Stem rot of peanut (Arachis hypogaea L.), caused by a soilborne fungus Athelia rolfsii (Curzi) C. C. Tu and Kimbr. (anamorph: Sclerotium rolfsii Sacc.), is one of the most important diseases in peanut production worldwide. Though new varieties with increased partial resistance to this disease have been developed, there is still a need to utilize fungicides for disease control during the growing season. Fungicides with activity against A. rolfsii are available, and several new products have been recently registered for control of stem rot in peanut. However, fungicides are most effective when applied before or during the early stages of infection. Current scouting methods can detect disease once signs or symptoms are present, but to optimize the timing of fungicide applications and protect crop yield, a method for early detection of soilborne diseases is needed. Previous studies have utilized optical sensors combined with machine learning analysis for the early detection of plant diseases, but these studies mainly focused on foliar diseases. Few studies have applied these technologies for the early detection of soilborne diseases in field crops, including peanut. Thus, the overall goal of this research was to integrate sensor technologies, modern data analytic tools, and properties of standard and newly registered fungicides to develop improved management strategies for stem rot control in peanuts. The specific objectives of this work were to 1) characterize the spectral and thermal responses of peanut to infection with A. rolfsii under controlled conditions, 2) identify optimal wavelengths to detect stem rot of peanut using hyperspectral sensor and machine learning, and 3) evaluate the standard and newly registered peanut fungicides with different modes of action for stem rot control in peanuts using a laboratory bioassay. For Objective 1, spectral reflectance and leaf temperature of peanut plants were measured by spectral and thermal sensors in controlled greenhouse experiments. Differences in sensor-based responses between A. rolfsii-infected and non-infected plants were detected 0 to 1 day after observation of foliar disease symptoms. In addition, spectral responses of peanut to the infection of A. rolfsii were more pronounced and consistent than thermal changes as the disease progressed. Objective 2 aimed to identify specific signatures of stem rot from reflectance data collected in Objective 1 utilizing a machine learning approach. Wavelengths around 505, 690, and 884 nm were repeatedly selected by different methods. The top 10 wavelengths identified by the recursive feature selection methods performed as well as all bands for the classification of healthy peanut plants and plants at different stages of disease development. Whereas the first two objectives focused on disease detection, Objective 3 focused on disease control and compared the properties of different fungicides that are labeled for stem rot control in peanut using a laboratory bioassay of detached peanut tissues. All of the foliar-applied fungicides evaluated provided inhibition of A. rolfsii for up to two weeks on plant tissues that received a direct application. Succinate dehydrogenase inhibitors provided less basipetal protection of stem tissues than quinone outside inhibitor or demethylation inhibitor fungicides. Overall, results of this research provide a foundation for developing sensor/drone-based methods that use disease-specific spectral indices for scouting in the field and for making fungicide application recommendations to manage stem rot of peanut and other soilborne diseases. / Doctor of Philosophy / Plant diseases are a major constraint to crop production worldwide. Developing effective and economical management strategies for these diseases, including selection of proper fungicide chemistries and making timely fungicide application, is dependent on the ability to accurately detect and diagnose their signs and/or symptoms prior to widespread development in a crop. Optical sensors combined with machine learning analysis are promising tools for automated crop disease detection, but research is still needed to optimize and validate methods for the detection of specific plant diseases. The overarching goal of this research was to use the peanut-stem rot plant disease system to identify and evaluate sensor-based technologies and different fungicide chemistries that can be utilized for the management of soilborne plant diseases. The specific objectives of this work were to 1) characterize the temporal progress of spectral and thermal responses of peanut to infection and colonization with Athelia rolfsii, the causal agent of peanut stem rot 2) identify optimal wavelengths to detect stem rot of peanut using hyperspectral sensor and machine learning, and 3) evaluate standard and newly registered peanut fungicides with different modes of action for stem rot control in peanuts using a laboratory bioassay. Results of this work demonstrate that spectral reflectance measurements are able to distinguish between diseased and healthy plants more consistently than thermal measurements. Several wavelengths were identified using machine learning approaches that can accurately differentiate between peanut plants with symptoms of stem rot and non-symptomatic plants. In addition, a new method was developed to select the top-ranked, non-redundant wavelengths with a custom distance. These selected wavelengths performed better than using all wavelengths, providing a basis for designing low-cost optical filters to specifically detect this disease. In the laboratory bioassay evaluation of fungicides, all of the foliar-applied fungicides provided inhibition of A. rolfsii for up to two weeks on leaf tissues that received a direct application. Percent inhibition of A. rolfsii decreased over time, and the activity of all fungicides decreased at a similar rate. Overall, the findings of this research provide a foundation for developing sensor-based methods for disease scouting and making fungicide application recommendations to manage stem rot of peanut and other soilborne diseases.

Orientador: Arlindo Leal Boiça Junior / Banca: Antonio Carlos Busoli / Banca: André Luiz Lourenção / Resumo: Este trabalho teve como objetivo avaliar possíveis fontes de resistência de cultivares de amendoim de hábitos de crescimento ereto e rasteiro, a Spodoptera frugiperda (J. E. Smith, 1797) (Lepidoptera: Noctuidae) dos tipos não-preferência para oviposição, alimentação (com e sem chance de escolha) e antibiose. Os experimentos foram conduzidos em laboratório, sob condições controladas de temperatura (25 ± 2°C), umidade (60 ± 10%) e fotofase (12 horas). Foram utilizadas cultivares de amendoim de hábitos de crescimento ereto (IAC 5, IAC 8112, IAC 22 e IAC Tatu ST) e rasteiro (IAC 503, IAC 505, IAC 147, IAC 125, IAC Caiapó e IAC Runner 886). Estas cultivares foram avaliadas separadamente devido ao hábito de crescimento do material em todos os testes. Os testes de não-preferência para oviposição foram realizados com adultos recém-emergidos, os quais foram alimentados com solução de mel a 10%, permanecendo nas gaiolas por quatro dias até o início das avaliações. Estas consistiram na quantificação do número de ovos e posturas, com posterior cálculo do número de ovos por postura. Para os testes de não-preferência para alimentação foram colocados discos foliares das cultivares em placas de Petri, liberando uma lagarta de terceiro ínstar por cultivar. Avaliou-se a atratividade a 1; 5; 10; 15; 30; 60; 120; 360; 720; 1440 minutos, contando o número de lagartas que se alimentavam nas cultivares e, ao término do experimento, quantificou-se a área foliar consumida por cultivar. No teste de antibiose, além da identificação de cultivares de amendoim resistentes a S. frugiperda, determinaram-se, também, os graus de resistência através da análise multivariada. As cultivares foram semeadas em campo. Lagartas de primeiro ínstar foram individualizadas em placas de Petri forradas com papel filtro umedecido. Diariamente, foram fornecidos folíolos novos. Avaliaram-se... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This study aimed to evaluate possible sources of resistance of peanut cultivars of the upright growth and runner growth habit, to Spodoptera frugiperda (J. E. Smith, 1797) (Lepidoptera: Noctuidae) by non-oviposition and non-feeding preference (tests choice and no-choice) and antibiosis. The experiments were conducted in laboratory under controlled conditions of temperature (25 ± 2°C), humidity (60 ± 10%) and photophase (12 hours). Peanut cultivars of upright growth habit (IAC 5, IAC 8112, IAC 22 and IAC Tatu ST) and runner growth habit (IAC 503, IAC 505, IAC 147, IAC 125, IAC Caiapó and IAC Runner 886) were evaluated. These cultivars were evaluated separately due to the material growth habit in all tests. Tests of non-oviposition preference were conducted with newly emerged adults, and they were fed with a 10% honey solution, remaining in the cages for four days until the start of evaluations. Evaluations consisted of quantifying the eggs and egg masses numbers, followed by calculation the number of eggs per egg masses. To perform non-feeding preference tests, leaves discs from different cultivars were placed in disposable Petri dishes followed by releasing of a third instar caterpillar for each cultivar. The attractiveness at 1; 5; 10; 15; 30; 60; 120; 360; 720 and 1,440 minutes was evaluated by counting the caterpillars number which were fed on cultivars, quantified the leaf area consumed by cultivar was evaluated at the end of the experiment. Additionally, identification of peanuts cultivars resistance to S. frugiperda, and the resistance degree was evaluated by multivariate analysis of the antibiosis test. The cultivars were planted in plots on the field. First instar larvae were placed individually in disposable Petri dishes plates, over a moistened filter paper. New leaflets were provided every day. The duration (days), weight (mg) and viability... (Complete abstract click electronic access below) / Mestre

Submitted by (ana.araujo@ufrpe.br) on 2017-02-17T12:38:37Z No. of bitstreams: 1 Jacqueline Wanessa de Lima Pereira.pdf: 684135 bytes, checksum: dc0f8da93d2685268558a2dc803e4044 (MD5) / Made available in DSpace on 2017-02-17T12:38:37Z (GMT). No. of bitstreams: 1 Jacqueline Wanessa de Lima Pereira.pdf: 684135 bytes, checksum: dc0f8da93d2685268558a2dc803e4044 (MD5) Previous issue date: 2010-07-07 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / Peanut is one of the most cultivated oily in the world. For countries of semi-arid climate, as Brazil, for example, the peanut is an important alternative to farming due to the low water requirement during the cycle and adaptation to environments of high temperature and solar radiation. Despite the tolerance to low water availability, peanuts’ requirements are not the same over the cycle. Water shortage during the reproductive phase directly affects the formation and filling of pods, even in cultivars notoriously resistant to water deficit. According to some authors, which makes the peanut plant tolerant to environmental adversities are the morphological and physiological mechanisms that maintain the plant turgidity, even under low water availability conditions. Among those are cited changes in water ratios (stomatal behavior and osmotic adjustment) and the expansion of the root system for deeper and wetter soil areas. Faced with this adaptability, understanding the role of water deficit during the production cycle of culture is essential for adopting management strategies that enable secure production in areas prone to drought. In this work, four peanut genotypes of different growth habits were subjected to 21 days of water stress in a greenhouse. The planting was performed in pots containing sandy-loam texture soil, previously limed and fertilized. The experimental design was randomized with a bi-factorial 4x2 scheme (4 genotypes x 2 water treatments) with 10 repetitions. the water treatment were control (daily irrigation) and stress (irrigation suspension). The variables evaluated were difusive resistance, transpiration, leaf water potential, relative water content, proline content, chlorophyll content, root length, dry weight of pods, harvest index and stress tolerance index (STI). Under stress conditions, stomatal behavior was changed from the second week, when all genotypes significantly increased abaxial surface diffusive resistance and reduced sweating, highlighting the isoline LBM Branco Moita/08. The water potential of all genotypes was significantly reduced, being more expressive in isolines LBM-Branco Moita/08 and LBR-Branco Rasteiro/08 reaching more negative values. The LBM-Branco Moita/08 also had higher levels of proline and along with a BR 1 had the greatest expansion of the root system as adaptive way. In the production aspect, the LBM-Branco Moita/08 revealed the lowest reductions in weight of pods and harvest index when subjected to water deficit. Regarding the STI, values obtained with the cv. BR1 confirm its suitability for management in semi-arid environments; the strains LBR-Branco Rasteiro/08 and LBM-Branco Moita/08 also showed significant production performance in environments with water restriction. / O amendoim é uma das oleaginosas mais cultivadas no mundo. Para os países de clima semi-árido, o Brasil, por exemplo, o amendoim é uma importante alternativa para a agricultura devido à baixa exigência hídrica durante o ciclo e adaptação aos ambientes com altas temperaturas e radiação solar. Apesar da tolerância à baixa disponibilidade hídrica, as exigências do amendoim não são as mesmas ao longo do ciclo. A escassez de água durante a fase reprodutiva afeta diretamente a formação e o enchimento das vagens, mesmo em cultivares notoriamente resistentes ao déficit hídrico. Segundo alguns autores, o que torna a planta do amendoim tolerante às adversidades ambientais são os mecanismos morfológicos e fisiológicos que mantêm a turgescência das plantas, mesmo sob condições de baixa disponibilidade de água. Entre as mudanças já estão em relações hídricas (comportamento estomático e ajustamento osmótico) e a expansão do sistema radicular para as áreas mais profundas e úmidas do solo. Confrontados com esta capacidade de adaptação, a compreensão do papel do déficit hídrico durante o ciclo produtivo da cultura é essencial para a adoção de estratégias de manejo que permitam uma produção segura em áreas propensas à seca. Neste trabalho, quatro genótipos de amendoim de diferentes hábitos de crescimento foram submetidos a 21 dias de estresse hídrico em casa de vegetação. O plantio foi realizado em vasos contendo solo de textura franco-arenosa, previamente corrigido e adubado. O delineamento experimental foi inteiramente casualizado, com um esquema bi-fatorial 4x2 (4 genótipos x 2 tratamentos de água), com 10 repetições. Os tratamentos hídricos foram: controle (rega diária) e estresse (suspensão de rega). As variáveis avaliadas foram: resistência difusiva, transpiração, potencial hídrico, teor relativo de água, teor de prolina, teor de clorofila, comprimento radicular, peso seco das vagens, índice de colheita e índice de tolerância ao stress (STI). Sob condições de estresse, comportamento estomático foi alterado a partir da segunda semana, quando todos os genótipos aumentaram significativamente a resistência difusiva da superfície abaxial e reduziram a transpiração, destacando a isolinha LBM-Branco Moita/08. O potencial de água de todos os genótipos foi significativamente reduzido, sendo mais expressivos em isolinhas LBM-Branco Moita/08 e LBR-Branco Rasteiro/08 atingindo valores mais negativos. A LBM-Branco Moita/08 também apresentou elevado acúmulo de prolina e, juntamente com um BR 1 teve a maior expansão do sistema radicular como forma de adaptação. No aspecto de produção, a LBM-Branco Moita/08 revelou as menores reduções no peso das vagens e índice de colheita, quando submetida ao déficit hídrico. Quanto ao STI, os valores obtidos com a cv. BR1 confirmar a sua aptidão para o manejo em ambientes semi-árido, as isolinhas LBR-Branco Rasteiro/08 e LBM-Branco Moita/08 também apresentaram desempenho significativo de produção em ambientes com restrição hídrica.

Groundnut or peanut (Arachis hypogaea L.) is an important legume cultivated in several developing countries in the tropics and subtropics. It plays a significant role as a food crop in regions with alarming population growth rates. The disease “peanut clump”, which is caused by viruses in the genus Pecluvirus, has been reported from India and from several countries of West Africa. In India, the causal agent is the Indian peanut clump virus (IPCV), which is transmitted by a soil-borne root parasite, Polymyxa graminis. The virus is also transmitted by infected seed and so far no economical method of control has been found. Therefore efforts have been concentrated on understanding the epidemiology of peanut clump disease with the aim of devising cultural methods of control. The work addressed in this thesis describes how investigation in various aspects of clump disease epidemiology, including identification of alternative hosts of the virus and the vector, and of factors that contribute to survival and spread of inoculum, has led to formulation of simple cultural practices that could reduce disease incidence.

Groundnut or peanut (Arachis hypogaea L.) is an important legume cultivated in several developing countries in the tropics and subtropics. It plays a significant role as a food crop in regions with alarming population growth rates. The disease “peanut clump”, which is caused by viruses in the genus Pecluvirus, has been reported from India and from several countries of West Africa. In India, the causal agent is the Indian peanut clump virus (IPCV), which is transmitted by a soil-borne root parasite, Polymyxa graminis. The virus is also transmitted by infected seed and so far no economical method of control has been found. Therefore efforts have been concentrated on understanding the epidemiology of peanut clump disease with the aim of devising cultural methods of control. The work addressed in this thesis describes how investigation in various aspects of clump disease epidemiology, including identification of alternative hosts of the virus and the vector, and of factors that contribute to survival and spread of inoculum, has led to formulation of simple cultural practices that could reduce disease incidence.

Made available in DSpace on 2014-06-11T19:25:18Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-02-16Bitstream added on 2014-06-13T18:53:09Z : No. of bitstreams: 1 campos_ap_me_jabo.pdf: 283557 bytes, checksum: 460ed3df0cf7a95babadb02e25a47755 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Este trabalho teve como objetivo avaliar possíveis fontes de resistência de cultivares de amendoim de hábitos de crescimento ereto e rasteiro, a Spodoptera frugiperda (J. E. Smith, 1797) (Lepidoptera: Noctuidae) dos tipos não-preferência para oviposição, alimentação (com e sem chance de escolha) e antibiose. Os experimentos foram conduzidos em laboratório, sob condições controladas de temperatura (25 ± 2°C), umidade (60 ± 10%) e fotofase (12 horas). Foram utilizadas cultivares de amendoim de hábitos de crescimento ereto (IAC 5, IAC 8112, IAC 22 e IAC Tatu ST) e rasteiro (IAC 503, IAC 505, IAC 147, IAC 125, IAC Caiapó e IAC Runner 886). Estas cultivares foram avaliadas separadamente devido ao hábito de crescimento do material em todos os testes. Os testes de não-preferência para oviposição foram realizados com adultos recém-emergidos, os quais foram alimentados com solução de mel a 10%, permanecendo nas gaiolas por quatro dias até o início das avaliações. Estas consistiram na quantificação do número de ovos e posturas, com posterior cálculo do número de ovos por postura. Para os testes de não-preferência para alimentação foram colocados discos foliares das cultivares em placas de Petri, liberando uma lagarta de terceiro ínstar por cultivar. Avaliou-se a atratividade a 1; 5; 10; 15; 30; 60; 120; 360; 720; 1440 minutos, contando o número de lagartas que se alimentavam nas cultivares e, ao término do experimento, quantificou-se a área foliar consumida por cultivar. No teste de antibiose, além da identificação de cultivares de amendoim resistentes a S. frugiperda, determinaram-se, também, os graus de resistência através da análise multivariada. As cultivares foram semeadas em campo. Lagartas de primeiro ínstar foram individualizadas em placas de Petri forradas com papel filtro umedecido. Diariamente, foram fornecidos folíolos novos. Avaliaram-se... / This study aimed to evaluate possible sources of resistance of peanut cultivars of the upright growth and runner growth habit, to Spodoptera frugiperda (J. E. Smith, 1797) (Lepidoptera: Noctuidae) by non-oviposition and non-feeding preference (tests choice and no-choice) and antibiosis. The experiments were conducted in laboratory under controlled conditions of temperature (25 ± 2°C), humidity (60 ± 10%) and photophase (12 hours). Peanut cultivars of upright growth habit (IAC 5, IAC 8112, IAC 22 and IAC Tatu ST) and runner growth habit (IAC 503, IAC 505, IAC 147, IAC 125, IAC Caiapó and IAC Runner 886) were evaluated. These cultivars were evaluated separately due to the material growth habit in all tests. Tests of non-oviposition preference were conducted with newly emerged adults, and they were fed with a 10% honey solution, remaining in the cages for four days until the start of evaluations. Evaluations consisted of quantifying the eggs and egg masses numbers, followed by calculation the number of eggs per egg masses. To perform non-feeding preference tests, leaves discs from different cultivars were placed in disposable Petri dishes followed by releasing of a third instar caterpillar for each cultivar. The attractiveness at 1; 5; 10; 15; 30; 60; 120; 360; 720 and 1,440 minutes was evaluated by counting the caterpillars number which were fed on cultivars, quantified the leaf area consumed by cultivar was evaluated at the end of the experiment. Additionally, identification of peanuts cultivars resistance to S. frugiperda, and the resistance degree was evaluated by multivariate analysis of the antibiosis test. The cultivars were planted in plots on the field. First instar larvae were placed individually in disposable Petri dishes plates, over a moistened filter paper. New leaflets were provided every day. The duration (days), weight (mg) and viability... (Complete abstract click electronic access below)

Resumo: O amendoinzeiro (Arachis hypogaea L.) tem o tripes do prateamento Enneothrips flavens como praga limitante à sua produção. O controle desse inseto atualmente é realizado com inseticidas convencionais, entretanto, a integração de táticas de controle poderá proporcionar uma solução mais estável e duradoura para o controle desta praga na cultura. Este trabalho teve por objetivo estudar o efeito de cultivares, espaçamentos e modos de aplicação de inseticidas sobre o tripes do prateamento E. flavens e seus reflexos na produção do amendoinzeiro. Os experimentos foram conduzidos na Fazenda de Ensino, Pesquisa e Extensão - FEPE/UNESP, localizada no município de Selvíria-MS. O primeiro experimento foi instalado na época da seca com semeadura realizada em 17/02/2004, no delineamento em blocos casualizados, com parcelas subdivididas, num esquema fatorial 2x2x4 representado por espaçamentos (0,70 e 0,90 m entre linhas), cultivares de crescimento rasteiro (IAC-Caiapó e Tégua) e modos de aplicação de inseticidas (1- granulado no solo + 8 pulverizações foliares; 2- tratamento de sementes; 3- 9 pulverizações foliares e 4- testemunha, sem controle). O segundo experimento foi instalado na época das águas com semeadura em 23/11/2004, no delineamento em blocos casualizados, com parcelas subdivididas, num esquema fatorial 2x2x3 representado por espaçamentos (0,70 e 0,90 m entre linhas), cultivares de crescimento rasteiro (IAC-Caiapó e IAC-886) e modos de aplicação de inseticidas (1-tratamento de sementes + 5 pulverizações foliares; 2- 6 pulverizações foliares e 3- testemunha, sem controle). Nas avaliações foram realizadas contagens de adultos e de ninfas do tripes em 10 folíolos fechados ou semi-abertos por parcela; para avaliar os sintomas de injúrias causadas pelos tripes no limbo foliar, utilizou-se uma escala visual de... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The peanut (Arachis hypogaea L.) has the silvery thrips Enneothrips flavens as the limiting pest of yield. Nowadays, the control of this insect is accomplished with conventional insecticides, however the integration of control taticals will be able to provide a stable and lasting solution for the control of this pest in the culture. This work has the goal of studying the effect of cultivars, spacings and insecticides application manners on the population of silvery thrips E. flavens, and its reflexes on yield. The experiments were conducted in the Fazenda de Ensino, Pesquisa e Extensão - FEPE/UNESP, located in the Selvíria-MS. The first experiment was installed at that time of the drought with sowing accomplished in 17/02/2004, in the design in randomized blocks, with subdivided plots, in the factorial outline 2x2x4 represented by spacings (0,70 and 0,90 m between lines), groundnut growth cultivars (IACCaiapó and Tégua) and insecticides application manners (1- granulated in the soil + 8 leaf insecticide applications; 2- seeds treatment; 3- 9 leaf insecticide applications and 4-control, without control). The second experiment was installed at the time of waters with sowing accomplished in 23/11/2004, in the design in randomized blocks, with subdivided plots, in the factorial outline 2x2x3 represented by spacings (0,70 and 0,90 m between lines), groundnut growth cultivars (IAC-Caiapó and IAC-886) and insecticides application manners (1-seeds treatment + 5 leaf insecticide applications, 2- 6 leaf insecticide applications and 3-control, without control). In the evaluations, thrips adults and nymphs were counted in 10 leaflets closed or half-open for plots; to evaluate the injury symptoms caused by thrips in the leaf blade it was used visual scale of notes from 1 to 9. The peanut yield was evaluated in 4 m of the two central lines... (Complete abstract, access undermentioned electronic address) / Orientador: Alcebíades Ribeiro Campos / Coorientador: Valter Veriano Valério Filho / Coorientador: Edson Lazarini / Banca: Marco Eustaquio de Sa / Banca: Edson Luiz Lopes Baldin / Mestre

The bulk of Zimbabwe’s groundnut (Arachis hypogaea L.) crop is grown on sandy soils in the smallholder sector where sustainable production is hindered by acid soil infertility. The study goal was thus to examine the effects of soil acidity amelioration by four Ca-containing materials on nutrient composition, vegetative and reproductive growth, and quality of groundnut to formulate ameliorative strategies to improve productivity on acid soils. The effectiveness of calcitic lime (CL), dolomitic lime (DL), gypsum (G) and single superphosphate (SSP) in ameliorating soil acidity was determined in field experiments conducted for three seasons at two Research Stations in Zimbabwe, and in greenhouse experiments conducted for two seasons at Harare Research Station. In both experiments the lime application rates were from 0 to 4000 kg ha-1, while G application rates were from 0 to 3450 kg ha-1, and those of SSP were from 0 to 250 kg ha-1. Calcitic or dolomitic lime applied at 2000 or 4000 kg ha-1 increased soil pH and Ca and Mg contents in the pod and root zones, and in the plant material. Gypsum and SSP applications at 200 and 250 kg ha-1 respectively, had no significant effects on pH, Ca and Mg levels, but when applied in equivalent amounts of Ca as lime, gypsum improved soil Ca status. Effects of the four ameliorants on the N, P and K levels in the soils and in plant material were generally neither significant nor consistent. The direct and residual benefits of application of CL or DL were manifested in improved plant stands, better growth, nodulation, productivity and quality of groundnut. Gypsum applied at equal Ca rates as CL or DL was the superior Ca-source in improving pod and kernel quality. By the end of the third season, the increases in cumulative kernel yields due to application of 4000 kg ha-1 lime over non-application were up to 319%. The major growth-limiting factors on the studied acid soils were identified as deficiencies of Ca and Mg, and low pH per se. In a field experiment conducted to evaluate the tolerance of 15 groundnut genotypes to soil acidity, significant differences in yield and nutrient utilization efficiency of the genotypes were observed, implying that productivity on acid soils can be increased by growing genotypes efficient in uptake and utilization of nutrients. Results from greenhouse and growth chamber studies conducted to examine the effects of pH (3.0 - 7.0) and its interactions with Ca (0 - 2000 µM Ca) on early seedling growth and reproductive growth of groundnut indicated that low pH per se has a major detrimental impact on seedling survival, growth, pod formation, yield and quality of groundnut, but not on germination. The adverse effects of low pH were more pronounced in the absence of Ca, and became progressively less as the solution Ca concentrations increased. Further experiments showed that it is feasible to mitigate the adverse effects of soil acidity on groundnut germination and seedling survival by pelleting seeds with small amounts of CaCO3, or priming with CaSO4. / Dissertation (PhD (Plant Production: Agronomy))--University of Pretoria, 2003. / Plant Production and Soil Science / unrestricted

Les femmes, élément central de la vie économique et sociale, jouent un rôle important dans la société sénégalaise. Dans cette thèse nous avons voulu mettre en valeur le dynamisme et l'héroïsme quotidien des femmes sénégalaises, de la région de Diourbel en particulier. Ce dynamisme est étudié à travers leurs activités quotidiennes, la recherche d’autonomie économique, et leurs associations. Diourbel était le centre du bassin arachidier dont les contours se sont modifiés avec le développement de l’arachide et les mutations du milieu. Ces dernières ne manquent pas de conséquences sur la vie des populations, des femmes en particulier qui doivent trouver des moyens pour s'adapter et faire face au départ des hommes et à l'accroissement des charges familiales. En partant des difficultés multidimensionnelles du vieux bassin arachidier, étudiées à travers la mauvaise articulation des politiques agricoles coloniales et nationales, qui ont participé à la crise agricole qui a été aggravée par la combinaison de facteurs anthropiques et physiques, nous avons rappelé le rôle actif des femmes dans la sphère familiale, d’abord et rendu visibles les activités collectives ou individuelles qu’elles ont déployées. Ensuite, les associations féminines se caractérisent par leur diversité dans leurs formes, leurs objectifs, leurs moyens et leur tissu relationnel. Devant les mutations observées, elles sont devenues incontournables et sont perçues comme des réponses féminines. Devant tous ces changements, les femmes du Baol ont leur mot à dire et leur force à apporter pour que l'édifice familial et social reste debout. Face aux efforts déployés par les femmes, des perspectives s'ouvrent. / Women play an important role in Senegalese society occupying a central position in the economic and social life of the nation. In this thesis we will highlight the dynamism and the heroic levels of energy that Senegalese women invest in their daily tasks. Our observations will focus on the region of Diourbel. Their dynamism will be assessed throughout their daily activities, including their efforts to reach an economic self-sufficiency and their work within organizations. Diourbel used to be the center of the groundnut (peanut) basin. The borders of this region changed with shifts in the techniques of peanut farming and modifications in the environment. The latter has had effects on the living conditions of the inhabitants, particularly on women who had to find ways to adapt to such challenges as men migrating and increases in the cost of running a household. We highlight the active role women play within the family, demonstrating their collective and individual activities. These details are presented within the context of such multidimensional issues facing the old groundnut basin, as the incoherence of the colonial and national agricultural policies which have been aggravated by the combination of anthropogenic and physical factors. In addition the women´s associations are characterized by their variety, objectives, methods and internal relationships. The analysis will show them to be an inevitable feminine response to the observed social, economic and environmental changes. Women of Baol play a substantial role and exert significant influence on the process of maintaining both the social and familiar structures of their communities. As women carry out these efforts, our analysis will reveal how these efforts generate new perspectives.