1,721,021 research outputs found
Xylella fastidiosa: il patogeno, le malattie e l’attuale situazione fitosanitaria
Full text linkXylella fastidiosa è un batterio fitopatogeno Gram negativo che appartiene alla famiglia delle Xanthomonadaceae.
È l’agente causale di numerose malattie d’importanti colture arboree, erbacee,
forestali e ornamentali e, a differenza di quanto molta parte dell’opinione pubblica crede, non è
un problema di recente comparsa, ma ha una lunga storia che affonda le sue radici ancora alla
fine del diciannovesimo secolo. L’etimologia e la semantica del nome assegnato al patogeno da
parte dei ricercatori che per primi lo isolarono in coltura pura svelano due aspetti fondamentali
della sua biologia: Xylella rivela la nicchia biologica del patogeno all’interno delle sue piante
ospiti, cioè lo xilema; fastidiosa indica la grande difficoltà che il batteriologo incontra durante il
processo d’isolamento e purificazione della coltura pura
The olive quick decline syndrome in south-east Italy: a threatening phytosanitary emergency
No full textThe olive quick decline syndrome (OQDS) is a disease that appeared suddenly a few years ago in the province of Lecce (Salento peninsula, southeastern Italy). Among the factors that may be involved in its aetiology, the most relevant is Xylella fastidiosa, a quarantine pathogen of American origin, whose presence in Italy represents its first confirmed record in the European Union. X. fastidiosa is a Gram-negative bacterium that invades the xylem of a wide range of hosts, from which it is acquired by xylem-feeding insect vectors and transferred to other plants. The bacterium multiplies within the plant vessels and occludes them, thus impairing water uptake. Besides olive, the Salentian strain of X. fastidiosa infects in nature a number of woody (almond, cherry) and shrubby (oleander, broom, Acacia saligna, Polygala myrtifolia, Westringia fruticosa, Rosmarinus officinalis, Rhamnus elaternus, Myrtus communis) hosts, with no evidence for grapevines or citrus being hosts. The bacterium was isolated in culture and identified as a genotype of X. fastidiosa subsp. pauca, molecularly identical to an isolate from Costa Rica. Philaenus spumarius (meadow spittlebug), a froghopper quite common in the Salento area where it thrives on olive, was identified as the main vector. Disease eradication and sanitation of infected olives are unfeasible. However, strategies are being enacted for restraining the spread of pathogen and vector(s) within the boundaries of the currently infected zone
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Survey of Auchenorrhyncha in the Salento peninsula in search of putative vectors of Xylella fastidiosa subsp. pauca CoDiRO strain
Full text linkXylella fastidiosa (Xf) was identified in September 2013 in olive trees affected by the Olive quick decline syndrome (OQDS) in the Salento peninsula (southern Italy) and denoted Xf strain CoDiRO. Xf is comprised of a group of genetically diverse bacteria in the class Gammaproteobacteria that causes severe plant diseases in many crops and ornamentals. The bacterium is acquired and transmit- ted by xylem-sap feeding hemipterans such as sharpshooter leaf- hoppers (Cicadellidae, Cicadellinae), froghoppers and spittlebugs (Aphrophoridae and Cercopidae) and, possibly, cicadas (Cicadidae and Tibicinidae). Due to the rapid spread and devastation associ- ated with OQDS, a survey of candidate vectors of Xf was conducted from September 2013 in the Gallipoli area in accordance to a EFSA list (EFSA, 2013). Four candidate vector species were identified: (i) Aphrophoridae: Philaenus spumarius L. and Neophilaenus camp- estris Fallen; (ii) Cercopidae: Cercopis sanguinolenta Scopoli; (iii) Ci- cadidae: Cicada orni L. Among these, only P. spumarius, the meadow spittlebug, was experimentally proven to be a vector of X. fastidiosa strain CoDiRO. A high percentage of meadow spittlebugs collected from OQDS-affected orchards, from May to September 2014, tested positive for X. fastidiosa by PCR. Transmission to periwinkle plants was successful. Laboratory tests, so far limited to the Philaenus-ex- posed periwinkle seedlings, will be extended to the entire panel of the host plants (olives, grapes, citrus, oleander and Prunus spp.) that were exposed to infectious spittlebugs. Further ongoing experiments include Xf-free spittlebugs that were allowed to feed on infected olives and other hosts plants prior to transferring onto receptor host plants. The results so far obtained have shown that olive is a source of inoculum from which P. spumarius is able to acquire the bacte- rium and transfer it to other olives. These data strongly suggest that the main vector of Xf in the area of it occurrence is P. spumarius. Transmission tests carried out with other xylem sap feeders found in the OQDS area are also discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Transcriptome profiling of two olive cultivars in response to Xylella fastidiosa infection
No full textThe implementation and validation of diagnostic tests included serological and molecular approaches with the aim of pursuing sensitive and reliable identification of the bacterium in a wide range of plant species, including symptomatic and asymptomatic hosts. Serological assays focused on ELISA and DTBIA procedures. The newly developed polyclonal antisera, raised against the CoDiRO strain, was processed as ELISA and DTBIA reagent, thus evaluated for testing a wide range of plant matrices. Indeed, an X. fastidiosa MopB recombinant protein was developed for being used as standardized reference positive control in the diagnostic kits, avoiding the manipulation and the use of bacterial suspension preparations. In addition, experiments have been made to determine the best procedure for preparing and preserving non-infectious samples (with inactivated bacterium) for diagnostic purposes, including the preparation of the samples to be used for interlaboratory validation and performance test studies. Specifically, freeze-drying and dehydration protocols were used to prepare experimental samples that can be safely manipulated by different diagnostic laboratories without specific quarantine requirements. For molecular assays, a commercial kit (DNeasy mericon food kit, Qiagen) was successfully adapted for the automatized purification of high-quality DNA from a wide range of host plants. The qPCR assay was implemented by including the simultaneous detection of a plant DNA internal control (multiplex qPCR). A sensitive bacterial detection was also obtained through the development of a real-time LAMP assay based on crude plant sap. All the currently available methods were then tested and compared to a panel of asymptomatic infected plants (olive, oleander, cherry). All approaches were able to identify at a different level the presence of the bacterium, with qPCR assays being the most sensitive tests detecting up to 102 CFU/ml
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
- …
