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dissertação
Caracterização da resistência de genótipos de soja a patótipos Phytophthora sojae
(Universidade Federal de Lavras, 2026-03-31) Santos, Giovana dos; Pereira, Welison Andrade; Pulcinelli, Carlos Eduardo; Baba, Viviane Yumi
Soybean (Glycine max (L.) Merrill) is one of the most important agricultural crops in Brazil and worldwide, with substantial economic, social, and environmental relevance. Among the factors limiting soybean productivity, Phytophthora root and stem rot, caused by the oomycete Phytophthora sojae, is one of the most destructive diseases, leading to severe yield losses. The use of genetically resistant cultivars, mainly through the deployment of specific Rps genes, is considered the most effective and sustainable strategy for disease management. However, the high genetic variability of the pathogen and the emergence of new pathotypes have reduced the durability of resistance over time. Therefore, this study aimed to evaluate the reaction of soybean genotypes to Phytophthora root and stem rot against different P. sojae races and to infer the possible Rps genes associated with resistance. A total of 144 soybean genotypes were evaluated using pathotypes corresponding to races 1, 3, 4, 17, and 25 of P. sojae. The experiments were conducted under greenhouse conditions at GDM Seeds, Cambé, Paraná, Brazil, during 2024 and 2025. Genotypes were arranged in experimental blocks for each P. sojae race, with two replications. Inoculation was performed by inserting macerated mycelium into the hypocotyl, and disease reaction was classified based on the percentage of dead seedlings, with genotypes showing up to 30% mortality considered resistant. The results revealed variation in the frequency of resistance among the evaluated races, with the highest proportion of resistant genotypes observed for race 1 (75.69%) and the lowest for race 25 (54.86%). Gene combinations involving Rps1a + Rps3a, Rps1k + Rps3a, and Rps1c + Rps3a predominated, indicating the use of gene pyramiding strategies in soybean breeding programs. Single resistance genes occurred less frequently, while a proportion of the genotypes showed no clear identification of specific resistance genes. These findings highlight the high variability of P. sojae populations and reinforce the importance of continuous monitoring of pathotypes in soybean-producing regions. The combined use of Rps genes and quantitative resistance represents a promising strategy to enhance resistance durability and support the development of soybean cultivars better adapted to the conditions of southern Brazil.
dissertação
Characterization of bioactivity and development of chitosan-based nanostructured systems containing Momordica charantia L. extracts
(Universidade Federal de Lavras, 2026-08-25) Kattah, Hoxana Xavier Lopes; Peconick, Ana paula; Bittencour, Wanderley José Mantovani; Varaschin, Mary Suzan; Valente, Fabrício Luciani; Santiago, Andrezza Fernanda
Momordica charantia L. contains bioactive compounds associated with antioxidant, enzymatic, and cytotoxic activities, attracting interest in the development of nanostructured systems for the delivery of plant extracts. This study aimed to evaluate the biological potential of hydroethanolic extracts from the leaves and fruits of M. charantia and to develop chitosan and sodium tripolyphosphate (CS/TPP)-based nanostructured systems, investigating their physicochemical characteristics and in vitro cytotoxic activity. Initially, the extracts were evaluated for their phenolic and flavonoid contents, antioxidant activity, total antioxidant capacity, α-amylase activity, and preliminary toxicity using Artemia salina. Subsequently, the extracts were incorporated into CS/TPP systems, which were characterized in terms of particle size, encapsulation efficiency, and Raman spectroscopic profile. The cytotoxicity of the formulations was evaluated using the MTT assay in HeLa and RAW 264.7 cells at different concentrations, with determination of IC₅₀ values. The extracts exhibited antioxidant and enzymatic activities, as well as concentration-dependent preliminary toxicity. The nanostructured formulations showed encapsulation efficiencies of 84.53% for the fruit extract and 81.00% for the leaf extract, with particles in the nanometric range and preservation of the main spectroscopic characteristics of the extracts after the encapsulation process. In the cytotoxicity assessment, the formulations exhibited concentration-dependent effects. In HeLa cells, formulations containing fruit and leaf extracts showed IC₅₀ values of 44.90 mg/mL and 54.30 mg/mL, respectively. In RAW 264.7 cells, the IC₅₀ values were 59.06 mg/mL and 23.96 mg/mL, respectively. Chitosan nanocapsules without extract also exhibited cytotoxicity, indicating that the polymeric matrix may contribute to the observed cellular response. The results demonstrated that M. charantia extracts exhibited bioactivity and that their incorporation into CS/TPP systems is feasible, with preservation of extract characteristics and in vitro cytotoxic activity. These findings support the potential of the developed systems for future investigations, particularly regarding cellular selectivity, mechanisms of action, stability, and preclinical evaluation.
tese
Pleurotus spp. and their proteases: a new approach to alternative helminth control in agriculture and livestock farming
(Universidade Federal de Lavras, 2026-08-10) Silva, Adriane Toledo Batista da; Soares, Filippe Elias de Freitas; Terra, Willian César; Castro, Clara Resende de Souza; Cardoso, Wilton Soares; Cardoso e Búfalo, Tatiana; Remédio, Rafael Neodini
The use of edible mushrooms and their cell-free proteolytic crude extract, especially from species of the genus Pleurotus, as biological and biochemical control agents presents itself as a sustainable alternative for parasite management in agriculture and livestock. In this context, the general objective of this thesis was to optimize enzyme production by Pleurotus spp. and evaluate both the antiparasitic activity of the fungi and their proteolytic enzymes on eggs and juveniles of plant-parasitic nematodes and larvae of gastrointestinal parasites of animals. The first article presented a review of the proteases produced by Pleurotus spp., addressing their production, biochemical properties, and biotechnological applications. The second article investigated the nematophagous activity of several species of the genus Pleurotus and the nematicidal activity of their proteases against Panagrellus sp. Significant correlations were observed between both assays. The third article evaluated the in vitro nematophagous activity of P. djamor and the nematicidal activity of its proteases on infective larvae of Trichostrongylus spp. and Strongyloides papillosus, showing a 75% reduction of nematodes in the nematophagous assay and 57% in the nematicidal assay. In the fourth article, the optimization of protease production by P. djamor was carried out using solid-state fermentation with agricultural residues, specifically wheat bran. The results indicated that moisture levels significantly influenced enzyme production. Also in this article, the proteases demonstrated significant in vitro anthelmintic activity against eggs of T. solium and Moniezia sp., with reductions of 33.44% and 45.43%, respectively. The fifth article analyzed the proteolytic profile and the nematicidal action of P. djamor proteases against larvae of Haemonchus spp. and Trichostrongylus spp., resulting in a 35% reduction in larvae. Zymogram analysis revealed at least two proteases with molecular weights between 75 and 100 kDa. The sixth article evaluated the nematicidal and ovicidal activity of P. djamor proteases on Meloidogyne incognita in vitro and under greenhouse conditions, demonstrating a 100% reduction in juveniles and 22% in eggs in vitro. Both extracts containing active proteases and denatured proteases of P. djamor significantly reduced egg numbers by 94% and 97%, respectively, and decreased gall formation under greenhouse conditions. Finally, the seventh article investigates the combined use of P. djamor proteases and papain, aiming at the development of more effective formulations for nematode control. The results of the articles highlight the potential of the fungus Pleurotus spp. and its proteases as a sustainable alternative for the management of important parasites present in agriculture and livestock.
dissertação
Alteração estomatal e respostas bioquímicas em cafeeiro resistente e suscetível à ferrugem
(Universidade Federal de Lavras, 2026-07-07) Carvalho, Diogo Aparecido de; Resende, Mário Lúcio Vilela de; Botelho, Deila Magna dos Santos; Orilio, Anelise Franco; Rodrigues, Fabrício de Ávila; Guimarães, Leonor De Castro Esteves Guerra
Coffee is widely consumed worldwide, with production concentrated in a few countries, among which Brazil is the largest producer. However, coffee cultivation is severely affected by coffee leaf rust, caused by Hemileia vastatrix, which is responsible for severe defoliation and significant yield losses. The high dispersal capacity of the pathogen, combined with the complexity of the host–pathogen interaction and the high cost of disease management, highlights the need for a better understanding of coffee resistance mechanisms. Therefore, the objective of this study was to characterize the interaction between coffee plants and Hemileia vastatrix through an integrated analysis of stomatal and biochemical responses throughout the infection process in a resistant cultivar (Arara) and a susceptible cultivar (Catuaí Vermelho IAC 144). Two greenhouse experiments were conducted. In the first experiment, a randomized complete block design with split plots over time was used to evaluate stomatal aperture, the activities of phenylalanine ammonia-lyase (PAL), peroxidase (POX), chitinase (CHI), and β1,3-glucanase (GLU), as well as total soluble phenolic compounds, soluble lignin, and lipid peroxidation (quantified as malondialdehyde, MDA). The second experiment confirmed the resistance and susceptibility of the cultivars using the area under the disease progress curve (AUDPC). The Arara cultivar exhibited early activation of defense mechanisms, evidenced by increased PAL, POX, and CHI activities at 5 days after inoculation, with relative activities compared with the control treatment (non-inoculated plants) that were 1.37-, 1.80-, 5.31-, and 1.80-fold higher for PAL, POX, CHI, and GLU, respectively. During the same period, increases in total phenolic compounds and soluble lignin contents were also observed, indicating activation of the phenylpropanoid pathway and enhanced lignification. Furthermore, the Arara cultivar showed an initial increase in MDA levels at 1 day after inoculation, followed by a reduction, indicating effective control of oxidative damage. In contrast, the Catuaí Vermelho IAC 144 cultivar exhibited increased MDA levels from 5 days after inoculation onward, which remained elevated throughout the evaluation period, suggesting progressive oxidative damage. The results demonstrate that the resistance of the Arara cultivar is associated with the early and coordinated activation of biochemical defense mechanisms, characterized by increased activity of defense-related enzymes, accumulation of phenolic compounds, and lignification, as well as more efficient control of oxidative damage.
dissertação
Aplicação foliar de selênio e calagem em mudas de Theobroma cacao L. para minimizar a toxicidade de cádmio
(Universidade Federal de Lavras, 2026-06-29) Santos, Jéssica Aires dos; Guilherme, Luiz Roberto Guimarães; Carvalho, Mariana Rocha de; Rabêlo, Flávio Henrique Silveira; Oliveira, Cynthia de
The presence of cadmium can compromise the physiological and nutritional performance of plants and pose a food safety concern. Selenium application and liming have been investigated as alternatives to minimize the effects of cadmium toxicity. In this context, this study evaluated the physiological and nutritional effects of selenium application on cadmium toxicity and content in Theobroma cacao L. seedlings (genotype CCN51) grown in soil with and without liming. The experiment was conducted in a greenhouse at the Federal University of Lavras using a 2 × 3 factorial design, involving two cadmium levels and three selenium doses (0, 10, and 20 mg L⁻¹) under two soil conditions (with and without liming). Physiological parameters, antioxidant enzyme activity, nutrient, cadmium, and selenium contents in leaf tissues, and available soil cadmium were evaluated. Cadmium impairs the chlorophyll index and alters stomatal conductance and nutrient dynamics. Selenium application reduces cadmium availability in the soil, both in the absence and presence of liming. However, no significant differences in leaf cadmium content were observed in response to selenium doses. Thus, selenium application helped minimize the effects of cadmium toxicity in T. cacao seedlings (genotype CCN51) but did not reduce cadmium content in leaf tissues.