Compilador tomado de preliminares

Digital. Bogotá : Biblioteca Nacional de Colombia, 2013. Recurso en línea (13 p.) : archivo de texto, PDF, 3.7 MB.

Descripción física : 15 p. ; 18 cm

A significant increase of 50.5 percent in the national production of cocoa was registered between 2011 and 2015 in Colombia. Nevertheless, 5,890 tons were imported in 2015 to supply domestic demand. Unlike other crops, the production of cocoa has made a significant contribution to the income of approximately 38,000 families of which 90 percent are small farm-producers with very little capital. Facilitating credit for investment is one of the main strategies of the national government to increase cocoa productivity. Correspondingly, the impact of the credit for investment on the cocoa agricultural productivity and if those investments have a spillover effect is studied in 584 municipalities in Colombia. I use a yearly municipal agricultural assessment combined with municipality socioeconomic variables and georeferenced data from 2007 to 2017 to measure this impact and spatial interactions, based on a fixed effect and a spatial autoregressive model - SAR. Overall, the results suggest a positive relationship of credit for investment on agricultural productivity. Similarly, I found positive and significant agricultural productivity spillover. My results suggest that access to credit for investment is fundamental in cocoa agricultural productivity but the impact is larger when spatial interactions are accounted for, which provides a rationale for the national government to increase the offer of credit for investment for the development of a regional economic agglomeration.

Traditional agricultural and livestock practices have been present for decades in the Romeral area of the Sumapaz Paramo in Colombia. To promote conservation of the Paramo and its ecosystem services, the government proposes policy instruments such as Payments for Environmental Services (PES). Farmers as prospective providers of PES have to decide whether or not to accept such payments. The purpose of this study is to evaluate which factors influence farmers' willingness to accept (WTA) PES. Semi-structured interviews were conducted in the field. Data from the interviews were tabulated and analysed with a WTA model. Significant variables were analysed using logistic regression in a stepwise function using R Studio software. The results suggested that attitudinal factors were predominant and that perception towards PES was not favourable. Further discussions are needed to address the negative views towards PES among the community members in the Romeral area. This suggests that there are several issues needing improvement before PES programs can be successfully implemented in the paramo. Hopeful is that the inhabitants in the area tend to favour environment preservation of the paramo for future generations.

Sustainable intensification is considered one of the major strategies to reduce the negative environmental impacts of the Colombian cattle sector, but current adoption of the associated technologies remains incipient. To promote adoption, stakeholders have acknowledged the need of understanding consumer demand for environmental attributes, and to identify potential markets for differentiated products. In this study, we employ a contingent valuation (CV) to determine the characteristics of a potential consumer segment for “eco-friendly” beef, and a discrete choice experiment (DCE) to estimate the consumers’ willingness to pay (WTP) for environmental and animal welfare attributes related to cattle production under silvopastoral systems with improved forages. Additionally, we have included an information treatment to measure the effect of information on consumers’ WTP. Our results show that income and education have a significant effect on defining the potential consumer segment. We found that potential consumers are willing to pay significant price premiums for both “eco-friendly” and “animal welfare” certified beef, with consumer education further increasing the premium for “eco-friendly” certified beef. The results suggest that there is a potential market in Colombia for environmentally differentiated beef products that responds to the animal welfare and environmental issues of the current cattle production system. Resumen: La intensificación sostenible se considera como una de las principales estrategias para reducir los impactos ambientales negativos del sector ganadero en Colombia, sin embargo, la adopción de las tecnologías relevantes aun es incipiente. Para promover la adopción, los actores del sector han reconocido la necesidad de entender la demanda del consumidor por atributos ambientales y de identificar mercados potenciales para productos diferenciados. En este estudio, empleamos un ejercicio de valoración contingente para determinar las características de un consumidor potencial de carne “eco-amigable”, y un experimento de selección discreta para estimar la disposición a pagar del consumidor por los atributos ambientales y de bienestar animal relacionados con la producción ganadera bajo sistemas silvopastoriles con forrajes mejorados. Adicionalmente, incluimos un tratamiento para estimar el efecto de la información en la disposición a pagar. Nuestros resultados muestran que el nivel de ingreso y educación son factores determinantes para definir el segmento del consumidor. Encontramos que en el segmento de mercado potencial, los consumidores están dispuestos a pagar una prima de precio para atributos de “eco-amigable” y bienestar animal bajo esquemas de certificación. A su vez, encontramos que la información aumenta de manera significativa la disposición a pagar por carne “eco-amigable”. Los resultados sugieren que existe un mercado potencial en Colombia para productos con diferenciaciones ambientales y de bienestar animal, que respondan a las problemáticas actuales del sector pecuario.

Abstract: The use of computer vision, deep learning, and drones has revolutionized agriculture by enabling efficient crop monitoring and disease detection. Still, many challenges need to be overcome due to the vast diversity of plant species and their unique regional characteristics. Olive trees, which have been cultivated for thousands of years, present a particularly complex case for leaf-based disease diagnosis as disease symptoms can vary widely, both between different plant variations and even within individual leaves on the same plant. This complexity, coupled with the susceptibility of olive groves to various pathogens, including bacterial blight, olive knot, aculus olearius, and olive peacock spot, has hindered the development of effective disease detection algorithms. To address this challenge, we have devised a novel approach that combines deep learning techniques, leveraging convolutional neural networks, vision transformers, and cloud computing-based models. Aiming to detect and classify olive tree diseases the experimental results of our study have been highly promising, demonstrating the effectiveness of the combined transformer and cloud-based machine learning models, achieving an impressive accuracy of approximately 99.6% for multiclass classification cases including healthy, aculus olearius, and peacock spot infected leaves. These results highlight the potential of deep learning models in tackling the complex-ities of olive leaf disease detection and the need for further research in the field. Resumen: El uso de visión por computadora, aprendizaje profundo y drones ha revolucionado la agricultura al permitir un monitoreo eficiente de cultivos y la detección de enfermedades. Sin embargo, aún existen muchos desafíos debido a la vasta diversidad de especies vegetales y sus características regionales únicas. Los olivos, que han sido cultivados durante miles de años, presentan un caso especialmente complejo para el diagnóstico de enfermedades basado en las hojas, ya que los síntomas pueden variar ampliamente, tanto entre diferentes variaciones de plantas como incluso dentro de hojas individuales en la misma planta. Esta complejidad, junto con la susceptibilidad de los olivares a varios patógenos, como la bacteriosis, el nudo del olivo, el aculo olearius y la mancha de pavo real del olivo, ha dificultado el desarrollo de algoritmos efectivos de detección de enfermedades. Para abordar este desafío, hemos ideado un enfoque novedoso que combina técnicas de aprendizaje profundo, aprovechando redes neuronales convolucionales, transformadores de visión y modelos basados en computación en la nube. Con el objetivo de detectar y clasificar enfermedades de los olivos, los resultados experimentales de nuestro estudio han sido muy prometedores, demostrando la efectividad de los modelos combinados de transformadores y aprendizaje automático basado en la nube, logrando una impresionante precisión de aproximadamente el 99.6% para casos de clasificación multiclase, que incluyen hojas sanas, infectadas con aculo olearius y mancha de pavo real. Estos resultados destacan el potencial de los modelos de aprendizaje profundo para abordar las complejidades de la detección de enfermedades en las hojas de olivo y la necesidad de más investigaciones en este campo.

Abstract: The egg weight (EW) increases as the hen ages, but unfortunately, eggshell quality does not improve with increasing EW. Dietary changes can help control the increase EW, resulting in improved eggshell quality. This experiment aimed to deterMomine the effect of different digestive lysine (dLYS) levels on the production performance and eggshell quality of 82-87-week-old Lohmann Brown hens and identify the optimal level of dLYS intake to achieve an optimal production performance and the level of dLYS that can improve eggshell quality by modifying EW. A total of 240 Lohmann Brown hens were selected for the experiment (79-87 weeks). These were distributed in individual cages and 6 treatments with 40 replicates per treatment. The cages were divided into 40 blocks of 6 consecutive cages. In each block, the treatments were randomly distributed in the room. The treatments were 6 different diets with different dLYS levels (6.72, 6.40 (control diet (CON)), 6.08, 5.76, 5.44, 5.12 g/kg). The production performance and eggshell quality were evaluated, and the ideal dLYS was calculated by linear broken-line regression. Modifying dLYS levels from 6.08 to 5.12 g/kg decreased a hen day egg production (HDEP) by 4.4%, and reduced egg mass (EM) by 3.2 g/d. Adjusting dLYS levels from 5.44 to 5.12 g/kg reduced 2.2 g the egg weight (EW). Changing dLYS levels from 6.40 to 5.44 g/kg increased the average feed daily intake (ADFI) by 5 g. The different dLYS levels did not affect the feed conversion ratio (FCR), but it showed a tendency (P = 0.074). Eggshell quality attributes were not affected by different dLYS levels. The optimal dLYS intake requirement was 713, 646, 626, and 627 mg/b/d to achieve an optimal HDEP, EW, EM, and FCR respectively. In conclusion, the results of this experiment can help the laying hen industry to determine the optimal dLYS for managing EW increase, keeping a good HDEP, EM, FCR, and maintaining eggshell quality in long-life laying hens.

Abstract: Metarhizium brunneum is a soil-borne fungal entomopathogen that can associate with plant roots. Previous studies have demonstrated that root colonization by beneficial fungi can directly affect soilborne pathogens through competition and antibiosis, and can activate a systemic response in plants, resulting in a primed state for a faster and/or stronger response to stressors. However, the mechanisms by which Metarhizium inoculation ameliorates symptoms caused by plant pathogens are not well known. This study evaluated the ability of M. brunneum to protect oilseed rape (Brassica napus L.) plants against the soil-borne pathogen Verticillium longisporum, and investigated whether the observed effects are a result of direct interaction and/or plant-mediated effects. In vitro and greenhouse experiments were conducted to measure fungal colonization of the rhizosphere and plant tissues, and targeted gene expression analysis was used to evaluate the plant response. The results show that M. brunneum delayed pathogen colonization of plant root tissues, resulting in decreased disease symptoms. Direct competition and antibiosis were found to be part of the mechanisms, as M. brunneum growth was stimulated by the pathogen and inhibited the in vitro growth of V. longisporum. Additionally, M. brunneum changed the plant response to the pathogen by locally activating key defence hormones in the salicylic acid (SA) and abscisic acid (ABA) pathways. Using a split-root setup, it was demonstrated that there is a plant-mediated effect, as improved plant growth and decreased disease symptoms were observed when M. brunneum was in the systemic compartment. Moreover, a stronger systemic induction of the gene PR1 suggested a priming effect, involving the SA pathway. Overall, this study sheds light on the mechanisms underlying the protective effects of M. brunneum against soil-borne pathogens in oilseed rape plants, highlighting the potential of this fungal entomopathogen as a biocontrol agent in sustainable agriculture Metarhizium brunneum es un hongo entomopatógeno del suelo que puede asociarse con las raíces de las plantas. Resumen: Estudios previos han demostrado que la colonización de raíces por hongos beneficiosos puede afectar a patógenos del suelo a través de la competencia, antibiosis, y activar respuesta sistémica en las plants. Sin embargo, los mecanismos por los cuales este hongo atenúa los síntomas causados por fitopatógenos no son bien conocidos. Este estudio evaluó la capacidad de M. brunneum para proteger las plantas de colza (Brassica napus L.) contra Verticillium longisporum, e investigó si los efectos observados son el resultado de una interacción directa y/o efectos mediados por la planta. Se realizaron experimentos in vitro y en invernadero para medir la colonización fúngica de la rizosfera y los tejidos de la planta, y se midió la expresión de genes específicos relacionados con la respuesta de la planta a patógenos. Los resultados muestran que M. brunneum retrasó la colonización del patógeno en las raíces de la planta, y disminuyo los síntomas de la enfermedad. La competencia directa y la antibiosis son parte de los mecanismos, ya que el crecimiento de M. brunneum fue estimulado por el patógeno e inhibió el crecimiento in vitro de V. longisporum. Además, M. brunneum cambió la respuesta de la planta hacia el patógeno al activar localmente genes de defensa mediadas por el ácido salicílico (SA) y del ácido abscísico. Mediante un experimento de raíces divididas, se demostró que existe un efecto mediado por la planta, ya que se observó un mejor crecimiento de la planta y una disminución de los síntomas de la enfermedad cuando M. brunneum estaba en el compartimento sistémico. Además, una mayor inducción sistémica del gen PR1 sugirió un efecto de ""priming"", mediado por SA.

Abstract: This thesis revolves around Metarhizium, fungi well-known for their entomopathogenic nature but recently discovered to have multifaceted lifestyles. They thrive in soil as saprophytes and engage in plant rhizospheres, positively impacting plant health. However, the mechanisms underlying these interactions remain elusive. The thesis examines Metarhizium brunneum's connections with plants, insects, and pathogens through five distinct chapters. These chapters entail: 1) identifying fungal isolates' differences and their efficacy as biocontrol agents, 2) exploring their association with crops, particularly oilseed rape and potatoes, and understanding their effects on insect pests and plant diseases, 3) studying the impact on herbivores like Psylliodes chrysocephala, Myzus persicae, and Brevicoryne brassicae feeding on Brassica napus plants, 4) evaluating their influence on the cabbage root fly (Delia radicum) and the mechanisms involved in plant defense pathways, and 5) examining their ability to protect oilseed rape plants against Verticillium longisporum, dissecting the mechanisms through in vitro and greenhouse experiments. These research aspects collectively elucidate the potential applications of Metarhizium brunneum and contribute to a deeper understanding of its role in agricultural systems. Resumen: Esta tesis gira en torno a Metarhizium, hongos bien conocidos por su naturaleza entomopatógena, pero de los que recientemente se ha descubierto que tienen estilos de vida polifacéticos. Prosperan en el suelo como saprofitos y se introducen en las rizosferas de las plantas, influyendo positivamente en su salud. Sin embargo, los mecanismos que subyacen a estas interacciones siguen siendo elusivos. La tesis examina las conexiones de Metarhizium brunneum con plantas, insectos y patógenos a través de cinco capítulos distintos. Estos capítulos comprenden: 1) identificar las diferencias de los aislados fúngicos y su eficacia como agentes de biocontrol, 2) explorar su asociación con los cultivos, en particular la colza y la patata, y comprender sus efectos sobre las plagas de insectos y las enfermedades de las plantas, 3) estudiar el impacto sobre herbívoros como Psylliodes chrysocephala, Myzus persicae, y Brevicoryne brassicae que se alimentan de plantas de Brassica napus, 4) evaluar su influencia en la mosca de la raíz de la col (Delia radicum) y los mecanismos implicados en las vías de defensa de las plantas, y 5) examinar su capacidad para proteger las plantas de colza oleaginosa contra Verticillium longisporum, diseccionando los mecanismos mediante experimentos in vitro y en invernadero. Estos aspectos de la investigación dilucidan colectivamente las aplicaciones potenciales de Metarhizium brunneum y contribuyen a una comprensión más profunda de su papel en los sistemas agrícolas.