analysis, in order to identify waves and Kelvin-Helmholtz vortices. As far as the reconnection is concerned, small scale signatures of flux-tube events (FTEs) had been identified by Walker and Russell (1985), based on a limited data-set from the Pioneers’ and Voyagers’ fly-bys. Here we will extend this search to the extensive dataset from all the missions that explored Jupiter’s system. [less ▲]

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See detailPsychological processes mediating the link between depression severity and the level of behavioural activation: Assessment of a conceputal model
Wagener, Aurélie ULg; Baeyens, Céline; Blairy, Sylvie ULg

Poster (2014, September 12)

INTRODUCTION. Depression is a common psychopathology characterized by a decrease of the level of behavioural activation (BA) that is the level of engagement in activities. The relationship between ... [more ▼]

INTRODUCTION. Depression is a common psychopathology characterized by a decrease of the level of behavioural activation (BA) that is the level of engagement in activities. The relationship between depression and BA is well-established in the scientific literature. According to theoretical models of depression, psychopathology is also characterized by biases in five sets of psychological processes (PP): self-image (e.g. self-esteem), negative repetitive thoughts (e.g. ruminative thoughts), experiential avoidance (e.g. mindfulness), environmental satisfaction (e.g. environmental reward observation) and emotional regulation (e.g. distress tolerance). Therefore, the present study aims to identify PP mediating the relationship between depression and the level of BA. In order to reach this objective, a conceptual model is tested. METHOD. 361 adults (x ̅ age=36, σ=15), from clinical and non-clinical settings, fulfilled a series of questionnaires assessing several variables: sociodemographic data, depression, anxiety, level of BA and the above-cited five sets of PP. Covariance structure analysis will be conducted in order to test the conceptual model mentioned above. RESULTS. Some preliminary results are presented. As expected, a negative significant correlation between depression and BA (r=-.66, p<.01) have been highlighted. Negative significant correlation appeared between BA and the measured PP: self-esteem (r=-.27, p<.01), ruminative thinking (r=-.53, p<.01), environmental reward observation (=-.13, p<.05). Positive significant correlations appeared between BA and mindfulness (r=.49, p<.01) and distress tolerance (r=.26, p<.01). DISCUSSION. The preliminary results are in line with our hypotheses. Indeed, the level of BA is negatively linked to PP usually biased in depression such as self-esteem. The mediating role of these PP between depression and the level of BA will be discussed. [less ▲]

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See detailValorisation de l’information pédologique numérisée pour la modélisation de la percolation des pesticides vers les eaux souterraines
Bah, Boubacar Billo ULg

Doctoral thesis (2014)

In Wallonia (southern Belgium), 81% of human drinking water is captured from groundwater tables. In spite of actions implemented under the European directives and thematic strategies, the required ... [more ▼]

In Wallonia (southern Belgium), 81% of human drinking water is captured from groundwater tables. In spite of actions implemented under the European directives and thematic strategies, the required standard (0.1 µg L-1 by pesticide and 0.5 µg L-1 for all pesticides) for human drinking water is most often exceeded at some catchments. Tools such as mechanistic models are appropriate since they allow an a priori estimation of pesticide concentrations leached at the bottom of soil profile, which could reach the groundwater tables. However, simulations often lead to a degree of uncertainty due to the approximations noted in the models, or due to the reliability of available data. The main objective of this thesis was to improve the usefulness of the Digital Soil Map of Wallonia (DSMW) and the associated soil analysis database named “Aardewerk” in the framework of the evaluation of the groundwater table contamination by pesticides, in order to reduce approximations associated with the GeoPEARL model and its meta-model MetaPEARL in the area of Condroz. In order to cover the broad spectrum of pesticides used in agriculture in Wallonia, nine theoretical pesticides have been defined. The first research question is to measure the sensitivity of GeoPEARL to two soil data parameterization schemes at the regional scale, depending on whether we first aggregate soil data at a regional scale before application of the model (AC approach); or we first apply the model to soil profiles and aggregate simulated leached concentrations afterwards (CA approach). The results show a significant difference between the two approaches, compared on the basis of a spatial threshold (80th percentile) calculated by soil type. Moreover, this difference varies depending on pesticide type, and is more important when the simulated concentrations are very low. It is also clear from this analysis that only pesticides located in certain ranges of DT50 (30 and 67 days) and Kom (58 and 252 dm3 kg-1) give concentrations more often above water potability standard of 0.1 µg L-1. The second research question is to calibrate MetaPEARL metamodel (simplified model) based on GeoPEARL simulated concentrations, from which it was derived by considering only the most sensitive parameters of GeoPEARL. The objective by developing a metamodel is to provide a simple tool, usable for a first evaluation of pesticides leaching in order to identify the most risk-prone areas, but also readily transposable for a global decision support system. In contrast to the approach of MetaPEARL calibration used until now, taking into account soil morphology through soil horizons (layers) types explains about 80% of the spatial variability of pesticide concentrations obtained from the complete original GeoPEARL model. The third research question is to take into account the spatial variability of input variables within the same soil typological unit using stochastic simulations to assess the uncertainty associated with deterministic simulations (taking into account average values by soil type for the input variables at the regional scale) obtained from MetaPEARL. The random spread of soil characteristics variability leads to a very significant spreading of simulated pesticide concentrations. Moreover, we obtain values of 80th spatial probabilistic percentile higher than those obtained from the deterministic approach. Consequently, for a risk mapping designed to aid decision-making tools, the probabilistic approach should be used since it allows, by taking into account the spatial variability of the model input parameters, to obtain more realistic concentrations of leached pesticides. [less ▲]

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See detailRebuilding the educational system in post-conflict context in Kosovo - Survival of the Unmik’s provisions to support the living together through primary education
Pierre, Alexia ULg

Poster (2014, September 12)

In the aftermaths of the Cold War, the International Community adopts the objective of Education for All. Indeed, Education appears as a tool of social and economical development worldwide and supports ... [more ▼]

In the aftermaths of the Cold War, the International Community adopts the objective of Education for All. Indeed, Education appears as a tool of social and economical development worldwide and supports global development. Education allows individuals to take part effectively and actively in the collective life of the society they belong to. Soon after the adoption of this objective, the war is identified as the major obstacle in the fulfillment of this objective of Education for All. The international stakeholders takes their stand in favor of the continuation of the schooling during protracted crisis and wars, what lead to the education in emergency. This education has to spread values, behaviors and attitudes that attack the roots of the conflict. An objective of peace building and conflict prevention is since added to education. In a same temporality, the Kosovo Albanians were submitted to a segregationist policy headed by the Government of Milosevic, the Republika Srpska. This Government aims to make the Kosovo an unmixed territory, inhabited only by Serbs. Kosovo Albanians are rejected from all the state positions and state-owned entreprises. Education appears as a convergent point of the communities antagonisms and a critical issue between Serbs and Albanians in Kosovo. The freedom of being educated in their mother tongue is denied to the Kosovo Albanians through the policy of the Republika Srpska. The Kosovo Albanians react in setting up a parallel education system, in which virtually all the Albanian children intend school from 1992 to 1998. This parallel education system can be seen as a strong element of the pacific resistance of the Kosovo Albanians and a factor of social strength. This parallel educational system collapsed in 1998 due to the war situation in Kosovo. During this internal armed conflict, violations of the Law of war and of the International humanitarian Law are so huge that Nato intervenes through a military air campaign. This military intervention is immediately followed by a civil administration mission, the Unmik, whose mandate is to normalize the life of the inhabitants of Kosovo. Unmik is a restorative model not dedicated to the war victims. The restorative aspects for victims can be seen in the reinstallation of the Kosovo Albanians as full-right citizens. When arriving in Kosovo, Unmik faces two systems of education. Unmik’s first objective is to rebuild a unified education system in Kosovo. Along with objectives of democratization and modernization of a system inherited from a communist model. This intervention is an opportunity to promote and support peace education and conflict prevention through education, in echo with the latest international provisions on education. To achieve this objective of peace building and conflict prevention through education, the pedagogical methods, the contents of teaching and the structure of the education system has to be reformed and restructured. My work aims to explore the reconstruction process of the education system in Kosovo and the operationalization of the provisions that turn education as a tool of peace and conflict prevention, in the primaries schools of Prishtina. My approach is qualitative, inspired by the systemic perspective. The aim of this research is not to evaluate the results of the new Kosovo education system. This work is designed to explore the process of this post-war reconstruction, and to understand how international provisions come within this process and are effectively implemented in the primaries schools. The research question is on the present survival and effectiveness of these provisions in the primaries schools of Prishtina. This work was done first by a confrontation between a corpus of international normative texts on education and a legislative and normative corpus of local texts on education. This first step was dedicated to the selection of the special provisions relative to education as a tool of peace building. It appears that Civic Education and History are the two main teachings in the broadcasting of elements that helps to create a social cohesion. The tools for the data collection were based on the elements selected through this bibliographical research, as the analysis table of the empirical datas. Standardized questionnaires has been completed by teachers in History and Civic Education, and by Directors of the primaries school of Prishtina. Interviews with Kosovo people who were involved in the rebuilding process of the education system were carried out. The results highlights that International Community massively imposed this new model of education, what is visible through the identical profiles of all the schools that participated to the research. It appears that such an intervention is limited by the specificities and the reality of the Kosovo, which were not taken into consideration enough to make this new education system fit well to the very specific aspects of Kosovo. The question of the adaptability of such a model, created out of the Kosovo and without sufficient rely on the local population, is raised through this study. Indeed, the actual education system in Prishtina faces huge challenges in terms of equipment, funding and space. These challenges were not met by the Unmik’s work and are still existing, when the legislative and normative frame is continually developed in respect of the international developments in the matter. Indeed, fundamental education has to be a way to get competencies leading to a democratic citizenship, instead of a way to acquire only school basic knowledge. The potential in peace building and conflict prevention of the present education system in Kosovo is not able to be fully developed. If all the international provisions are well translated into the local provisions and operationalized in the primaries schools, the system has reached its limits and is not able to overcome its numerous challenges. Moreover, there is still two independent systems of education in Kosovo, and the education dedicated to the peace building and conflict prevention reaches only children intended schools of the official system. Serbs children are still educated in the same perspective than during the war. In a long terme perspective, the Kosovo education system will not be able to produce the expected outcomes. This contains risks of resurgence of the conflict. [less ▲]

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See detailWeakening of Jupiter’s main auroral emission in response to magnetospheric hot plasma injections
Badman, Sarah; Bonfond, Bertrand ULg; Fujimoto, M. et al

Conference (2014, September 11)

We present images of Jupiter’s northern UV aurorae taken by the Hubble Space Telescope as part of a large observing campaign in January 2014. The high time resolution observations allow the dynamics of ... [more ▼]

We present images of Jupiter’s northern UV aurorae taken by the Hubble Space Telescope as part of a large observing campaign in January 2014. The high time resolution observations allow the dynamics of the different components of the aurorae to be observed. Particular features of interest are large regions of diffuse emission, which occurred equatorward of the main oval, enveloping the auroral footprint of Ganymede. These diffuse, low latitude emissions are caused by the injection of hot plasma from the outer magnetosphere, a process which has previously been related to interchange between the flux tubes from the outer magnetosphere and outward-moving flux tubes loaded with iogenic plasma. Over the two-week observing interval the auroral signatures of two large injection events were observed, while the main oval generally decreased in intensity. We suggest that the overall dimming of the main oval results from the weakening of the corotation-enforcement currents that drive the main emission, following the replacement of the radially-stretched, mass-loaded flux tubes by more dipolar flux tubes containing rarefied hot plasma. [less ▲]

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See detailHighlights of the 2014 Jupiter observing campaign by multi - spectral remote sensing using space telescopes
Kimura, T.; Badman, S.; Tao, C. et al

Conference (2014, September 11)

From January to April 2014, two observing campaigns by multi-wavelength remote sensing from X-ray to radio were performed to uncover energy transport process in Jupiter’s plasma environment using space ... [more ▼]

From January to April 2014, two observing campaigns by multi-wavelength remote sensing from X-ray to radio were performed to uncover energy transport process in Jupiter’s plasma environment using space telescopes and ground-based facilities. These campaigns were triggered by the new Hisaki spacecraft launched in September 2013, which is an extremely ultraviolet (EUV) space telescope of JAXA designed specifically for planetary observations. In the first campaign in January, Hubble Space Telescope made imaging of far ultraviolet (FUV) aurora with a high special resolution (0.08”) through two weeks while Hisaki continuously monitored aurora and plasma torus emissions in EUV wavelength with a high temporal resolution (1 min<). We discovered new magnetospheric activities from the campaign data: e.g., internally-driven type auroral brightening associated with hot plasma injection, and plasma and electromagnetic filed modulations in the inner magnetosphere externally driven by the solar wind modulation. The second campaign in April was performed by Chandra X-ray Observatory, XMM newton, and Suzaku satellite simultaneously with Hisaki. Relativistic auroral accelerations in the polar region and hot plasma in the inner magnetosphere were captured by the X-ray space telescopes simultaneously with EUV monitoring of aurora and plasma torus. In this presentation, we show remarkable scientific results obtained these campaigns mainly focusing on Jupiter’s aurora. [less ▲]

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See detailEffects of concentrate level on milk production and traffic of grazing cows milked by a mobile automatic milking system on pasture
Lessire, Françoise ULg; Hornick, Jean-Luc ULg; Dufrasne, Isabelle ULg

in Hopkins, Alan; Collins, Rosemary; Fraser, Marieacia (Eds.) et al EGF at 50: The future of European Grasslands (2014, September 10)

Cows milked by an automatic milking system in pastures were assigned in 2 groups receiving different amounts of concentrates (2.1 kg vs 4.1 kg). The effect of concentrates’ level on milk yield (MY) and ... [more ▼]

Cows milked by an automatic milking system in pastures were assigned in 2 groups receiving different amounts of concentrates (2.1 kg vs 4.1 kg). The effect of concentrates’ level on milk yield (MY) and returns to the robot was assessed. Concentrates’ level had a positive influence on daily milk production over the grazing period as cows of low concentrates group produced 21.43 ± 0.62 kg compared with 24.33 ± 0.62 kg in high concentrates group. However this effect was modulated subsequently to grass quality and availability. Regarding daily voluntary returns to the robot, high concentrates group showed higher frequency (3.66 ± 0.05, compared with 3.22 ± 0.04 in low concentrates group) demonstrating positive impact of complement distribution on cows’ traffic. [less ▲]

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See detailEffects of mild heat stress periods on milk production, milking frequency and rumination time of grazing cows milked by an automatic milking system
Lessire, Françoise ULg; Hornick, Jean-Luc ULg; Dufrasne, Isabelle ULg

Poster (2014, September 10)

Grazing dairy cows milked by an automatic system (AS) experienced mild heat stress (HS) periods, twice during the summer. The daily temperature humidity index (THI) during these periods were higher than ... [more ▼]

Grazing dairy cows milked by an automatic system (AS) experienced mild heat stress (HS) periods, twice during the summer. The daily temperature humidity index (THI) during these periods were higher than 72. Milk production, as well as milking frequency, rumination time and milk fat to protein ratio (F/P) during these periods were compared to adjacent periods with mean THI of 61. The daily milking frequency, the total number of visits to AS and the milk production were significantly higher in HS periods (2.12 vs 1.97, 2.99 vs 2.69, and 19.7 vs 18.5 kg milk per cow, respectively). There were significant interactions between times and periods for milking frequency and number of visits, while the daily rumination time was significantly lower (339 vs 419 min) and the F/P in milk tended to be decreased (1.17 vs 1.23). These results could be explained by changes in cow behaviour during HS periods. [less ▲]

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See detailAnalyse de la variabilité naturelle du climat : application à l’aide des ondelettes
Mabille, Georges ULg

Doctoral thesis (2014)

Ce travail a pour but de mettre en évidence des cycles méconnus et cachés de la transformée de Fourier dans les séries temporelles liées au climat. Les périodes recherchées, à l’aide de l’outil ondelettes ... [more ▼]

Ce travail a pour but de mettre en évidence des cycles méconnus et cachés de la transformée de Fourier dans les séries temporelles liées au climat. Les périodes recherchées, à l’aide de l’outil ondelettes développé à l’Institut de Mathématique de l’Université de Liège, sont de l’ordre de quelques dizaines de mois. [less ▲]

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See detailPressure-impulse diagram of a beam under explosion - Influence of the indirectly affected part
Hamra, Lotfi ULg; Demonceau, Jean-François ULg; Denoël, Vincent ULg

in Landolfo, Raffaele; Mazzolani, Frederico (Eds.) Proceeding of the 7th European conference on steel and composite structures (Eurosteel 2014) (2014, September 10)

The paper studies the structural response of a beam subjected to a close-field local internal blast loading. In the literature, the pressure-impulse (p-I) diagram is commonly used to design elements or ... [more ▼]

The paper studies the structural response of a beam subjected to a close-field local internal blast loading. In the literature, the pressure-impulse (p-I) diagram is commonly used to design elements or structures for a given blast loading. The p-I diagram is a spectrum representing the level sets of damage or required ductility for a given structural system, nonlinear beam in this paper. This representation is much appreciated because a simple reading for the actual pressure p and impulse I of the considered load indicates the ductility demand of the structural system. Recent works of quasi-static behaviour have indicated the crucial need to account for the membrane effects taking place in the extreme loading of frame beams. This paper will thus extend the state-of-art features, establishing thus the p-I diagram for a beam including the lateral restraints offered by the rest of the structure, the development of non-linear membrane action and also, the M-N interaction that develops in the plastic hinges. [less ▲]

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See detailAssessing the operation rules of a reservoir system based on a detailed modelling-chain
Bruwier, Martin ULg; Erpicum, Sébastien ULg; Pirotton, Michel ULg et al

in Natural Hazards & Earth System Sciences Discussion (2014), 2

According to available climate change scenarios for Belgium, drier summers and wetter winters are expected. In this study, we focus on two muti-purpose reservoirs located in the Vesdre catchment, which is ... [more ▼]

According to available climate change scenarios for Belgium, drier summers and wetter winters are expected. In this study, we focus on two muti-purpose reservoirs located in the Vesdre catchment, which is part of the Meuse basin. The current operation rules of the reservoirs are first analysed. Next, the impacts of two climate change scenarios are assessed and enhanced operation rules are proposed to mitigate these impacts. For this purpose, an integrated model of the catchment was used. It includes a hydrological model, one-dimensional and two-dimensional hydraulic models of the river and its main tributaries, a model of the reservoir system and a flood damage model. Five performance indicators of the reservoir system have been defined, reflecting its ability to provide sufficient drinking, to control floods, to produce hydropower and to reduce low-flow condition. As shown by the results, enhanced operation rules may improve the drinking water potential and the low-flow augmentation while the existing operation rules are efficient for flood control and for hydropower production. [less ▲]

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See detailMultiscale Finite Element Modeling of Nonlinear Quasistatic Electromagnetic Problems
Niyonzima, Innocent ULg

Doctoral thesis (2014)

The effective use of composite materials in the technology industry requires the development of accurate models. Typical such materials in electrotechnical applications are lamination stacks and soft ... [more ▼]

The effective use of composite materials in the technology industry requires the development of accurate models. Typical such materials in electrotechnical applications are lamination stacks and soft magnetic composites, used in the so-called magnetoquasistatic (low frequency) regime. Current homogenization models (e.g. the classical homogenization method, mean field homogenization, ...) fail to handle all the difficulties raised by the modeling of these materials, particularly taking into account the complexity of their microstructure and their nonlinear/hysteretic behaviour. In this thesis we develop a multiscale computational method which allows to effectively solve multiscale magnetoquasistatic problems. The technique is inspired by the HMM (heterogeneous multiscale method), which involves the resolution of two types of problems: a macroscale problem that captures slow variations of the overall solution, and many mesoscale problems that allow to determine the constitutive laws at the macroscale and to construct accurate local fields. Macroscale and mesoscale weak, b-conform and h-conform formulations, are derived starting from the two-scale convergence and the periodic unfolding methods. We also use the asymptotic homogenization method for deriving the homogenized linear material laws and, in the end, we derive scale transitions for bridging the scales. Numerical tests carried out in the two-dimensional case allow to validate the models. In the case of b-conform formulations, it is shown that the macroscale solution approximates well the average of the reference solution and that the resolution of the mesoscale problems allows to reconstruct accurate local fields and to compute accurate Joule losses and this, for materials with (non)linear and hysteretic behavior. Similar findings were obtained for the h-conform formulations. In both cases, the deterioration of the accuracy for mesoscale problems located near the boundary of the computational domain could be treated by defining suit- able mesoscale problems near such boundaries. The extension of the model to three-dimensional problems, to multiphysical problems and the inclusion of the mesoscale domains with a stochastic distribution of phases are also some of the possible prospects for improving this work. [less ▲]

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See detailDéveloppement de nouvelles méthodes de marquage au fluor-18 pour peptides et oligonucléotides en vue de leur études par tomographie par émission de positons
Flagothier, Jessica ULg

Doctoral thesis (2014)

Positron Emission Tomography is a highly sensitive imaging technique currently available in nuclear medicine for diagnostic. In regard to his physical and nuclear characteristics, fluorine-18 appears ... [more ▼]

Positron Emission Tomography is a highly sensitive imaging technique currently available in nuclear medicine for diagnostic. In regard to his physical and nuclear characteristics, fluorine-18 appears often as the radionuclide of choice for the preparation of short-lived positron-emitter radiotracers for PET studies. The fluorine-18 labelling reaction for biomolecules requires very mild conditions. The current method for highly efficient fluorine-18 labelling of biomolecules is the conjugation of a [18F]prosthetic group with a reactive function on the organic compound. During this thesis, two techniques were developed to label biomolecules via a [18F]prosthetic group: the first one to label tyrosine-containing peptides and the second one to label a siRNA. The first part of this work present the synthesis of the [18F]F-PTAD which is a agent for specific radiolabelling of tyrosine. [18F]F-PTAD was coupled with a tyrosine with a global radiochemical yield (synthesis, coupling, purification) of 20% (DC) and the synthesis lasts 2h30. During the second part of this work, two alkyne-bearing linkers were synthesized. These linkers were ligated with siRNA and then reacted with azide-bearing [18F]prosthetic group via a Huisgen cycloaddition reaction. The [18F]siRNA is then obtained with an global radiochemical yield of 12% (DC) and the synthesis lasts 2h00. In conclusion, two methods for labeling biomolecules have been developed. [less ▲]

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See detailRANS and Large Eddy Simulation of the hydrodynamics inside mini-bioreactors designed for stem cell culture
Collignon, Marie-Laure ULg; Martin, Céline; Blanchard, Fabrice et al

Conference (2014, September 07)

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See detailCARACTÉRISATION DE LA DIVERSITÉ GÉNÉTIQUE DE CULTIVARS D’OIGNON (ALLIUM CEPA L.) DU NIGER EN VUE DE LEUR CONSERVATION IN SITU ET DE LEUR AMÉLIORATION
Abdou, Rabiou ULg

Doctoral thesis (2014)

Plante monocotylédone, allogame, entomophile, avec un cycle cultural annuel pour la production des bulbes, bisannuel pour celle des graines, l’oignon est l’un des légumes le plus important au Niger en ... [more ▼]

Plante monocotylédone, allogame, entomophile, avec un cycle cultural annuel pour la production des bulbes, bisannuel pour celle des graines, l’oignon est l’un des légumes le plus important au Niger en raison de son utilisation en alimentation et en médecine. Le semis en pépinière suivi d’un repiquage des planches est le mode de culture le plus fréquent chez les producteurs nigériens. Cette étude explore la diversité génétique des cultivars d’oignon du Niger. La diversité est à comprendre ici au sens de la diversité nommée, la diversité morphologique et la diversité moléculaire. Cette thèse se propose d’utiliser ces trois approches complémentaires pour identifier et caractériser les variétés et écotypes selon la perception des producteurs, de caractériser la diversité morphologique et agronomique à partir des descripteurs du genre Allium établis par Bioversity International, et d’analyser la diversité moléculaire des variétés et écotypes d’oignon du Niger à partir des marqueurs moléculaires microsatellites. Cinquante-deux écotypes nommés ont été inventoriés, mais après analyse et regroupement des synonymes, il ressort que dix-sept écotypes sont cultivés au Niger. Les principaux critères des paysans pour caractériser un écotype local sont la couleur des bulbes et la zone de provenance. Les variables quantitatives et qualitatives les plus distinctives entre les écotypes d’oignon sont la longueur et le diamètre des feuilles, le poids des bulbes, la couleur des feuilles, la forme et la couleur des bulbes, l’uniformité de la forme et de la couleur des bulbes. La distance génétique est plus grande, d’une part, entre les écotypes les plus éloignées géographiquement, et d’autre part, entre les écotypes les plus différents au niveau des caractères morphologiques. Le nombre de morphotypes varie de un à neuf par écotype testé. Les analyses moléculaires confirment la forte variabilité à l’intérieur des écotypes et les conclusions relatives à la distance génétique observée à partir des données morphologiques. A l’issue de ces travaux de caractérisation génétique de l’oignon, il est donc utile de combiner des stratégies de conservation in situ et ex situ, et l’exploitation de ces ressources génétiques pour améliorer la production et la rusticité des cultivars d’oignon du Niger. [less ▲]

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See detailRegards sur la "Wallonie prussienne" et la Première Guerre mondiale
Brüll, Christoph ULg

Conference given outside the academic context (2014)

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