Coffee leaf scorch caused by a strain of Xylella fastidiosa from citrus

Citrus variegated chlorosis (CVC) and coffee leaf scorch (CLS) are two economically important diseases in Brazil caused by the bacterium Xylella fastidiosa. Strains of the bacterium isolated from the two plant hosts are very closely related, and the two diseases share sharpshooter insect vectors. In order to determine if citrus strains of X. fastidiosa could infect coffee and induce CLS disease, plant inoculations were performed. Plants of coffee, Coffea arabica 'Mundo Novo', grafted on Coffea canephora var, robusta 'Apuatao 2258' were mechanically inoculated with triply cloned strains of X. fastidiosa isolated from diseased coffee and citrus. Three months postinoculation, 5 of the 10 plants inoculated with CLS-X. fastidiosa and 1 of the 10 plants inoculated with CVC-X. fastidiosa gave positive enzyme-linked immunosorbent assay (ELISA) and/or polymerase chain reaction (PCR). Eight months postinoculation, another six plants inoculated with CVC-X. fastidiosa gave positive PCR results. The two X. fastidiosa strains were isolated from the inoculated plants and showed the same characteristics as the original clones by microscopy, ELISA, and PCR. None of the plants inoculated with sterile periwinkle wilt (PW) medium as controls gave positive reactions in diagnostic tests, and none developed disease symptoms. Six months postinoculation, seven plants inoculated with CLS-X. fastidiosn and eight inoculated with CVC-X. fastidiosa began to develop characteristic CLS symptoms, including apical and marginal leaf scorch, defoliation, and reductions of internode length, leaf size, and plant height, terminal clusters of small chlorotic and deformed leaves, and lateral shoot dieback. We have demonstrated that X, fastidiosa from citrus plants is pathogenic for coffee plants. This has important consequences for the management of CLS disease and has implications for the origin of citrus variegated chlorosis disease.

Saprophytic colonization of citrus twigs by Diaporthe citri and factors affecting pycnidial production and conidial survival

Melanose, caused by Diaporthe citri, produces reddish brown lesions on the fruit, leaves, and twigs of citrus trees, and greatly reduces the marketability of fresh fruit. Most of the inoculum is produced in pycnidia on dead twigs in the tree canopy, which exude large numbers of conidia in slimy masses. In this study, detached twigs inoculated with conidia were readily colonized and produced large numbers of pycnidia within 30 to 40 days when they were soaked 3 to 4 h on alternate days. Conidial production was measured by wetting twigs in a rain tower periodically and collecting the conidia in the runoff water. Production began after 80 days and continued for nearly 300 days. In other experiments, production of mature pycnidia on detached twigs was greatest at 94 to 100% relative humidity (RH) and at 28 degrees C. Low RH and temperature, however, favored survival of conidia in exuded masses on twigs. In the field, colonization of detached twigs by D. citri was high in rainy season, moderate in spring and early fall, and minimal in late fall and winter. Twig colonization was positively related to the number of rain days and average temperature, but not to total rainfall. In another experiment, inoculated twigs placed in the tree canopy developed pycnidia and then produced conidial masses for about 200 days. D. citri is a serious pathogen, but a weak parasite, that survives primarily by colonization and reproduction on dead twigs.

Citrus and coffee strains of Xylella fastidiosa induce Pierce's disease in grapevine

Xylella fastidiosa causes citrus variegated chlorosis (CVC) disease in Brazil and Pierce's disease of grapevines in the United States. Both of these diseases cause significant production problems in the respective industries. The recent establishment of the glassy-winged sharpshooter in California has radically increased the threat posed by Pierces disease to California viticulture. Populations of this insect reach very high levels in citrus groves in California and move from the orchards into the vineyards, where they acquire inoculum and spread Pierce's disease in the vineyards. Here we show that strains of X. fastidiosa isolated from diseased citrus and coffee in Brazil can incite symptoms of Pierce's disease after mechanical inoculation into seven commercial Vitis vinifera varieties grown in Brazil and California. Thus, any future introduction of the CVC strains of X. fastidiosa into the United States would pose a threat to both the sweet orange and grapevine industries. Previous work has clearly shown that the strains of X. fastidiosa isolated from Pierce's disease- and CVC-affected plants are the most distantly related of all strains in the diverse taxon X. fastidiosa. The ability of citrus strains of X. fastidiosa to incite disease in grapevine is therefore surprising and creates an experimental system with which to dissect mechanisms used by X.,fastidiosa in plant colonization and disease development using the full genome sequence data that has recently become available for both the citrus and grapevine strains of this pathogen.

Obtencao e interpretacao de dados de Reflexao Sismica Superficial (Rasa) - exemplos e aplicacoes

Successful application of shallow seismic reflection method is related directly to the ability of the ground to transmit high-frequency seismic energy from a seismic source. The dominant frequencies of reflection data are in the range of 50 to 100 Hz and depend on the surface materials and water table. A spread of geophones send the siemsic signal to be recorded on a 12, 24 or 48 channel portable seismograph, using a single high-frequency geophone per channel. Although it is possible to find seismographs with display and processing unities, it is also possible to transfer digitalized data to a personal computer to be processed and interpreted by using specific programs. Some results of two recent field studies to specify the underground structure in the tidal flats area of Baie St. Paul (Quebec-Canada) and in glacial terrains, in the Waterloo (Ontario-Canada) region. -from English summary

Scanning electron microscope analysis of internal adaptation of materials used for pulp protection under composite resin restorations

Purpose: The aim of this study was to evaluate the interfacial microgap with different materials used for pulp protection. The null hypothesis tested was that the combination of calcium hydroxide, resin-modified glass ionomer, and dentin adhesive used as pulp protection in composite restorations would not result in a greater axial gap than that obtained with hybridization only. Materials and Methods: Standardized Class V preparations were performed in buccal and lingual surfaces of 60 caries-free, extracted human third molars. The prepared teeth were randomly assessed in six groups: (1) Single Bond (SB) (3M ESPE, St. Paul, MN, USA); (2) Life (LF) (Kerr Co., Romulus, MI, USA) + SB; (3) LF + Vitrebond (VT) (3M ESPE) + SB; (4) VT + SB; (5) SB + VT; (6) SB + VT + SB. They were restored with microhybrid composite resin Filtek Z250 (3M ESPE), according to the manufacturer's instructions. However, to groups 5 and 6, the dentin bonding adhesive was applied prior to the resin-modified glass ionomer. The specimens were then thermocycled, cross-sectioned through the center of the restoration, fixed, and processed for scanning electron microscopy. The specimens were mounted on stubs and sputter coated. The internal adaptation of the materials to the axial wall was analyzed under SEM with × 1,000 magnification. Results: The data obtained were analyzed with nonparametric tests (Kruskal-Wallis, p ≤ .05). The null hypothesis was rejected. Calcium hydroxide and resin-modified glass ionomer applied alone or in conjunction with each other (p < .001) resulted in statistically wider microgaps than occurred when the dentin was only hybridized prior to the restoration. ©2005 BC Decker Inc.

Influência da contaminação da dentina por cimentos temporários na resistência da união de sistemas adesivos

Objective: The aim of this study was to assess the bond strength of adhesive systems to dentin contaminated by temporary cements with or without eugenol. Method: Flat dentin surfaces were obtained from twenty-four human third molars. With exception of the control group (n=8), the surfaces were covered with Interim Restorative Material (Caulk Dentsplay, Milford, DE, USA) or Cavit (3M ESPE, St. Paul, MN, USA) and kept in an oven at 37°C for seven days. After removing the cements, the adhesive systems Adper Single Bond (3M ESPE, St. Paul, MN, USA) or Clearfil SE Bond (Kuraray Co. Ltd., Osaka, Japan) were applied in accordance with the manufacturers' recommendations, and then the crowns were constructed in of resin composite. The teeth were sectioned into specimens with a cross-sectional bond area of 0.81mm2, which were submitted to microtensile testing in a mechanical test machine at an actuator speed of 0.5mm/min. The data were analyzed by t- and ANOVA tests, complemented by Tukey tests (α=0.05). Results: For Adper Single Bond (3M ESPE, St. Paul, MN, USA), bond strength did not differ statistically (p>0.05) for all the experimental conditions. For Clearfil SE Bond (Kuraray Co. Ltd., Osaka, Japan), only the Interim Restorative Material (Caulk Dentsplay, Milford, DE, USA) Group showed significantly lower bond strength (30.1 ± 13.8 MPa) in comparison with the other groups; control (38.9 ± 13.5 MPa) and Cavit (3M ESPE, St. Paul, MN, USA) (42.1 ± 11.0 MPa), which showed no significant difference between them. Conclusion: It was concluded that the previous covering of dentin with temporary cement containing eugenol had a deleterious effect on the adhesive performance of the self-etching system only.

Influence of artificial aging in marginal adaptation of mixed class V cavities

The aim of this study was to investigate whether the artificial aging by thermal cycling had influenced the marginal adaptation of class V restorations with/without chlorhexidine application in the bond process. Twelve intact human third molars were used. Class V cavity preparations were performed on the buccal surface and the teeth received 35% phosphoric acid-etching procedure (Ultradent Products Inc., South Jordan, Utah, USA). Subsequently, the samples were divided in two groups: Untreated acid-etched dentin and chlorhexidine application as an adjunct in the bond process. The adhesive Single Bond 2 (3M ESPE, St. Paul, MN, USA) was used after 2% chlorhexidine application, and the restorations were performed with FiltekTM Z350 XT (3M ESPE) composite resin. The specimens were submitted to artificial aging by thermal cycling with 3,000 cycles. Analyzes were performed on scanning electron microscopy using replicas of marginal adaptation in percentage of continuous margin before and after the artificial aging. The data were analyzed by paired test and the results showed statistically significant differences in the percentage of continuous margin with/without chlorhexidine treatment before and after thermal cycling. This study concluded that the artificial aging by thermal cycling influenced the marginal adaptation of mixed class V composite restorations.