Navegando por Autor "Rios, Jonas Alberto"
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Item Effects of fungicide and host resistance on the epidemiology of wheat blast and on plant physiology and changes in the source-sink relationship on wheat during the infection process of Pyricularia oryzae(Universidade Federal de Viçosa, 2016-02-17) Rios, Jonas Alberto; Rodrigues, Fabrício de Ávila; http://lattes.cnpq.br/1157022372359214Two field experiments (Exp. 1 and Exp. 2) were carried out to evaluate the spike blast development as well as the physiological performance and grain yield of wheat cultivars BR-18 (partially resistant) and Guamirim (susceptible) inoculated with Pyricularia oryzae and treated or untreated with the fungicide 13.3% epoxiconazole + 5% pyraclostrobin. Relative to Guamirim-untreated, BR-18-untreated (resistance alone) led to 44 and 64% control of final incidence and severity, respectively, in Exp. 1, and 3 and 49% control, respectively, in Exp. 2. Guamirim-treated (fungicide alone) led to 65% control of incidence and 77% control of severity in Exp. 1, and 64% control of incidence and 95% control of severity in Exp. 2. Similarly, there was reduction higher than 75 % in the temporal rate of spike blast progress when host resistance and fungicide were combined. Results from regression analyses indicated that spike and leaf blast severity at 10-14 days after anthesis resulted in greater yield losses (highest negative slope) than severity at 18 to 22 days after anthesis, and that spike blast severity had a greater negative effect on yield than leaf blast severity. Relative to Guamirim-untreated, there was a 0.3 and 16% increase in mean yield for BR-18-untreated (resistance alone), 20 and 61% increase for Guamirim treated (fungicide alone), and 26 and 83% for BR-18 treated (moderate resistance + fungicide) in Exp. 1 and 2, respectively. By virtue of their effects on blast severity, fungicide application and cultivar resistant resulted in higher measures of leaf health (mean HAD, HLAI, HAA and HRI) and photosynthetic performance (based on F v /F m , F m , Y(II), and Y(NPQ)) of both spikes and leaves than the untreated susceptible reference treatment. Results from this study suggesting that the integration of these strategies may be the best approach for managing spike blast and useful for future efforts to develop crop loss models and management guidelines for wheat blast. Additionally, two experiments were carried out in greenhouse conditions to assess the changes associated with photoassimilates production and their partitioning in source-sink relationship on flag leaves and spikes of wheat plants infected with Pyricularia oryzae. Flag leaves and spikes were inoculated at 10 days after anthesis (daa) (Exp. 1) and at 20 daa (Exp. 2) with a conidial suspension of P. oryzae. There was an impairment on chlorophyll a fluorescence parameters (analyzed by F m , F v /F m YII and Y(NO)) on the infected flag leaves and spikes coupled with reduced concentrations of chlorophyll a + b and carotenoids as well as lower capacity of CO 2 fixation by RuBisCO in the infected flag leaves. In these leaves and grains obtained from the infected spikes, there were lower concentration of soluble sugars and an increase on the hexoses to sucrose ratio on the flag leaves. In the infected flag leaves, there was a lower sucrose phosphate synthase (SPS) activity and lower expression of sucrose synthase (Susy) gene coupled with higher expression and activity of acid invertases. These alterations, associated with synthase and degradation of sucrose, suggestss a status sink in the infected flag leaves. At advanced stages of fungal infection, the concentration of starch was reduced on grains whereas on the infected flag leaves its concentration was kept elevated. There were reduction on the activity of ADP-glucose pyrophosphorylase and on the expression of ADP-glucose pyrophosphorylase genes and down regulation of β- and α-amylase expression at late stages of fungal infection on flag leaves and spikes. In conclusion, the greatest effect of blast on both grains quality and yield can be associated with alterations in the production and partitioning of carbohydrates during the grain filling process.Item Induction of resistance to Pyricularia oryzae in wheat by acibenzolar-S-methyl, ethylene and jasmonic acid(Tropical Plant Pathology, 2014-05) Rios, Jonas Alberto; Rodrigues, Fabrício Ávila; Debona, Daniel; Resende, Renata Sousa; Moreira, Wiler Ribas; Andrade, Camila Cristina LageThis study investigated the effects of acibenzolar-S-methyl (ASM), ethylene (ET) and jasmonic acid (JA) on the resistance of two wheat cultivars (BRS-229 and BR-18) to infection by Pyricularia oryzae. The treatments included spraying plants with ASM (300 mg L-1), ET (0.5 mM), JA (0.1 mM) and distilled water (control) 48 h before inoculation with P. oryzae. Malondialdehyde concentration, an indicative of oxidative damage to the lipids in the leaf cells, was significantly higher for plants sprayed with ASM compared to plants sprayed with JA and ET. Plants sprayed with JA and ET showed reduced values for the number of lesions per cm2 of leaf area and area under blast progress curve, but these hormones had no effect on the incubation period and lesion size (in mm). Plants sprayed with JA and ET showed reduce blast symptoms in comparison to plants sprayed with ASM due to greater peroxidase, polyphenoloxidase, chitinase and β-1,3-glucanase activities.Item Microscopic aspects of the colonization of Pyricularia oryzae on the rachis of wheat plants supplied with silicon(Bragantia, 2015-04) Cruz, Maria Fernanda Antunes da; Silva, Larisse Arantes Freitas; Rios, Jonas Alberto; Debona, Daniel; Rodrigues, Fabrício ÁvilaConsidering the importance of blast, caused by Pyricularia oryzae, to reduce wheat yield, this study investigate how silicon (Si) could reduce the wheat blast symptoms in the rachis tissues using light microscopy and scanning electron microscopy. Wheat plants (cv. BR 18) were grown in hydroponic culture with either 0 (–Si) or 2 mM (+Si) of Si. Blast symptoms were very well developed on the spikes of the –Si plants, which showed intense discoloration in contrast with the spikes of the +Si plants. At 72 hours after inoculation (hai), fungal hyphae extensively colonized the epidermis and the collenchyma tissue in the radial direction in the rachis of the –Si plants. In the +Si plants, fungal hyphae colonized the epidermis and the collenchyma cells to a lesser extent than in the –Si plants. At 96 hai, fungal hyphae were observed in the epidermis, vascular bundles and cortical tissue in the rachis node of the -Si plants. In the +Si plants, a phenolic-like material was detected in the parenchyma with lower fungal colonization in comparison with the –Si plants. In scanning electron microscopy, fungal hyphae were scarcely observed in the upper epidermal, collenchyma and parenchyma cells in the rachis tissue of the +Si plants, whereas in the rachis tissue of the –Si plants, fungal hyphae extensively colonized the epidermis, collenchyma, parenchyma and vascular bundles.Item Potassium- modulated physiological performance of mango plants infected by Ceratocystis fimbriata(Bragantia, 2017-10) Cacique, Isaias Severino; Bispo, Wilka Messner Silva; Araujo, Leonardo; Aucique- Pérez, Carlos Eduardo; Rios, Jonas Alberto; Silva, Leandro Castro; Rodrigues, Fabrício ÁvilaMango wilt, caused by the fungus Ceratocystis fimbriata, is an important disease affecting mango production. In view of the beneficial effects of potassium (K) in other profitable crops and the lack of information about the effect of macronutrients on mango wilt development, the present study aimed to evaluate how mango plants supplied with K respond physiologically when infected by C. fimbriata. Mango plants (» 3 years old) from cultivar Ubá were grown in plastic pots containing 58 mg of K·dm−3 (original K level based on the chemical analysis of the substrate) or in plastic pots with substrate amended with a solution of 0.5 M potassium chloride (KCl) to achieve the rate of 240 mg K·dm−3. Disease symptoms were more pronounced in inoculated plants grown at the lower K level. Substantial declines in stomatal conductance, in line with decreases in the internal-to-ambient CO2 concentration ratio and the absence of detectable changes in the chlorophyll a fluorescence parameters, suggest that the decrease in the net carbon assimilation rate is due, at least initially, to stomatal limitations. High concentrations of K and manganese were found in the stem tissues of inoculated plants and supplied with the highest K rate, most likely due to the involvement of these tissues in the local development of defense mechanisms. The results of this study suggest that the supply of K favored the physiological performance of mango plants and their resistance against C. fimbriata infection.Item Resistência induzida na interação trigo - Pyricularia oryzae e elaboração de uma escala diagramática para estimar a severidade da brusone(Universidade Federal de Viçosa, 2012-02-14) Rios, Jonas Alberto; Rodrigues, Fabrício de ávila; http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4709080E6; http://lattes.cnpq.br/1157022372359214; Cunha, Luis Claudio Vieira da; http://lattes.cnpq.br/9367947173322278; Resende, Renata Sousa; http://lattes.cnpq.br/6797798856725246A brusone, causada pelo fungo Pyricularia oryzae (Cooke) Sacc., é uma das principais doenças que afetam a cultura do trigo (Triticum aestivum L.). O presente trabalho objetivou investigar o efeito do acibenzolar-S-metil (ASM), ácido jasmônico (AJ) e etileno (ET) na resistência do trigo em resposta à infecção por Pyricularia oryzae, bem como elaborar e validar uma escala diagramática para quantificar a severidade da brusone do trigo. No primeiro estudo, dois experimentos foram conduzidos em casa de vegetação no delineamento inteiramente casualizado com 4 tratamentos e 4 repetições. Plantas de trigo das cultivares BRS-229 e BR-18 foram cultivadas em vasos plásticos com capacidade de 1 dm3 de substrato. Os tratamentos utilizados foram: T1- água destilada (testemunha), T2 - 0,1 mM de ácido jasmônico (AJ), T3 - 300 mg/L de acibenzolar-S-metil (ASM) e T4 - 0,5 mM de etileno (ET) (Ethephon). Foram avaliados os componentes de resistência: período de incubação (PI), número de lesões (NL) por cm2 de área foliar, tamanho de lesão (TL) em mm e a severidade. Os valores de severidade foram utilizados para calcular a área abaixo da curva do progresso da brusone (AACPB). Para avaliar o efeito dos indutores sobre os mecanismos bioquímicos de resistência foi determinada a atividade de peroxidases (POX), polifenoloxidases (PFO), fenilalanina amônia-liases (FAL), quitinases (QUI), β-1,3-glucanases (GLU) e lipoxigenases (LOX), além da concentração de aldeído malônico (MDA). Para a cultivar BRS-229, a AACPB foi reduzida significativamente em 57, 35 e 61%, respectivamente, com a aplicação de AJ, ASM e ET em relação ao tratamento controle (água destilada). Houve redução significativa de 53, 35 e 59% na AACPB com a aplicação de AJ, ASM e ET nas plantas da cultivar BR 18 em relação ao tratamento controle. A aplicação de AJ, ASM e ET proporcionou uma redução de 69, 38 e 68%, respectivamente, no NL para a cultivar BRS-229 e de 63, 41 e 66% para a cultivar BR-18. O NL e a AACPB foram significativamente maiores com a aplicação de ASM em relação à aplicação de AJ e ET para as duas cultivares. Não houve diferença significativa entre os tratamentos para o PI e o TL nas duas cultivares Plantas pulverizadas com os viindutores apresentaram maiores atividades da POX, PFO, QUI, GLU e LOX em relação ao tratamento controle. Concluiu-se que a aplicação dos indutores AJ, ASM e ET aumentou a atividade das enzimas nas plantas de trigo durante o processo infeccioso de P. oryzae diminuindo, assim, a severidade da brusone. No segundo estudo, foi elaborada uma escala diagramática com dez níveis de severidade, a saber: 0,1; 1; 2; 4; 8; 16; 24; 32; 52; 72%. Para validar a escala, 10 avaliadores inexperientes estimaram a severidade da brusone. A acurácia e a precisão dos avaliadores foram analisadas pelo coeficiente de correlação concordante de Lin s (ρ c) e regressão linear simples entre a severidade real e a severidade estimada sem e com o uso da escala. A escala proporcionou satisfatória acurácia e precisão (R2 médio de 94,5%) com erros absolutos em torno de 15%. Os valores de u, υ e ρc foram melhorados em 90, 100 e 90% dos avaliadores, respectivamente, com o uso da escala. A reprodutibilidade entre os avaliadores utilizando a escala foi elevada (R2 superior a 0,90 para 64,4% dos casos). A escala obtida é adequada para estimar a severidade da brusone do trigo e pode ser utilizada em estudos onde faz-se necessário quantificar essa doença.Item A set of standard area diagrams to assess severity of frogeye leaf spot on soybean(European Journal of Plant Pathology, 2015-03-14) Debona, Daniel; Nascimento, Kelly Juliane Telles; Rezende, Danielle; Rios, Jonas Alberto; Bernardeli, Arthur Martins Almeida; Silva, Leandro Castro; Rodrigues, Fabrício ÁvilaA set of standard area diagrams (SADs) was developed and validated to aid visual assessment of severity of frogeye leaf spot (FLS) caused by Cercospora sojina. The SAD has eight color images of diseased leaflets with severity values that ranged from 0.1 to 39.9 %. The SAD was validated by a group of 20 raters [10 experienced (ER) and 10 inexperienced (IR)], who assessed the same set of 50 images twice, the first without SADs and the second using SADs as an aid. The SADs significantly improved accuracy [coefficients of bias (C b ) were 0.64 and 0.99 for IR and 0.98 and 0.99 for ER, without and with SADs, respectively], precision [correlation coefficients (r) were 0.89 and 0.95 for IR and 0.94 and 0.97 for ER, without and with SADs, respectively] and overall agreement [Lin’s concordance correlation coefficients (ρ c ) were 0.57 and 0.94 for IR and 0.92 and 0.97 for ER without and with SADs, respectively]. The estimates of severity of FLS were more reliable when using SADs. Both the inter-rater reliability (coefficient of determination, R:^2 ) and intra-class coefficient (ρ) were significantly increased by using SADs. Therefore, it is believed that the SADs proposed in the present study will be a useful tool to aid accurate, precise and reliable estimates of severity of FLS in experiments (e.g., fungicide screening, assessment of partial resistance of soybean genotypes to FLS) and to aid in decision-making purposes.Item Silicato de potássio, acibenzolar-S-metil e fungicidas no controle da ferrugem da soja(Ciência Rural, 2009-11) Duarte, Henrique da Silva Silveira; Zambolim, Laércio; Rodrigues, Fabrício de Ávila; Rios, Jonas Alberto; Lopes, Ueder PedroA produção da soja pode ser afetada pela ocorrência de várias doenças. Dentre estas, a ferrugem, causada pelo fungo Phakopsora pachyrhizi, tem se destacado. Atualmente, novas estratégias de controle para essa doença devem ser pesquisadas. Assim, este trabalho teve como objetivo avaliar a eficiência do silicato de potássio (KSi), acibenzolar-S-metil e fungicidas no controle da ferrugem da soja. Um experimento foi conduzido em condições de campo, em delineamento em blocos ao acaso, utilizando-se 10 tratamentos, com três repetições. Foi utilizada a cultivar 'Monarca' por ser suscetível à ferrugem. Os tratamentos utilizados foram: T1 - testemunha (pulverização com água); T2 - KSi (1,2kg ha-1); T3 - KSi (2,4kg ha-1); T4 - KSi (3,6kg ha-1); T5 - KSi (4,8kg ha-1); T6 - tebuconazole (125g de i.a. ha-1); T7 - cloreto de potássio (61,72g L-1); T8 - mancozebe (2400g de i.a. ha-1); T9 - mancozebe (2400g de i.a. ha-1) + KSi (1,2kg ha-1) e T10 - acibenzolar-S-metil (125g de i.a. ha-1). As plantas da bordadura foram inoculadas com uma suspensão de 5x105 uredosporos mL-1 no estádio V4 para constituírem fonte de inóculo, para as parcelas centrais. As plantas foram pulverizadas com os produtos que constituíram os tratamentos T2, T3, T4, T5, T7, T8 e T9 nos estádios V5, R1, R4 e R5.4 e os tratamentos T6 e T10 nos estádios R1, R4 e R5.4. As plantas foram pulverizadas com atomizador costal manual de bico cônico empregando-se um volume de calda de 200L ha-1. Foram realizadas cinco avaliações da severidade da ferrugem nos terços inferior, médio e superior das plantas utilizando-se uma escala diagramática variando de 0,6 a 78,5%, e os dados obtidos foram utilizados para calcular a área abaixo da curva do progresso da ferrugem (AACPF). Não houve efeito significativo das doses de KSi na AACPF e severidade máxima (Ymax) nos terços inferior, médio e superior das plantas, além da produtividade. Os tratamentos 8, 9 e 10 apresentaram eficiência intermediária no controle da ferrugem. O tratamento 6 foi o mais eficiente no controle da doença por resultar nos menores valores da AACPF e Ymax para os terços inferior, médio e superior, além de uma produtividade significativamente maior em relação aos demais tratamentos.