Coffee Leaf Scorch Research Articles

Evidence of Xylella fastidiosa Infection and Associated Thermal Signatures in Southern Highbush Blueberry (Vaccinium corymbosum Interspecific Hybrids).

Xylella fastidiosa, a gram-negative bacterium vectored to plants via feeding of infected insects, causes a number of notorious plant diseases throughout the world, such as Pierce's disease (grapes), olive quick decline syndrome, and coffee leaf scorch. Detection of Xf in infected plants can be challenging because the early foliar disease symptoms are subtle and may be attributed to multiple minor physiological stresses and/or borderline nutrient deficiencies. Furthermore, Xf may reside within an infected plant for one or more growing seasons before traditional visible diagnostic disease symptoms emerge. Any method that can identify infection during the latent period or pre-diagnostic disease progress state could substantially improve the outcome of disease control interventions. Because Xf locally and gradually impairs water movement through infected plant stems and leaves over time, infected plants may not be able to effectively dissipate heat through transpiration-assisted cooling, and this heat signature may be an important pre-diagnostic disease trait. Here, we report on the association between thermal imaging, the early stages of Xf infection, and disease development in blueberry plants, and discuss the benefits and limitations of using thermal imaging to detect bacterial leaf scorch of blueberries.

Coffee bacterial diseases: a plethora of scientific opportunities

Coffee is a very important crop for several tropical countries across different continents. The diseases bacterial halo blight (BHB), bacterial leaf spot (BLS), bacterial leaf blight (BLB) and coffee leaf scorch (CLS), caused by the bacterial pathogens Pseudomonas syringae pv. garcae (Psgc), P. syringae pv. tabaci (Psta), Pseudomonas cichorii (Pch) and Xylella fastidiosa subsp. pauca (Xfp), respectively, cause significant reductions in coffee production, although other minor bacterial diseases have also been reported in some countries. Little research progress has been made on aspects that are relevant for control and management of these diseases. In all cases, there is an urgent need to develop rapid and more reliable methods for early detection of the pathogens in order to minimize their negative impact on coffee production. Because of the high rate of intra‐ and intersubspecific recombination occurring in X. fastidiosa, a permanent revision of the detection methods is necessary. Greater efforts should be made to understand the genetic and virulence diversity of Psgc, Psta and Pch populations. Early studies reported the identification of potential sources of resistance against Psgc and Psta, but, to date, no resistance gene has been isolated. Little effort has been made to understand the biology and molecular mechanisms underlying the interaction between Coffea spp. and these pathogenic bacteria. This review discusses the recent progress on the molecular mechanisms used by these bacteria to cause diseases on other plant species, in order to provide a guideline for the establishment of future research programmes.

Xylella fastidiosa: an examination of a re-emerging plant pathogen.

Bacteria; Gammaproteobacteria; family Xanthomonadaceae; genus Xylella; species fastidiosa. Gram-negative rod (0.25-0.35×0.9-3.5μm), non-flagellate, motile via Type IV pili-mediated twitching, fastidious. Xylella fastidiosa has a broad host range that includes ornamental, ecological and agricultural plants belonging to over 300 different species in 63 different families. To date, X.fastidiosa has been found to be pathogenic in over 100 plant species. In addition, it can establish non-symptomatic associations with many plants as a commensal endophyte. Here, we list the four distinct subspecies of X.fastidiosa and some of the agriculturally relevant diseases caused by them: X.fastidiosa ssp. fastidiosa causes Pierce's disease (PD) of grapevine (Vitis vinifera); X.fastidiosa ssp. multiplex causes almond leaf scorch (ALS) and diseases on other nut and shade tree crops; X.fastidiosa ssp. pauca causes citrus variegated chlorosis (CVC) (Citrus spp.), coffee leaf scorch and olive quick decline syndrome (OQDS) (Olea europaea); X.fastidiosa ssp. sandyi causes oleander leaf scorch (OLS) (Nerium oleander). Significant host specificity seemingly exists for some of the subspecies, although this could be a result of technical biases based on the limited number of plants tested, whereas some subspecies are not as stringent in their host range and can infect several plant hosts. Most X.fastidiosa-related diseases appear as marginal leaf necrosis and scorching of the leaves. In the case of PD, X.fastidiosa can also cause desiccation of berries (termed 'raisining'), irregular periderm development and abnormal abscission of petioles. In olive trees affected with OQDS, leaves exhibit marginal necrosis and defoliation, and overall tree decline occurs. Plants with ALS and OLS also exhibit the characteristic leaf scorch symptoms. Not all X.fastidiosa-related diseases exhibit the typical leaf scorch symptoms. These include CVC and Phony Peach disease, amongst others. In the case of CVC, symptoms include foliar wilt and interveinal chlorosis on the upper surfaces of the leaves (similar to zinc deficiency), which correspond to necrotic, gum-like regions on the undersides of the leaves. Additional symptoms of CVC include defoliation, dieback and hardening of fruits. Plants infected with Phony Peach disease exhibit a denser, more compact canopy (as a result of shortened internodes, darker green leaves and delayed leaf senescence), premature bloom and reduced fruit size. Some occlusions occur in the xylem vessels, but there are no foliar wilting, chlorosis or necrosis symptoms . USEFUL WEBSITES: http://www.piercesdisease.org/; https://pubmlst.org/xfastidiosa/; http://www.xylella.lncc.br/; https://nature.berkeley.edu/xylella/; https://ec.europa.eu/food/plant/plant_health_biosecurity/legislation/emergency_measures/xylella-fastidiosa_en.

Functional and Evolutionary Characterization of a UDP-Xylose Synthase Gene from the Plant Pathogen Xylella fastidiosa, Involved in the Synthesis of Bacterial Lipopolysaccharide.

Xylella fastidiosa is a plant-infecting bacillus, responsible for many important crop diseases, such as Pierce's disease of vineyards, citrus variegated chlorosis, and coffee leaf scorch (CLS), among others. Recent genomic comparisons involving two CLS-related strains, belonging to X. fastidiosa subsp. pauca, revealed that one of them carries a frameshift mutation that inactivates a gene encoding an oxidoreductase of the short-chain dehydrogenase/reductase (SDR) superfamily, which may play important roles in determining structural variations in bacterial glycans and glycoconjugates. However, the exact nature of this SDR has been a matter of controversy, as different annotations of X. fastidiosa genomes have implicated it in distinct reactions. To confirm the nature of this mutated SDR, a comparative analysis was initially performed, suggesting that it belongs to a subgroup of SDR decarboxylases, representing a UDP-xylose synthase (Uxs). Functional assays, using a recombinant derivative of this enzyme, confirmed its nature as XfUxs, and carbohydrate composition analyses, performed with lipopolysaccharide (LPS) molecules obtained from different strains, indicate that inactivation of the X. fastidiosa uxs gene affects the LPS structure among CLS-related X. fastidiosa strains. Finally, a comparative sequence analysis suggests that this mutation is likely to result in a morphological and evolutionary hallmark that differentiates two subgroups of CLS-related strains, which may influence interactions between these bacteria and their plant and/or insect hosts.

Diversity of endophytic bacteria from Citrus and Inga trees in the coffee agro-ecosystem and fluctuations by location, shade management and season

Coffee, Coffea arabica L., is planted in diverse agro-ecological environments in the mountains of Puerto Rico (PR). The pathogen, Xylella fastidiosa Wells et al., is a xylem-limited phytopathogenic bacterium transmitted by insects that causes coffee leaf scorch, citrus-variegated chlorosis and vascular diseases of many other plant species. The objective of this study was to characterize the fastidious endophytes occupying a similar niche as X. fastidiosa in the vascular system of Citrus sinensis and Inga vera trees in low diversity and high diversity shade environments where coffee is grown In PR. Sampling was conducted over two years in four localities: Adjuntas, Jayuya, Las Marías and Yauco during the dry and rainy seasons. Citrus sinensis and Inga vera were generally the only shade treesin coffee plantations described as "low diversity"; in "high diversity" plantations these same species were present along with Pithocellobium carbonarium, Gliricidia sepium and Andira inermis. Endophyte population (EP) and endophyte diversity (ED) were contrasted using factorial arrangements of shade, locality, season and year. Endophytes were clustered using multivariate analysis. Neither shade nor season had an effect on EP in Citrus. In Inga vera, EP was about three times higher in the second year compared to the first year regardless of season, location or shade. In both Citrus and Inga, ED was low. The highest ED was detected in Jayuya and the lowest in Las Marías. Ward's algorithm combined Citrus and Inga fastidious strains into four and five clusters for Gram-negative and Gram-positive bacteria, respectively. Endophyte diversity of Citrus and Inga was determined by the plant species, not by location or shade. However, ED was higher in shaded coffee with low diversity of tree species. Thus, effects of shade (low versus high diversity) altered the community structure of endophytes prevalent in the vascular tissue and may impact host plant resistance to pathogens such as X. fastidiosa.

Distribución espacial de cafetos (Coffea arabica L.) posiblemente enfermos con el encorchamiento de la hoja causado por Xylella fastidiosa en Puerto Rico

El café (Coffea arabica L.) es un cultivo de importancia económica y social. En Puerto Rico en el año 2012 la producción de café tuvo su nivel más bajo en toda la historia de la isla, tanto por los problemas de crisis económica como por los problemas fitosanitarios. Entre las principales enfermedades que afectan al cultivo está el encorchamiento de la hoja ('coffee leaf scorch', CLS) o crespera, causada por la bacteria Xylella fastidiosa (Xf) que ocasiona pérdidas económicas importantes en varios países. En la Cuenca del Caribe, Xf se encuentra en cafetos de Costa Rica, mientras que en Brasil la bacteria causa serias epidemias. Para determinar la distribución espacial de los cafetos posiblemente infectados con Xf, se muestrearon cafetos con síntomas similares a los de CLS. Para detectar a la bacteria en los árboles muestreados se realizó una prueba serológica comercial (DAS-ELISA) específica para Xf. Con datos de los árboles potencialmente infectados se realizaron conglomerados espaciales usando el programa SatScan. Muy pocos (< 5%) de los cafetos dieron lecturas de absorbancia dentro de los valores aceptados como positivos para Xf (a 0.7). Hubo una diferencia (p<0.0001, x2) en la época seca versus la lluviosa en la proporción de cafetos seropositivos según la prueba para Xf. Además, el porcentaje de cafetos seropostivos a Xf varió dependiendo de la localidad muestreada (p<0.05 X2). Los conglomerados espaciales permitieron asociar con mayor riesgo relativo de enfermedad (sospechosos de CLS) a las localidades de mayor altitud: Adjuntas, Jayuya y Yauco (riesgo relativo mayor a 14; P<0.001), lo que estuvo relacionado con conteos altos de vectores potenciales en estas localidades.

Comparative genomic analysis of coffee-infecting Xylella fastidiosa strains isolated from Brazil.

Strains of Xylella fastidiosa constitute a complex group of bacteria that develop within the xylem of many plant hosts, causing diseases of significant economic importance, such as Pierce's disease in North American grapevines and citrus variegated chlorosis in Brazil. X. fastidiosa has also been obtained from other host plants, in direct correlation with the development of diseases, as in the case of coffee leaf scorch (CLS)--a disease with potential to cause severe economic losses to the Brazilian coffee industry. This paper describes a thorough genomic characterization of coffee-infecting X. fastidiosa strains, initially performed through a microarray-based approach, which demonstrated that CLS strains could be subdivided in two phylogenetically distinct subgroups. Whole-genomic sequencing of two of these bacteria (one from each subgroup) allowed identification of ORFs and horizontally transferred elements (HTEs) that were specific to CLS-related X. fastidiosa strains. Such analyses confirmed the size and importance of HTEs as major mediators of chromosomal evolution amongst these bacteria, and allowed identification of differences in gene content, after comparisons were made with previously sequenced X. fastidiosa strains, isolated from alternative hosts. Although direct experimentation still needs to be performed to elucidate the biological consequences associated with such differences, it was interesting to verify that CLS-related bacteria display variations in genes that produce toxins, as well as surface-related factors (such as fimbrial adhesins and LPS) that have been shown to be involved with recognition of specific host factors in different pathogenic bacteria.

Efecto de la época y tipo de sombra sobre bacterias endófitas en cafetos (Coffea arabica) en Puerto Rico.

El café, Coffea arábica, es un cultivo de i mportancia económica mundial. En la zona montañosa de Puerto Rico se siembra solo o formando un agroecosistema importante desde el punto de vista económico y ecológico. Xylella fastidiosa Wells et al., una bacteria endófita limitada al xilema y que produce el encorchamiento de la hoja del cafeto, representa una seria amenaza para este cultivo. La gran mayoría de las bacterias endófitas colonizan un nicho ecológico similar al de los organismos fitopatógenos; por lo tanto, algunas cepas son potenciales agentes de control biológico. El presente estudio buscó aislar y caracterizar las bacterias de colonización endofítica en hojas y ramas de cafetos bajo sombra y a sol, durante la época seca y la época lluviosa. Durante dos años, en fincas de café de los pueblos de Adjuntas, Jayuya, Las Marías y Yauco, se determinó el efecto de época, localidad, tipo de sombra y año sobre la cantidad y diversidad de bacterias endófitas asociadas al café. Para contrastar las poblaciones de bacterias endófitas, se analizaron las poblaciones y la diversidad de cepas bacterianas, esto es, unidades formadoras de colonias (UFC/mL), y el número de cepas fenotípicamente distintas (diversidad de cepas) aisladas de hojas y ramas de los cafetos. Se obtuvieron poblaciones bacterianas más altas en las ramas versus las nervaduras de hojas (P menor que 0.0001), por lo que, para obtener mayor representatividad de la diversidad bacteriana, los aislamientos deben realizarse de las ramas y no de las hojas. La interacción tipo de sombra por época fue la que mostró significación estadística en mayor número de veces, indicativo de que el efecto de época dependerá del tipo de sombra utilizado. Durante la época seca se detectaron diferencias estadísticas (P menor que 0.05) en el factor tipo de sombra y localidad en los aislamientos realizados a partir de muestras de ramas y hojas. En la época lluviosa se detectaron diferencias para diversidad de bacterias por árbol para el factor tipo de sombra en muestras de hoja y rama. En general, un número alto de bacterias en una localidad, época o tipo de sombra fue asociado con un alto nivel de diversidad de cepas. Existe la posibilidad de que ciertas cepas endófitas interactúen de forma antagonista con X. fastidiosa, siendo esto una alternativa con potencial para el manejo de la enfermedad.

The complex biogeography of the plant pathogen Xylella fastidiosa: genetic evidence of introductions and Subspecific introgression in Central America.

The bacterium Xylella fastidiosa is a plant pathogen with a history of economically damaging introductions of subspecies to regions where its other subspecies are native. Genetic evidence is presented demonstrating the introduction of two new taxa into Central America and their introgression into the native subspecies, X. fastidiosa subsp. fastidiosa. The data are from 10 genetic outliers detected by multilocus sequence typing (MLST) of isolates from Costa Rica. Six (five from oleander, one from coffee) defined a new sequence type (ST53) that carried alleles at six of the eight loci sequenced (five of the seven MLST loci) diagnostic of the South American subspecies Xylella fastidiosa subsp. pauca which causes two economically damaging plant diseases, citrus variegated chlorosis and coffee leaf scorch. The two remaining loci of ST53 carried alleles from what appears to be a new South American form of X. fastidiosa. Four isolates, classified as X. fastidiosa subsp. fastidiosa, showed a low level of introgression of non-native DNA. One grapevine isolate showed introgression of an allele from X. fastidiosa subsp. pauca while the other three (from citrus and coffee) showed introgression of an allele with similar ancestry to the alleles of unknown origin in ST53. The presence of X. fastidiosa subsp. pauca in Central America is troubling given its disease potential, and establishes another route for the introduction of this economically damaging subspecies into the US or elsewhere, a threat potentially compounded by the presence of a previously unknown form of X. fastidiosa.

Genomic Sequencing of Two Coffee-Infecting Strains of Xylella fastidiosa Isolated from Brazil.

Here, we describe the draft genome sequences of two Xylella fastidiosa strains: Xf6c and Xf32, which have been obtained from infected coffee plants in Brazil, and are associated with the disease known as coffee leaf scorch (CLS).

Detecting genetic introgression: high levels of intersubspecific recombination found in Xylella fastidiosa in Brazil.

Documenting the role of novel mutation versus homologous recombination in bacterial evolution, and especially in the invasion of new hosts, is central to understanding the long-term dynamics of pathogenic bacteria. We used multilocus sequence typing (MLST) to study this issue in Xylella fastidiosa subsp. pauca from Brazil, a bacterium causing citrus variegated chlorosis (CVC) and coffee leaf scorch (CLS). All 55 citrus isolates typed (plus one coffee isolate) defined three similar sequence types (STs) dominated by ST11 (85%), while the remaining 22 coffee isolates defined two STs, mainly ST16 (74%). This low level of variation masked unusually large allelic differences (>1% divergence with no intermediates) at five loci (leuA, petC, malF, cysG, and holC). We developed an introgression test to detect whether these large differences were due to introgression via homologous recombination from another X. fastidiosa subspecies. Using additional sequencing around these loci, we established that the seven randomly chosen MLST targets contained seven regions of introgression totaling 2,172 bp of 4,161 bp (52%), only 409 bp (10%) of which were detected by other recombination tests. This high level of introgression suggests the hypothesis that X. fastidiosa subsp. pauca became pathogenic on citrus and coffee (crops cultivated in Brazil for several hundred years) only recently after it gained genetic variation via intersubspecific recombination, facilitating a switch from native hosts. A candidate donor is the subspecies infecting plum in the region since 1935 (possibly X. fastidiosa subsp. multiplex). This hypothesis predicts that nonrecombinant native X. fastidiosa subsp. pauca (not yet isolated) does not cause disease in citrus or coffee.

New Records on the Geographical Distribution of South American Sharpshooters (Cicadellidae: Cicadellinae: Proconiini) and their Potential as Vectors ofXylella fastidiosa

Wells et al. 1978, which occurs only in the xylemof plants (Marucci et al. 2002).Strains of X. fastidiosa cause diseases such as“Pierce’ s Disease” (PD) in grape ( Vitis vinifera L.),“Phony Peach Disease” (PPD), “Coffee LeafScorch” (CLS), “Oleander Leaf Scorch” (OLS), and“Citrus Variegated Chlorosis” (CVC) among oth-ers. These incurable maladies produce substan-tial economic losses in a diverse variety of crops(Hernandez-Martinez et al. 2006).In South America the major threat is CVCwhich has spread rapidly throughout Brazil(Lopes 1996). X. fastidiosa is also present inUnited States, Mexico, Venezuela, Brazil, Para-guay, Uruguay, Argentina (Redak et al. 2004), andCosta Rica (Aguilar et al. 2005). However, CVC isnot yet reported from the USA although it has thepotential to threaten orange (

Identification of defence-related genes expressed in coffee and citrus during infection by Xylella fastidiosa

One of the phytosanitary problems of coffee cultivation in Brazil is Coffee Leaf Scorch (CLS) disease, caused by the phytopathogenic bacterium Xylella fastidiosa. Due to the economic importance of coffee to Brazil and the losses caused by X. fastidiosa, a cDNA library (RX1) was constructed using infected coffee stems. This library is one of the 37 coffee EST libraries constructed using different organs and tissues and biological conditions (Coffee Genome Project-CafEST). The objective of this study was to identify genes potentially involved in defence processes in response to X. fastidiosa infection by in silico analysis of the transcripts from the RX1 library as well as compare the coffee ESTs to citrus Xylella-infected ESTs. Clustering analysis of the RX1 library grouped a total of 7,501 sequences into 3,248 contigs, 19 of which were not found in the other 36 libraries. Additionally, 119 contigs were considered differentially expressed in comparison with the other libraries and according to statistical criteria. The global analysis of these contigs showed several genes involved in dehydration and photosynthesis. A total of 2,235 singlets were also obtained in the RX1 library and several of these genes are classically involved in defence processes. The comparison to a Xylella-infected citrus EST library revealed several genes similarly modulated in both species, indicating common defence mechanisms in both host plants in response to X. fastidiosa. The results obtained showed that water deprivation and response to osmotic and oxidative stress were expressed in a similar way in both coffee and citrus libraries. This is the first study to propose a common mechanism shared by citrus and coffee plants in response to the same pathogen.

Quantification of yield loss due to coffee leaf scorch

Coffee leaf scorch caused by Xylella fastidiosa is widespread in major coffee-growing regions of Brazil. This study was done to quantify the yield loss caused by this disease. The severity data of the disease were collected during the 2006, 2007 and 2008 seasons at commercial plantations growing Coffea arabica ‘Catuaí’ in São Gotardo-MG in 250 plants of three blocks of 7000 coffee plants each. Fifty selected plants per block with different disease severities were determined. The linear regression showed a significant relationship ( P < 0.01) between disease severity and bean yield and between disease severity and grain size in all years. The relationship between yield and the disease severity was significant ( P < 0.01). For each 1% increase in the disease severity, there was a decrease of 1.22, 1.34 and 2.02 bags of bean yield/ha in 2006, 2007 and 2008, respectively, thus showing the importance of the disease in reducing coffee bean yields.

Biodiversidad y ecología de vectores potenciales (Insecta: Hemiptera: Auchenorryncha) de Xylella fastidiosa Wells et al. en los cafetos en Puerto Rico.

Xylella fastidiosa (Xf) es una bacteria limitada al xilema y es el agente causal de la enfermedad conocida como el encorchado de la hoja del café (CLS) en América Central. El objetivo de esta investigación fue determinar insectos vectores potenciales de Xf en plantaciones de café, Coffea arabica L., de Puerto Rico. Los catastros se realizaron de junio a noviembre de 2006 en cuatro fincas localizadas en los municipios de Yauco, Juana Díaz y Adjuntas. La colección de insectos para cada sitio se realizó cada 15 días. Se recolectaron 7,423 individuos distribuidos en cinco familias y 12 especies. La familia Cicadellidae fue la dominante en número de especies e individuos. Los índices de dominancia, abundancia, frecuencia y constancia determinaron a Agallia pulchra, Apogonalia imitatrix, Caribovia coffeacola y Hortensia similis como las especies dominantes. Los índices de diversidad mostraron diferencias significativas entre localidades. Los valores más altos de diversidad y equidad de abundancia fueron para las fincas de Yauco y el de la dominancia para Adjuntas. De las cuatro especies dominantes Apogonalia imitatrix, C. coffeacola y H. similis correspondieron a insectos que se alimentan del xilema; por tanto, son considerados vectores potenciales de Xf. Apogonalia imitatrix representa el primer informe de la especie para Puerto Rico.

Temporal and spatial dynamics of coffee leaf scorch caused byXylella fastidiosa

Field experiments were conducted at a commercial coffee (Coffea arabica) field in the counties of Sao Gotardo and Ervalia in the state of Minas Gerais, Brazil, to study the spatial and temporal dynamics of coffee leaf scorch (CLS) by assessing the incidence and severity of the disease. The spatial distribution of CLS were analysed using ordinary runs on rows and across rows, analyses of the dynamics and structure of foci, as well as analysis using modified Taylor’s law. The temporal distribution of CLS was analysed using the real and cumulative incidence of the disease, and the data were used to calculate the rate of the disease progress. Diseased plants were aggregated according to modified Taylor’s law and by the analysis of ordinary runs and structure of foci. Dissemination of the disease occurred mainly in plant rows. Diseased plants occurred at the beginning in isolated foci, and with an increase in disease incidence they later became more aggregated. The maximum values for CLS incidence occurred in December, when the rate of disease progress was 0.18 plants/month, whereas in the winter months the CLS rate of progress was close to zero.

Transmission Efficiency of &lt;I&gt;Xylella fastidiosa&lt;/I&gt; by Sharpshooters (Hemiptera: Cicadellidae) in Coffee and Citrus

Xylella fastidiosa (Wells, Raju, Hung, Weisburg, Mandelco-Paul, and Brenner) is a bacterial pathogen transmitted by several sharpshooters in two tribes of Cicadellinae (Proconiini and Cicadellini). Here, we compared the transmission efficiency of X. fastidiosa in coffee (Coffea arabica L.) and citrus [Citrus sinensis (L.) Osbeck] by Cicadellini [Bucephalogonia xanthophis (Berg) and Dilobopterus costalimai Young] and Proconiini [Homalodisca ignorata Melichar and Oncometopia facialis (Signoret)] sharpshooters that occur in both crops. At different seasons, healthy adults of each species were submitted to a 48-h acquisition access period on citrus or coffee source plants infected with X. fastidiosa isolates that cause Citrus variegated chlorosis (CVC) and Coffee leaf scorch (CLS), respectively, and then confined on healthy seedlings of the corresponding host plant for a 48-h inoculation access period. No significant effect of inoculation season was observed when comparing infection rates of citrus or coffee plants inoculated by vectors at different times of the year. In citrus, the transmission rate by single insects was significantly higher for H. ignorata (30%) in relation to B. xanthophis (5%) and O. facialis (1.1%), but there was no difference among vector species in coffee, whose transmission rates ranged from 1.2 to 7.2%. Comparing host plants, H. ignorata was more effective in transmitting X. fastidiosa to citrus (30%) in relation to coffee (2.2%), whereas the other vectors transmitted the bacterium to both hosts with similar efficiencies. Despite these variations, vector efficiency in coffee and citrus is lower than that reported in other hosts.

Genetic characterization of Xylella fastidiosa isolated from citrus and coffee plants

The Citrus Variegated Chlorosis and the Coffee Leaf Scorch are some of the many destructive diseases caused by Xylella fastidiosa, a gram-negative bacterium limited to the xylem of affected plants. As its genetic characterization is still not well established, different isolates of X. fastidiosa from citrus and coffee were evaluated through RAPD (Random Amplified Polymorphic DNA) technique to characterize and classify these isolates based on similarity coefficients. Sixteen isolates of X. fastidiosa were used on this trial, obtained from citrus, coffee and almond. The genetic polymorphism evaluation was performed using six arbitrary 10-base primer pairs. It was possible to establish a dendogram in which the isolates were classified into five groups (A, B, C, D and E). A prevalence of citrus isolates in groups A and D was observed. In groups B and C, there was a prevalence of coffee isolates meanwhile the group D consisted of the almond isolate, solely.

An Effective and Low-Cost Culture Medium for Isolation and Growth of Xylella fastidiosa from Citrus and Coffee Plants

Buffered charcoal-yeast extract medium (BCYE) has been used for isolation of Xylella fastidiosa from citrus (Citrus sinensis) and coffee (Coffea arabica) plants affected by citrus variegated chlorosis (CVC) and coffee leaf scorch (CLS). BCYE is composed of ACES (2-[2-amino-2oxoethyl) amino]-ethanesulfonic acid) buffer, activated charcoal, yeast extract, L-cysteine, ferric pyrophosphate, and agar. ACES buffer is costly and not always commercially available in Brazil, and the L-cysteine and ferric pyrophosphate need to be filter sterilized in 0.22-mum pore membranes before inclusion in the medium. Omission of L-cysteine, addition of magnesium sulfate, and replacements of ACES and ferric pyrophosphate for potassium phosphate and ferrous sulfate resulted in an effective, less expensive, and entirely autoclavable medium, named phosphate buffered charcoal-yeast extract medium (PCYE). The final cost of PCYE was approximately one tenth that of BCYE. Its effectiveness was tested for the isolation of X. fastidiosa from symptomatic leaves collected from 52 citrus plants affected by CVC and 43 coffee plants affected by CLS. PCYE was as effective as BCYE and has been used routinely in our and other laboratories for isolation, growth, and quantification of X. fastidiosa from plant tissues.

Two new species of Kapateira Young from Costa Rica (Auchenorrhyncha: Cicadellidae: Cicadellinae)

The genus Kapateira was described by Young (1977), who included one species from Colombia but noted that the genus also occurs in Panama, Venezuela, Eucador, and Bolivia. In this paper two new species are decribed, K. peruana from Peru and K. coffea from Costa Rica. The latter species is associated with coffee and citrus, and information is provided on its biology. DAS-ELISA tests for the bacterium, Xylella fastidiosa, yielded numerous positive results, suggesting that K. coffea is a potential vector of diseases such as coffee leaf scorch and citrus variegation chlorosis.