1,721,037 research outputs found
Multilocus Genetic Characterization of Phytoplasmas
No full textClassification of phytoplasmas into 16S ribosomal groups and subgroups and ‘Candidatus Phytoplasma’ species designation have been primarily based on the conserved 16S rRNA gene. However, distinctions among closely related ‘Ca. Phytoplasma’ species and strains based on 16S rRNA gene alone have limitations imposed by the high degree of rRNA nucleotide sequence conservation across diverse phytoplasma lineages and by the presence in a phytoplasma genome of two, sometimes sequence heterogeneous, copies of this gene. Thus, in recent years, moderately conserved genes have been used as additional genetic markers with the aim to enhance the resolving power in delineating distinct phytoplasma strains among members of some 16S ribosomal subgroups. The present chapter is divided in two parts: the first part describes the non-ribosomal single-copy genes less conserved (housekeeping genes) such as ribosomal protein (rp), secY, secA, rpoB, tuf, and groEL genes, which have been extensively used for differentiation across the majority of phytoplasmas; the second part describes the differentiation of phytoplasmas in the diverse ribosomal groups using multiple genes including housekeeping genes and variable genes encoding surface proteins
Biological control of Hyalesthes obsoletus Signoret, the main insect vector of ‘Candidatus Phytoplasma solani’, using entomopathogenic nematodes and fungi
No full textHyalesthes obsoletus Signoret is a univoltine, polyphagous species completing its complex life cycle, including the nymph subterranean cryptic stage, on herbaceous wild plants in European countries. In vineyards, it occasionally transmits ‘Candidatus Phytoplasma solani’, an obligate parasitic bacterium associated with Bois noir disease of grapevine, from its preferred host plants to grapevine. As no effective control measures targeting phytoplasmas are available, main strategies to manage the disease is based on the vector control. In the case of H. obsoletus, insecticide treatments on grapevine canopy are completely inefficient due to its life cycle. Consequently, the control of this planthopper focuses on its nymphs living on the host plant roots. In the present study, the control activity of entomopathogenic nematodes (EPNs; (Steinernema carpocapsae, S. feltiae, Heterorhabditis bacteriophora) and fungi (EPFs; Beauveria bassiana, Metarhizium anisopliae, Paecilomyces fumosoroseus, Lecanicillium muscarium) against H. obsoletus nymphs and adults were evaluated by laboratory bioassays and semi-field trials. Statistical analyses demonstrated that the majority of the examined EPNs and EPFs are able to control H. obsoletus nymphs and adults, exhibiting a range of effectiveness. In all the conducted trials, S. carpocapsae and P. fumosoroseus were found as the most effective biocontrol agents among EPNs and EPFs, respectively. Interestingly, considering their ability to colonize the soil after their inoculation, EPNs and EPFs can reduce the H. obsoletus population density for long time. Ecological competency and conditions that can impede or enhance the EPNs and EPFs performance should be investigated to optimize their performance in field conditions
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Bacterial diversity and community structure differences between ‘Candidatus Phytoplasma solani’ infected and non-infected insect vectors in North Italy vineyards
No full textIn the present study, we described the bacterial diversity and community structure of the ‘Candidatus Phytoplasma solani’ infected and non-infected insect vectors (Cicadella viridis, Dictyophara europaea, Euscelis incisus, Euscelidius variegatus, Philaenus spumarius, and Psammotettix alienus), newly discovered in northern Italy alongside the main vector Hyalesthes obsoletus and a known host but non-vector, Cicadella viridis. A total of 300 individuals were captured with sweep entomological net and pooter in mid-June 2018 and transferred to the laboratory in 100% alcohol for molecular analyses. ‘Ca. P. solani’ was detected by nested PCR-based amplification of the stamp gene using as templates the total nucleic acids extracted from the insect specimens. Depending on the result of this PCR, specimens were separated into the “infected” and “non-infected” groups. A total of 14 individuals per species (7 specimens per group) were sent to Personal Genomics (Verona, Italy) for Illumina sequencing of the V3-V4 hypervariable region of the bacterial 16S rRNA gen
Variations on the Author
Get PDF“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
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe 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
Get PDFWe 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
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