Fitopatologia

URI permanente para esta coleçãohttps://locus.ufv.br/handle/123456789/173

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Resultados da Pesquisa

Agora exibindo 1 - 10 de 430
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    Sensibilidade de isolados brasileiros de Plasmopara viticola a oomicidas
    (Universidade Federal de Viçosa, 2024-03-27) Sousa, Daniel Yuri Xavier de; Mizubuti, Eduardo Seiti Gomide; http://lattes.cnpq.br/4731473137735755
    O míldio da videira, causado por Plasmopara viticola, possui como principal estratégia de controle a aplicação de fungicidas inibidores da quinona interna e externa e inibidor do modo de ligação da estigmatelina (ametoctradin (QioSI)), amida de ácido carboxílico (CAA) (dimethomorph), polimerização de tubulina (Zoxamide) e RNA polimerase I (Mefenoxam). Durante os anos de 2023 e 2024, 26 isolados coletados em 18 regiões distribuídas em quatro estados brasileiros foram testados e avaliados em ensaios sensibilidade a fungicidas por meio da metodologia de folhas destacadas. Dos 26 isolados, 17 eram provenientes da região sul do Brasil de vinhedos convencionais. Todos os isolados foram considerados sensíveis a ametoctradin e zoxamide, 42% foram considerados resistentes a mandipropamid, e dimethomorph, 19% dos isolados foram classificados como de baixo nível de resistência à mefenoxam e 11% foram resistente ao mefenoxam. Esse isolados foram utilizados para determinação da frequência de CE50 ao ametoctradin, zoxamide, mandipropamid, variando entre 0.01 e 1 (ametroctradin e zoxamide) e 0.01 e 100 µg/mL (Mandipropamid), 11 isolados esporularam na dose discriminatória de 1.6 µg/mL e oito isolados apresentaram resistência ao mefenoxam. Resistência cruzada a CAA e múltipla a CAA e inibidor da RNA polimerase I em Plasmopara viticola foi confirmada pela primeira vez no Brasil. Estudos futuros devem ser realizados para mitigar o aparecimento de populações resistentes a CCA e inibidores da RNA polimerase I no Brasil. Palavras-chave: Oomicetos. Míldio. Resistência a fungicidas.
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    Machine learning for tomato late blight outbreak and progress forecast in the Espírito Santo region, Brazil
    (Universidade Federal de Viçosa, 2023-09-29) González Villasanti, Federico José; Mizubuti, Eduardo Seiti Gomide; http://lattes.cnpq.br/4652120875529736
    Tomato late blight (TLB) caused by Phytophthora infestans (Mont.) de Bary is one of the most destructive diseases of tomato crops (Solanum lycopersicum). Due to its economic importance, several integrated management tools were developed to improve its control, including disease forecast models. Available models in the market rely mostly on weather-based risk alerts and empirical approaches, while recent technologies such as machine learning provide new capabilities for modeling and forecasting. Six field trials in two years were conducted to gather disease measurements. Each trial had a hyperlocal weather station installed to record meteorological data. A Support Vector Machine (SVM) model was used to forecast disease onset with an accuracy of 95%. Two machine learning models constructed to forecast TLB progress were tested and compared: Random Forest Regressor (RF) and an Extreme Gradient Boosting Regressor (XGBR). The XGBR returned a lower symmetric mean absolute percentage error when compared to the RF for the exponential stage of the epidemics and a similar error for the asymptote stage. The weather variables that affected TLB progress were related to water availability. ML models can predict the onset and development of TLB, despite clear limitations regarding a small disease dataset. Machine learning models can be used to forecast disease and become part of a disease support system aimed at improving TLB management. Keywords: Phytophthora infestans; Solanum lycopersicum; Disease Support Systems; Predictive Models; Artificial intelligence.
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    The role of secondary metabolites of Clonostachys spp. on plant disease control and comparative genomics of selected strains
    (Universidade Federal de Viçosa, 2024-03-26) Silva, Hiago Antonio Oliveira da; Abreu, Lucas Magalhães de; http://lattes.cnpq.br/7334699411809635
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    Unveiling the hidden threat: The interactions between soybean and Oomycetes, with a focus on Pythium-like and Phytophthora sojae
    (Universidade Federal de Viçosa, 2023-11-20) Batista, Izabel Cristina Alves; Mizubuti, Eduardo Seiti Gomide; http://lattes.cnpq.br/0943580960513162
    Revelando uma ameaça oculta: As interações entre a soja e os oomicetos, com foco nos organismos semelhantes a Pythium e Phytophthora sojae. Orientador: Eduardo Seiti Gomide Mizubuti. Este estudo aborda oomicetos patogênicos habitantes do solo que podem afetar a produção de soja devido a doenças causadas por estes micro-organismos como a podridão de sementes e raízes e tombamento de plântulas. No primeiro capítulo, diversas espécies de Pythium, Globisporangium, Phytophthora, Phytopythium e Aphanomyces, foram isoladas de áreas afetadas na região Centro-Sul do Brasil. A identificação foi realizada por meio de análises filogenéticas, destacando a prevalência de Pythium myriotylum, Globisporangium irregulare e Pythium deliense, além de Phytophthora sojae, a espécie de oomiceto já conhecida por causar a podridão da raiz e da haste (PRH). A patogenicidade de isolados semelhantes a Pythium foi avaliada, com destaque para G. ultimum, G. ultimum var. sporangiiferum, G. irregulare e P. myriotylum, que apresentaram o maior Índice de Severidade da Doença em ensaios de semente. Além disso, a sensibilidade dessas espécies a vários oomicidas foi avaliada, sendo mefenoxam particularmente eficaz. No segundo capítulo, o estudo se concentra na dinâmica de P. sojae, o oomiceto que causa a PRH. A pesquisa caracteriza 40 isolados de uma região com alta incidência no Brasil, identificando 28 patótipos. Uma mudança significativa na diversidade de patótipos na última década destaca a importância do monitoramento das populações de P. sojae para o uso estratégico de genes de resistência em programas de melhoramento de soja. No terceiro capítulo, a pesquisa explorou a diversidade genética e a evolução temporal das populações de P. sojae em regiões produtoras de soja no Brasil ao longo de uma década. Utilizando marcadores microssatélites e determinando patótipos com base nas respostas a linhagens diferenciais de soja, foram identificados 37 patótipos únicos em 2023, indicando um aumento na diversidade em comparação com 2013. Essas descobertas contribuem para uma compreensão mais aprofundada da diversidade e patogenicidade de oomicetos na soja, fornecendo informações valiosas para o manejo de doenças. Elas destacam a importância da resistência genética e a necessidade de abordagens estratégicas no desenvolvimento de novas cultivares com genes de resistência. Palavras-chave: Patogenicidade. Resistência. Soja. Podridão da raiz. Genética populacional.
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    Desenvolvimento de um biofungicida formulado à base de Bacillus e seus metabólitos para o controle de doenças de parte aérea da soja
    (Universidade Federal de Viçosa, 2023-07-18) Corrêa, Jessiane dos Santos; Abreu, Lucas Magalhães de; http://lattes.cnpq.br/5177803214958930
    Espécies de Bacillus produtoras de lipopeptídeos, metabólitos secundários com ação antifúngica e antibacteriana, estão entre os organismos mais promissores para o manejo de doenças de parte aérea. Produtos compostos por misturas de endósporos bacterianos e metabólitos são comercializados para a proteção foliar, mas seu emprego em grandes culturas, como a soja, é limitado, pois ainda faltam tecnologias que aumentem estabilidade físico-química e o período residual na filosfera. Neste trabalho, foram testados componentes para a formulação de um biofungicida à base de células e concentrado de lipopeptídeos de Bacillus velezensis UCBB48, para o controle de doenças de parte aérea da soja, utilizando mancha alvo da soja, causada pelo fungo Corynespora cassiicola, como modelo. Para o desenvolvimento do biofungicida, foram realizados testes de proteção do produto concentrado contra a luz UV utilizando pontos quânticos de carbono, testes de estabilidade físico-química e de fitotoxicidade dos componentes da formulação e testes de atividade antifúngica e controle da mancha alvo. Uma formulação do tipo suspensão concentrada foi selecionada, contendo proporções otimizadas de tampão aquoso, óleo, surfactantes e adjuvantes. Esta manteve a viabilidade das células de Bacillus e bioatividade do produto concentrado mesmo após seis meses de armazenamento. Em um ensaio de controle da mancha alvo, em casa de vegetação, o número médio de lesões foliares nas plantas tratadas com a formulação (n=20) foi significativamente menor do que nas plantas do controle (n=70) e similar ao observado no tratamento com fungicida. Palavras-chave: Fungicida biológico. Lipopeptídeos. Suspensão concentrada (SC).
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    Clonostachys chloroleuca e seus metabólitos secundários: controle de doenças foliares, otimização de cultivo e formulação
    (Universidade Federal de Viçosa, 2023-09-13) Leite, Iris Carolina Henrique de Lima; Abreu, Lucas Magalhães de; http://lattes.cnpq.br/0050548629408050
    Espécies de Clonostachys são micoparasitas comumente encontradas como saprófitas ou endófitos. Clonostachys rosea é a espécie mais bem investigada desse gênero, e utilizada como agente de biocontrole em formulações comerciais. O gênero contém cerca de 70 espécies, algumas com atividade antagonista semelhante ou superior a C. rosea e com potencial uso no biocontrole de doenças de plantas, como a espécie C. chloroleuca. Durante o micoparasitismo, Clonostachys produz enzimas hidrolíticas que causam a desestruturação da parede celular dos fungos alvo e metabólitos secundários com atividade antifúngica. Nesta tese, foram desenvolvidos dois estudos usando um isolado de C. chloroleuca com objetivo de avaliar a sua eficácia no controle de doenças foliares em tomate e batata, e investigar o papel dos metabólitos secundários bioativos no mecanismo de controle, sob condições controladas. No primeiro estudo, o uso da suspensão de conídios foi eficaz no controle de oídio e pinta preta do tomateiro. A utilização do extrato orgânico no controle da pinta preta também resultou em eficácia de controle acima de 90%, semelhante ao fungicida químico. Análises químicas dos componentes presentes na suspensão de conídios e no extrato orgânico evidenciaram a predominância de peptaibols, permitindo correlacionar a presença destes metabólitos ao efeito de controle. No segundo estudo, experimentos envolvendo modificações nas condições de cultivo de C. chloroleuca em substrato sólido resultaram em um aumento de 10 vezes na produção de conídios e de 2 vezes no efeito antifúngico do extrato orgânico, em ensaios de inibição contra Alternaria linariae. Duas formulações estáveis, do tipo suspensão concentrada, foram compostas com o extrato orgânico do isolado, com ou sem a adição de conídios. Em um ensaio de campo, o uso das formulações resultou em uma redução significativa da severidade da pinta preta da batata, com eficácia média de controle de 54%, similar ao controle com fungicida. Os resultados obtidos nesta tese evidenciam o papel da produção e liberação de metabólitos secundários no antagonismo de C. chloroleuca frente a outros fungos e sugerem a utilização de extratos orgânicos ricos em metabólitos secundários como uma estratégia promissora para o controle de doenças foliares. Palavras-chave: Antibiose. Biocontrole. Suspensão de conídios. Extrato orgânico.
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    Physiological, biochemical, and molecular aspects of induced resistance in soybean against rust using a nitrogen-and calcium-polyphenols compound and a phosphite of nickel and potassium
    (Universidade Federal de Viçosa, 2023-10-25) Fontes, Bianca Apolônio; Rodrigues, Fabrício de Ávila; http://lattes.cnpq.br/9624787372310476
    Soybean rust (SR), caused by Phakopsora pachyrhizi, is an aggressive disease that severely reduces the production of soybean crops worldwide. The SR control has been done by spraying fungicides and using cultural practices (e.g., early sowing dates, early detection of the rust symptoms development, cultivars of early maturing, and 60 to 90 days without growing soybean). However, sustainable control methods are preferred nowadays. In this point of view, induced resistance using biotic and abiotic defense elicitors plays an important role in plant disease management. The present study investigated the potential of Cautha® [calcium (11.01%) and nitrogen (3.3%) complexed with polyphenols (10%)] and Blindage Ni® [potassium (20% K2O, 280 g/L), nickel (0.5% Ni, 7 g/L), and phosphorous acid (500 g/L)] in displaying biochemical, molecular, and physiological resistance mechanisms against P. pachyrhizi. In the first study, plants were sprayed with water (control) or Cautha® (referred to as induced resistance [IR] stimulus after that) and inoculated or non-inoculated with P. pachyrhizi. The germination of urediniospores was reduced by 26% in vitro at the same dose of IR stimulus used to spray soybean plants. The rust severity and area under the disease progress curve lowered by 41% (at 15 days after inoculation) and 27%, respectively, for IR stimulus-sprayed plants compared to water-sprayed plants. The IR stimulus treatment greatly reduced the cellular damage caused by P. pachyrhizi infection in soybean tissues, maintained a great content of photosynthetic pigments, enhanced activities of defense-related enzymes, and built a robust antioxidative metabolism compared with the control treatment. In the second study, the factors investigated were water (control) or Blindage Ni® (referred to as induced resistance [IR] stimulus after that) inoculated or non-inoculated with P. pachyrhizi. In vitro, the urediniospores germination was reduced by 99% by IR stimulus. The soybean rust severity and area under the disease progress curve was decreased by 73% (at 15 days after inoculation) and 74%, respectively, in IR stimulus-sprayed plants compared to water-sprayed plants. The infected plants sprayed with IR stimulus maintain the proper functionality of photosynthetic apparatus and a good concentration of pigments. In addition, this treatment reduced the damage and lipid peroxidation in plant tissue, up-regulated the expression of several defense-related genes in plants infected by P. pachirhizi, kept a great concentration of potassium and nickel in soybean tissues, and increased the concentrations of phenolics and lignin in contrast with the control plants. The results of the present study highlighted the positive role of both IR stimuli in activating defense mechanisms against P. pachyrhizi in soybean crop and reducing disease severity. Keywords: Soybean rust. Glycine max. Plant defense mechanisms. Management of plant disease.
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    Substitution of amino acid residues in the cytochrome b protein from Phytophthora infestans: functional implications and azoxystrobin sensitivity
    (Universidade Federal de Viçosa, 2023-07-31) Alves, Gabriel; Mizubuti, Eduardo Seiti Gomide; http://lattes.cnpq.br/6557908950444361
    Late blight is caused by the oomycete Phytophthora infestans and is one of the main biotic factors that compromise yields of potato and tomato crops. Management of late blight is almost exclusively dependent on the application of oomicides. Azoxystrobin is a site-specific active ingredient that has "transkingdom" action, once it can be effective against fungal and oomycete plant pathogens. Unfortunately, reports of both fungal and oomycetes resistant to azoxystrobin are relatively common. Nevertheless, to date, there is no report of resistance in populations of P. infestans to azoxystrobin. The use of computational methods of molecular modeling applied to the study of proteins can help in the evaluation of the reasons why events of resistance to azoxystrobin have not been observed so far. For P. infestans, all positions in cytochrome b protein (cytB) that correspond to the loss of efficiency to azoxystrobin are set back one position in relation to the sequences of cytB of other microorganisms, with position 142 being the most important for the loss of efficiency of the molecule. The region around the site of interaction with the oomicide in P. infestans cytB is slightly variable, supporting less than 33% of the total number of possible substitutions. Position 142 can support a large number of residues without compromising stability, but which lead to resistance to azoxystrobin, which highlights the high risk of resistance events to this molecule. The non-occurrence of resistance to azoxystrobin in P. infestans seems to be related to a genomic factor that governs the stability of the cytochrome b gene sequence, since from the biophysical point of view there is no impediment to resistance to azoxystrobin. Such an approach may favor the understanding of the rules that govern the oomicide-protein molecular target interaction, serving as a theoretical subsidy for predicting the probability of loss of sensitivity in the plant pathogen population, as for other molecules that target the same protein. It is also expected that the adoption of this approach may help in the rational design of other oomicides and fungicides, and also control efficiency monitoring. Keywords: Molecular modeling. Oomicides. Protein diversity.
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    Taxonomic characterization of Aphelenchoides besseyi sensu lato and the study of diseases angular leaf spot in jambu (Acmella oleracea) and green stem and foliar retention syndrome in soybean (Glycine max)
    (Universidade Federal de Viçosa, 2023-10-30) Silva, Marcela de Freitas; Buonicontro, Dalila Sêni; http://lattes.cnpq.br/3276820050547414
    Aphelenchoides besseyi is considered one of the most threatening nematodes to global agriculture. Despite this, there is little information about genetic diversity, host range and some aspects related to its interaction with its host plants. Recently it was proposed to reclassify A. besseyi into a species complex composed of: A. besseyi sensu stricto, A. oryzae e A. pseudobesseyi. Thus, the objectives of this work were: i) to identify the species of Aphelenchoides causing angular leaf spot in jambu (Acmella oleracea); ii) to biologically and molecularly characterize populations of A. besseyi sensu lato from different hosts, comparing them with other populations from the A. besseyi species complex already described; iii) evaluate aspects of the interaction of this plant parasitic nematode with soybean through histopathological analyses. Morphological, morphometric, and phylogenetic characterizations were carried out, and A. pseudobesseyi was identified as the causal agent of angular leaf spot in jambu. Moreover, the biological characterization of A. besseyi s.l. populations from rice, jambu and soybean, indicated that they reproduce through amphimixis and exhibit sexual compatibility. Phylogenetic and species delimitation analyses, based on nuclear ribosomal and mitochondrial DNA, supported the presence of A. besseyi sensu stricto, A. oryzae, and A. pseudobesseyi within the A. besseyi species complex, with the populations in this study clustering within the A. pseudobesseyi clade. Furthermore, these populations infected soybean, cotton, common beans, and jambu, but they did not infect strawberry and rice. In the interaction of this nematode with soybean, A. pseudobesseyi migrates on the external parts of the plant, targeting shoots, leaves, flowers, and pods, causing alterations as hypertrophy, hyperplasia and cell collapse. However, the nematode is incapable of infecting the seeds. The results of this research point out that A. pseudobesseyi is the etiological agent of angular spot in jambu. All populations of the A. besseyi species complex studied, originating from different hosts, are A. pseudobesseyi. The evidence presented corroborates the recognition of A. oryzae, A. besseyi and A. pseudobesseyi as valid species. The mtCOI gene is the most suitable molecular marker for the phylogenetic study of populations of this species complex. In soybean crops, A. pseudobesseyi parasitism occurs mainly in the regions of sprouts, in leaves and flower buds, with the nematode migrating externally to the plant tissue until reaching such locations. On the leaf blade, the nematode penetrates the tissues, feeding on mesophyll cells. In other organs, parasitism occurs externally to the tissues. However, A. pseudobesseyi is not capable of infecting soybean seeds, and its spread through these is unlikely. Keywords: Foliar nematode. Phylogeny. Etiology. Histopathology
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    Common bacterial blight of common bean: insights into host resistance and bacterial virulence mechanisms
    (Universidade Federal de Viçosa, 2023-10-31) Alves, Francisco Henrique Nunes da Silva; Pacheco, Jorge Luis Badel; http://lattes.cnpq.br/9683209136098886
    Common Bacterial Blight (CBB), induced by the Gram-negative bacteria Xanthomonas phaseoli pv. phaseoli (Xpp) and Xanthomonas citri pv. fuscans (Xcf) is a substantial menace to common bean production worldwide. To contribute to unveiling the molecular mechanisms of host resistance and bacterial virulence subjacent to the interaction between common bean with Xanthomonas, in this study, first (Chapter 1) 80 common bean cultivars of the carioca and black groups were classified based on their resistance upon inoculation with a Xpp strain. The disease was assessed based on symptom severity and the Area Under Disease Progress Curve (AUDPC). The cultivars were subsequently grouped into four resistance/susceptibility categories according to their disease severity values. Three carioca and three black bean cultivars exhibited the lowest disease severity and AUDPC values and were classified as highly resistant to Xpp. A positive correlation between AUDPC and disease severity was observed. Following this classification, an exploratory Genome-Wide Association Study (GWAS) was undertaken using 384 Single Nucleotide Polymorphism (SNP) markers and data on disease severity from the same set of 80 cultivars. Five SNPs significantly associated with resistance were found on three different common bean chromosomes. These SNPs are within genes coding for a range of potential biochemical functions, including a light-regulated Lir1 protein, a proton-dependent oligopeptide transporter family protein, a metallo-dependent phosphatase-like protein, a WPP domain-interacting tail-anchored protein 2, and a pectin lyase-like superfamily protein. In the second phase (Chapter 2), aiming to explore the bacterial virulence mechanisms, 35 genome sequences of Xcf and 36 genome sequences of Xpp were utilized in pangenomic analyses and dendrogram constructions using gene presence/absence. The pangenomic analyses revealed significant genomic diversity and plasticity for both pathovars. The dendrograms did not indicate an evident clustering by geographic origin. Additionally, Xcf and Xpp genes activated by HrpG and HrpX were predicted bioinformatically searching for hrp box sequences within the promoter regions in their genomes. A total of 51 HrpG- and HrpX-dependent genes were found in Xcf and 49 genes in Xpp. Furthermore, to identify Type III Secreted Effectors (T3SEs), Blastp searches of all annotated proteins from the Xpp and Xcf genomes were conducted against databases of known Xanthomonas and Pseudomonas T3SEs. These searches led to the identification of 39 T3SEs, with the effector XopAL2 found exclusively in Xcf, six effectors were unique to Xpp, and seven effectors were shared with phytopathogenic Pseudomonas. This study brings significant contributions to the scientific community. It offers insights into common bean genotypes displaying high levels of resistance to Xpp, identifies candidate genes potentially associated with common bean resistance to Xpp, and sheds light on the mechanisms that Xanthomonas species might employ to cause disease in common bean plants. Keywords: Xanthomonas citri pv. fuscans. Xanthomonas phaseoli pv. phaseoli. Phaseolus vulgaris