oalib
Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
Analysis of expressed sequence tags from Citrus sinensis L. Osbeck infected with Xylella fastidiosa
Souza, Alessandra A. de;Takita, Marco A.;Coletta-Filho, Helvécio D.;Targon, Maria Luisa P.N.;Carlos, Eduardo F.;Locali-Fabris, Eliane C.;Amaral, Alexandre M.;Freitas-Astúa, Juliana;Silva-Pinhati, Ana Carla O.;Boscariol-Camargo, Raquel L.;Berger, Irving J.;Rodrigues, Carolina M.;Reis, Marcelo S.;Machado, Marcos A.;
Genetics and Molecular Biology , 2007, DOI: 10.1590/S1415-47572007000500023
Abstract: in order to understand the genetic responses resulting from physiological changes that occur in plants displaying citrus variegated chlorosis (cvc) symptoms, we adopted a strategy of comparing two est libraries from sweet orange [citrus sinensis (l.) osbeck]. one of them was prepared with plants showing typical cvc symptoms caused by xylella fastidiosa and the other with non-inoculated plants. we obtained 15,944 ests by sequencing the two cdna libraries. using an in silico hybridization strategy, 37 genes were found to have significant variation at the transcriptional level. within this subset, 21 were up-regulated and 16 were down-regulated in plants with cvc. the main functional categories of the down-regulated transcripts in plants with cvc were associated with metabolism, protein modification, energy and transport facilitation. the majority of the up-regulated transcripts were associated with metabolism and defense response. some transcripts associated with adaptation to stress conditions were up-regulated in plants with cvc and could explain why plants remain alive even under severe water and nutritional stress. others of the up-regulated transcripts are related to defense response suggesting that sweet orange plants activate their defense machinery. the genes associated with stress response might be expressed as part of a secondary response related to physiological alterations caused by the infection.
Comparative analysis of differentially expressed sequence tags of sweet orange and mandarin infected with Xylella fastidiosa
Souza, Alessandra A. de;Takita, Marco A.;Coletta-Filho, Helvécio D.;Campos, Magnólia A.;Teixeira, Juliana E.C.;Targon, Maria Luísa P.N.;Carlos, Eduardo F.;Ravasi, Juliano F.;Fischer, Carlos N.;Machado, Marcos A.;
Genetics and Molecular Biology , 2007, DOI: 10.1590/S1415-47572007000500024
Abstract: the citrus ests sequencing project (citest) conducted at centro apta citros sylvio moreira/iac has identified and catalogued ests representing a set of citrus genes expressed under relevant stress responses, including diseases such as citrus variegated chlorosis (cvc), caused by xylella fastidiosa. all sweet orange (citrus sinensis l. osb.) varieties are susceptible to x. fastidiosa. on the other hand, mandarins (c. reticulata blanco) are considered tolerant or resistant to the disease, although the bacterium can be sporadically detected within the trees, but no disease symptoms or economic losses are observed. to study their genetic responses to the presence of x. fastidiosa, we have compared est libraries of leaf tissue of sweet orange pêra iac (highly susceptible cultivar to x. fastidiosa) and mandarin ?ponkan? (tolerant) artificially infected with the bacterium. using an in silico differential display, 172 genes were found to be significantly differentially expressed in such conditions. sweet orange presented an increase in expression of photosynthesis related genes that could reveal a strategy to counterbalance a possible lower photosynthetic activity resulting from early effects of the bacterial colonization in affected plants. on the other hand, mandarin showed an active multi-component defense response against the bacterium similar to the non-host resistance pattern.
High temperature effects on the response of photosynthesis to light in sweet orange plants infected with Xylella fastidiosa
Ribeiro, Rafael Vasconcelos;Machado, Eduardo Caruso;Oliveira, Ricardo Ferraz de;Pimentel, Carlos;
Brazilian Journal of Plant Physiology , 2003, DOI: 10.1590/S1677-04202003000200004
Abstract: the objective of this study was to evaluate the high temperature effects on the response of photosynthesis to light in sweet orange plants infected with xylella fastidiosa. this vascular bacterium is the causal agent of the citrus variegated chlorosis that causes severe economical losses to the brazilian citrus industry. the responses of the photosynthetic oxygen evolution and the parameters related to chlorophyll a fluorescence to the increase in light intensity were evaluated at 35oc and 45oc in both healthy and infected leaf discs. the increase in temperature affected the photosynthetic apparatus of both healthy and infected plants, although infected plants showed higher photochemical sensitivity at the higher temperature (e.g. in the potential quantum efficiency of photosystem ii, maximum and basal fluorescence yield, and in the relation between variable and basal fluorescence yield). this higher sensitivity of infected plants was not reflected in the overall photosynthetic reaction, since photosynthetic oxygen evolution values did not vary at 45oc. healthy and infected plants showed differences in photosynthetic oxygen evolution but displayed similar effective quantum efficiency of photosystem ii as well as apparent electron transport rates at 35oc. these results suggest that the limitations in photosynthesis observed on the infected plants might arise through impaired biochemical reactions.
High temperature effects on the response of photosynthesis to light in sweet orange plants infected with Xylella fastidiosa  [cached]
Ribeiro Rafael Vasconcelos,Machado Eduardo Caruso,Oliveira Ricardo Ferraz de,Pimentel Carlos
Brazilian Journal of Plant Physiology , 2003,
Abstract: The objective of this study was to evaluate the high temperature effects on the response of photosynthesis to light in sweet orange plants infected with Xylella fastidiosa. This vascular bacterium is the causal agent of the citrus variegated chlorosis that causes severe economical losses to the Brazilian citrus industry. The responses of the photosynthetic oxygen evolution and the parameters related to chlorophyll a fluorescence to the increase in light intensity were evaluated at 35oC and 45oC in both healthy and infected leaf discs. The increase in temperature affected the photosynthetic apparatus of both healthy and infected plants, although infected plants showed higher photochemical sensitivity at the higher temperature (e.g. in the potential quantum efficiency of photosystem II, maximum and basal fluorescence yield, and in the relation between variable and basal fluorescence yield). This higher sensitivity of infected plants was not reflected in the overall photosynthetic reaction, since photosynthetic oxygen evolution values did not vary at 45oC. Healthy and infected plants showed differences in photosynthetic oxygen evolution but displayed similar effective quantum efficiency of photosystem II as well as apparent electron transport rates at 35oC. These results suggest that the limitations in photosynthesis observed on the infected plants might arise through impaired biochemical reactions.
Aspectos biológicos das cigarrinhas Acrogonia gracilis (Osborn), Dilobopterus costalimai Young e Oncometopia facialis (Signoret) (Hemiptera: Cicadellidae) em Citrus sinensis L. Osbeck
Paiva, Paulo E.B.;Benvenga, Sérgio R.;Gravena, Santin;
Neotropical Entomology , 2001, DOI: 10.1590/S1519-566X2001000100005
Abstract: the biological aspects of the leafhoppers acrogonia gracilis (osborn), dilobopterus costalimai young and oncometopia facialis (signoret) on young plants of citrus sinensis l. osbeck was studied at 25±2oc, relative humidity of 60±10% and photophase of 12h. these species are vectors of xylella fastidiosa wells to citrus. five instars were observed for d. costalimai and o . facialis and six for a. gracilis. the mean duration from egg to adult and longevity were, respectively, 54.5 and 72.4 days for a. gracilis, 54.7 and 36.4 days for d. costalimai and 67.1 and 15.5 days for o. facialis.
Monitoramento populacional das cigarrinhas vetoras de Xylella fastidiosa, através de armadilhas adesivas amarelas em pomares comerciais de citros
Molina, Rúbia de Oliveira;Nunes, William Mário de Carvalho;Gon?alves, Aline Maria Orbolato;Nunes, Maria Júlia Corazza;Zanutto, Carlos Alexandre;
Ciência e Agrotecnologia , 2010, DOI: 10.1590/S1413-70542010000700008
Abstract: citrus variegated chlorosis (cvc) is the disease caused by the bacteria xylella fastidiosa wells. dissemination occurs through insect vectors belonging to the order hemiptera, family cicadellidae (subfamily cicadellinae), which transmit the bacteria after feeding on infected plants. the objective of this study was to identify the species of insect vectors in an orchard in the municipality of paranavaí, in the state of paraná. the experiment was conducted in a commercial stand of sweet orange (citrus sinensis (l.) osbeck), pêra variety with 1,000 10-year-old plants. monitoring was performed using yellow sticky traps, distributed in the central and peripheral areas of the orchard with two traps on each one. the stickers were distributed between the 5th and 30th plant in each 10 rows, totaling 20 traps in the orchard and renewed every thirty days during the evaluation period, which was between june 2005 and september 2006. the main species caught were cicadellinae acrogonia citrina marucci & cavichioli dilobopterus costalimai young and macugonalia cavifrons stal. these species occurred constantly, with frequencies of 3.97%, 4.2%, and 13.0% respectively, compared to the total leafhoppers collected.
Ingest?o de seiva do xilema de laranjeiras 'Pêra' e 'Valência' (Citrus sinensis (L.) Osbeck) sadias e infectadas por Xylella fastidiosa, pelas cigarrinhas vetoras Oncometopia facialis e Dilobopterus costalimai (Hemiptera: Cicadellidae)
Montesino, Luiz Henrique;Coelho, Juliana Helena Carvalho;Felippe, Marcos Rogério;Yamamoto, Pedro Takao;
Revista Brasileira de Fruticultura , 2006, DOI: 10.1590/S0100-29452006000200010
Abstract: it was studied the effect of xylella fastidiosa infection, causal agent of citrus variegated chlorosis (cvc), on the xylem sap ingestion rate of citrus plants by two sharpshooters species (hemiptera: cicadellidae). seedlings of sweet orange pera and valencia (citrus sinensis) were used and infected by x. fastidiosa, strain 9a5c, obtained by mechanical inoculation. the insects used in the experiments were collected in the field, one from cicadellini tribe (dilobopterus costalimai) and another from proconiini tribe (oncometopia facialis). the xylem sap ingestion rate by o. facialis was quantified in seedling twigs, and by d. costalimai in leaves and twigs, by means of evaluation of the liquid volume (honeydew) excreted by time unity. the consumption by o. facialis sharpshooter in diseased plants was inferior to healthy plants. in the diseased pera variety the consumption was lower, not permitting a xylem sap quantification. in healthy pera and healthy and diseased valencia, o. facialis showed expressive rate of consumption, with high feeding during the day. in the healthy plants of both varieties, the consumption by d. costalimai sharpshooter was higher than in cvc diseased plants. comparing both varieties, the rate was higher in the valencia variety, and concerning parts of the plant, leaves and twigs, the ingestion rate was higher in the twigs of both varieties, with higher consumption during the day.
CO2 assimilation, photosynthetic light response curves, and water relations of 'Pêra' sweet orange plants infected with Xylella fastidiosa
Habermann, Gustavo;Machado, Eduardo Caruso;Rodrigues, Jo?o Domingos;Medina, Camilo Lázaro;
Brazilian Journal of Plant Physiology , 2003, DOI: 10.1590/S1677-04202003000200003
Abstract: plants with citrus variegated chlorosis (cvc), a disease caused by the xylem-limited bacteria xylella fastidiosa, have leaves with water deficiency symptoms and are associated with decreases on the net photosynthesis and transpiration rates. using healthy and cvc-affected 'pêra' sweet orange plants on 'rangpur' lime rootstock, the leaf gas exchange variables were measured with an open-gas portable photosynthesis system. all plants were watered and the leaf water potential (yw) was measured by isopiestic thermocouple psychrometric technique. the net photosynthesis (a) vs. internal leaf co2 concentration (a/ci curves) was analyzed. the relative effect of stomatal resistance on photosynthesis (s%) and the estimation of carboxylation efficiency were calculated. the rates of photosynthesis and transpiration, stomatal conductance, and internal leaf co2 concentration (ci) were also measured while varying the photosynthetic photon flux density (ppfd). the s% values were approximately 30 % greater in infected plants when compared to healthy ones. the light compensation point for diseased plants was higher than in the healthy ones, and the saturation light point in plants with cvc was twofold lower. the lower yw in diseased plants favours the hypothesis of xylem occlusion, which probably caused a lower water supply to the mesophyll, thus decreasing the photosynthesis and transpiration rates. nevertheless, there was also a reduction in the photosynthetic metabolic activities, represented by lower carboxylation efficiency and photochemical disturbances that were detected in diseased plants.
CO2 assimilation, photosynthetic light response curves, and water relations of 'Pêra' sweet orange plants infected with Xylella fastidiosa  [cached]
Habermann Gustavo,Machado Eduardo Caruso,Rodrigues Jo?o Domingos,Medina Camilo Lázaro
Brazilian Journal of Plant Physiology , 2003,
Abstract: Plants with citrus variegated chlorosis (CVC), a disease caused by the xylem-limited bacteria Xylella fastidiosa, have leaves with water deficiency symptoms and are associated with decreases on the net photosynthesis and transpiration rates. Using healthy and CVC-affected 'Pêra' sweet orange plants on 'Rangpur' lime rootstock, the leaf gas exchange variables were measured with an open-gas portable photosynthesis system. All plants were watered and the leaf water potential (Yw) was measured by isopiestic thermocouple psychrometric technique. The net photosynthesis (A) vs. internal leaf CO2 concentration (A/Ci curves) was analyzed. The relative effect of stomatal resistance on photosynthesis (S%) and the estimation of carboxylation efficiency were calculated. The rates of photosynthesis and transpiration, stomatal conductance, and internal leaf CO2 concentration (Ci) were also measured while varying the photosynthetic photon flux density (PPFD). The S% values were approximately 30 % greater in infected plants when compared to healthy ones. The light compensation point for diseased plants was higher than in the healthy ones, and the saturation light point in plants with CVC was twofold lower. The lower Yw in diseased plants favours the hypothesis of xylem occlusion, which probably caused a lower water supply to the mesophyll, thus decreasing the photosynthesis and transpiration rates. Nevertheless, there was also a reduction in the photosynthetic metabolic activities, represented by lower carboxylation efficiency and photochemical disturbances that were detected in diseased plants.
Análise espa o-temporal da clorose variegada dos citros no Noroeste do Paraná, com uso de PCR para detec o de Xylella fastidiosa = Spatio-temporal analysis of the citrus variegated chlorosis (CVC) in the Northwest of Paraná, using PCR for detection of Xylella fastidiosa
William Mário de Carvalho Nunes,Carlos Alexandre Zanutto,Maria Júlia Corazza- Nunes,Rúbia de Oliveira Molina
Acta Scientiarum : Agronomy , 2006,
Abstract: A citricultura é afetada por inúmeras doen as, como a clorose variegada do citros (CVC), causada pela bactéria Xylella fastidiosa. O objetivo deste trabalho foi determinar a distribui o espacial da doen a dentro de pomares comerciais do Noroeste do Paraná com o uso de métodos moleculares. Foram selecionados pomares sintomáticos para CVC com as variedades ‘Pêra’, ‘Valência’ e ‘Folha Murcha’ (Citrus sinensis Osbeck). Foram marcadas para cada variedade, 4 plantas-referência positivas para CVC (por sintomas e análise molecular) e 8 plantas ao redor de cada uma das plantas-referência foram amostradas, num total de 36 plantas por variedade. Realizou-se o teste da Rea o da Polimerase em Cadeia (PCR) para detec o da bactéria e na mesma época foram conduzidas avalia es visuais de sintomas de CVC. Os resultados da análise temporal, utilizando-se os modelos Monomolecular, Logístico e Gompertz, apontaram o modelo Logístico como o que melhor se ajustou para descrever o comportamento da doen a no tempo, para todas as variedades estudadas. Observou-se que o comportamento espacial da doen a diferiu quando a mesma área foiavaliada pelos métodos visual e molecular, resultando em uma diferen a no padr o espacial das áreas avaliadas. Portanto, ambos os métodos empregados, sintomas e PCR, foram capazes de constatar asmudan as no padr o espacial apresentado, sendo que a análise molecular (PCR) foi mais sensível para detectar as mudan as ocorridas. Countless diseases affect the citriculture, as the citrus variegated chlorosis (CVC) which is caused by the bacteria Xylella fastidiosa.The aim of this work was to determine the space distribution of the disease inside commercial orchards in the Northwest of Paraná, using molecular methods. Symptomatic orchards were selected for CVC with the varieties 'Pêra', 'Valência' and 'Folha Murcha' (Citrus sinensis Osbeck). For each variety, 4 positive reference-plant for CVC (presence of CVC symptoms or molecular analysis by PCR) and 8 plants around of each one reference-plant were evaluated, totaling 36 plants for variety. The detection of the bacteria was conduced by Polimerase Chain Reaction (PCR) technique. Simultaneously, evaluations through visual symptoms of CVC were conducted. The results of the temporal analysis were obtained using the Monomolecular, Logistic and Gompertz models. The Logistic model was the one that best fit to describe the behavior of the disease in the time, for all the studied varieties. Data showed that the space behavior of the disease differed when the same area was evaluated by visual and molecular method
Page 1 /100
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.