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Prevalence, incidence and distribution of citrus variegated chlorosis in Bahia, Brazil
Laranjeira, Francisco F.;Silva, Leonardo G.;Fonseca, Eliana L.;Silva, Suely X. B.;Rocha, Jemine B.;Santos-Filho, Hermes P.;Ledo, Carlos Alberto S.;Hau, Bernhard;
Tropical Plant Pathology , 2008, DOI: 10.1590/S1982-56762008000500001
Abstract: citrus variegated chlorosis (cvc) is one of the most important diseases for brazilian citricultureit is caused by xylella fastidiosa subsp. pauca, a xylem limited, cycadelid and budwood transmitted bacterium. in bahia, the second most important citrus region in brazil, cvc has been present since 1997. our objectives were to characterize the regional spatial pattern of cvc and to establish a relationship between epidemiological variables and horticultural practices, as well as to evaluate whether control measures used so far have been effective and, based on that, to conceive suitable control measures. a series of surveys were performed in two regions of bahia state (rec?ncavo baiano and litoral norte), along with a survey of horticultural and control practices associated with sampled groves. cvc was restricted to litoral norte region, especially to three municipalities along the border between bahia and sergipe statesthe mean cvc incidence in these municipalities followed a gradient, higher in the countryside and decreasing along the coast. presence and dissemination of cvc was related to poor nursery practices, a massive use of a susceptible orange variety, and an extreme concentration of orange groves in high incidence municipalities, as well as to the absence of specific cvc control. considering that cvc was not found in rec?ncavo baiano, this region could be considered a "cvc free zone" by the local government.
Comparative analysis for quantification of Citrus Variegated Chlorosis in the field
Gon?alves, Fabrício Packer;Louren?o, Silvia Afonseca;Stuchi, Eduardo Sanches;Hau, Bernhard;Amorim, Lilian;
Scientia Agricola , 2011, DOI: 10.1590/S0103-90162011000500008
Abstract: citrus variegated chlorosis (cvc) caused by xylella fastidiosa is one of the most important diseases for brazilian citriculture. the cvc is a vascular disease with a long incubation period and symptoms similar to other disorders, and this factors difficult the cvc quantification in the field. two methods of cvc assessment were compared in this study. the first method was based on a descriptive rating scale with four ratings, commonly used for the disease quantification. the second one was based on the incidence of symptomatic branches. the quantification of cvc through these two methods was carried out in a 10-year-old 'natal' sweet orange orchard. the descriptive scale considered the symptoms of the entire plant. the disease incidence was evaluated in 36 branches in each plant. the assessments were conducted by three raters in 144 plants in july 2006 and july 2007 as well as in march and november 2008. the descriptive scale did not allow an accurate assessment and resulted in a moderate strength of agreement among the raters. on the other hand, the incidence quantification of cvc through the symptomatic branches showed high repeatability among the raters. we suggest the use of incidence of symptomatic branches as variable for cvc quantification.
Gas exchanges and carbohydrate metabolism in orangetrees with citrus variegated chlorosis
Gomes, Mara de Menezes de Assis;Lag?a, Ana Maria Magalh?es Andrade;Machado, Eduardo Caruso;Medina, Camilo Lázaro;Machado, Marcos Ant?nio;
Brazilian Journal of Plant Physiology , 2003, DOI: 10.1590/S1677-04202003000100004
Abstract: gas exchanges, sucrose, starch and reducing sugar contents were analyzed in leaves of orange trees with and without citrus variegated chlorosis (cvc), a disease caused by the bacteria xylella fastidiosa. healthy plants (hp) and diseased plants (dp) were evaluated 20 and 26 months after bacterial inoculation, in october 1998 and april 1999, respectively. on the first evaluation date, co2 assimilation rates for hp were greater than dp in the early morning and midday, but on the second date they were greater in hp all along the day. on the first date, there was an increase in the sucrose content of dp at 15:00 h and 17:00 h in relation to hp. on the second evaluation date, dp presented greater reducing sugar content only in the early morning while sucrose content showed a decrease at 15:00 h. also, on the second date, the concentrations of starch were always lower for dp compared to hp. it is suggested that this variation in starch levels might be related to energy availability in dp, as they also showed lower photosynthetic rates. soluble sugars did not show any correlation with the disease and photosynthetic parameters.
Gas exchanges and carbohydrate metabolism in orangetrees with citrus variegated chlorosis  [cached]
Gomes Mara de Menezes de Assis,Lag?a Ana Maria Magalh?es Andrade,Machado Eduardo Caruso,Medina Camilo Lázaro
Brazilian Journal of Plant Physiology , 2003,
Abstract: Gas exchanges, sucrose, starch and reducing sugar contents were analyzed in leaves of orange trees with and without Citrus Variegated Chlorosis (CVC), a disease caused by the bacteria Xylella fastidiosa. Healthy plants (HP) and diseased plants (DP) were evaluated 20 and 26 months after bacterial inoculation, in October 1998 and April 1999, respectively. On the first evaluation date, CO2 assimilation rates for HP were greater than DP in the early morning and midday, but on the second date they were greater in HP all along the day. On the first date, there was an increase in the sucrose content of DP at 15:00 h and 17:00 h in relation to HP. On the second evaluation date, DP presented greater reducing sugar content only in the early morning while sucrose content showed a decrease at 15:00 h. Also, on the second date, the concentrations of starch were always lower for DP compared to HP. It is suggested that this variation in starch levels might be related to energy availability in DP, as they also showed lower photosynthetic rates. Soluble sugars did not show any correlation with the disease and photosynthetic parameters.
Nutritional deficiency in citrus with symptoms of citrus variegated chlorosis disease
Silva-Stenico, ME.;Pacheco, FTH.;Pereira-Filho, ER.;Rodrigues, JLM.;Souza, AN.;Etchegaray, A.;Gomes, JE.;Tsai, SM.;
Brazilian Journal of Biology , 2009, DOI: 10.1590/S1519-69842009000400013
Abstract: it is well known that citrus plants that have been infected by xylella fastidiosa display nutritional deficiencies, probably caused by production of extracellular polymers by the bacteria that block normal nutrient flow through the xylem. the aim of this work was to study the mineral composition of specific foliar areas in different stages of infection in citrus. thus, the concentrations of macro and micronutrients in leaves of citrus infected by x. fastidiosa were measured. samples from four infected citrus orchards in the state of s?o paulo, brazil, were respectively collected from santa rita do passa quatro, neves paulista, gavi?o peixoto and paraíso counties. the presence of x. fastidiosa in leaves was confirmed by polymerase chain reaction (pcr) using specific pcr primers. to understand the variation in leaf-nutrient content in citrus plants, we used foliar nutrient values from control (non-symptomatic) plants as a reference. chemometric analysis showed that the deficiency of p and k in symptomatic trees for all orchards and high concentrations of fe, mn and zn were observed in chlorotic areas, although other studies revealed deficiency of zinc in leaves. this is the first report showing that a correlation between chlorotic citrus leaf and higher concentrations of fe, mn and zn are observed when infected and healthy plants were compared.
Alternation of host plants as a survival mechanism of leafhoppers Dilobopterus costalimai and Oncometopia facialis (Hemiptera: Cicadellidae), vectors of the Citrus Variegated Chlorosis (CVC)
Milanez, José Maria;Parra, José Roberto Postali;Magri, Denise Cristina;
Scientia Agricola , 2001, DOI: 10.1590/S0103-90162001000400008
Abstract: dilobopterus costalimai (young) and oncometopia facialis (signoret) are two of the most important species of citrus leafhoppers, vectors of bacterium xylella fastidiosa which causes the citrus variegated chlorosis (cvc) disease. to develop a rearing technique for these species under laboratory conditions, the egg laying preference and nymph development were studied in different breeding systems: rangpur lime (citrus limonia) and "falso boldo" (vernonia condensata) as host plants. trials were set up in a randomized block design with three treatments (n=8). females of d. costalimai had particular preference for ovipositing on rangpur lime leaves while o. facialis females placed a higher number of eggs on "falso boldo", but it did not differ statistically from the rangpur lime. the nymphal viability of d. costalimai was null in rangpur lime and 58% in "falso boldo". for o. facialis the nymphal viability was 25 and 78% in rangpur lime and "falso boldo", respectively. "falso boldo" is more suitable as a host plant to rear the two species of citrus leafhoppers. the alternation of host plants seems to be an important survival mechanism of the cvc-vector species, as shown in natural conditions.
Alternation of host plants as a survival mechanism of leafhoppers Dilobopterus costalimai and Oncometopia facialis (Hemiptera: Cicadellidae), vectors of the Citrus Variegated Chlorosis (CVC)  [cached]
Milanez José Maria,Parra José Roberto Postali,Magri Denise Cristina
Scientia Agricola , 2001,
Abstract: Dilobopterus costalimai (Young) and Oncometopia facialis (Signoret) are two of the most important species of citrus leafhoppers, vectors of bacterium Xylella fastidiosa which causes the Citrus Variegated Chlorosis (CVC) disease. To develop a rearing technique for these species under laboratory conditions, the egg laying preference and nymph development were studied in different breeding systems: Rangpur lime (Citrus limonia) and "falso boldo" (Vernonia condensata) as host plants. Trials were set up in a randomized block design with three treatments (n=8). Females of D. costalimai had particular preference for ovipositing on Rangpur lime leaves while O. facialis females placed a higher number of eggs on "falso boldo", but it did not differ statistically from the Rangpur lime. The nymphal viability of D. costalimai was null in Rangpur lime and 58% in "falso boldo". For O. facialis the nymphal viability was 25 and 78% in Rangpur lime and "falso boldo", respectively. "Falso boldo" is more suitable as a host plant to rear the two species of citrus leafhoppers. The alternation of host plants seems to be an important survival mechanism of the CVC-vector species, as shown in natural conditions.
Enhanced Reliability and Accuracy for Field Deployable Bioforensic Detection and Discrimination of Xylella fastidiosa subsp. pauca, Causal Agent of Citrus Variegated Chlorosis Using Razor Ex Technology and TaqMan Quantitative PCR  [PDF]
Ping Ouyang, Mohammad Arif, Jacqueline Fletcher, Ulrich Melcher, Francisco Manuel Ochoa Corona
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0081647
Abstract: A reliable, accurate and rapid multigene-based assay combining real time quantitative PCR (qPCR) and a Razor Ex BioDetection System (Razor Ex) was validated for detection of Xylella fastidiosa subsp. pauca (Xfp, a xylem-limited bacterium that causes citrus variegated chlorosis [CVC]). CVC, which is exotic to the United States, has spread through South and Central America and could significantly impact U.S. citrus if it arrives. A method for early, accurate and sensitive detection of Xfp in plant tissues is needed by plant health officials for inspection of products from quarantined locations, and by extension specialists for detection, identification and management of disease outbreaks and reservoir hosts. Two sets of specific PCR primers and probes, targeting Xfp genes for fimbrillin and the periplasmic iron-binding protein were designed. A third pair of primers targeting the conserved cobalamin synthesis protein gene was designed to detect all possible X. fastidiosa (Xf) strains. All three primer sets detected as little as 1 fg of plasmid DNA carrying X. fastidiosa target sequences and genomic DNA of Xfp at as little as 1 - 10 fg. The use of Razor Ex facilitates a rapid (about 30 min) in-field assay capability for detection of all Xf strains, and for specific detection of Xfp. Combined use of three primer sets targeting different genes increased the assay accuracy and broadened the range of detection. To our knowledge, this is the first report of a field-deployable rapid and reliable bioforensic detection and discrimination method for a bacterial phytopathogen based on multigene targets.
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
A Cellular Automata Model for Citrus Variagated Chlorosis  [PDF]
M. L. Martins,G. Ceotto,S. G. Alves,C. C. B. Bufon,J. M. Silva,F. F. Laranjeira
Physics , 2000, DOI: 10.1103/PhysRevE.62.7024
Abstract: A cellular automata model is proposed to analyze the progress of Citrus Variegated Chlorosis epidemics in S\~ao Paulo oranges plantation. In this model epidemiological and environmental features, such as motility of sharpshooter vectors which perform L\'evy flights, hydric and nutritional level of plant stress and seasonal climatic effects, are included. The observed epidemics data were quantitatively reproduced by the proposed model varying the parameters controlling vectors motility, plant stress and initial population of diseased plants.
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