Xylella Fastidiosa Wells Research Articles

Comparações sazonais do efeito da Xylella fastidiosa em cultivares de cafeeiro

Há muitos anos, o cafeeiro vem apresentando problemas de atrofia e seca dos ramos, atribuídos a um esgotamento nutricional devido às altas taxas de produção. Entretanto, hoje sabe-se que esse problema é causado pela presença da bactéria Xylella fastidiosa Wells et al. cujos sintomas estão relacionados a fatores de estresse. Embora essa bactéria tenha sido muito estudada nos Estados Unidos, devido aos danos causados à videira, pouco se conhece sobre a relação patógeno-hospedeiro-vetor nas diferentes culturas. O objetivo deste trabalho foi o de avaliar a obstrução de elementos de vaso do xilema nas diferentes partes da planta, em ramos com e sem sintomas externos de infecção, de cultivares de cafeeiro (porta-enxertados ou pé-franco), em duas épocas do ano, a fim de verificar o efeito da bactéria na estrutura da planta e na sua nutrição. Foi utilizado um experimento instalado em 1986, em Garça (SP), sendo as amostras retiradas em 2000. Para o estudo anatômico foram obtidas amostras em dois períodos: abril/maio (estação seca) e novembro/dezembro (estação chuvosa) e para as análises foliar e edáfica foram retiradas amostras em abril. A proporção de obstrução de elementos de vaso do xilema devido ao efeito ocasionado pela bactéria foi maior na estação seca, no período de estresse hídrico, do que na estação chuvosa. O órgão que apresentou uma proporção maior de obstrução de elementos de vaso foi o caule, seguido do pecíolo, limbo e raiz. Não houve diferença significativa na proporção de elementos de vaso obstruídos entre os tratamentos nos dois períodos do ano; também, não houve diferença significativa na composição nutricional foliar nas condições do estudo, porém as amostras retiradas dos ramos com sintoma de infecção, de alguns tratamentos, apresentaram menores concentrações de alguns elementos químicos em relação àquelas amostras retiradas de ramos sem sintoma da presença da bactéria.

Appearance of Xylella Fastidiosa in Pierce's Disease resistant and Susceptible Grapevines

Pierce's Disease (PD) is a major factor limiting grape production in the southeast United State. This disease is caused by a bacterium, Xylella fastidiosa Wells et al., which is transmitted to the xylem system of the grapevines primarily by glassy-winged sharpshooters (Homalodisca coagulata Say). Once it is in the xylem, the X. fastidiosa will use the xylem sap as a nutrient source to multiply, colonize, and eventually plug the xylem vessels and cause the PD in susceptible cultivars. On the other hand, symptoms of PD in tolerant cultivars do not appear until fruit maturation, and symptoms are rarely observed in PD resistant cultivars. In order to understand the correlation between X. fastidiosa and PD symptom development, a study was initialed to monitor X. fastidiosa in xylem of resistant, tolerant, and susceptible vines on a monthly basis. Presence of X. fastidiosa was detected directly from xylem sap of field-grown vines by medium culture and confirmed by polymerase chain reaction (PCR). Xylella fastidiosa was detectable throughout the growing season in PD susceptible cultivar `Chardonnay', PD tolerant Florida hybrid grape `Blanc du Bois', and muscadine cultivar `Carlos'. The bacteria were also appeared in the dormant vines with high density in cultivars `Chardonnay' and `Blanc du Bios'. Although X. fastidiosa was also found in dormant canes of `Carlos', the density decreased throughout the late fall and winter months, and they were hardly found before June. The results indicated that X. fastidiosa were carried over from previous season in cultivars `Chardonnay' and `Blanc du Bois', while in PD tolerant cultivar `Carlos', they were newly acquired from the sharpshooter feedings during the growing season.

Stylet Penetration Behaviors of <I>Graphocephala atropunctata</I> (Signoret) (Hemiptera, Cicadellidae): EPG Waveform Characterization and Quantification

We analyzed the probing (stylet penetration) behaviors of the sharpshooter leafhopper Graphocephala atropunctata (Signoret) on grape with an alternating current (AC) electrical penetration graph (EPG) monitor. We characterized waveforms likely to represent stylet penetration pathway phase and xylem ingestion. The total probing duration of the cohort represented 68% of all 20-h monitoring periods for all insects, yet only a small proportion of that probing time was spent in high amplitude/pathway activities. Few changes in behavior occurred once a probe had started. This was shown by the low number of waveform events (i.e., uninterrupted occurrences of a behavior) per probe for each waveform type, which varied from a mean of 1–2.43. Conditional probability analysis supported that hypothesis, because insects usually terminated a probe and began a new one after ingestion-related events, rather than repeating in the same probe the previously performed waveforms. The size of grape leaves used for the assays directly influenced the amount of time insects ingested from xylem or performed other low-amplitude waveforms. Information from this work establishes benchmarks for future research addressing the mechanisms of Xylella fastidiosa Wells et al. transmission and sharpshooter ecology.

Multiplicação in vitro da ameixeira 'Santa Rosa': efeito da citocinina BAP

A ameixeira 'Santa Rosa' apresenta alta produtividade, ótimo sabor e aparência dos frutos para a comercialização. No entanto, por ser altamente suscetível à escaldadura das folhas (Xylella fastidiosa Wells), esta variedade apresenta problemas de cultivo no sul do Brasil. As técnicas de cultura in vitro permitem propagar e rapidamente espécies de interesse, além de permitir a limpeza de patógenos e a produção de matrizes com qualidade genética e sanitária comprovada. Porém, o uso prático da propagação in vitro requer a otimização das condições de cultura para cada espécie e/ou variedade. Dentre os fatores que mais influenciam a micropropagação, estão as citocininas, com destaque para o BAP. O objetivo principal deste trabalho foi avaliar o potencial de multiplicação in vitro da ameixeira 'Santa Rosa' sob diferentes concentrações de BAP. Após três subculturas em meio MA1, segmentos nodais com 0,5-1,0 cm foram submetidos a diferentes concentrações de BAP (0,5; 1,0; 2,0 e 3,0 mg.L-1). Os resultados mostraram que não ocorreram diferenças significativas no número de brotos para as diferentes concentrações de BAP testadas. No entanto, o maior número de brotos por explante (3,6) obteve-se na concentração de 2,0 mg.L-1 e a maior altura média dos brotos foi obtido na concentração de 0,5 mg.L-1 de BAP. Concentrações maiores que a 0,5 mg.L-1 de BAP inibiram o crescimento dos brotos. A micropropagação da ameixeira 'Santa Rosa' a partir de ápices caulinares e gemas laterais em meio de cultura MA1 mostrou-se eficaz.

Transmission of the Citrus Variegated Chlorosis Bacterium Xylella fastidiosa with the Sharpshooter Oncometopia nigricans.

Citrus variegated chlorosis (CVC) is an economically important, destructive disease in Brazil and is caused by the bacterium Xylella fastidiosa Wells. The bacterium has been found to be transmitted in Brazil by sharpshooter leafhoppers (Cicadellidae). Sharpshooters are present in most citrus growing areas of the United States. The sharpshooter leafhopper, Oncometopia nigricans Walker, frequently is found feeding on citrus in Florida. This sharpshooter transmits the X. fastidiosa strains that cause Pierce's disease of grape and ragweed stunt. Research was initiated to determine if O. nigricans was capable of vectoring the X. fastidiosa that causes CVC. In 59 different transmission tests, using 1 to 57 insects per test, transmission of the bacterium was observed 12 times (20.3%). Symptom development in the greenhouse was not a reliable indicator of transmission. Transmission was verified by specific polymerase chain reaction-based assays. Individual insects were able to transmit the bacterium. This information on sharpshooter transmission of CVC is needed to assess the threat posed by the CVC disease to the citrus industries in the United States.

Effect of selected insecticides on Homalodisca coagulata (Homoptera: Cicadellidae) and transmission of oleander leaf scorch in a greenhouse study.

Homalodisca coagulata (Say) is a recent introduction to California. It is known to spread a strain of the bacterium Xylella fastidiosa Wells, Raju, Hung, Weisberg, Mandelco-Paul & Brenner that induces oleander leaf scorch disease in oleander, Nerium oleander L. Oleander leaf scorch is lethal to oleander and threatens to decimate one of the most important landscape shrubs in California. Towards developing a management strategy for H. coagulata-spread oleander leaf scorch, we documented the affects of selected insecticides on H. coagulata mortality, feeding behavior, and disease transmission in a greenhouse study. Oleanders treated with fenpropathrin, fenpropathrin + acephate, and imidacloprid caused significant mortality to caged H. coagulata within 4 h of exposure. Within 24 h, these pesticides caused nearly 100% mortality 3 wk after treatment. In other experiments, acetamiprid and fenpropathrin treatments reduced time spent feeding and total time on plants. H. coagulata on fenpropathrin-, acetamiprid-, and imidacloprid-treated oleander died in less than 13 min on average. Oleander leaf scorch transmission by H. coagulata was blocked by applications of foliar-applied acetamiprid, and soil-applied imidacloprid and thiamethoxam.

In Situ Conservation of America's Wild Grapes

In Situ Conservation of America's Wild Grapes

Aspectos biológicos das cigarrinhas Acrogonia gracilis (Osborn), Dilobopterus costalimai Young e Oncometopia facialis (Signoret) (Hemiptera: Cicadellidae) em Citrus sinensis L. Osbeck

Foram estudados os aspectos biológicos das cigarrinhas Acrogonia gracilis (Osborn), Dilobopterus costalimai Young e Oncometopia facialis (Signoret) em plantas jovens de laranja Citrus sinensis L. Osbeck em condições controladas de 25±2ºC, 60±10% de umidade relativa e 12h de fotofase. Essas cigarrinhas são vetoras de Xylella fastidiosa Wells em citros. Foram observados cinco ínstares em D. costalimai e O. facialis e seis em A. gracilis. O período médio de duração de ovo a adulto e a longevidade foram, respectivamente, 54,5 e 72,4 dias para A. gracilis, 54,7 e 36,4 dias para D. costalimai e 67,1 e 15,5 dias para O. facialis.

Effects of temperature on the flight activity of Graphocephala atropunctata (Hemiptera: Cicadellidae).

Graphocephala atropunctata (Signoret) is the principal vector of Xylella fastidiosa (Wells, Raju, Hung, Weisberg, Mandelco-Paul and Brenner), the bacterium that causes Pierce's disease of grapevine in coastal California. Monitoring the activity of C. atropunctata in the early spring is important for timing insecticide sprays and assessing the potential for disease spread to adjacent vineyards. Trapping studies with yellow sticky traps over 3 yr in Napa Valley, CA, established a significant correlation between early spring trap catch and temperature. Sticky trap catches of G. atropunctata occurred in the springs of 1996-1998 only when temperature was greater than or equal to 14.5 degrees C. In 1997 and 1998, the degree-hours (> 14.5 degrees C) per day from sunrise to sunset during March and April, but not in May, correlated significantly with trap catches. The temperature threshold of 14.5 degrees C in the early spring can be used to improve the timing of insecticidal applications aimed at reducing C. atropunctata populations in vineyards affected by Pierce's disease.

Coffee Leaf Scorch Bacterium: Axenic Culture, Pathogenicity, and Comparison with Xylella fastidiosa of Citrus.

Symptoms of coffee leaf scorch (CLS) appear on young flushes of field plants as large marginal and apical scorched areas on recently mature leaves. Affected leaves drop, shoot growth is stunted, and apical leaves are small and chlorotic. Symptoms may progress to shoot dieback. Only scorched leaves which could not be related to other known agents consistently contained bacteria and bacterial agglomerates when observed with light microscopy. Only plants with these symptoms were positive in enzyme-linked immunosorbent assay (ELISA) tests using antiserum to Xylella fastidiosa Wells et al. The bacterium Xylella fastidiosa Wells et al. was isolated in November 1995 from coffee (Coffea arabica) leaves with scorch symptoms on supplemented periwinkle wilt medium. Colonies were circular, dome-shaped, white, and 0.5 to 1.5 mm in diameter. Two of 10 young coffee seedlings stem-inoculated with a suspension of the isolated X. fastidiosa in January 1996 showed leaf scorch symptoms 3 to 5 months later, contained bacteria in xylem extracts, and reacted positively in ELISA using antiserum to the citrus variegated chlorosis (CVC) strain of X. fastidiosa. ELISA-positive bacteria were reisolated from this plant. None of the symptomless plants, including controls, revealed bacteria on microscopic examinations, ELISA, or isolation attempts. Antisera developed against cultured bacteria from both CLS and CVC plants reacted positively against plant extracts of both diseases in dot immunobinding assays (DIBA). The level of detection was about 5 × 105 bacteria ml-1 for both homologous and heterologous reactions. The polymerase chain reaction amplification products produced by CLS and CVC strains of X. fastidiosa were indistinguishable. Geographical distribution of these strains is not the same. CLS is widespread and usually occurs if coffee is adjacent to CVC-affected citrus. However, CVC does not always occur when citrus is grown adjacent to CLS-affected coffee. The bacteria are closely related, if not identical.

Budding Method Affects Transmission of Xylella fastidiosa in Plum

Detection of Xylella fastidiosa Wells et al. by enzyme-linked immunosorbent assay indicated that plums (Prunus hybrids) had higher absorbance values than peaches [Prunus persica (L.) Batsch]. The slip-budded trees had lower readings than those that were chip budded; however, the scion × method interaction was significant. Further comparison of slip vs. chip budding indicated that the lower absorbance value of slip budding occurred in plums only; there was no difference between budding methods in peach.

Acquisition and Retention ofXylella fastidiosaby an Efficient Vector,Graphocephala atropunctata

The blue-green sharpshooter (BGSS), Graphocephala atropunctata (Signoret), is an efficient vector of Xylella fastidiosa Wells et al, the causal bacterium of Pierce's disease of grapevine. In experiments to assess changes over time in vector transmission efficiency and populations of bacteria in BGSS, 81 of 120 BGSS that were fed for 12 h on infected grapevine acquired the bacterium. Individual infective BGSS were exposed 4 times (1 h, and 7, 21, and 60 days after acquisition) to uninfected grapevines for 3-h inoculation feeding periods to determine the efficiency of transmission to grapevine. After each inoculation efficiency test, some BGSS were tested by culturing for X. fastidiosa to determine the bacterial population in the vector heads and bodies. Transmission efficiency increased from 56 to 92% between 1 h and 7 days post-acquisition, and remained high thereafter (91% at 21 days and 76% at 60 days). Bacterial population size in the heads of the inoculative vectors also increased between 1 h and 7 days, but did not consistently increase further. Xylella fastidiosa was not recovered by culture from about 40% of the inoculative insects. Populations below the detection limit (100 bacteria) in the BGSS heads were enough for efficient transmission

Shoot-tip Culture of Muscadine Grape to Eliminate Pierce's Disease Bacteria

Pierce's disease, caused by the bacterium Xylella fastidiosa Wells et al., is widespread among muscadine grapes (Vitus rotundifolia Michx). To determine whether shoot-tip culture would be effective in eliminating X. fastidiosa, shoot tips of infected grape plants were cultured on Murashige and Skoog medium amended with 9 μm benzyladenine. Shoots and callus that developed tested negative for the presence of X. fastidiosa. Shoot-tip culture appears to be a promising method of obtaining muscadine grape plants free of Pierce's disease. Chemical name used: 6-benzylaminopurine (benzyladenine).

Rate of Spread of Citrus Blight Reduced When Sharpshooter Leafhoppers (Homoptera: Cicadellidae) Are Controlled

Insect traps were used to monitor populations of sharpshooter leafhopper vectors, Oncometopia nigricans (Walker) and Homalodisca coagulate (Say), of Xylella fastidiosa Wells et al., a xylem-limited bacterium, in four 11-ha plots of ‘Valencia’ oranges, Citrus sinensis (L.) Osb., and four 6-ha plots of ‘Pineapple’ oranges in a grove infected with citrus blight. When trap catches indicated that leafhopper populations were increasing, supplemental applications of insecticides were applied to half of the plots. One to three extra applications of insecticides per year were made to maintain significant differences in leafhopper populations between the routine care plots and the supplemental insecticide plots. Linear regression equations, with percentage citrus blight as a function of time in months, were fitted to the data for the supplemental insecticide and routine care plots. In the ‘Valencia’ plots, the slope of the regression line for the routine care plot was significantly greater than the slope for the supplemental insecticide plots; therefore, the rate of spread of blight was reduced significantly where supplemental insecticide applications were made. In ‘Pineapple’ plots, the trend was similar but the difference in slope was not statistically significant.

FICHES INFORMATIVES OEPP SUR LES ORGANISMES DE QUARANTAINE EPPO DATA SHEETS ON QUARANTINE ORGANISMS

EPPO BulletinVolume 19, Issue 4 p. 677-682 Free Access FICHES INFORMATIVES OEPP SUR LES ORGANISMES DE QUARANTAINE EPPO DATA SHEETS ON QUARANTINE ORGANISMS Xylella fastidiosa Wells et al. First published: December 1989 https://doi.org/10.1111/j.1365-2338.1989.tb01159.xCitations: 1AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume19, Issue4December 1989Pages 677-682 ReferencesRelatedInformation

Phony peach . [Distribution map

Abstract A new distribution map is provided for Phony peach . Host: Peach ( Prunus persica ). Information is given on the geographical distribution in NORTH AMERICA, USA (S.E. & S. states west to Missouri & Texas). This map has since been incorporated into Map No. 262, Xylella fastidiosa Wells et al.