Navegando por Autor "Silva, Leandro Castro"
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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 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 Trocas gasosas e estresse oxidativo em plantas de algodoeiro supridas com silício e infectadas por Ramularia areola(Bragantia, 2013-11-10) Curvêlo, Carmen Rosa da Silva; Rodrigues, Fabrício Ávila; Pereira, Lucas Felisberto; Silva, Leandro Castro; DaMatta, Fábio Murilo; Berger, Paulo GeraldoConsiderando o efeito positivo do silício (Si) na melhoria do desempenho fisiológico de várias espécies de plantas quando infectadas por patógenos, este trabalho teve como meta investigar o efeito desse elemento na capacidade fotossintética e no metabolismo antioxidativo de plantas dos cultivares de algodoeiro NuOpal e BRS Buriti, supridas ou não com Si, durante o processo infeccioso de Ramularia areola. A infecção por R. areola afetou negativamente a taxa líquida de fixação do CO2 (A), a condutância estomática (gs), a transpiração e a razão entre concentração interna e ambiente de CO2 nas plantas dos cultivares NuOpal e BRS Buriti não supridas com Si em relação às plantas supridas com esse elemento. Na presença do Si, houve aumento em A e gs além das concentrações de clorofila a, clorofila b e carotenóides nas plantas dos dois cultivares. A concentração foliar de Si aumentou, o que contribuiu para decrescer em 38% a área abaixo da curva do progresso da mancha de ramulária nas plantas supridas com Si, em relação às plantas não supridas com esse elemento. O fornecimento de Si às plantas de algodoeiro dos dois cultivares aumentou a atividade da dismutase do superóxido (SOD), da peroxidase do ascorbato (APX) e da lipoxigenase (LOX), mas houve redução na atividade da catalase (CAT) e na concentração de peróxido de hidrogênio (H2O2) e de aldeído malônico (MDA), houve ainda uma maior perda de eletrólitos. A atividade da glutationa redutase (GR) foi maior nas plantas do cultivar BRS Buriti supridas com Si, enquanto que nas plantas do cultivar NuOpal houve aumento da atividade da glutationa redutase apenas aos 21 dias após inoculação (dai). Conclui-se que a capacidade fotossintética e o sistema antioxidativo das plantas supridas com Si sofreram menor impacto durante o processo infeccioso de R. areola.