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    Desenvolvimento e validação de marcadores microssatélites para Calonectria pteridis e espécies associadas à mancha-de-calonectria no Sul do Brasil
    (Universidade Federal de Viçosa, 2026-05-27) Cardoso, Renata Sena; Alfenas, Rafael Ferreira; http://lattes.cnpq.br/6077115148753146
    A mancha-de-calonectria constitui uma das principais doenças foliares do eucalipto no Brasil, causando desfolha severa, redução do crescimento e, consequentemente, redução da produtividade de madeira. A etiologia dessa doença é complexa, envolvendo múltiplas espécies do gênero Calonectria, cuja elevada similaridade morfológica e diversidade taxonômica dificultam a identificação precisa dos agentes etiológicos e a compreensão de sua dinâmica epidemiológica. Embora Calonectria pteridis seja amplamente reconhecida como o principal agente causal da doença em regiões tropicais e equatoriais do Brasil, pouco se conhece sobre estrutura genética populacional, variabilidade intraespecífica e dinâmica evolutiva associada aos isolados pertencentes ao complexo Calonectria pteridis. Adicionalmente, evidências recentes indicam que a etiologia da mancha-de-calonectria em regiões subtropicais do Sul do Brasil difere substancialmente daquela observada em áreas de clima mais quente, com predomínio de espécies pertencentes ao complexo Calonectria candelabrum. Nesse contexto, esta tese teve como objetivo ampliar o conhecimento sobre a diversidade e estrutura genética populacional de Calonectria e sobre as espécies associadas à mancha-de-calonectria em eucalipto no Brasil, integrando ferramentas de genética populacional e filogenia. No primeiro capítulo, foram desenvolvidos e validados marcadores microssatélites (SSR) genômicos e gênicos para isolados pertencentes ao complexo Calonectria pteridis, posteriormente aplicados à investigação da diversidade genética e da estrutura populacional em diferentes regiões produtoras de eucalipto no Brasil. Os resultados revelaram diversidade genética moderada, estruturação populacional significativa entre regiões geográficas e evidências de predominância de reprodução clonal, além de elevada transferibilidade dos marcadores para espécies filogeneticamente relacionadas. No segundo capítulo, análises filogenéticas multilocus permitiram identificar as espécies associadas à mancha-de-calonectria em plantios de eucalipto localizados no Sul do Brasil, demonstrando a predominância de espécies pertencentes ao complexo Calonectria candelabrum, além da identificação de linhagens filogeneticamente distintas potencialmente não descritas. Em conjunto, os resultados ampliam o entendimento da diversidade de Calonectria e das espécies associadas à mancha- de-calonectria no Brasil, subsidiando o refinamento taxonômico, o manejo da doença e o melhoramento do eucalipto para resistência. Palavras-chave: marcadores moleculares; filogenia; estudo etiológico; clima; Cylindrocladium.
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    From standard area diagram-aided human assessment to computer vision–assisted severity estimation: a case study of coffee leaf rust
    (Universidade Federal de Viçosa, 2026-03-24) Romero Benavides, Mary Paz; Del Ponte, Emerson Medeiros; http://lattes.cnpq.br/5222998295816930
    Accurate quantification of coffee leaf rust (CLR), caused by Hemileia vastatrix, remains a central challenge in phytopathometry, particularly under heterogeneous field conditions where symptom variability, illumination differences, and observer subjectivity affect disease severity estimates. Because severity is fundamental for epidemic monitoring, resistance screening, and management decision-making, improving both the reliability and operational efficiency of assessment methods is essential. This dissertation addresses CLR severity estimation from two complementary perspectives: human vision–assisted assessment and computer vision–based segmentation. First, a simplified two-color, 10-diagram standard area diagram (SAD) was developed and empirically validated against an existing 21- diagram scale and unaided visual assessment. Across 17 raters, the new SAD achieved high agreement with reference values (Lin’s concordance correlation coefficient > 0.93), improved coverage probability, and maintained strong interrater reliability (ICC > 0.90). Importantly, the simplified design reduced assessment time by approximately 11–13% while preserving predefined precision targets, thereby improving sampling efficiency and operational feasibility in field conditions. Second, a foundation model–assisted computer vision pipeline was developed for quantitative, pixel-level severity estimation. A two-stage detection–segmentation workflow integrating YOLOv8 and Segment Anything Models (SAM2 and zero-shot SAM3) enabled robust leaf extraction and lesion delineation from complex field images. Among evaluated approaches, the zero-shot foundation model (SAM3) achieved the highest segmentation performance (Dice 0.91; IoU 0.83) and the strongest agreement with reference severity estimates at the leaf level, outperforming both classical threshold-based methods and a supervised DeepLabV3+ model. Classical image processing approaches showed systematic positive bias, whereas foundation models provided more balanced precision and recall under heterogeneous acquisition conditions. By jointly evaluating statistical agreement, measurement bias, operational time costs, and computational robustness, this work advances an integrated framework for CLR severity estimation that spans visual and automated approaches. The findings demonstrate that both; the optimized diagrammatic scale and the foundation model–based segmentation canenhance the accuracy, reproducibility, and scalability of disease monitoring, supporting more precise and efficient decision-making in coffee production systems. Keywords: Hemileia vastatrix; Coffea arabica; phytopathometry; standard area diagram.
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    Development and application of biochar for energy purposes, physicochemical characterization for soil applications, and activated adsorbent material
    (Universidade Federal de Viçosa, 2026-07-06) Peres, Letícia Costa; Carneiro, Angélica de Cássia Oliveira
    Biochar is a material with many promising applications, with increasing interest due to its use in bioenergy, carbon sequestration and adsorption materials. In this scenario, this study uses eucalypt waste, vastly available in Brazil due to extensive silviculture, to produce biochar and evaluates its use for energy, soil amendment, and activated for wastewater treatment. Residue was obtained in the form of undersized eucalypt chips for kraft pulp production. Biochar was produced in a muffle oven at three temperatures (450, 600 and 750 °C) and characterized. For energy applications, combustion parameters were calculated through oxidizing atmosphere thermogravimetric analysis. Ignition and final combustion temperatures increased for the biochar produced at higher temperatures. Biochar made at lower temperature (450 °C) had higher yield and better combustion indexes, while those made at higher temperatures (600 and 750 °C) had higher energy density. For soil amendment use, physical and chemical characterization was performed and data were subjected to principal component analysis (PCA), considering O/C, N/C, H/Corg ratios, electrical conductivity, pH, volatile matter, ash and fixed carbon contents and Cstored, which showed that the pyrolysis temperature variation produced three distinct biochar with varying properties. The production of biochar at 600 °C yielded good chemical properties and a higher surface area and it is the most promising for this application. Then, biochar was ground to powder and activated using 35% hydrogen peroxide (H2O2 ) at three activation times (1, 2 and 3 hours) and temperatures (55, 70 and 85 °C). The best performing treatment in a methylene blue adsorption test (pyrolyzed at 450 °C, activated at 85 °C for 3 hours) was selected for comprehensive characterization and further adsorption studies. The activated biochar had higher oxygen content, as indicated by FTIR through the increase in carbonyl surface functional groups, which were possibly responsible for the increase in methylene blue adsorption. Different applications for eucalypt wood residue were investigated, indicating that pyrolysis temperature is a key element in the production of biochar best suited for each application.
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    LC3-type multicomponent Portland Cement binders incorporating calcined clays, red mud, and ornamental stone waste: rheological, mechanical, and eco-efficiency performance
    (Universidade Federal de Viçosa, 2026-08-12) Souza, Ariel Miranda de; Carvalho, José Maria Franco de; http://lattes.cnpq.br/2538544610961549
    This study presents the development of a new LC3-type cement (Limestone Calcined Clay Cement) incorporating industrial residues to reduce environmental impacts and adjust the rheological behavior of the binder to resemble conventional Portland cement, enabling potential commercial application. Three conventional clays from Ijaci, Brazil (IC – Ijaci Clay), as well as red mud (RM) and ornamental stone waste (OSW), were investigated as components in LC3 systems. The materials were evaluated considering rheological behavior, mechanical strength, and pozzolanic reactivity, and the most suitable ones were selected for a compositional optimization study. The optimization was conducted using multivariate statistical analysis considering clay type, filler type, clay/filler ratio, and the interaction between RM and conventional calcined clay fractions. Response surface methodology and regression models were used to evaluate their effects on rheology and mechanical performance. Results showed that the clay fraction predominantly controls the rheological behavior of LC3 mixtures, while compressive strength is mainly governed by total clay content due to the pozzolanic contribution of calcined clay. Although red mud improved some rheological aspects, its incorporation reduced mechanical strength under the conditions evaluated. The optimal formulation was obtained using calcined clay from Ijaci (IC) combined with ornamental stone waste (OSW) as filler. In this system, the pozzolanic reactivity of IC ensured adequate mechanical strength, while OSW improved the rheological behavior of the mixtures. These results demonstrate the feasibility of producing LC3-type binders incorporating ornamental stone waste while maintaining mechanical performance compatible with structural cement and rheological behavior closer to conventional Portland cement, contributing to the development of cementitious materials with lower environmental impact.
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    Microaeration in the anaerobic digestion of organic substrates: impacts on methane production, stability, and microbial dynamics
    (Universidade Federal de Viçosa, 2026-06-25) Febroni, Laís Veloso; Rosa, André Pereira
    Anaerobic digestion (AD) is a well-established technology for treating organic wastes and wastewaters while recovering energy through biogas production. However, its efficiency and stability may be limited by slow hydrolysis, accumulation of metabolic intermediates, and the complexity of anaerobic microbial interactions, particularly under high organic loading rates and short hydraulic retention times (HRT). In this context, microaeration (MA), defined as the controlled addition of small amounts of oxygen to anaerobic systems, has emerged as a promising strategy to improve substrate degradation and process resilience. Nevertheless, its mechanisms remain incompletely understood, and its effectiveness depends on substrate characteristics and operating conditions. This thesis investigated the application of MA in the anaerobic digestion of different organic substrates through an integrated approach combining evidence synthesis, controlled experiments, and continuous reactor operation to evaluate its effects on methane production, degradation kinetics, process stability, and microbial community dynamics. Initially, a systematic review and meta-analysis of the literature on MA in anaerobic digestion was conducted. The results showed increasing scientific interest in the technology, with studies mainly focused on laboratory-scale batch systems. The quantitative synthesis demonstrated that the effects of MA on methane production are substrate- and process-dependent, with the greatest improvements observed for specific substrates under mesophilic conditions and intermediate volatile solids concentrations, highlighting the need for tailored operating strategies. Subsequently, MA was evaluated as a pretreatment for swine wastewater in biochemical methane potential (BMP) assays using experimental design, response surface methodology, and kinetic modelling. MA increased methane production by up to 31.9% compared with conventional anaerobic digestion. Kinetic analysis showed increases of up to 28% in the methane production rate constant and up to 85% in the maximum methane production rate, indicating faster degradation. The optimal condition, 45 mL air g VS1 for 2 days, maximised methanogenic performance and demonstrated the potential of MA for process intensification. Finally, continuous MA was assessed in a continuously stirred tank reactoroperated under progressively more challenging conditions, including reduced HRT and increased organic loading rate. HRT reduction destabilised the process, increasing volatile fatty acid accumulation approximately fifteen-fold and reducing organic matter removal. Under these conditions, continuous MA promoted process recovery by reducing metabolic intermediate accumulation by up to 60%, mitigating fluctuations in biogas production, and stimulating the functional reorganisation of the microbial community. Microbial analyses indicated that MA favoured syntrophic populations and enhanced hydrogenotrophic methanogenesis, contributing to greater process resilience under operational stress. Overall, the results demonstrate that MA is a multifunctional strategy for anaerobic digestion, enhancing methane production while improving degradation pathways, operational stability, and microbial interactions. By integrating evidence synthesis, experimental optimisation, kinetic modelling, and microbial ecology, this thesis advances the understanding of MA mechanisms and provides a scientific basis for developing more efficient and resilient anaerobic treatment processes for organic wastes and wastewaters.