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.

Abstract: Soil available water capacity (AWC) is a key function for human survival and well-being. However, its direct measurement is laborious and spatial interpretation is complex. Digital soil mapping (DSM) techniques emerge as an alternative to spatial modeling of soil properties. DSM techniques commonly apply machine learning (ML) models, with a high level of complexity. In this context, we aimed to perform a digital mapping of soil AWC and interpret the results of the Random Forest (RF) algorithm and, in a case study, to show that digital AWC maps can support agricultural planning in response to the local effects of climate change. To do so, we divided this research into two approaches: In the first approach, we showed a DSM using 1857 sample points in a southeastern region of Brazil with laboratory-determined soil attributes, together with a pedotransfer function (PTF), remote sensing and DSM techniques. In the second approach, the constructed AWC digital soil map and weather station data were used to calculate climatological soil water balances for the periods between 1917–1946 and 1991–2020. The result showed the selection of covariates using Shapley values as a criterion contributed to the parsimony of the model, obtaining goodness-of-fit metrics of R2 0.72, RMSE 16.72 mm m?1, CCC 0.83, and Bias of 0.53 over the validation set. The highest contributing covariates for soil AWC prediction were the Landsat multitemporal images with bare soil pixels, mean diurnal, and annual temperature range. Under the current climate conditions, soil available water content (AW) increased during the dry period (April to August). May had the highest increase in AW (?17 mm m?1) and decrease in September (?14 mm m?1). The used methodology provides support for AWC modeling at 30 m resolution, as well as insight into the adaptation of crop growth periods to the effects of climate change.

Abstract: The consequences of converting tropical rainforest to oil palm are well-documented, but the impacts of oil palm conversion on natural savanna landscapes remain little-known. Natural savannas in South America have been identified as fertile grounds for future oil palm expansion, partly due to perceived low biodiversity impacts relative to forest systems. We quantify the impacts of oil palm conversion for bird communities inhabiting natural savannas in the Colombian Llanos. Bird species richness and abundance were significantly reduced at sampling points in oil palm relative to adjacent natural savannas, with marked concomitant shifts in community composition. Aquatic, forest and grassland specialists all showed significantly lower abundances in oil palm habitat relative to savanna, as did migratory species and carnivorous/insectivorous dietary guilds. In both habitats, point-level species richness and total bird abundance increased with proximity to remnant forest patches. Within savanna, total bird abundance also decreased with proximity to adjacent oil palm, though species richness was not significantly affected. Within oil palm, point-level abundance increased with proximity to savanna, suggesting that communities in both habitats may be impacted by reciprocal edge or spill-over effects. Point-level abundance in oil palm also increased significantly with the presence of an invasive vine ‘kudzu’, a species introduced in some plantations as a soil protection measure, although species richness was not affected. Our work underlines the need for careful monitoring of further large-scale agro-industrial conversion in the Llanos. In particular, we suggest greater efforts to direct oil palm expansion towards already degraded lands (e.g. improved grassland areas currently used for intensive cattle grazing) to ensure remaining natural savannas are spared.

Abstract: Entomopathogenic fungi infect insects via spores but also live inside plant tissues as endophytes. Frequently, colonization by entomopathogens provides plants with increased resistance against insects, but the mechanisms are little understood. This study investigated direct, local, and systemic root-mediated interactions between isolates of the fungus Metarhizium brunneum and larvae of the cabbage root fly (CRF) Delia radicum attacking Brassica napus plants. All fungal isolates infected CRF when conidia were present in the soil, leading to 43–93% mortality. Locally, root-associated M. brunneum isolates reduced herbivore damage by 10–20% and in three out of five isolates caused significant insect mortality due to plant-mediated and/or direct effects. A split-root experiment with isolate Gd12 also demonstrated systemic plant resistance with significantly reduced root collar damage by CRF. LC-MS analyses showed that fungal root colonization did not induce changes in phytohormones, while herbivory increased jasmonic acid (JA) and glucosinolate concentrations. Proteinase inhibitor gene expression was also increased. Fungal colonization, however, primed herbivore-induced JA and the expression of the JA-responsive plant defensin 1.2 (PDF1.2) gene. We conclude that root-associated M. brunneum benefits plant health through multiple mechanisms, such as the direct infection of insects, as well as the local and systemic priming of the JA pathway. Resumen: Los hongos entomopatógenos infectan a los insectos a través de esporas, pero también viven en el interior de los tejidos vegetales como endófitos. Con frecuencia, la colonización por entomopatógenos proporciona a las plantas una mayor resistencia contra los insectos, pero los mecanismos son poco conocidos. Este estudio investigó las interacciones directas, locales y sistémicas mediadas por la raíz entre los aislamientos del hongo Metarhizium brunneum y las larvas de la mosca de la raíz de la col (CRF) Delia radicum que atacan las plantas de Brassica napus. Todas las cepas del hongo infectaron a la CRF cuando las conidias estaban presentes en el suelo, provocando una mortalidad del 43-93%. Localmente, las cepas de M. brunneum asociados a la raíz redujeron el daño de los herbívoros en un 10-20% y tres de las cinco cepas causaron una mortalidad significativa de los insectos debido a efectos mediados por la planta y/o directos. Un experimento de raíz dividida con la cepa Gd12 también demostró la resistencia sistémica de la planta con una reducción significativa del daño en el cuello de la raíz por parte de CRF. Los análisis de LC-MS mostraron que la colonización de la raíz por el hongo no indujo cambios en las fitohormonas, mientras que la herbivoría aumentó las concentraciones de ácido jasmónico (JA) y glucosinolato. También aumentó la expresión de genes inhibidores de proteinasas. La colonización fúngica, sin embargo, aumentó el ácido jasmónico inducido por los herbívoros y la expresión del gen de la defensina vegetal 1.2 (PDF1.2) que responde al ácido jasmónico. Concluimos que M. brunneum asociado a las raíces beneficia la salud de las plantas a través de múltiples mecanismos, como la infección directa de los insectos, así como el Priming local y sistémica de la vía de JA.

Abstract: Potato farming is relevant for global carbon balances and greenhouse emissions, of which gross primary productivity (GPP) is one of the main drivers. In this study, the net carbon ecosystem exchange (NEE) was measured using the Eddy Covariance (EC) method in two potato crops, one of them with an irrigation system, the other under rainfed conditions. Accurate NEE partition into GPP and ecosystem respiration (RECO) was carried out by fitting a light response curve. Direct measurements of dry weight and leaf area were performed from sowing to the end of canopy life cycle and tuber bulking. Agricultural drought in the rainfed crop resulted in limited GPP rate, low leaf area index (LAI), and low canopy carbon assimilation response to the photosynthetically active radiation (PAR). Hence, in this crop, there was lower efficiency in tuber biomass gain and NEE sum indicated net carbon emissions to atmosphere (NEE = 154.7 g C m?2 ± 30.21). In contrast, the irrigated crop showed higher GPP rate and acted as a carbon sink (NEE = ?366.6 g C m?2 ± 50.30). Our results show, the environmental and productive benefits of potato crops grown under optimal water supply.

Abstract: Estimating gross primary production (GPP) is important to understand the land–atmosphere CO2 exchange for major agroecosystems. Eddy covariance (EC) measurements provide accurate and reliable information about GPP, but flux measurements are often not available. Upscaling strategies gain importance as an alternative to the limitations of the use of the EC. Although the potato provides an important agroecosystem for worldwide carbon balance, there are currently no studies on potato GPP upscaling processes. This study reports two GPP scaling-up approaches from the detailed leaflevel characterization of gas exchange of potatoes. Multilayer and big leaf approaches were applied for extrapolating chamber and biometric measurements from leaf to canopy. Measurements of leaf area index and photosynthesis were performed from planting to the end of the canopy life cycle using an LP-80 ceptometer and an IRGA Li-Cor 6800, respectively. The results were compared to concurrent measurements of surface–atmosphere GPP from the EC measurements. Big-leaf models were able to simulate the general trend of GPP during the growth cycle, but they overestimated the GPP during the maximum LAI phase. Multilayer models correctly reproduced the behavior of potato GPP and closely predicted both: the daily magnitude and half-hourly variation in GPP when compared to EC measurements. Upscaling is a reliable alternative, but a good treatment of LAI and the photosynthetic light-response curves are decisive factors to achieve better GPP estimates. The results improved the knowledge of the biophysical control in the carbon fluxes of the potato crop.

Abstract: Drosophila suzukii (Matsumura), also known as the spotted wing Drosophila (SWD), is a fastspreading polyphagous pest. Native from South-east Asia, it is well known for causing serious damage in soft-skinned fruit due to the puncture made by the enlarged serrated ovipositor of adult females and the subsequent larvae feeding. Currently, the most commonly used approaches to control D. suzukii infestation are the frequent foliar application of synthetic insecticides and non-selective traps. However, these strategies are inefficient to control D. suzukii spread and crop infestation. Through this study, we aimed to evaluate Drosophila suzukii responses to two different types of chemical stimuli (attractive and repulsive) to be implemented as part of a push-pull system. Both, push and pull components were separately evaluated for a better understanding of Drosophila suzukii behavior. As attractive candidates, aggregation pheromones were studied and to evaluate repellent and oviposition deterrent responses, the following chemical candidates: 1-heptanol, 2-heptanol, 1-hexanol, 2-hexanol, delta-undecalactone (dUDL) and propionic acid were tested. Our results suggest that aggregation pheromones influence different D. suzuki females' and males' host choices. Repellence responses were observed in 1-hexanol and 2-hexanol treatments and oviposition deterrence behavior was observed in 1-hexanol as well, but also in 1-heptanol and 2-heptanol treatments. Our results offer new insights into the use of two-choice assays in D. suzukii behavior studies and new knowledge related to the mechanisms underlying these promising push-pull elements.

Abstract: Specialization of agriculture in the Colombian Andes has increased smallholder vulnerability to climate change and global price fluctuations and has also affected the socio-economic and environmental conditions. Promoting sustainable agriculture in the region requires a holistic understanding of complex agroecosystems. This study identifies and analyzes the main challenges for agriculture and possibilities for agroecological transition of small-scale farms in Guachetá, Colombia. Using the Tool for Agroecology Performance Evaluation (TAPE), 10 elements of agroecology and core performance criteria were evaluated on seven farms. Several key actors were then interviewed, to triangulate data and understand current challenges and possible future pathways. It was found that drier climate and variations in rainfall patterns pose major challenges to current production systems. Limited possibilities for participation in land governance, lack of interest in agriculture among young people, and lack of access to markets hinder the development of sustainable agriculture. Current specialized practices in dairy and potato production are associated with reduced agricultural biodiversity and dependency on agrochemicals, leading to weak synergies and low profitability within agroecosystems. Implementation of agroecological principles and practices such as crop and income diversification and promoting joint action in agricultural development could help overcome sustainability issues in Guachetá. Resumen: La especialización de la agricultura en los Andes colombianos ha aumentado la vulnerabilidad de los pequeños agricultores al cambio climático y las fluctuaciones de los precios globales y también ha afectado las condiciones socioeconómicas y ambientales. Promover la agricultura sostenible en la región requiere una comprensión holística de los agroecosistemas complejos. Este estudio identifica y analiza los principales desafíos para la agricultura y las posibilidades de transición agroecológica de las pequeñas explotaciones agrícolas en Guachetá, Colombia. Utilizando la Herramienta para la Evaluación del Desempeño Agroecológico (TAPE), se evaluaron 10 elementos de la agroecología y criterios básicos de desempeño en siete fincas. Luego se entrevistó a varios actores clave para triangular los datos y comprender los desafíos actuales y los posibles caminos futuros. Se descubrió que el clima más seco y las variaciones en los patrones de lluvia plantean desafíos importantes para los sistemas de producción actuales. Las limitadas posibilidades de participación en la gobernanza de la tierra, la falta de interés en la agricultura entre los jóvenes y la falta de acceso a los mercados obstaculizan el desarrollo de la agricultura sostenible. Las prácticas especializadas actuales en la producción de lácteos y papa están asociadas con una biodiversidad agrícola reducida y una dependencia de los agroquímicos, lo que genera sinergias débiles y una baja rentabilidad dentro de los agroecosistemas. La implementación de principios y prácticas agroecológicas, como la diversificación de cultivos y de ingresos, y la promoción de acciones conjuntas en el desarrollo agrícola podrían ayudar a superar los problemas de sostenibilidad en Guachetá.

Desde 1998 la Federación Nacional de Cacaoteros, ha venido desarrollando con diferentes entidades un trabajo de masificación de la cultura cacaotera en el departamento de Cundinamarca. Una de estas entidades es la Gobernación del departamento, que especialmente desde la fi rma del convenio Marco 003 del 2002 que busca “El Fomento y consolidación de una cultura cacaotera moderna y efi ciente en el Departamento de Cundinamarca”, ha venido contribuyendo a consolidar la actividad cacaotera de Colombia. Fruto de este trabajo conjunto y continuo y gracias al desarrollo de nuevos convenios podemos presentar con orgullo los resultados del primer convenio específi co No. 001, que materializa el arriba mencionado convenio marco, el cual ofrece a los campesinos cundinamarqueses una alterna

En el departamento del Meta, hasta hace poco tiempo, existlan 8.000 Has. de cacao que explotaron 2.000 familias campesinas, durante mas de 20 años y sostenran alrededor de 6.000 empleos productivos directos y unos 2.000 empleos indirectos. Para el año 1986 coincidiendo con la aparición de la Moniliasis (enfermedad de la mazorca) se presenta una confluencia de diferentes factores negativos (propios de la crisis agropecuaria nacional y mundial) para los cuales los agricultores no estaban preparados ni mental, ni técnica, ni pedagógicamente, procediendo a iniciar la mas cruda, cruel y sistematica erradicación del arbol protector y por naturaleza conservacionista, que con su sombrío sumaban mas de ocho millones de arboles permanentes, manteniendo ecosistemas equilibrados. La desaparición de este renglón de la economía trajo innumerables problemas de orden so· cial, económico y ambiental reflejado en los desplazamientos de la mayoría de los productores a las ciudades, a zonas de reserva y cultivos ilicitos, en el desempleo, la pobreza y muchas otras consecuencias y efectos que son motivo de preocupación de la sociedad y los gobiernos y sobre los cuales la ANUC consideró en sus análisis para la búsqueda de soluciones y elaboración del Proyecto