1,720,980 research outputs found
Harnessing the Power of Electrical Penetration Graph Technology to Understand Psyllid-Transmitted Fastidious Bacterial Diseases
No full textSin financiación.Psyllids, also called plant lice, are hemipteran insects that feed on phloem sap. In addition to the direct damage they cause to plants, they are vectors of many phloem-restricted bacterial pathogens belonging to the ‘Candidatus Liberibacter’ spp. and ‘Candidatus Phytoplasma’ spp. from the apple proliferation group (16SrX). Although ‘Candidatus Liberibacter’ spp. cells possess cell walls unlike those of the phytoplasmas, they both share a reduced genome and unavailability in culture. In addition, psyllids transmit both species of bacteria in a persistent, circulative, and propagative manner. Because of the similarity of these pathosystems, the electrical penetration graph (EPG) was employed to study the probing behavior of psyllids. Such studies may assist in understanding the specific interactions between the fastidious bacteria, plant hosts, and insect vectors and lead to innovative control strategies. Herein, we discuss the potential of the EPG to study and understand the tritrophic interactions that secure a successful transmission from plant to plant. In addition, the use of the EPG in evaluating psyllid control strategies including pesticides and tolerant varieties is reviewed.Peer reviewe
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
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
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
Better together: the use of virus-induced gene silencing technique to repress the expression of two endogenous citrus genes simultaneously
No full textVirus-induced gene silencing is a promising technique for functional genomics studies. Citrus tristeza virus was employed successfully to create an infectious clone that was used to silence endogenous citrus genes. Phytoene desaturase (PDS) and delta (δ)-aminolevulinic acid dehydratase (ALAD) were targeted successfully in citrus. Silencing PDS usually results in a photo-bleached leaf phenotype while silencing ALAD causes discrete yellow spots in leaves. Silencing two or more genes simultaneously using the same infectious clone could be difficult due to the capacity of the plasmid and subsequent cloning. On the other hand, inoculating a new construct into a citrus plant pre-infected with another construct fails due to the superinfection exclusion phenomenon. Herein, I report our successful trials whereby we simultaneously graft-inoculate constructs targeting PDS and ALAD. The budwoods were graft-inoculated into the same tree but on two different branches. Interestingly, a new phenotype was produced because of the silencing of the two genes, which we called “color-breaking”. The phenotype was observed in both branches. Gene expression analysis showed a significant reduction of PDS and ALAD transcripts. This finding suggests the possibility of targeting more than one gene using different constructs, however, the graft-inoculation must be at the same time
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
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Citrus leaf volatiles response to ‘Candidatus Liberibacter asiaticus’ and to its insect vector Asian citrus psyllid
Full text linkPlant volatiles play an important role in defending plants against insects and pathogens attack. Released volatiles from insect-damaged plants may result in direct or indirect defense against insect, and volatile accumulation in pathogen-infected plants may inhibit the movement of the pathogens within plant tissues. However, available information about the response of citrus leaf volatiles to Asian citrus psyllids (ACP) feeding and ‘Candidatus Liberibacter asiaticus’ (Clas) infection is limited. Here we investigate the effect of ACP feeding, Clas infection, and simultaneous attack by ACP and Clas on the volatile content of Valencia leaves. Leaf volatiles were extracted using hexane and analyzed with gas chromatography-mass spectrometry (GC-MS). Eighteen out of twenty-seven detected volatiles were induced (2 to 10-folds) in ACP-infested plants. On the other hand, only four volatiles were induced in Clas-infected plants (d-limonene, β-phelandrene, citronellal, and undecanl). The abundance of latter compounds was induced 4-folds in Clas-infected plants, except for limonene, which was induced more than 20-folds. In addition, citrus plants that were subjected to a simultaneous attack by ACP and Clas reduced their volatiles production compared to those that experience an attack only by ACP. Our results suggested that insect and pathogen attack not only changes the profile of plant released volatiles, but also influences the volatile contents of the attacked plants. The result of this study might contribute to better understanding of citrus response to ACP and Clas attacks and provide more information about the relation between stored and released volatiles
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Composition of citrus phloem sap and honeydew produced by the citrus phloem sap feeder, the Asian citrus psyllid, Diaphorina citri (Homopetera: Psyllidae)
Full text linkThe honeydew composition of Asian citrus psyllids (ACP), the vector of citrus Huanglongbing (HLB), was studied using gas chromatography-mass spectrometry (GC-MS). Honeydew samples were collected from healthy ACP that were reared on one-year Valencia trees inside an insectary at a University of Florida’s Citrus Research and Education Center (CREC) grove in Lake Alfred, FL, USA. Dried samples (1 mg) were mixed with 30 μL of methoxyamine hydrochloride solution in pyridine (2%) and allowed to react for 17 h at room temperature. After methoximation, silylation reactions were induced by adding 80 μL of N-methyl-N-trimethylsilyl) trifluoracetamide (MSTFA) for 2 h at room temperature and 0.5 μL of derivatized sample was injected into the GC-MS running in the full scan mode. To check for amino acids, a 10 mg of alkaline honeydew sample was reacted with methylchloroformate (MCF) in a mixture of pyridine and methanol. The MCF derivatives were extracted with chloroform and analyzed with GC-MS. The moisure content was determined by drying the honeydew samples to a constant weight at a 100 °C. The major honeydew composition was as follows: 74.5 ± 2.8 sucrose, 12.4 ± 0.5 D-fructose, 6.4 ± 3.0 mannose, 1.8 ± 0.6 trehalose, myo-inositol 2.8 ± 0.8, ribitol 0.5 ± 1, galactose 0.4 ± 0.2, quinic acid 0.4± 0.3, and malic acid 0.3 ± 0.1. The moisture content of honeydew was 22.6 ± 2.6 No amino acids were detected as TMS or as MCF derivatives
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