Fitopatologia - Artigos
URI permanente para esta coleçãohttps://locus.ufv.br/handle/123456789/11741
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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 Cytological aspects of the infection process of Pyricularia oryzae on leaves of wheat plants supplied with silicon(Tropical Plant Pathology, 2013-11) Sousa, Rodrigo Silva; Rodrigues, Fabrício Ávila; Schurt, Daniel Augusto; Souza, Naiara Fernandes Abreu; Cruz, Maria Fernanda AntunesBlast, caused by Pyricularia oryzae, has become one of the most important diseases on wheat in Brazil. Knowing the beneficial effects of silicon (Si) in reducing rice blast severity, this study aimed to examine the cytological events occurring during the infectious process of P. oryzae on the leaves of wheat plants non-supplied (-Si) or supplied (+Si) with Si in an experiment arranged in a completely randomized design. The high foliar Si concentration for the +Si plants contributed to decrease the blast symptoms. Hyphae of P. oryzae grew successfully and formed an extensively branched mycelium in the first-invaded epidermal cell and invaded several neighboring cells on the -Si plants, while on the +Si plants fungal hyphae was restricted to the first-invaded epidermal cell. The number of brown adaxial epidermal cells and their intensity of browning were significantly lower for the +Si plants in comparison to the -Si plants. The frequency of appressorial sites showing type B reaction (infection hyphae within the epidermal cell and absence of cytoplasm granulation) was lower for the +Si plants than for the -Si plants from 72 to 96 hours after inoculation because the frequency of appressorial sites showing type A reaction (unsuccessful penetration) was kept higher in comparison to the -Si plants. This study provides novel cytological evidence of the negative effect of Si on the infection process of P. oryzae on leaves of wheat plants contributing, therefore, to reduce the blast symptoms.Item Effects of silicon on the penetration and reproduction events of Meloidogyne exigua on coffee roots(Bragantia, 2015-04) Silva, Rodrigo Vieira; Oliveira, Rosângela D’Arc de Lima; Ferreira, Patrícia da Silva; Castro, Douglas Barbosa; Rodrigues, Fabrício ÁvilaConsidering that the root-knot nematode Meloidogyne exigua has caused great yield losses to coffee production in Brazil, this study aimed to determine whether the penetration and the reproduction events of this nematode on the roots of plants from two coffee cultivars with different levels of basal resistance to this nematode could be affected by silicon (Si). Coffee plants from the cultivars Catuaí and IAPAR 59, which are susceptible and resistant, respectively, to M. exigua, were grown in pots containing Si-deficient soil that was amended with either calcium silicate (+Si) or calcium carbonate (–Si). The Si concentration on the root tissue significantly increased by 159 and 97% for the +Si plants from the cultivars Catuaí and IAPAR 59, respectively, compared to the –Si plants of these cultivars. The population of M. exigua, the number of galls and the number of eggs were significantly reduced on the roots of the +Si plants of the cultivars Catuaí and IAPAR 59 compared to the –Si plants of these cultivars. It was concluded that the development and reproduction events of M. exigua were negatively impacted on the roots of coffee plants supplied with Si.Item Antagonistic rhizobacteria and jasmonic acid induce resistance against tomato bacterial spot(Bragantia, 2015-10) Ferraz, Hélvio Gledson Maciel; Resende, Renata Sousa; Moreira, Poliana Coutinho; Silveira, Patrícia Ricardino; Milagres, Elisângela Aparecida; Oliveira, José Rogério; Rodrigues, Fabrício ÁvilaTomato bacterial spot on tomato may be caused by four species of Xanthomonas and among them X. gardneri(Xg) is the most destructive one, especially in areas irrigated using a center pivot system in Minas Gerais state and the midwest region of Brazil. Due to the ineffectiveness of chemical control and the lack of cultivars with high levels of genetic resistance, this study investigated the potential of three antagonists (Streptomyces setonii (UFV618), Bacillus cereus (UFV592) and Serratia marcescens (UFV252)), and the hormone jasmonic acid (JA) as a positive control, to reduce bacterial spot symptoms and to potentiate defense enzymes in the leaves of tomato plants infected by Xg. Tomato seeds were microbiolized with each antagonist, and the soil was drenched with these bacteria. The plants were sprayed with JA 48 h before Xginoculation. The final average severity on the tomato plants was reduced by 29.44, 59.26 and 61.33% in the UFV592, UFV618 and JA treatments, respectively. The UFV618 antagonist was as effective as JA in reducing bacterial spot symptoms on tomatoes, which can be explained by the greater activities of defense enzymes that are commonly involved in host resistance against bacterial diseases. These results suggest that JA and the UFV618 antagonist can be used in the integrated management of bacterial spot on tomatoes.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 Infection Process of Cercospora coffeicola on Coffee Leaf(Journal of Phytopathology, 2011-01) Souza, André Gomes Coelho; Rodrigues, Fabrício Ávila; Maffia, Luiz Antônio; Mizubuti, Eduardo Seiti GomideBrown eye spot, caused by Cercospora coffeicola, is an important disease of coffee. Both adaxial and abaxial leaf surfaces were inoculated with a conidial suspension of C. coffeicola. Samples were collected from 4 to 168 h after inoculation and then again at 35 days. Germinated conidia showed positive tropism to stomata where attempted penetrations occurred. Appressoria were not observed. After penetration, C. coffeicola colonized the lacunous parenchyma both inter and intracellularly. Sporulation occurred through or around the stomata. Results from this study provide new insights into the infection process of C. coffeicola on coffee leaf.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 Silicon and manganese on rice resistance to blast(Bragantia, 2012-05-14) Cacique, Isaías Severino; Domiciano, Gisele Pereira; Rodrigues, Fabrício Ávila; Vale, Francisco Xavier Ribeiro doBlast, caused by the fungus Pyricularia oryzae, is the most important fungal disease of rice. The effect of silicon (Si) and manganese (Mn), and their interaction, on rice resistance to blast was investigated. Rice plants (cultivar "Metica 1") were grown in hydroponic solution with 0 or 2 mmol L-1 of Si and with 0.5, 2.5, and 10 mmol L-1 of Mn. Sixty-day-old plants were inoculated with a conidial suspension of P. oryzae and the incubation period (IP), the number of lesions (NL) per cm2 of leaf area, the lesion size (LS), and blast severity were evaluated. Blast severity was scored at 48, 72, 96, and 144 hours after inoculation and data were used to obtain the area under blast progress curve (AUBPC). Silicon concentration was significantly higher in leaf tissues of plants supplied with this element than on its absence, regardless of Mn rates. There was no significant difference in Si concentration among the Mn rates for both - Si and +Si treatments. The Mn concentration was significantly higher in the tissues of plants from the - Si treatment as compared to plants of the +Si treatment, but only at the rate of 10 mmol L-1 of Mn. There was a significant increase in Mn concentration as the rates of this micronutrient increased from 0.5 to 10 mmol L-1 regardless of the Si treatments. The IP significantly increased in the +Si treatment. The Mn rates had no effect on the IP regardless of the Si treatments. The NL was significantly lower in the presence of Si regardless of the Mn rates. The Mn rates had no effect on NL regardless of the Si treatments. The addition of Si to the nutrient solution significantly reduced both LS and AUBPC regardless of Mn rates. However, in the absence of Si, the values for LS and AUBPC were significantly lower at the Mn rate of 10 µmol L-1 as compared to the rate of 0.5 µmol L-1. Overall, the results from this study showed the potential of Si to decrease blast development on rice regardless of the foliar concentration of Mn.Item Effect of root and leaf applications of soluble silicon on blast development in rice(Bragantia, 2013-08-18) Cacique, Isaias Severino; Domiciano, Gisele Pereira; Moreira, Wiler Ribas; Rodrigues, Fabrício Ávila; Cruz, Maria Fernanda Antunes; Serra, Núria Sierras; Català, Ana BottaBlast, caused by Pyricularia oryzae, is the most important fungal disease of rice worldwide. This study aimed to compare root and foliar supply of soluble silicon (Si) on rice resistance to blast. The application of soluble Si to the roots increased Si concentration in leaf tissues as compare to plants grown in soil amended with calcium silicate. There was no increase in leaf Si concentration after soluble Si spray, regardless if the leaves were washed or not before analysis. X-ray microanalysis revealed that Si deposition was very similar on the leaf epidermis of plants sprayed with soluble Si, root amended with soluble Si or grown in soil amended with calcium silicate. The lesion size, the number of lesions per cm2 of leaf and the area under blast progress curve were reduced for rice plants grown in soil that received the application of soluble Si or was amended with calcium silicate. The results of this study showed that the supply of soluble Si to the roots or its spray onto to the rice leaves can decrease blast symptoms.Item Silício no processo infeccioso de Phakopsora pachyrhizi em folíolos de plantas de soja(Pesquisa Agropecuária Brasileira, 2011-12-30) Cruz, Maria Fernanda Antunes da; Silva, Larisse de Freitas; Rodrigues, Fabrício Ávila; Araujo, João Marcos de; Barros, Everaldo Gonçalves deThe objective of this work was to evaluate the effect of silicon (Si) on the infection process of Phakopsora pachyrhizi in leaflets of soybean plants grown in nutrient solution with or without Si. Observations done with light microscope and scanning electron microscope indicated that, in leaflets of plants supplied with Si, uredia were smaller and fewer in number. There were reductions of 27, 23 and 60% in the number of lesions, closed uredia and open uredia, respectively, in leaflets of plants with Si. Soybean plants supplied with Si show reduction in Asian soybean rust symptoms.