CIAT Theses Supervised
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Item Evaluación productiva y potencial de mitigación de la producción de metano del pasto (Urochloa híbrido cv. CIAT BRO2/1752) en sistemas silvopastoriles mejorados en el trópico húmedo de Costa Rica(Report, 2020) David Lagos, Kenia Lizeth; Villanueva, Cristóbal; Ibrahim, Mohamed N.M.; Pezo, Danilo A.; Hoek, Rein van derItem Desarrollo de un protocolo para la regeneración de plantas a partir de protoplastos aislados de estructuras embriogénicas organizadas de yuca (Manihot esculenta Crantz)(Thesis, 2019) Arciniegas Vega, Juan Pablo; Chavarraga Aguirre, Paul; Pachón García, JorgeLa yuca (Manihot esculenta Crantz) se caracteriza por ser una raíz con un alto contenido de almidón que tiene usos alimenticios e industriales. Debido a esto, es una especie de interés para mejoramiento genético mediante técnicas biotecnológicas como la edición de genomas. Estas técnicas son necesarias ya que la manipulación genética en yuca presenta barreras por ser una planta altamente heterocigota, lo que hace difícil la segregación de transgenes sin que se pierdan características de genotipos establecidos comercialmente en el proceso. Es por esto que es crucial el desarrollo de métodos de edición libres de ADN. Para este fin, se propuso desarrollar un protocolo de regeneración de plantas a partir de protoplastos aislados de estructuras embriogénicas organizadas. Los aislamientos tuvieron un rendimiento de 6,47 x 106 células/gramo de pesos fresco y una viabilidad del 89,5%. Se probaron dos sistemas de cultivo, pero se optó por las gotas de agarosa por generar estructuras con una forma tridimensional definida. Se comparó el efecto del genotipo, densidad hormonal y densidad celular inicial y se evaluó el número de microcolonias producidos. Los genotipos no mostraron diferencias significativas, contrario a la combinación hormonal y la densidad celular inicial. La combinación de factores con mejores rendimientos fue 2 x 105 células/ml en medio con 2 mg/L de kinetina, 1 mg/L de NAA y 1 mg/L BAP. Adicional a esto, en esta combinación de factores se evidenció formación y crecimiento de microcallos del genotipo TMS 60444 de forma esporádica. Para mejorar la frecuencia de formación de microcallos y la subsecuente embriogénesis somática se sugiere hacer cultivos con protoplastos embebidos en agarosa con medio suplementado con 2 mg/L de kinetina, 1 mg/L de NAA y 1 mg/L BAP, utilizar una densidad celular inicial 2 x 105 células/ml o superior y agregar otros factores como células nodrizas o proteína LEC2.Item Machine learning and big data techniques for satellite-based rice phenology(Thesis, 2019-08) Aguilar-Ariza, AndrésNew sources of information are required to support rice production decisions. To cope with this challenge, studies have found practical applications on mapping rice using remote sensing techniques. This study attempts to implement a methodology aimed at monitoring rice phenology using optical satellite data. The relationship between rice phenology and reflectance metrics was explored at two levels: growth stages and biophysical modifications caused by diseases. Two optical moderate-resolution missions were combined to detect growth phases. Three machine-learning approaches (random forest, support vector machine, and gradient boosting trees) were trained with multitemporal NDVI data. Analytics from validation showed that the algorithms were able to estimate rice phases with performances above 0.94 in f-1 score. Tested models yielded an overall accuracy of 71.8%, 71.2%, 60.9% and 94.7% for vegetative, reproductive, ripening and harvested categories. A second exploration was carried out by combining Sentinel-2 data and ground-based information about rice disease incidence. K-means clustering was used to map rice biophysical changes across reproductive and ripening phases. The findings ascertained the remote sensing capabilities to create new information about rice for Colombia’s conditions.Item Community based agricultural extension as a participatory organizational learning process in producer organizations: lessons from a case study in rural Colombia(Thesis, 2019-10-10) Hering, Johannes; Dentoni, Domenico; Carraresi, LauraCommunity-based agricultural extension (CBAE) facilitates the implementation of knowledge in rural communities, often making use of existing organizational structures. Organizational Learning (OL) and Knowledge Management (KM) theory generally explain the mechanisms of the introduction and implementation of knowledge in organizations and how to create a learning culture within them. OL and KM both deal with the adaptation- and learning-process of organizations and could therefore benefit from each other’s body of literature. By carrying out a mix of inductive and deductive analysis of the co-creation process of a CBAE-platform in a Colombian livestock producer organization, this research establishes a link between CBAE and OL/KM. Potentials and limitations of interdisciplinary thinking between the two fields are identified. Based on a qualitative analysis, a knowledge framework that was key to the observed learning processes on ground is evolved. This framework follows a similar logic as suggested in OL/KM theory, where the notions acquire, create, apply, share and store knowledge lie at the center of organizational learning. This analysis suggests adding the themes network, facilitation and participation to this concept. Results indicate that along all layers and stages of the project’s development, the identified knowledge framework provided an underlying structure for the process of integrating knowledge into the organizational memory of the producer organization. It can be concluded that CBAE projects should aim for institutionalizing knowledge by making use of existing organizational structures. OL/KM frameworks provide help to structure and explain this process, if adapted to the context of agricultural extension. The participatory character of CBAE could in turn contribute to OL/KM theory by supporting the process of creating a learning culture in organizations outside the context of agricultural extension. To make optimal use of existing knowledge, a strong practical and theoretical interdisciplinary perspective in the fields of CBAE and OL/KM is recommended.Item Multispectral image quality assessment to enhance classification rates of rice hoja blanca virus (RHBV) in rice breeding programs.(Thesis, 2018) Delgado Fajardo, Cristhian CamiloLos métodos automáticos para la detección de enfermedades de las plantas de arroz son vitales para la protección de cultivos contra los agentes de infecciones virales, como el virus Hoja Blanca (hoja blanca) (RHBV), que es transmitido por el vector plano Thagosodes orizicolus y prevalece en América Latina causando severas pérdidas de rendimiento en el arroz. Dado que los programas de mejoramiento de arroz clásico se basan en costosos y lentos protocolos de detección, existe la necesidad de alternativas como la selección de variedades de arroz a través de fenotipos basados en imágenes. Las imágenes multiespectrales aéreas proporcionan una forma rápida y no destructiva de escanear plantas en regiones enfermas y han sido utilizadas por varios investigadores para clasificar los niveles de síntomas en el perfil espectral de una planta. Sin embargo, las imágenes están sujetas a distorsiones durante la adquisición, compresión, transmisión y procesamiento. Estos deterioros de imagen afectan el rendimiento de los algoritmos de clasificación que apoyan la búsqueda de variedades de arroz resistentes. El objetivo de esta investigación es analizar y corregir el impacto de las distorsiones de imágenes multiespectrales en las tasas de clasificación / detección de los programas de mejoramiento de arroz RHBV. Comparamos la calidad de imagen de dos ortomosaicos. Métodos de mezcla (algoritmos de mezcla de mosaico y promedio) y un algoritmo de compresión Lempel-Ziv-Welch (LZW). Realizamos análisis comparativos de rendimiento de tres algoritmos supervisados de aprendizaje automático en tres escenarios diferentes: imágenes prístinas, imágenes borrosas y Compresión LZW. La Máquina de vectores de soporte (SVM), Random Forest (RF) y k-Nearest Los métodos de los vecinos (kNN) no fueron significativamente diferentes en su capacidad para separar a los susceptibles de clases no susceptibles, pero los mejores clasificadores SVM mostraron una mejor sensibilidad en las tasas de 0,74 (SVM), 0,71 (RF) y 0,68 (KNN). El rendimiento de todos los algoritmos ML fue negativo. Afectado por la distorsión de desenfoque, pero no fue afectado por la distorsión LZW. La calidad de las imágenes multiespectrales se evaluó para detectar distorsión borrosa en multiespectrales. imágenes para cambiar a un modelo ML pre-entrenado SVM (0.77) bajo esta condición de distorsión. La evaluación se llevó a cabo en diferentes bandas espectrales (azul, verde, rojo, borde rojo e infrarrojo cercano) y la evaluación de la banda de infrarrojo cercano (NIR) proporcionó una mejor predicción de la calidad de la tarea de clasificación.Item Ex-ante impact assessment of feed interventions in smallholder dairy production systems in the Southern Highlands of Tanzania(Thesis, 2018) Osele, VivienAn increasing demand for animal products has been observed in developing countries due to a high rise in population and increasing buying power. In developing countries such as Tanzania over 70% of meat and milk are generated in mixed crop-livestock systems that provide livelihood for most rural poor people. Simultaneously animal keeping is related to an undesirable environmental impact. Therefore, taking into account both, the positive effects on food security and livelihoods alongside with the potential to minimize environmental impacts, becomes crucial. This thesis focuses on oppor-tunities to sustainably increase livestock production by optimization of quality and quantity of feeds. The project gives insights on how dairy farmers can directly benefit from climate smart feeding op-tions, by enhanced production, while minimizing the negative environmental impacts of production. We focused on 10 case study farms in the Southern Highland of Tanzania. Each farmer was given a selection of improved forage seeds to be planted on their farm. Dairy cow and bio-physical farm per-formance before the introduction of the forages were then compared ex-ante with introduced forag-es scenarios. To quantify impacts of the forage plots on farm level and animal level two models FarmDESIGN and RUMINANT were employed. Through participatory scenario finding with farmers we selected a best bet scenario with a 10% milk increase goal. This scenario was realistic in terms of land allocated for forages and the impact on milk increase was visible especially if forage was pri-marily fed in the dry season. The scenario with 10% milk increase through feeding introduced forages had an overall positive effect on productivity while reducing emission intensity. Introduced forages had an indirect positive impact on income, especially when the new forage plot was planted on un-cultivated land and thus hardly any opportunity costs occurred. Furthermore, time spent for fetching natural grasses in the dry season was reduced. Additionally, the leguminous plants amongst the in-troduced forages promoted an overall increase of nitrogen balance and also GHG emission intensity per liter of milk was reduce by over 5%. We concluded that introducing forages is indeed a feasible way of sustainable intensification, both in terms of environmental efficiency and economic benefits.Item An assessment of heat stress status in pigs and adaptation options in Lira district Uganda(Thesis, 2018) Zaake, PaulThere is limited attention to impacts of climate change on pigs in Uganda by stakeholders despite the potential vulnerability of pigs to climate change, especially heat stress. Pigs are very sensitive to heat stress as they do not have functioning sweat glands (as other livestock species do) and have small lungs which reduces their ability to disseminate heat by panting. The objectives of the study were to determine the heat stress status in pigs, factors influencing heat stress and explore the heat-stress adaptation options towards better pig production in Lira District, Uganda. Lira was selected because of low pig density, high poverty level and expected heat stress throughout the year in the district. The data including management systems, age, color, breeds, body/skin temperature, rectal temperature and others were collected from 104 households and 259 pigs during the hot months in Ojwina and Barr sub-counties- Lira district. More data on adaptation options were collected during the four gender disaggregated focus group discussions. 63.46 % of the respondents were female and 36.54% of respondents were male. Majority of the respondents during the household survey were from Barr sub-county (56%) and the remainder (44%) were from Ojwina sub-county, which were the rural area and urban area respectively. Rectal temperature (RT=39.06°C ±0.83°C) and body/skin temperature (ST=36.32°C ±2 °C) were the key heat stress indicators (dependent variables) as have been used by other researchers. According to the farmers, 48.45% of the pigs had no heat stress, 51.55% of the pigs were heat stressed and these groups were significantly different (p<0.01). There was a statistically significant correlation between heat stress status and heat stress action (p<0.01). The results showed that rectal temperature is influenced by the external temperature humidity index, pig management system, pig category, color, heart girth, water quantity given during day in dry season, pig’s body condition score, and time of the day. The results showed that skin temperature is significantly influenced by external temperature humidity index, pig category, pig management, time of the day and body condition score. According to the farmers, the most preferred adaptation options (using a rating scale of 1 to 5 where 1 was the least preferred option and 5 the highest preferred) to heat stress included: constructing a high pig pen roof and allow easy air flow (Average Preference Rating =APR=4.75); pouring water on the pigs (APR=4.63); allowing pigs to swim/wallow (APR=4.48). Allowing pigs to rest by not disturbing them (APR=4.38); providing more water for drinking to pigs (APR=4.33); reducing stocking density (APR=4.30); constructing well-designed pigsty (APR=4.25); providing shade (APR=4.07); mixing/addition of water to the feed (APR=4.07); and constructing grass thatched pigsty (APR=4.00). The medium preferred adaptation options to heat stress included feeding pigs during the coolest time of the day (APR=3.75); pouring water on the ground/floor (APR=3.73); leaving door of the pigpen open for more air circulation (APR=2.45); and chopping feeds into small particles (APR=2.25). The least preferred adaptation options to heat stress included giving salt to replace lost electrolytes (APR=1.25); and addition of fans (APR=1.03). Between 4.81% and 100% of survey-respondents who had heard of an adaptation-option had applied it for all adaptations options. The percentage of the female members of the household making decisions and providing labour for particular adaptation options was higher relative to the male household members and non-household members; except for the adaptation option of constructing the pig houses. To adapt to heat stress, pig shelters should be designed to minimize overcrowding while incorporating ways to improve air flow and evaporative cooling by having a high roof, and / or using grass. Availing water ad lib or even mixing water in the feed is critical to reducing heat stress. Pig swimming/wallowing and pouring water on the pigskin are some of the interventions farmers may use. However, there is need for more awareness about the suitable adaptation option to heat stress while putting the local context into consideration.Item Model-Based Assessment of Grazing Impact on Soil Organic Carbon Stocks and Dynamics of a Kenyan Rangeland(Thesis, 2019) Kuntu-Blankson, KateAs the largest terrestrial ecosystem carbon (C) sink, soils store about 2500 Pg C in the top 1 m depth. Rangelands make up around 40 % of global land surface and contain about 30 % of global terrestrial soil organic carbon (SOC). Grazing is the most important use of rangelands worldwide which when managed properly, can make rangelands potential sequesters of significant amounts of previously lost C. This will not only offset anthropogenic C emissions and contribute to climate change (CC) mitigation but also improve soil quality and productivity to ensure food security in the worlds’ poorest regions. Rangelands in East Africa cover 75 % of the total land area, but despite the importance outlined, little scientific studies have been carried out to quantify the effects of grazing management on SOC sequestration potentials and there exists a knowledge gap. The heterogeneous nature of rangelands worldwide makes it impossible to generalize grazing management recommendations across different regions as same studies have produced different results in comparable places. We aimed to investigate the long-term effect (30 years) of four grazing regimes on three selected sites under mid-future CC scenarios of the Representative Concentration Pathways (RCPs) 4.5 and 8.5 on SOC stocks of a rangeland in Southern Kenya. Heavy (HG) lead to SOC losses in all sites with the most loss of 206 kg C ha-1 observed on one sandy site “sand_light”. Moderate grazing (MG) increased SOC stocks in all three sites, the highest of 141 kg C ha-1 occurred at our clay site “clay_heavy”. RG (yearly rotation) and ALT (monthly rotation) caused SOC to increase only for the clay_heavy site. We observed small reductions in SOC stocks from the baseline scenario with a more negative impact of RCP4.5 than RCP8.5 but the observed differences were not dramatically different. The possible reasons for higher SOC stocks under RCP8.5 could be attributed to higher primary productivity of the C4 grassland under elevated CO2 and also more production of lignified plant materials that are less decomposable. We conclude that grazing management and soil texture will be the major factors controlling SOC stocks dynamics in the future as major differences was observed under those than under the CC scenarios.Item Modelo de simulación de yuca (Manihot esculenta Crantz) en el trópico(Thesis, 2018) Moreno Cadena, Leidy PatriciaActualmente pocos modelos representan el desarrollo fisiológico del cultivo de la yuca. DSSAT (Decision Support System for Agrotechnology Transfer), tiene un submodelo de yuca que simula el crecimiento del cultivo con diferentes fases fenológicas, sin tener en cuenta que la yuca es un cultivo indeterminado. El principal objetivo de este estudio fue desarrollar un nuevo modelo de yuca disponible en DSSAT que evite el concepto de fases fenológicas. El programa CurveExpert fue usado para definir los algoritmos, mientras que el software Simile evaluó el desempeño de la simulación de ecuaciones individuales y el programa FITEVAL calculó la bondad de ajuste del modelo. Adicionalmente, se realizó un análisis de sensibilidad del modelo considerando la estrategia de muestreo de Morris para definir los coeficientes del modelo. Como resultado, los nuevos algoritmos para ramificación, peso de nudo individual, tamaño potencial de hoja, tasa de formación de hojas y duración de las hojas, permiten un continuo crecimiento sin una etapa final del ciclo de cultivo. El modelo incluye un nuevo factor de estrés hídrico que afecta la germinación, formación de hojas, ramificación, área foliar e incremento en el peso de la planta; de acuerdo con el contenido de agua en el suelo. Este nuevo factor de estrés remplaza al estimado previamente como la fracción entre transpiración potencial y actual. El nuevo modelo muestra un buen ajuste bajo condiciones de estrés hídrico para el número de hojas, sin embargo, es necesario evaluar el umbral de estrés hídrico implementado. El peso de los tallos también registra un buen ajuste (coeficiente de eficiencia Nash & Sutcliffe, NSE=0.86; error cuadrático medio, RMSE= 1045). No obstante, el índice de área foliar (NSE =-0.28) y el peso de las hojas (NSE = -5.79) son sobrestimados por el modelo afectando el ajuste del rendimiento. El análisis de sensibilidad arrojó que 13 de los 16 parámetros afectan la variación en las salidas del modelo., //Abstract: Few crop models represent the physiological development of cassava. The current cassava model of DSSAT (Decision Support System for Agrotechnology Transfer) represents the development of a determinate crop with distinct phenological phases, which is not well-suited to cassava as an indeterminate crop. The main aim of this study was to develop a new cassava sub-model in DSSAT which replaces the concept of phenological phases. CurveExpert was used to define the algorithms, the software Simile evaluated the performance of the simulation of individual equations and the program FITEVAL assess the goodness of fit of the model. Additionally, a sensitivity and uncertainty analysis of the model was done considering Morris as sampling method. The algorithms for branching, individual node weight, potential leaf size, leaf appearance and leaf duration are developed considering a continuous growth with no fixed end of the growth cycle. The model also includes a new water stress factor according with the soil water content instead of the ratio between potential and actual transpiration, which affects the germination, leaf appearance, branching, leaf size and biomass increase. The new model shows a good fit under water stress for the number of leaves, however, it is necessary to evaluate the threshold used to define the water stress. The stem weight has a good fit (NSE=0.86, RMSE=1045). Nevertheless, the leaf area index (NSE =-0.28) and dry weight of leaves (NSE = -5.79) are overestimated by the model affecting the performance of the simulations of yield. The sensitivity analysis shows that 13 of the 16 coefficients are affecting the variability of the outputs of the model.Item Opiniones de los colaboradores del CIAT sobre las acciones de comunicación interna centradas en medios y contenidos que se han implementado en el último año en la sede principal Cali(Thesis, 2017) Pineda Ramos, Sylvia MariaEl presente trabajo consiste en conocer las opiniones de los colaboradores del CIAT sobre las acciones de comunicación interna centradas en medios y contenidos que se han implementado en el último año en la sede principal Cali. Como elemento central de la investigación, se desarrolló una encuesta a los colaboradores de la organización, con el fin de conocer la percepción frente a los medios internos y sus contenidos. Mediante los resultados obtenidos en la encuesta se pudo diagnosticar para proponer algunas acciones de mejora para el desarrollo de las estrategias de comunicación. El trabajo contiene aspectos preliminares al análisis de los resultados, como es el planteamiento del problema, la formulación del problema y la metodología utilizada en el desarrollo del trabajo que hace énfasis en el enfoque mixto. El trabajo a través del marco teórico reconoce autores como Jorge Aguilera, Maritza Cuervo, Idalberto Chiavenato, Carlos Fernández Collado, José Luis Sanchis, que permiten explicar el tema o han dado inicio a la teoría de investigación; estos a su vez otorgan una propuesta de solución al tema. La investigación se establece de acuerdo al objetivo central y los objetivos específicos. Como objetivo central se identificaron las opiniones de los colaboradores en cuanto a los medios internos y sus contenidos. En cuanto los objetivos específicos de la investigación, se establecieron las acciones de comunicación interna centradas en medios y contenidos que ha implementado el CIAT en el último año a los colaboradores de la sede principal de Cali; seguido por analizar la comunicación interna de medios y contenidos generados en el último año a la comunidad del CIAT y plantear posibles acciones de comunicación interna de medios y contenidos con base en las opiniones generadas en un diagnóstico comunicativo por parte de los colaboradores para posterior implementación en la organización.Item Geographic analysis for supporting conservation strategies of crop wild relatives. Thesis (Ph.D.)(Thesis, 2016-03) Castañeda Álvarez, Nora P.Crop wild relatives are important for agriculture due to the genetic richness they possess. They have been used in plant breeding to develop high yielding varieties; varieties with improved resistance to biotic and abiotic stresses, and enhanced nutritional content. Securing their conservation in the long-term is critical to enable the continuous development of crops’ varieties able to respond to future challenges. The work presented in this thesis is a contribution to the effort of understanding the ex situ conservation gaps of crop wild relatives, their expected response to climate change and their needs for conservation. Methods used in this thesis include species distribution modelling, gap analyses, a case study assessing the preliminary IUCN Red List categories, species distribution projections onto future climate change scenarios, and an estimation of the global value of crop wild relatives based on their likelihood of being used in plant breeding, and the contributions of their associated crops to human diets and agricultural production systems. The methods used here can be applied to more crop gene pools for global conservation planning, and can also be adapted for analysis at the regional and national level. The results presented here are being used to improve the conservation of the wild relatives of 29 crops.Item Uso de recombinantes de Phaseolus vulgaris L., P. coccineus L. y P. acutifolius A. Gray para mejorar la tolerancia del frijol común a diferentes tipos de estrés abiótico. Thesis (Ph.D.)(Thesis, 2015) Chaves-Barrantes, Néstor FelipeEl frijol común, Phaseolus vulgaris L., es una de las leguminosas de consumo humano más importantes a nivel mundial y su cultivo está principalmente en manos de pequeños productores, que enfrentan una serie de limitantes bióticas y abióticas para su producción. Dentro de las abióticas están el estrés por sequía, alta temperatura, deficiencia de fósforo y toxicidad por aluminio, que afectan entre el 30 y 73% de las áreas de siembra a nivel mundial y que se agravarán por los efectos del cambio climático. El objetivo general de este trabajo fue seleccionar líneas de frijol para la obtención de tolerancia a estrés abiótico por sequía, alta temperatura, bajo fósforo y toxicidad por aluminio, que puedan responder mejor a los efectos generados por el cambio climático y a las condiciones de los pequeños productores de frijol en los países tropicales. Para ello, inicialmente se caracterizó fisiológica y agronómicamente germoplasma promisorio y comercial de frijol por su tolerancia a sequía terminal y su desempeño en condiciones sin estrés durante el 2012 y 2013. Dentro de ese grupo, se incluyó a RCB 593, ALB 74 e INB 841, progenitores de las líneas SEF, generadas mediante el cruzamiento (ALB 74 x INB 841)F1 x RCB 593, donde ALB 74 aporta genes de P. coccineus L. e INB 841 genes de P. acutifolius A. Gray. Las líneas SEF fueron evaluadas y caracterizadas del 2012 al 2014 en condición sin estrés y por su tolerancia a sequía terminal en el Centro Internacional Agricultura Tropical (CIAT) en Palmira, Valle; por tolerancia a alta temperatura en Armero, Tolima, y por su respuesta a bajo fósforo y alto aluminio en Quilichao, Cauca. Dentro del germoplasma promisorio, SEN 56, BFS 29, NCB 226 y SER 16 mostraron mayores rendimientos en riego y sequía terminal que los testigos comerciales EAP 9510-77, DOR 390, Bribrí, Carioca y Calima. De las líneas con genes interespecíficos, SEF 10, SEF 16, SEF 42 y SEF 56 obtuvieron mejor rendimiento que EAP 9510-77 en sequía terminal. El mayor rendimiento en sequía terminal estuvo basado en una mayor formación de biomasa, aceleración de la madurez, mayor número de granos/m2, media geométrica superior y menor índice de susceptibilidad a sequía, así como en una mayor removilización de fotosintatos hacia los órganos reproductivos, expresada a través de mayores índices de cosecha, de cosecha de vainas, de partición a vainas y de llenado de grano. Los genotipos SEF 14, SEF 15, SEF 16 y SEF 60 son capaces de soportar un aumento de 3,8°C sobre la temperatura media nocturna límite para el cultivo (21°C), lo que permitiría mitigar el aumento de 2 a 5°C en la temperatura media anual, proyectado para el año 2100 por efecto del cambio climático, y aumentar las áreas actuales de siembra del cultivo en más de un 50%. Su tolerancia se basó en una mayor viabilidad de polen, heredada de P. acutifolius a través del padre INB 841. Por su parte, las líneas SEF 42, SEF 44, SEF 45, SEF 49, SEF 52 y SEF 55 poseen un buen desempeño tanto en alto aluminio como en condición sin estrés, mientras que SEF 42, SEF 49, SEF 60, SEF 62 y RCB 593 fueron los mejores genotipos en bajo fósforo y sin estrés. Por último, se determinó que dentro de los genotipos más estables en rendimiento a través de ambientes, SEF 15, SEF 42 y SEF 60 presentaron tolerancia a dos o más tipos de estrés abiótico en forma individual y excelente rendimiento en condición sin estrés. Al conjuntar y complementar las características valiosas de tres especies de Phaseolus, se logró identificar un grupo de genotipos con rendimiento superior a la media tanto en el ambiente de estrés estudiado como en el ambiente sin estrés, lo que representa la posibilidad de mitigar los efectos negativos del estrés abiótico y del cambio climático para los pequeños productores de frijol. A su vez, constituyen padres potenciales para programas de mejoramiento genético en tolerancia a estrés abiótico.Item Morpho-physiological analysis of adaptive responses of common bean (Phaseolus vulgaris L.) to drought stress. Thesis (Ph.D.)(Thesis, 2016-09) Polanía Perdomo, José A.Common bean (Phaseolus vulgaris L.) is the most important food legume in the diet of poor people in the tropics. This legume is cultivated by small farmers and is usually exposed to unfavorable conditions with minimum use of inputs. Drought and low soil fertility, especially phosphorus (P) and nitrogen (N) deficiencies, are major limitations to bean yield in smallholder systems. Beans can derive part of their required N from the atmosphere through symbiotic nitrogen fixation (SNF). Drought stress severely limits SNF ability of plants. Identification of traits associated with drought resistance contributes to improving the process of designing bean genotypes adapted to these conditions. Field studies were conducted at the International Center for Tropical Agriculture (CIAT), Palmira, Colombia to determine the relationship between grain yield and different parameters in elite lines selected for drought resistance over the past decade. The selected traits were effective use of water (EUW), canopy biomass, remobilization of photosynthates to grain (pod partitioning index, harvest index and pod harvest index) and SNF ability. Moreover, in field trials we also validated the use of 15N natural abundance in grain tissue to quantify phenotypic differences in SNF ability for its implementation in breeding programs aiming to improve SNF in common bean. Carbon isotope discrimination (CID) was used for estimation of water use efficiency (WUE) and effective use of water (EUW). A set of 36 bean genotypes belonging to the Middle American gene pool were evaluated under field conditions with two levels of water supply (irrigated and rainfed) over two seasons. Additionally, a greenhouse study was conducted at CIAT using plastic cylinders with soil inserted into PVC pipes, to determine the relationship between grain yield and different root parameters such as total root length, fine root production and visual root growth rate in same group of elite lines under drought stress. Eight bean lines (NCB 280, NCB 226, SEN 56, SCR 2, SCR 16, SMC 141, RCB 593 and BFS 67) were identified as resistant to drought stress. Resistance to terminal drought stress was positively associated with EUW combined with a deeper and vigorous root system, better plant growth, and superior mobilization of photosynthates to pod and seed production, but negatively associated with days to flowering and days to physiological maturity. Based on phenotypic differences in CID, leaf stomatal conductance, canopy biomass and grain yield under drought stress, the tested lines were classified into two groups, water savers and water spenders. These groups also differ in their root characteristics, water spenders with a vigorous and deeper root system and water savers genotypes with a moderate to shallow root system and more presence of fine roots. We used 15N natural abundance method to compare SNF ability estimated from shoot tissue sampled at mid-pod filling growth stage vs. grain tissue sampled at harvest. The results showed a significant positive correlation between nitrogen derived from the atmosphere (Ndfa), estimated using shoot tissue at mid-pod filling, and Ndfa estimated using grain tissue at harvest. The method showed phenotypic variability in SNF ability under both drought and irrigated conditions. A significant reduction in SNF ability was observed under drought stress. We suggest that the method of estimating Ndfa using grain tissue (Ndfa-G) can be applied in bean breeding programs to improve SNF ability. Using this method of Ndfa-G, we identified four bean lines (RCB 593, SEA 15, NCB 226 and BFS 29) that combine greater SNF ability with higher grain yield under drought stress. These lines could serve as potential parents to further improve SNF ability of common bean. Better SNF ability under drought stress was related with superior presence of thick roots. Superior N uptake from the soil was associated with a large root system with more presence of fine roots. Pod harvest index, grain CID and Ndfa using grain tissue could be a useful selection criterion in breeding programs to select for drought resistance in common bean.Item Bio-economic evaluation of forage cultivation scenarios in crop-dairy systems in Lushoto District, Tanzania. Farming Systems Ecology Thesis(Thesis, 2016) Heemskerk, Stijn J.Lushoto District is part of Tanzania’s most important milk production regions; depending on the village, 25-95% of households own improved dairy cows. However, land pressure is high and both income and food security are low. The aim of this study has been to assess the potential of various forage cultivation intensification strategies (‘scenarios’) to improve physical production and income of smallholder crop-dairy farmers in Lushoto district, Tanzania. Representative farms were created in the FarmDESIGN model with data from household surveys, feed analyses, milk measurements, soil samples and GPS measurements from 20 farms in Ubiri village. Two baseline farms were modeled, to account for the sample range in labor availability: 4 farm households were headed by a single (grand)parent; as such, available labor was about half the level of households with at least two members active on-farm full-time. The baseline farm without such labor-constraints (‘HL’ for ‘high labor’) owns two dairy cows, the baseline farm with limited labor (‘LL’) does not own cattle. A participatory scenario development workshop revealed the most promising intensification strategy: Napier cultivation on the plots close to the homesteads. Bio-economic performance under this scenario was modeled for each representative farm, the main management difference between HL and LL being that the latter does not collect natural grasses from public land in addition to Napier cultivation. The scenario shows potential for substantial improvement compared to the baseline: a tripling of milk production, a net cash income increase of 147%, and no reduction in household food production on the representative farm without labor constraints. This scenario seems promising for both farms, but it should be noted that [1] the farms would become structurally reliant on mineral fertilizers and imported maize bran, and [2] the LL farm runs a negative carbon balance because it does not import natural grasses, thereby threatening long-term soil fertility. Results needs to be validated by future research, but they show potential for improving livelihoods of smallholder dairy farmers in Lushoto.Item Governance and gender dynamics in global value chains: A case study of the industrial dairy value chain in Matiguás, Nicaragua(Thesis, 2016) Hülssiep, M.This thesis analyzes the interaction of governance and gender within global value chains on the basis of the industrial dairy value chain in Matiguás, Nicaragua. First, it explains the three different dairy value chains existing in this region to then examine the governance structures prevailing in the exporting chain. Second, I am exploring how women are integrated as milk producers into the industrial dairy value chain, and what factors and mechanisms of exclusion exist, to finally combine the findings in an integrative approach to understand the interaction of governance and gender within this value chain. The global value chain theory and the sustainable livelihood approach are applied as tools for the analysis. The results are based on a case study in central Nicaragua, where cattle farming is one of the most important sources of income. The research focuses on two cooperatives and their corresponding milk providers. Their livelihood activities are influenced through dynamic and mutually constructed relations between household members, intermediaries, cooperatives, and transnational firms. These firms have the most influence in the industrial dairy value chain and therefore indirectly over the lives of farmers. By running pasteurization plants in the country they act as lead firms; setting quality standards and prices. However, power asymmetries are not only established vertically but also horizontally along various categories, one of them being gender. Gender is the main category along which participation is shaped. Women have been historically excluded from the traditionally male domain of cattle farming, making women’s contribution to milk production invisible. To assess their participation their access to and control over resources, services, financial capital, decision-making power, household dynamics and the perception, treatment and involvement of women in cooperatives, collection centers and the community is analyzed. It is taken into account that equal participation per se is not a determinant factor for gender equality, but the terms to which women participate. Producers encounter various barriers hindering their participation in the industrial dairy chain, such as access to membership in cooperatives, quality standards, lack of financial capital, geographic location and traditional gender roles. These factors are interlinked through missing information, and are affecting female producers more severely. Improving access to information, especially for women, I therefore consider to have a positive leverage effect on women’s livelihoods. Regarding the interaction of gender dynamics and governance the analysis examines the macro, meso and micro level. It can be concluded that on all levels women are facing unequal access to information, lack of decision-making power and restricted bargaining power putting them in a disadvantaged position in the governance structure of the industrial dairy value chain.Item Adding value to smallholder forage-based dual-purpose cattle value chains in Nicaragua, in the context of carbon insetting. Thesis (MSc. in Agricultural Sciences in the Tropics and Subtropics)(Thesis, 2015) Phelan, Lisette TaraThe thesis explores the extent to which payment for the ecosystem service of carbon sequestration provided in a value chain context, through an innovative climate change mitigation and adaptation strategy known as 'carbon insetting', could generate 'win-win' outcomes for all actors. Drawing on examples of where the concept of carbon insetting has been adopted in coffee and cocoa value chains in Mexico and Honduras respectively, the thesis investigated the feasibility of providing a payment for ecosystem services (PES) where there was an explicit aim to generate social, economic, and environmental and productivity benefits. Taking the dual-purpose cattle value chain in Nicaragua as a case study, the thesis used a mixed methods approach to assessing the current climate change scenario faced by actors in the value chain, and in analysing incentives to directly engage in or facilitate strategies leading to adaptation and mitigation of climate change impact. A household questionnaire was administered to a sample of 40 smallholder farmers, while a diverse range of national as well as international public and private sector actors were consulted through key informant interviews. The results of the study indicate that while smallholder farmers in Nicaragua are most vulnerable to climate change, the ripple effect as regards impact is felt by the value chain as a whole, and there is growing consensus among actors as regards the need to work together in identifying and implementing innovative PES and climate change adaptation and mitigation strategies with the capacity to generate shared benefits. Linking PES scheme outcomes to willingness to pay (WTP) and accept (WTA) payment for service provision, the thesis evaluates the scope for carbon insetting, in particular, to positively impact on and contribute towards the improved livelihood security and sustainability of the primary link in the value chain in Nicaragua - smallholder farmers engaged in dual-purpose cattle production.Item Talking about the weather in Chiapas, Mexico: rural women’s approaches to climate change in national and global context. Thesis (Master of Arts)(Thesis, 2015) Lookabaugh, LaraThrough an examination of the climate change perceptions and adaptive practices of three groups of organized rural women in and around San Cristóbal de las Casas, Chiapas, Mexico, together with a critical reading and analysis of the United Nations’ Climate Smart Agriculture Strategy and strategies outlined in a Central America-specific project, this thesis explores how place-based approaches in Chiapas interact with processes and ideas operating at national and global scales. I found that the women in all three organizations studied, La Red de Productores y Consumadores Responsables Comida Sana y Cercana, Mujeres y Maíz Criollo, and K’inal Antsetik, not only observed changes in climate but were also working with their organizations to actively adapt to and mitigate them. Their strategies were influenced by personal experience, gender identity and the household or community gender division of labor, indigenous or campesino identity, and organizational affiliation. I argue that many of the practices and perceptions I observed in the field could be considered Climate Smart Agriculture approaches, however they were successful due to their local creation, specificity to the people involved, and their context. In Tortillas on the Roaster there is a 10 greater divide between what practices were observed in this thesis, those promoted as adaptation strategies, and the conceptualization of what it means to truly adapt to or mitigate climate change. I conclude by arguing that a food sovereignty approach to climate change adaptation and mitigation is a more appropriate site-specific approach than Climate Smart Agriculture.Item Desarrollo de una técnica para evaluar la tolerancia en maíz a suelos ácidos y estudio de su herencia(Thesis, 1995) Urrea Gómez, Ramiro; Ceballos, H.; Pandey, S.