DSpace Collection:

Uma perspectiva histórica e espacial da ocorrência e distribuição de populações de Calophyllum brasiliense Cambess. e Platymiscium ulei Harms no Médio Solimões, Amazonas

Fri, 07 Aug 2026 00:00:00 GMT

Title: Uma perspectiva histórica e espacial da ocorrência e distribuição de populações de Calophyllum brasiliense Cambess. e Platymiscium ulei Harms no Médio Solimões, Amazonas Abstract: Historical logging in the Middle Solimões region drastically reduced populations of Calophyllum brasiliense (Jacareúba) and Platymiscium ulei (Macacaúba), creating an urgent need to understand their current spatial arrangements to support management and conservation efforts. This study investigated the occurrence and structure of three Jacareúba populations (JAC1, JAC2, JAC3) and two Macacaúba populations (MAC1, MAC2) in the Mamirauá Sustainable Development Reserve, correlating them with soil physicochemical attributes collected in the field between 2023 and 2025 (with analytical determinations completed in 2026). The methodology integrated geostatistical tools (variography, ordinary kriging, cross-validation) and multivariate analysis (Exploratory Factor Analysis) applied to 313 georeferenced tree specimens and 259 soil samples. Results revealed contrasting post-disturbance trajectories. C. brasiliense maintained, across its clusters, an aggregated spatial pattern with moderate spatial dependence and practical ranges between 274 m and 288 m, demonstrating resilience and autonomous recovery capacity. In contrast, P. ulei exhibited an independent pattern with Pure Nugget Effect in both remaining populations, characterizing severe demographic collapse associated with a potential Allee effect. In MAC1, the species was restricted to an equally random bipolar fertility/acidity gradient (pH, V, H+Al), whereas in MAC2 the abiotic matrix proved chaotic, precluding Factor Analysis (KMO = 0.17). It is concluded that the same historical pressure produced distinct dynamic responses according to the intrinsic vulnerability of each taxon. Passive protection is sufficient for Jacareúba regeneration, whereas Macacaúba requires active enrichment interventions and differentiated silvicultural management.

Cultivo de sorgo granífero sobre diferentes coberturas em cultivo isolado e consorciadas no Cerrado mineiro em diferentes épocas de plantio

Mon, 15 Dec 2025 00:00:00 GMT

Title: Cultivo de sorgo granífero sobre diferentes coberturas em cultivo isolado e consorciadas no Cerrado mineiro em diferentes épocas de plantio Abstract: Sorghum is a widely cultivated crop for both grain production and forage during the off-season in the Brazilian Cerrado due to its hardiness, drought tolerance, high nitrogen use efficiency, good adaptability to different soil types, and lower production cost. It is generally planted in a no-till system over the residues of the previous crop. However, it is rarely cultivated over a previously formed mulch for its cultivation in consecutive cycles. The objective of this study was to evaluate the production, decomposition, and nutrient cycling of cover crop residues in isolated and intercropped cultivations, as well as their relationships with grain sorghum production in two consecutive cycles. The experiment was set up in a randomized block design, where seven types of soil cover were evaluated: 1- Brachiaria (B); 2- Millet (M); 3- Crotalaria ochroleuca (CO); 4- Intercropping 1 (MIX 1): Buckwheat, Crotalaria ochroleuca, millet, C. breviflora, Brachiaria, Coracana grass, and Crambe; 5- Intercropping 2 (MIX 2): Buckwheat, C. ochroleuca, C. breviflora, Coracana grass, Crambe, and Brachiaria; 6 - Intercropping 3 (MIX 3): Brachiaria, Coracana grass, millet, forage sorghum, cowpea, and pigeon pea, all with four replications. The production of fresh (FM) and dry (DM) matter, decomposition, half-life (T1/2 life), and nutrient cycling of the residues were evaluated, as well as the agronomic parameters and productivity of grain sorghum in two consecutive cycles. In the first cycle, it was observed that in the isolated cultivation, MIX 2 presented higher DM production, greater accumulation and cycling of nutrients, and lower decomposition rate and half-life of its residues. In the intercropped cultivations, MIX 2 presented DM production similar to that of MIX 1 and MIX 3, greater accumulation and cycling of nutrients, higher decomposition rate, and lower half-life of its residues compared to MIX 1 and 3. The highest residue decomposition rate occurred in the isolated cultivation and in MIX 2, where the plant was present with two species (C. ochroleuca and C. breviflora). Regarding the half-life (T1/2) of nutrient release, the following increasing order was observed: Mg < K < Ca < N < P < S. The lowest values for fresh and dry mass of grain and panicle, as well as grain yield of grain sorghum, occurred when it was grown on MIX 1. The cover crops used did not influence the agronomic parameters: number of panicles, plant height, panicle insertion height, and basal stem diameter.

Planta sentinela para o monitoramento do vetor Rhopalosiphum padi (Linnaeus) (Hemiptera: Aphididae) e desenvolvimento de um genossensor colorimétrico para detecção de Luteovirus pavhordei

Wed, 29 Apr 2026 00:00:00 GMT

Title: Planta sentinela para o monitoramento do vetor Rhopalosiphum padi (Linnaeus) (Hemiptera: Aphididae) e desenvolvimento de um genossensor colorimétrico para detecção de Luteovirus pavhordei Abstract: Winter cereals, particularly wheat, barley and oats, constitute fundamental pillars of global food security and contemporary agricultural economy. These crops play multiple strategic roles in production systems, providing essential nutrients for human and animal nutrition, while also integrating rotation systems that optimize land use. However, the productivity of these crops is significantly limited by pests and diseases, particularly by aphids. Among the most relevant aphid species, Rhopalosiphum padi (Linnaeus) stands out, a hemimetabolous insect with cosmopolitan distribution, polyphagous nature and high dispersal capacity. Its most devastating impact occurs through the transmission of barley yellow dwarf virus (BYDV), a virus belonging to the genus Luteovirus. BYDV is responsible for the cereal yellow dwarf syndrome, causing production losses that can exceed 80% in untreated crops. Transmission occurs in a persistent-circulatory and non-propagative manner, where R. padi acquires the virus by feeding on infected plants and transports it internally through complex molecular mechanisms mediated by bacterial endosymbionts. The BYDV complex comprises several viral species, including BYDV-PAV, BYDV-GAV and BYDV-MAV, with variable geographic distribution. Given the economic and phytosanitary relevance of R. padi and BYDV, it becomes imperative to develop effective monitoring and diagnostic strategies. In this context, sentinel plants emerge as promising tools for early monitoring of the vector. Experimental studies demonstrate that oats exhibit superior efficiency as a sentinel plant compared to wheat, exhibiting greater colonization consistency, greater population support capacity and greater probability of detecting R. padi, with a preference ratio of 56.4:1. This superiority allows optimizing early monitoring strategies, facilitating assertive decision-making in integrated pest management. Complementing monitoring strategies, rapid, sensitive and low-cost diagnostic methods are essential for efficient BYDV detection. In this perspective, colorimetric genosensors based on gold nanoparticles functionalized with thiolated DNA probes represent an innovative approach for visual BYDV diagnosis. These devices demonstrate satisfactory analytical performance, with high linearity, adequate sensitivity and detection and quantification limits compatible with phytosanitary applications. Stability exceeding 95% for up to 40 days under refrigeration reinforces the potential of this technology for implementation in phytosanitary monitoring programs for winter cereals. Therefore, the integration of knowledge about R. padi biology, BYDV transmission dynamics, the efficiency of sentinel plants and the development of innovative diagnostic tools constitutes an essential multidisciplinary approach to mitigate economic losses, reduce dependence on chemical insecticides and ensure the sustainability of cold-season cereal production chains on a global scale.

Dessecação pré-colheita do feijoeiro: taxa de aplicação, adjuvantes e monitoramento por RPA

Tue, 26 May 2026 00:00:00 GMT

Title: Dessecação pré-colheita do feijoeiro: taxa de aplicação, adjuvantes e monitoramento por RPA Abstract: Pre-harvest desiccation of common beans is a strategic practice, but its effectiveness depends on optimizing application technology and precise monitoring methods. This study aimed to evaluate the impact of different application rates and the addition of adjuvants on desiccation efficacy, integrating scientometric analysis, field trials, and physicochemical characterization in the laboratory. Initially, a global bibliometric mapping was performed in the Scopus and Web of Science databases to assess the evolution of the use of remotely piloted aircraft (RPAs) and the NDVI index in agriculture. In the field, the effect of three application rates (50, 100, and 150 L ha-1) and the addition of an organosilicone adjuvant on spray deposition, defoliation, and grain moisture was evaluated over two growing seasons. Simultaneously, the accuracy of NDVI indices obtained by multispectral and RGB sensors in monitoring senescence was validated. In the laboratory, the droplet spectrum, surface tension, and viscosity of the spray solutions were determined in a completely randomized design (3 x 4 factorial), combining the three application rates with four spray solution compositions (without adjuvant, polydimethylsiloxane, D'limonene, and nonylphenol ethoxylate). Scientometric analysis showed the exponential growth of publications on ARPs and NDVI, consolidating them as technological pillars of modern agricultural monitoring. In the field, the 100 L ha-1 application rate promoted deposition and efficacy similar to 150 L ha-1 and superior to 50 L ha-1. The organosilicone adjuvant did not alter the physical deposition of the spray solution, but significantly accelerated moisture loss from the grains, suggesting optimization in absorption. In monitoring, the correlation of the RGB sensor degraded after application, rejecting the hypothesis that it can replace the multispectral sensor with the same accuracy. In the laboratory, polydimethylsiloxane provided the greatest reduction in surface tension and the greatest increase in volume median diameter (VMD), resulting in the lowest percentage of droplets susceptible to drift (%<100 µm). It is concluded that a rate of 100 L ha-1 represents the best technical and operational balance. Its association with the organosilicone adjuvant enhances the effectiveness of desiccation. Furthermore, the use of air-induction nozzles overrides the physicochemical effect of adjuvants in primary atomization, ensuring application safety, a process that should preferably be monitored by multispectral sensors mounted on UAVs.