Literatura científica selecionada sobre o tema "Agronomie – Diagnostic"

SummaryCrop production surveys, which integrate the collection of data on both agronomic and economic variables, are increasingly common in on-farm research. A conceptual framework for designing and analysing such surveys is provided. Methodological issues in conducting crop production surveys are reviewed with respect to type of information collected, level of field observation, degree of quantification, frequency of observation, sampling, measurement of yields and yield components, and analysis of yield limiting factors. It is concluded that, while better integration of agronomic and economic perspectives in diagnosis may increase costs, the information and analysis obtained have considerable potential to improve the efficiency of experimentation.

A high throughput technique used to determine a part of the nucleotide sequence of an organism’s genome is called next generation sequencing (NGS). NGS has been Proven revolutionary in genomics. Clinical diagnostics, Plant diseases diagnostic and other aspects of medical are now made possible by sequencing. Techniques of NGS: there are different techniques of NGS which are being used in real life sciences i.e., Illumina sequencing, Pyrosequencing, Roche 454 sequencing and Ion torrent sequencing. All vintage methods like culturing in bacterial, fungal, and viral samples are being suppressed by next generation sequencing. The potential for random metagenomic sequencing of sick samples to find potential pathogens has surfaced with the development of next-generation high-throughput parallel sequencing technology. NGS enables highly efficient, rapid, low-cost DNA or RNA high-throughput sequencing of plant virus and viroids genomes, as well as specific small RNAs generated during infection. Although this technique is not so much familiar in the field of plant diseases. However, its widespread application in agronomic sciences will make it possible to create solutions to future food-related challenges that involve biotic stress.

Diagnostic horizons, properties and materials are commonly applied building units of national and international soil classification systems. The presence, depth or absence of diagnostic information supports the process of objective soil classification, such as the World Reference Base (WRB). While the diagnostic units and associated descriptive qualifiers convey information that reflect pedogenesis, they also indicate important, and often complex properties that are related to soil fertility and other soil functions. The spatial extent or the continuum of diagnostic information is often different from the spatial extent of the mapping units in general soil maps (mostly reflecting soil types). This paper presents the spatial distribution of selected diagnostic units and qualifiers for the European Union and describes their significance for key soil functions. The derivation of selected diagnostics was performed based on the information provided in the European Soil Database and by taking into consideration the definitions, rules and allocation procedure of soils to the appropriate Reference Soil Group (RSG) defined by the WRB key. The definition of the presence/absence of the diagnostic units were performed by extracting information related to the first level of the WRB classification and to the qualifiers provided by the ESDB on the Soil Taxonomic Units (STU) level. The areal percentage of the STUs (thus, the derived diagnostics) within Soil Mapping Units (SMUs) was calculated and was visualized on separate maps. The study demonstrated the importance of the spatial information that the diagnostic elements convey, especially related to soil functions.

The failure to adequately identify plant pathogens from culture-based morphological techniques has led to the development of culture-independent molecular approaches. Increasingly, diagnostic laboratories are pursuing fast routine methods that provide reliable identification, sensitive detection, and accurate quantification of plant pathogens. In addition, since plants or parts thereof can be infected by multiple pathogens, multiplex assays that can detect and quantify different pathogens simultaneously are highly desirable. Technologies that can meet these requirements, especially those involving polymerase chain reaction, are being developed and implemented in horticultural and agricultural practice. Currently, DNA array technology is the most suitable technique for multiplex detection of plant pathogens. Recently, a quantitative aspect was added to this technology, making DNA arrays highly attractive for various research and practical applications. Here, we review the most important recent advances in molecular plant pathogen diagnostics, with special attention to fungal molecular diagnostics. In addition to their applicability in practice, the different criteria that have to be fulfilled for developing robust detection procedures that can routinely be used by diagnostic laboratories are discussed.

The online community resource Phytophthora database (PD) was developed to support accurate and rapid identification of Phytophthora and to help characterize and catalog the diversity and evolutionary relationships within the genus. Since its release in 2008, the sequence database has grown to cover 1 to 12 loci for ≈2,600 isolates (representing 138 described and provisional species). Sequences of multiple mitochondrial loci were added to complement nuclear loci-based phylogenetic analyses and diagnostic tool development. Key characteristics of most newly described and provisional species have been summarized. Other additions to improve the PD functionality include: (i) geographic information system tools that enable users to visualize the geographic origins of chosen isolates on a global-scale map, (ii) a tool for comparing genetic similarity between isolates via microsatellite markers to support population genetic studies, (iii) a comprehensive review of molecular diagnostics tools and relevant references, (iv) sequence alignments used to develop polymerase chain reaction-based diagnostics tools to support their utilization and new diagnostic tool development, and (v) an online community forum for sharing and preserving experience and knowledge accumulated in the global Phytophthora community. Here we present how these improvements can support users and discuss the PD's future direction.

The ideas for plant sanitary diagnostic using modern computer technology and internet service were discussed in this article. Digital photos, multimedia resources and FAQ website can serve the agronomist with summarized information concerning plant protection and methods for damage prevention in the area of crop cultivation.

Advances in next-generation sequencing (NGS) allow for rapid development of genomics resources needed to generate molecular diagnostics assays for infectious agents. NGS approaches are particularly helpful for organisms that cannot be cultured, such as the downy mildew pathogens, a group of biotrophic obligate oomycetes that infect crops of economic importance. Unlike most downy mildew pathogens that are highly host-specific, Pseudoperonospora cubensis causes disease on a broad range of crops belonging to the family Cucurbitaceae. In this study, we identified candidate diagnostic markers for P. cubensis by comparing NGS data from a diverse panel of P. cubensis and P. humuli isolates, two very closely related oomycete species. P. cubensis isolates from diverse hosts and geographical regions in the United States were selected for sequencing to ensure that candidates were conserved in P. cubensis isolates infecting different cucurbit hosts. Genomic regions unique to and conserved in P. cubensis isolates were identified through bioinformatics. These candidate regions were then validated using PCR against a larger collection of isolates from P. cubensis, P. humuli, and other oomycetes. Overall seven diagnostic markers were found to be specific to P. cubensis. These markers could be used for pathogen diagnostics on infected tissue, or adapted for monitoring airborne inoculum with real-time PCR and spore traps.

While there is universal recognition of the dangers of antimicrobial resistance (AMR) to human health, far less attention has been directed towards the steady growth of resistance to the pesticides and herbicides that safeguard global food security. As a major constraint on crop productivity, weed competition causes greater losses than invertebrate pests and fungal pathogens combined, with the development of herbicide resistance now a primary agronomic threat to arable agriculture and horticulture. Here in the UK, our dominant crop, winter wheat, is now subject to annual losses of 1 million tons of grain equating to an estimated £0.5 billion, primarily due to the mass evolution of herbicide resistance in the highly competitive weed blackgrass (Alopecurus myosuroides). Informed by strategies being developed in healthcare to combat AMR through its rapid identification, we now look to new tools to combat herbicide and pesticide resistance informed by molecular diagnostics.

L'activité de l'agronome s'ancre dans la parcelle cultivée. La parcelle expérimentale lui sert à connaître les processus biophysiques de production agricole ; la parcelle paysanne le confronte à la gestion de cette production. Pour identifier les déterminants de cette gestion, l'agronome doit élargir son champ d'analyse et changer d'échelle d'observation. Le diagnostic agronomique relie alors ces déterminants aux modalités de conduite des cultures et à leurs conséquences biophysiques. L'agronome peut aussi proposer d'améliorer les performances du processus de production en jouant sur des leviers biophysiques, techniques ou organisationnels. La conception d'outils d'aide à la décision relève de ces propositions et s'alimente des connaissances issues du diagnostic. Cette démarche de recherche-action est illustrée dans la vallée du Sénégal et concerne le développement de la riziculture irriguée dans des aménagements hydro-agricoles. Le diagnostic de la situation articule plusieurs échelles : parcelle, exploitation, périmètre irriguée, filière rizicole. La proposition qui est faite pour améliorer les performances de cette riziculture concerne l'organisation des producteurs au sein d'un aménagement. Mais d'autres propositions pourraient être faites à une échelle plus vaste pour réduire les dysfonctionnements de la filière entière. Restant dans le domaine de l'irrigation, le projet de recherche concerne la représentation de la demande agricole en eau. Un cadre de modélisation s'appuyant sur un concept simple d'activité de production associée à un espace géographique est proposé. Ce cadre est utilisé pour construire avec les acteurs une représentation des activités agricoles à l'échelle régionale. La spatialisation des résultats de ces activités et leur superposition avec d'autres cartes constituent ensuite des bases de réflexion sur les interrelations entre usages et ressources. Car c'est l'évolution de ces interrelations qui est au cœur de l'anthropisation des milieux, de sa maîtrise et de son caractère durable.

An early diagnosis of melanoma is essential to reduce mortality of patients. The diagnosis is also fundamental to predict the outcome of patients and to select the most adapted treatment. Current diagnostic assessments are obtained after visual inspection of the histological section of the primary tumor. The pathologist has first to determine the malignant nature of the lesion and then to assess the potential of the lesion to form metastases. Depending on several characteristics of the primary tumor (mainly tumor thickness, ulceration and mitotic rate), the sentinel node is surgically removed and the detection of tumor cells is based on its histopathological examination. These assessments are time consuming, to some degree subjective and are particularly challenging. Among melanoma patients that are not subject to sentinel node surgery, 6.5 % will develop metastases while 20 % of patients that undergo sentinel node surgery will effectively present metastases. The search for biomarkers that can identify malignant cells, evaluate potential of invasion or help selecting a treatment is still on.

In this thesis we used a new and promising technique of imaging based on infrared spectroscopy to study melanoma primary tumors and metastatic lymph nodes. Infrared spectroscopy brings information on the biochemical composition of the main components of the cells. When combined with a microscope and with multivariate statistical analyses, images that are generated allow the identification of melanoma cells and stromal cells in the biopsy. We also focused on the immune infiltration as it was shown to carry an important prognosis value for melanoma patients.

The first part of the thesis was a prerequisite for the rest of the study. It addresses the effects of the process of fixation that tissues obtained by surgical resection undergo for their long term preservation. In chapter III, we showed that Formalin-Fixation and Paraffin-Embedding (FFPE) procedure induces small but significant modifications in the infrared spectra of cells but these are very similar for different cell lines. In turn, it preserves the potential to identify closely-related cell lines by infrared spectroscopy.

We thus pursued our study on primary melanomas. In chapter IV, we first developed an automatic tool capable of identifying melanoma cells and the main cells of the tumor microenvironment in tissue sections. Importantly, we built a second model that brings information on the presence of metastases on the basis of the spectral signature of the primary tumor.

The next chapter is dedicated to the prediction of the response of melanoma to dacarbazine, the first-line chemotherapy to treat stage IV patients. Infrared spectra of the primary tumor were shown to contain information capable of predicting whether dacarbazine will be a useful treatment.

In the last two chapters, we focused on lymphocytes. In chapter VI, we first demonstrated that helper and cytotoxic T cells purified from peripheral blood can be identified on the basis of their infrared signature. Then, in chapter VII we investigated metastatic lymph nodes. We created different statistical models using infrared spectra that first identified the melanoma cells invading the lymph nodes and secondly, the different subpopulations of lymphocytes (B and T cells).

In conclusion, we developed an automatic and reliable tool of imaging to help pathologists in the anatomopathological assessment of primary lesions and lymph nodes./Le mélanome est la forme de cancer cutané la plus mortelle, provoquant environ 80% des décès dus à un cancer de la peau. Lorsque le mélanome est localisé, la chirurgie est le principal traitement et est suffisante pour 80% des patients. A l’opposé, lorsque le mélanome primaire a formé des métastases, le cancer devient beaucoup plus difficile à traiter et la survie de ces patients diminue drastiquement. Seuls 10% des patients vont vivre 5 ans lorsqu’ils développent des métastases à distance. C’est pourquoi un diagnostic précoce est essentiel pour diminuer la mortalité causée par le mélanome. L’étape du diagnostic est également très importante pour donner un pronostic et pour planifier les traitements. Le diagnostic actuel du mélanome est basé sur l’analyse en microscopie optique de sections de la tumeur primaire. Sur base de la morphologie cellulaire et de l’architecture du tissu, cette étape permet premièrement d’identifier le caractère cancéreux de la lésion et deuxièmement d’évaluer son potentiel métastatique. Une analyse du ganglion sentinelle permet également de détecter la présence de métastases. Dans le cadre de cette thèse, nous proposons d’utiliser une nouvelle technique d’imagerie basée sur la spectroscopie infrarouge qui apporte une information complète et unique sur la biochimie de la cellule et des tissus. Les résultats présentés ici indiquent que lorsque les spectres infrarouges sont combinés à des analyses statistiques multivariées, des images sont reconstituées et révèlent les structures et les composants cellulaires majeurs présents dans les coupes de mélanomes. Une étude préliminaire a d’abord pu démontrer que la fixation au formol subies par les biopsies pour les conserver n’entrave pas l’étude de celles-ci par spectroscopie infrarouge. Nous nous sommes alors intéressés aux tumeurs primaires de mélanome et avons développé un modèle statistique, à partir des spectres infrarouges, identifiant automatiquement les cellules de mélanome dans le tissu ainsi que les autres cellules du microenvironnement de la tumeur. Dans ce chapitre, nous avons également créé un autre modèle statistique capable de prédire le potentiel métastatique de la tumeur primaire en se basant sur sa signature spectrale. Nous avons ensuite mis en évidence une signature spectrale corrélée à la réponse à la dacarbazine chez des patients traités pour leurs métastases. Nous avons également montré que des sous-populations de lymphocytes purifiées d’échantillons sanguins pouvaient être identifiées sur base de leur spectre. Cette capacité de la spectroscopie infrarouge à distinguer les différents types de lymphocytes a ensuite été démontrée pour les lymphocytes infiltrant les métastases. Finalement, nous avons mis en évidence l’utilité de cette technique d’imagerie pour la détection de métastases ganglionnaires.

Doctorat en sciences agronomiques et ingénierie biologique
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As the most prevalent cause of dementia worldwide, Alzheimer’s disease (AD) has become a global issue of public health. By current criteria, diagnosis of this neurodegenerative disorder requires both clinical confirmation of dementia and post-mortem detection of the so-called neurofibrillary tangles and senile plaques in the brain. Yet the main proteinaceous component of these plaques, the amyloid beta peptide (Abeta) is now widely believed to initiate a cascade of events that ultimately leads to Alzheimer’s disease. Besides, extensive evidence supports a pathogenic role of soluble oligomers formed upon Abeta aggregation in the onset of the disease, which, unlike Abeta fibrils, present distinct neurotoxic properties and correlate well with disease progression. Their detrimental effects have been suggested to appear decades before the first signs of cognitive impairment, making them biomarkers of choice in the study of the pathology.

Given that present guidelines for AD diagnosis are increasingly considered as ill-defined, reliable and early-stage detection methods taking into account the presence of toxic Abeta species are highly awaited by the medical community. In this regard, this thesis work describes the development of a sensing device aiming at the specific detection of the amyloid beta peptide in solution via recognition by antibodies grafted at the surface of functionalized germanium crystals. This new type of BIA-ATR (Biospecific Interaction Analysis - Attenuated Total Reflection) biosensor resorts on ATR-FTIR (Attenuated Total Reflection - Fourier Transform Infrared) spectroscopy, which is extremely sensitive to the secondary structure of proteins. The ATR mode uses germanium as optical transduction element combined to the evanescent wave principle to allow selective online monitoring of peptide-antibody binding events.

In the first part of this work, evaluation of the photochemistry on germanium optical elements have been the subject of intense research focus. Our investigations led to the elaboration of a quality control of functionalization efficiency based on infrared spectroscopy. We also set up in the lab an original ELISA method for selecting antibodies in terms of their true affinity for the Abeta peptide.

Thereafter binding experiments were carried out on the BIA-ATR sensor using different antibodies and Abeta isoforms, leading to the establishing of a standardized protocol for the detection of molecules of interest. Our results showed that Abeta detected on the biosensor corresponded precisely to antibody-bound peptide, whereas Abeta assemblies, and especially Abeta 1-42 oligomeric conformations, could be discriminated with respect to their spectral signature. This point, which was later confirmed by unsupervised statistical analysis, could be considered as particularly interesting and innovative, since to our knowledge, such conformation-sensitivity has never been observed with existing AD diagnostic methods. Moreover, effective recycling of the functionalized crystals has been demonstrated, which confers thereby a second major advantage to the biosensor.

In parallel to these experiments, a structural characterization study of Abeta species was undertaken in order to generate a database of IR spectra, as reference for future comparative analysis of physiological fluids on the biosensor. ATR-FTIR measurements revealed a strong dependency on the ratio between oligomers and fibrils within a mixture and their relative ratio in antiparallel and parallel beta-sheet content. Interestingly, separation trials of oligomeric entities demonstrated a specific effect of Cu2+ ions on Abeta aggregation. Stabilization of small oligomeric aggregates at equimolar Cu2+:Abeta ratios, which had never been clearly evidenced so far, could help to unravel some aspects of the complex role of copper in AD development.

These investigations illustrate the applicability of the so-called BIA-ATR methodology to online detection of different forms of the Abeta peptide in solution and the potential of this new sensor technology to fulfill current pitfalls in providing a reliable and comprehensive approach of AD diagnosis.
Doctorat en Sciences agronomiques et ingénierie biologique
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Résumé

Les recherches menées dans cette thèse ont porté sur la réactualisation des données sur la flore et la végétation de deux grandes zones agro-écologiques du Sénégal (les Niayes et le Bassin arachidier) en utilisant l’approche terroir pour mieux envisager la gestion conservatoire des ressources ligneuses. Dans les zones de savanes et de végétations sub-guinéennes respectivement du Bassin arachidier et des Niayes au Sénégal, 288 relevés ont été réalisés par stratification basée sur les villages ou groupes ethniques (Peul, Sérer et Wolof), les systèmes d’utilisation des terres et la topographie dans 6 terroirs villageois et 25 dans les sites de référence. Dans ces terroirs, la connaissance, la priorisation à la conservation des espèces, leur utilisations, comme préalables à la gestion durable de la biodiversité des agrosystèmes, ont aussi été abordées sur 124 espèces ligneuses par enquête ethnobotanique auprès de 216 répondants équitablement répartis entre les ethnies, âges et genres. Ces informants ont aussi évalué la dynamique des formations végétales suivant leur position sur la toposéquence. Les informations sur la dynamique d’occupation des terres ont été obtenues par la cartographie multi-date à partir de photo-aériennes (1954, 1989) et d’image Google earth 2006. Une expérimentation factorielle à trois facteurs (espèces, hauteur et diamètre de coupe) avec 15 répétitions, a été conduite dans le Bassin arachidier sur la régénération des souches des deux principales Combretaceae de la zone (Combretum glutinosum et Guiera senegalensis). Les données obtenues ont été soumises à des analyses multi et uni-variées.

Les résultats phytosociologiques ont montré l’individualisation de onze groupements (G) dont d’une part, deux de savane (G4 et G8), un de forêts secondaires (G10) et deux autres issus des végétations semi-aquatiques (G1 et G5) qui sont les plus proches des situations naturelles, et d’autre part deux de milieux perturbés (G6 et G7) et quatre de milieux cultivés et post-culturaux (G2, G3, G9 et G11). Les premiers groupements sont progressivement envahis par les espèces des milieux perturbés, et les seconds par les espèces rudérales et nitrophiles. La position synsystématique de ces groupements a été donnée. 336 espèces ont été recensées :260 dans les Niayes et 176 dans le Bassin arachidier. La richesse des critères de naturalités des terroirs peuls n’est pas toujours supérieure à celle des autres terroirs dans les deux zones.

Les résultats d’enquête montrent une subdivision des espèces en quatre classes de priorité à la sauvegarde. Les plus prioritaires sont à usages multiples. En outre, les résultats ethnobotaniques montrent clairement que les villages des Niayes sont globalement séparés de ceux du Bassin arachidier mais aussi que les villages homologues sont différents. L’évaluation ethnobotanique de la diversité végétale est plus importante dans la zone du Bassin arachidier comparée aux Niayes. Elle augmente avec la densité dans les Niayes comme dans le Bassin arachidier excepté dans le terroir wolof de ce dernier. Les villages du Bassin arachidier ne présentent aucune restriction dans le choix des espèces destinées à satisfaire leurs différents besoins. Ce manque de sélectivité y est total et renseigne sur le niveau de rareté des ressources ligneuses.

Les résultats cartographiques montrent que les zones des Niayes et du Bassin arachidier connaissent une transformation importante du paysage essentiellement due au processus de création ou d’agrégation des champs en vigueur partout. Cela s’est fait au détriment des formations végétales :suppression des savanes arborées dans les deux zones, suppression et agrégation des savanes arbustives dans les Niayes, fragmentation et dissection dans le Bassin arachidier.

Dans le régime de taillis à courte rotation du Bassin arachidier, il serait plus indiqué de pratiquer une coupe sélective suivant les classes de diamètre et les espèces afin de concilier productivité et durabilité en favorisant le développement des rejets proventifs.

Une extension de l’approche terroir dans les autres zones éco-géographiques du pays devrait être testée pour vérifier les tendances obtenues dans ce travail et recenser et suivre les groupements végétaux, les intégrer dans la classification moderne afin de faciliter le suivi de leur évolution spatio-temporelle. Elle permettrait sans doute l’évaluation de la variabilité locale de l’importance des espèces.

Abstract

Researches carried out in this thesis about updating flora and vegetation data from two major agroecological regions of Senegal (Niayes and Peanut Basin) used village-scale based methodology in order to better consider ligneous resources conservation. In savannas and sub-guinean vegetations of respectively Peanut Basin and Niayes, 288 records were realized upon stratification method based on ethnic groups (Wolof, Peul and Sérer), land use systems and topography in 6 villages and 25 records in the reference sites. In these villages, knowledge, priorisation and uses, prior to sustainable agrobiodiversity management, were also addressed on 124 ligneous species by ethnobotanic survey with 216 respondants equally distributed to ethnic groups, ages and gender. Respondants also addressed vegetation dynamics a long topographic position. Informations on land occupation trends were gained by air-photography cartography and Google earth 2006 image. Factorial experimentation on 3 factors (species, high and diameter of sprouting) with 15 repetitions was implemented on stump regeneration dynamics of the 2 principal Combretaceae in the Peanut Basin region (Combretum glutinosum and Guiera senegalensis). Multivariate and univariate analysis were performed on the data.

Phytosociological results showed discrimination of 11 vegetation groups (G). Two of them (G4 and G8) are savannas samples, one secondary forest (G10), two from semi-aquatic vegetation (G1 and G5); in the other hand, two groups of disturbed situations (G6 and G7) and four cultivated and postcultural groups were found (G2, G3, G9 and G11). The first groups were progressively invaded by cultural and poscultural species and the second groups by ruderary and adventitious species. Systematic position of these groups was indicated. 336 species were recorded: 260 in the Niayes and 176 in the Peanut Basin). Richness in wilderness criterion was not always superior in peul villages.

Ethnobotanical results showed subdivision of species diversity in 4 classes of conservation priority. Most conservation priority species were multipurpose trees. A clear separation between Niayes villages and Peanut basin ones, and also between counterparts’ villages was found. Ethnobotanical valuation of species was higher in the Peanut Basin area. It grows with human density a part from wolof village of the Peanut basin. Villages of the Groundnut Basin showed no selectivity in the choice of species to meet their different needs. This lack of selectivity is complete and translates woody resources scarcity.

Cartographic results show an important landscape transformation in Niayes and Peanut basin areas due to fields creation or aggregation processes running everywhere. This occurred against vegetation formations :attrition of woody savanna in the two zones, attrition and aggregation of shrubby savanna in Niayes area, fragmentation and dissection in Peanut basin.

In short term cutting system of the Peanut Basin, it should be better to practise a selective logging method according to species and diameter classes in order to reconcile productivity and sustainability by ensuring stumps’ low-stem resprouting.

An extension of terroir approach methodology in other local eco-geographical zones of Senegal should be tested in order to complete the identification and monitoring of the dynamics of plant communities, their integration into modern classification to facilitate the monitoring of their spatio-temporal evolution. It should allow the assessment of species local importance variability.

Doctorat en Sciences agronomiques et ingénierie biologique
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L'agriculture itinérante sur brulis (ai) est un mode de culture pratique sans intrant. Après deux ou trois cycles de cultures, la dégradation de la fertilité des sols contraint les agriculteurs à déplacer leurs cultures et le terrain est laisse en jachère. La jachère permet de reconstituer une biomasse, qui libèrera lors de la période de production suivante, après brulis, des éléments minéraux nécessaires à la croissance et au développement des cultures. Cette étude consistait, à fournir des éléments d'appui à la décision, dans le but d'une fixation à terme de ces systèmes traditionnels. Elle a nécessité que l'on présente une analyse de la gestion des systèmes d'q. I. , composante importante de la reproductibilité de la fertilité, et condition de la fixation. Dans un premier temps, la gestion spatiale de ces systèmes et leurs capacités à faire face aux contraintes agro-écologiques et socio-économiques du milieu, pour se reproduire, ont été étudiées. Cette étude a été effectuée à l'échelle du système agraire et plus précisément a l'échelle des systèmes de production qui correspondent au niveau des choix et décisions des agriculteurs. Dans un deuxième temps, l'évolution des composantes de la fertilité, susceptible d'influencer le rendement de manioc, a été analysée - le manioc constituant la principale culture de l'ouest Guyane -. Trois niveaux ont été considères : le système de culture qui permet de comprendre les modes de conduite et d'association des cultures, mais surtout la parcelle cultivée et la placette d'expérimentation, lieu de mesures et de suivi. Dans la première étape de ce travail, une capacité d'équilibration des abattis est établie à partir du modelé de Piaget. Cette typologie permet d'identifier 5 types fonctionnels d'abattis dans la région et 2 modes d'évolution. Dans la deuxième étape, lors d'un premier cycle d'abattis, après foret secondaire, l'évolution des stocks de carbone, d'azote et des bases échangeables montre qu'il n'y a pas de dégradation en relation avec la matière organique du sol. En revanche, on assiste à une diminution des bases échangeables suite à la mise en culture et en particulier du potassium. La comparaison de cette diminution avec les besoins de la culture, a permis d'identifier le potassium, comme facteur limitant la production
Shifting cultivation on brulis (ai) is a convenient method of cultivation without inputs. After two or three crop cycles, the degradation of soil fertility forces farmers to move their crops and the land is left fallow. Fallowing can be used to reconstitute a biomass, which will release during the next production period, after burning, the mineral elements necessary for the growth and development of crops. The purpose of this study was to provide support for the decision, with a view to eventually establishing these traditional systems. It required an analysis of the management of Qi systems, an important component of reproducibility of fertility, and the condition of fixation. At first, the spatial management of these systems and their capacity to cope with the agro-ecological and socio-economic constraints of the environment, to reproduce, were studied. This study was carried out at the scale of the agrarian system and more precisely at the level of the production systems which correspond to the level of the choices and decisions of the farmers. In a second step, the evolution of the components of fertility, likely to influence the yield of cassava, was analyzed - the cassava constituting the main crop of West Guiana. Three levels were considered: the cropping system that allows to understand the modes of behavior and association of crops, but especially the cultivated plot and the experimental plot, place of measurement and monitoring. In the first stage of this work, a balancing capacity of the giblets is established from the Piaget model. This typology makes it possible to identify 5 functional types of giblets in the region and 2 modes of evolution. In the second stage, during a first cycle of giblets, after secondary forest, the evolution of stocks of carbon, nitrogen and exchangeable bases shows that there is no degradation in relation to the material organic soil. On the other hand, there is a decrease in exchangeable bases following the cultivation and in particular potassium. Comparing this decrease with the needs of the crop, it was possible to identify potassium as a factor limiting production

La cacaoculture est aujourd'hui considérée comme un des principaux facteurs de déforestation en milieu tropical. Dans de nombreux pays, elle repose en effet sur un modèle technique peu durable de monoculture intensive impliquant le déplacement des zones de production. Souvent délaissés par la recherche en raison de leurs faibles rendements en cacao marchand, les systèmes agroforestiers à base de cacaoyer apparaissent aujourd'hui comme une alternative crédible pour faire face aux nouveaux enjeux de la cacaoculture mondiale. Au Centre-Sud du Cameroun, la cacaoculture repose en grande partie sur des cacaoyères agroforestières anciennes, ce qui pose l'hypothèse qu'un modèle de cacaoculture durable basé sur des systèmes de culture agroforestiers est possible. Notre objectif est de mieux comprendre le fonctionnement de ces systèmes agroforestiers à base de cacaoyer, à travers leurs caractéristiques, leurs évolutions et leurs déterminants, ainsi que les conditions de leur production en cacao marchand sur le long terme. Notre démarche articule à la fois une évaluation des systèmes agroforestiers complexes à l'échelle de la parcelle et une analyse compréhensive des pratiques techniques sur le temps long. La thèse repose sur un dispositif de recherche mis en place dans la région du Centre, dans trois zones de culture différenciables par leurs conditions pédo-climatiques (Bokito, Zima et Ngomedzap). Une enquête d'agriculteurs a été réalisée à grande échelle (1 171 exploitations regroupant 1 638 cacaoyères), complétée par des observations spécifiques réalisées dans un réseau de 61 cacaoyères exploitées par 40 agriculteurs. Résultats. (1) Nos résultats d'enquête, complétés par des observations spécifiques, ont confirmé la durabilité des systèmes agroforestiers à base de cacaoyer aux plans agro-écologique et socio-économique. (2) Dans la zone de transition forêt-savane, considérée comme sub-optimale pour la cacaoculture, nous avons montré que le modèle technique adopté par les agriculteurs leur permet d'installer sur savane des cacaoyères viables sur le long terme. (3) Une méthode participative de quantification de la valeur d'usage des espèces par les agriculteurs, appliquée sur le réseau d'observation, a confirmé la multifonctionnalité des systèmes agroforestiers et mesuré la place qu'y occupe la composante cacaoyère. (4) L'évaluation des peuplements cacaoyers, réalisée en adaptant la méthode de diagnostic agronomique régional aux systèmes complexes, a permis d'identifier les facteurs limitant le rendement en cacao marchand. Celui-ci s'avère étroitement lié à la structure des peuplements cacaoyers et à celle des peuplements associés. (5) Enfin, l'analyse compréhensive des pratiques des agriculteurs sur le long terme, en lien avec l'évolution technique des peuplements cacaoyers a confirmé la flexibilité des systèmes agroforestiers à base de cacaoyer. Cette flexibilité peut être traduite par des trajectoires d'évolution des pratiques et des trajectoires de structures spécifiques. Ce travail fournit une nouvelle base méthodologique pour l'analyse et l'évaluation des systèmes agroforestiers complexes. L'ensemble des résultats et des connaissances produites dans ce travail permet de formuler des propositions pour la mise au point d'un nouveau modèle technique en cacaoculture
Cocoa cultivation is generally considered as one of the main deforestation factors in the Tropics. Indeed, in many countries it is based on a low-sustainability technical model of intensive monocrops with shifting production zones. Cocoa agroforests, which are often neglected by research due to their low fermented dried cocoa yields, now appear to be a credible alternative for taking up the new challenges facing world cocoa production. In Centre-South Cameroon, cocoa cultivation is largely based on old cocoa agroforests, which suggests that a sustainable cocoa growing model based on agroforestry systems is possible. Our aim was to more effectively understand how these cocoa agroforests function, through their characteristics, their evolution and their determinants, along with the conditions for their long-term fermented dried cocoa production. Our approach consisted of an evaluation of cocoa agroforests on a plot scale and a comprehensive analysis of technical practices over the long term. The thesis is based on an experimental design set up in the Centre region, in three growing zones that could be differentiated through their pedo climatic conditions (Bokito, Zima and Ngomedzap). A large-scale survey was undertaken (1,171 farms grouping 1,638 cocoa plantations) completed by specific observations collected in a network of 61 cocoa agroforests managed by 40 farmers. Results. (1) Our survey results, completed by specific observations, confirmed the sustainability of the cocoa agroforestry systems from an agro ecological and socio-economic viewpoint. (2) In the forest-savannah transition zone, which is considered sub-optimum for cocoa cultivation, we confirmed that the technical model adopted by the farmers enabled them to set up cocoa agroforests on savannah that were viable over the long term. (3) In the network, a participatory method applied to quantify the use value given to the species by the farmers confirmed the multi-functionality of cocoa agroforests and measured the place occupied in it by cocoa. (4) The evaluation of the cocoa tree stands, achieved by adapting the regional agronomic diagnosis method to complex systems, revealed the factors limiting cocoa yield. It was proved that cocoa yield is closely linked to the structure of the cocoa tree stand and that of the intercropped stands. (5) Lastly, a comprehensive analysis of farmer practices over the long term, in association with the evolution of the technical management of the cocoa tree stands, confirmed the flexibility of cocoa agroforestry systems. This flexibility was reflected in the evolution pathways for specific practices and structures. This work provides a new methodological basis to assess the performance of complex agroforestry systems. All the results and knowledge produced by this work make it possible to draw up proposals for developing a new technical model for cocoa growing

La région de Hounde au Burkina Faso est en pleine mutation en raison de l'intensification des systèmes de production agricole et de l'installation de populations venant des zones défavorisées au nord du pays. Face à ces transformations, les méthodes de conservation du milieu naturel traditionnellement utilisées sont peu à peu dépassées. Plusieurs techniques de diagnostic ont été utilisées afin de mettre en évidence l'évolution des paysages agricoles et le niveau de fertilité des sols. Dans une soixantaine de situations culturales, réparties dans deux villages de cette région, l'analyse des indicateurs de fertilité a montré que les seuils définis dans des dispositifs en milieux contrôlés ne sont pas encore atteints. La production agricole dans les systèmes de culture actuels assure aux populations autosuffisance alimentaire et revenus monétaires. L’avenir de cette région ne peut toutefois reposer sur ce constat optimiste et les dangers d'une dégradation physique et chimique des sols cultivés ressortent de cette étude

La culture bananière dédiée à l'export est industrielle et implantée sur de grandes surfaces monovariétales. Cette culture est intensive en intrants, en main d'oeuvre et est soumise à des contraintes environnementales et sociétales qui imposent une amélioration des pratiques agricoles. L’Agriculture de Précision (AP) est une approche technique qui est apparue sur les grandes cultures pour optimiser leur rendement, la qualité des récoltes et pour diminuer leur impact environnemental. Cette approche s'appuie sur les données spatialisées des exploitations pour réaliser un état des lieux de la production. Son objectif est de mettre en évidence les conditions variables de croissance et d'identifier celles qui sont contrôlables afin d'optimiser les procédés de production en fonction du potentiel local dans l'exploitation. La culture bananière présente des particularités par rapport aux grandes cultures qui n’ont pas été étudiées et qui remettent en cause l’utilisation directe des méthodes d’analyse des données des exploitants. Notamment, les bananiers sont asynchrones, leur cycle de développement n'est pas saisonnier et n'est pas synchronisé par le mode de culture. En conséquence, les parcelles sont constituées de bananiers à différents stades phénologiques. Ainsi, contrairement aux grandes cultures qui sont, elles, synchrones, les observations que l'on peut faire sur une bananeraie à un moment donné ne dépendent pas seulement des conditions de croissance mais aussi du stade phénologique variable des plants. L'objectif de cette thèse est de proposer de nouvelles méthodes pour valoriser les données produites en bananeraies afin de faciliter le diagnostic agronomique dans une démarche d’AP. Les données sur lesquelles nous avons travaillées sont issues d'observations classiquement réalisées dans les bananeraies pour gérer les récoltes. Nous nous sommes aussi intéressés à la télédétection et nous avons proposé des méthodes d’analyse qui permettent d'étudier la variabilité spatiale en diminuant le biais lié à l'asynchronisme.Le premier travail de la thèse a été de proposer des méthodes de caractérisation de l’asynchronisme des parcelles. Pour cela nous avons définis plusieurs indicateurs : la durée du cycle de développement des bananiers ; l’hétérogénéité des conditions de croissance ; le stade phénologique moyen d’une parcelle et enfin la variabilité des stades présents dans une parcelle. Ces méthodes ont été appliquées sur les données de floraisons d’une plantation industrielle au Cameroun. Nous avons ainsi mis en évidence un effet de l’environnement et des pratiques des producteurs sur l’asynchronisme. Un deuxième pan du travail de thèse a été de proposer un modèle qui permet d’identifier la variabilité liée à l’environnement à partir de données de production. Le but était de générer des cartes interprétables agronomiquement sans biais lié à l’asynchronisme. Le modèle que nous avons proposé a été appliqué sur un indicateur particulier : le temps entre la floraison des plants et le moment de leur maturité. On suppose que cette méthode est suffisamment générale pour être appliquée à d’autres propriétés comme le poids des régimes à la récolte.Enfin, le dernier sujet étudié a été l’intérêt de la télédétection dans les bananeraies malgré la diversité des stades phénologiques. Nous avons quantifié l'importance de différentes sources de variabilité sur la teneur en chlorophylle des feuilles de bananier mesurée à partir d'un capteur piéton et nous avons construit un indice qui permet de prédire cette teneur par drone. Des cartes de variabilités de la chlorophylle intra-parcellaire ont été produites par ce moyen mais l’interprétation agronomique doit être faite avec précaution car les stades phénologiques ne sont pas connus et leurs effets ne peuvent être corrigés. Les conditions permettant d’interpréter ces cartes sont discutées
Exported bananas are produced on industrial plantations covering large areas and relying most of the times on clones of the Cavendish cultivars. This crop is input and labour intensive and is subject to environmental and societal constraints that impose an improvement in agricultural practices. Precision Agriculture (PA) is a methodological approach that has emerged on arable crops to optimize their yield, quality and reduce their environmental impact. This approach uses geo-referenced producer’s data and studies their spatial variability to increase the farming performance by adjusting the management by area. Its objective is to highlight the variable growth conditions and identify those that are manageable in order to optimize production processes according to the specific potential of the sites on the farm. Unlike arable crops, bananas exhibit unique characteristics that must be taken into account when studying production and yields. In particular, banana plants are asynchronous, their development cycle is not seasonal and is not synchronized by the cropping system. As a result, the fields are made up of banana plants at different phenological stages. Thus, unlike arable crops which are synchronous, the observations that can be made on a banana plantation at a given time depend not only on growing conditions but also on the variable phenological stages of the plants. The objective of this doctoral thesis was to propose new methods for using data produced in banana plantations in order to facilitate agronomic diagnosis in a PA approach. The data used are mainly those recorded to manage the harvests. These are observations classically recorded in banana plantations. We also studied remote sensing data and proposed analytical methods to study spatial variability by reducing the bias due to the asynchronism of banana plants.The first thesis work consisted in proposing methods to characterize the asynchronism of the fields. For this purpose, we defined several indicators: the average duration of the banana plant development cycle; the heterogeneity of growing conditions; and finally the average phenological stage of a field and the within field variability of the stages. These methods were applied to flowering data from an industrial plantation in Cameroon. An effect of the environment and producers' practices on asynchronism was highlighted. A second part of the thesis work consisted in proposing a model that identifies variability related to the environment and producers' choices using production data. The purpose of this method was to generate maps that could be interpreted agronomically, without the asynchronism bias. The model we proposed was applied to a particular property: the time between flowering and commercial maturity. It is assumed that this method is general enough to be applied to other agronomic properties such as the weight of bunches at harvest.Finally, the last subject we studied was the relevancy of remote sensing in banana plantations despite the diversity of phenological stages. We assessed the importance of different sources of variability on the chlorophyll content of banana leaves measured from a pedestrian sensor and constructed an index to predict this content by drone. Maps of within field variability of chlorophyll content have been produced by this method, but agronomic interpretation must be done with caution because the phenological stages are not known and their effects cannot be corrected. The conditions for interpreting these maps are discussed

Obtaining income from farming activities is intrinsically linked to economic, social, and environmental bias. In this sense, seeking to understand income generation, eight rural properties in the municipality of Nova Esperança do Sudoeste - PR were studied, relating quantitative indicators of Gross Product (PB), Intermediate Consumption (CI), and Agricultural Income (RA). This analysis used the variables produced by the extension project and discipline Planning of Rural Properties that is practiced in an academic and social environment in the agronomy course of the Federal Technological University of Paraná, Campus Dois Vizinhos, whose methodology is divided into three main parts: diagnosis, rural planning and feedback to rural producers. In this context, information was used about the production systems of the properties mainly focused on dairy production, an agricultural area, PB/ha, CI/ha, AR/ha, and two indices calculated through the contrast between the indicators (RA(ha)/ CI(ha)) and (RA(ha)/PB(ha)). In this analysis, different income generation strategies were noted, being differentiated by the degree of investment with inputs, where, in general, the properties that invested more, obtained better returns, with exceptions in which the gross wealth produced was not consistent with the amount invested, generating economic inefficiency of the activity.

The productivity of the grasslands is determined by the biodiversity of the plant species present in the vegetation, their quality, but also their exploitation. For their inventory, a series of determination methods are used, methods that are difficult to manage and that require a good knowledge of the plant species. For an agronomic characterization of the plots, it is sufficient to consider only the main species that dominate the plant biomass. A more simplified method is that of botanical surveys which focus only on recognizing the dominant grasses in grasslands. This method allows for an agronomic diagnosis of a grassland without modifying the variables studied, namely, the percentage of biomass participation and the percentage of each functional type of grasses. The method allows the application of a functional typology that can estimate the value of use (forage quality, productivity, precocity or lateness) of a grassland. The purpose of this work is to classify the species by plant families, establish the pastoral value and inventory the grass species, as well as classify them from a morphofunctional point of view, in order to implement some management strategies aimed at ensuring an optimal exploitation of the grasslands taken into study. The measurements were made on three grasslands belonging to the town of Sasca Montana, Romania, located in the south of the Western Carpathians (44�53'13"N 21�42'33"E), at an altitude of 237 m. In this area, the average annual temperatures is between 9 - 10�C, and the precipitation level is between 700 and 800 mm. The three studied grasslands have a similar floristic composition, but with a different participation percentage of species. The dominant grass species, from a morpho-functional point of view, are species of type C (Festuca valesiaca being the dominant species), which shows that these grasslands are weak and do not adapt to mowing practices, although the species included in this morpho-functional type are species with a fairly good fodder value in the vegetative phase.

Understanding the audience is the key to successful communication. Therefore, an effective teacher has to consider manifold differences among the students in any given classroom: the characteristics of the students, the mindset of the generation, the variety of learning styles, the students’ needs and goals, and their educational background. Since Aleksandras Stulginskis University (ASU) awards the degrees in food sciences and agriculture, a sizeable part of the students come to study from rural areas. Recent educational research in the USA, UK and Lithuania have revealed a significant difference in the academic performance of the students from rural and urban areas, however, it is still an unresolved problem for the educational institutions in Lithuania. This area has an insubstantial amount of research documented. Thus, the current research aims at investigating the relationship between the location of the school, a student graduated from, and the results of the English Language Diagnostic Test as well as analysing the academic performance of the Agronomy Faculty students through the 2nd, 3rd and 4th semesters. The study focuses on our current undergraduate students - the always-connected, app-happy, smartphone-dependent, born with the Internet, technology, and social media Generation Z. The research methods involve the statistical and comparative analyses of the urban and rural student academic performance (diagnostic test results, examination grades of the 2nd, 3rd and 4th semesters) in the English language; the theoretical assumptions based on the related scientific literature and documents on educational statistics, and the investigation of motivational factors influencing the academic performance of the Generation Z students in line with the processed survey results. The research was initiated in 2015, student academic performance was monitored through the period from 2015 to 2017, and the survey was administered in 2017. The research findings indicate that students from rural schools have an inferior level of the English language compared to the students that finished schools in urban areas, whereas the examination results through the second, third and fourth semesters unveiled an unexpected tendency. Figures show that students from rural schools not only managed to catch up with their colleagues from urban schools, but also outperformed their urban-school peers by roughly increasing rates of their performance. The research evidence could aid teachers and education policy makers, providing a better understanding of Generation Z students from rural and urban areas and factors influencing students' performance.

Tree species are characterized by their perennial growth habit, woody morphology, long juvenile period phase, mostly outcrossing behaviour, highly heterozygosity genetic makeup, and relatively high genetic diversity. The economically important trees have been an integral part of the human life system due to their provision of timber, fruit, fodder, and medicinal and/or health benefits. Despite its widespread application in agriculture, industrial and medicinal values, the molecular aspects of key economic traits of many tree species remain largely unexplored. Over the past two decades, research on forest tree genomics has generally lagged behind that of other agronomic crops. Genomic research on trees is motivated by the need to support genetic improvement programmes mostly for food trees and timber, and develop diagnostic tools to assist in recommendation for optimum conservation, restoration and management of natural populations. Research on long-lived woody perennials is extending our molecular knowledge and understanding of complex life histories and adaptations to the environment, enriching a field that has traditionally drawn its biological inference from a few short-lived herbaceous species. These concerns have fostered research aimed at deciphering the genomic basis of complex traits that are related to the adaptive value of trees. This review summarizes the highlights of tree genomics and offers some priorities for accelerating progress in the next decade.