1,720,994 research outputs found
Endophytic distribution of Pseudomonas syringae pv. actinidiae after a five-year latency into Actinidia chinensis var. chinensis plants: a real-time-PCR analysis
No full textThe ability of phytopathogenic bacteria to survive for long time within asymptomatic host plants represents one of the main critical factors to control outbreaks. The epidemiological role of the bacterial latency phase is very important since the control strategies are based on preventive chemical treatments by spraying on plant surfaces. In seven-year-old plants of Actinidia chinensis var. chinensis ‘Hort16A’ inoculated five years before with a virulent Pseudomonas syringae pv. actinidiae gfp-expressing/rifampicin-resistant strain (Psagfp-Rifres) at low inoculum dose, the dangerous latency phase of Psagfp-Rifres was studied dissecting the whole plants by cutting, from the apex to the root collar, the shoots/stems in segments of 20 cm (approx. 10-15/plant). In this study, to better clarify the endophyte distribution in asymptomatic plants and the preference of the pathogen for certain portions of the plant stem, the data previously obtained from microbiological (direct isolation on selective media, DI), biological (pathogenicity/HR assay) and PCR (Bio- and Nested) analyses were compared with those from Real-time PCR (RT-PCR) analysis. In the pathosystem Psa–Actinidia, the pathogen reached a high degree of pathoadaptation which is highlighted by the pluriannual latency period of Psa. The RT-PCR of the DNA extracted and quantified by the different segments of each entire plant confirmed the results previously obtained from microbiological and Bio/Nested PCR analyses and allowed to detect Psagfp-Rifres in segments of the stem that in Bio/Nested PCR analyses were Psagfp-Rifres-negative. Direct isolation revealed the Psagfp-Rifres presence in accordance with the RT-PCR data. The long time required for DI of Psagfp-Rifres from plant samples five years after the plant inoculation was largely compatible with the low concentrations of Psagfp-Rifres detected by RT-PCR
CRITICAL FEATURES OF THE DIAGNOSIS OF CLAVIBACTER MICHIGANENSIS subsp. MICHIGANENSIS FROM TOMATO SEED
No full textBacterial canker, caused by Clavibacter michiganensis subsp.
michiganensis (Cmm) is one of the most important bacterial disease
of tomato (Solanum lycopersicum) worldwide. Seeds are the
main pathway for the transmission of the bacterium, listed as an A2
quarantine pest, consequently the reliability of seed detection tests
represents a critical point to prevent the introduction and spread
of the pathogen. In this study some conventional (isolation and immunofluorescence)
and molecular (end-point PCR) methods for the
detection of Cmm from tomato seed samples were compared by an
inter-laboratory comparison (ITC). Several Italian laboratories, belonging
to different institutions, analysed the same panel consisting
of 11 Cmm-spiked tomato seed samples for the evaluated methods.
The obtained results showed that end-point PCR gave acceptable
performance values, even if the choice of enzyme in the PCR reaction
was crucial. Currently the EPPO protocol (Standard PM7/42 2)
does not contemplate a preliminary screening phase based on molecular
methods, but suggests two parallel flow diagrams that use,
as first step, the isolation and immunofluorescence, respectively.
Since these latter techniques showed low values of performance
criteria, the study highlighted the necessity to integrate the EPPO
protocol with a preliminary molecular screening test. It is advisable
to validate new molecular methods more specific and sensitive than
end-point PCR, based on systems such as real time PCR, LAMP
and digital PCR
Mass Spectrometry-Based Targeted Lipidomics and Supervised Machine Learning Algorithms in Detecting Disease, Cultivar, and Treatment Biomarkers in Xylella fastidiosa subsp. pauca-Infected Olive Trees
Full text linkIn 2013, Xylella fastidiosa (Xf) was detected for the first time in Apulia and, subsequently, recognized as the causal agent of the olive quick decline syndrome (OQDS). To contain the disease, the olive germplasm was evaluated for resistance to Xf, identifying cultivars with different susceptibility to the pathogen. Regarding this, the resistant cultivar Leccino has generally a lower bacterial titer compared with the susceptible cultivar Ogliarola salentina. Among biomolecules, lipids could have a pivotal role in the interaction of Xf with its host. In the grapevine Pierce’s disease, fatty acid molecules, the diffusible signaling factors (DSFs), act as regulators of Xf lifestyle and are crucial for its virulence. Other lipid compounds derived from fatty acid oxidation, namely, oxylipins, can affect, in vitro, biofilm formation in Xf subsp. pauca (Xfp) strain De Donno, that is, the strain causing OQDS. In this study, we combined high-performance liquid chromatography-mass spectrometry-MS-based targeted lipidomics with supervised learning algorithms (random forest, support vector machine, and neural networks) to classify olive tree samples from Salento. The dataset included samples from either OQDS-positive or OQDS-negative olive trees belonging either to cultivar Ogliarola salentina or Leccino treated or not with the zinc-copper-citric acid biocomplex Dentamet(®). We built classifiers using the relative differences in lipid species able to discriminate olive tree samples, namely, (1) infected and non-infected, (2) belonging to different cultivars, and (3) treated or untreated with Dentamet(®). Lipid entities emerging as predictors of the thesis are free fatty acids (C16:1, C18:1, C18:2, C18:3); the LOX-derived oxylipins 9- and 13-HPOD/TrE; the DOX-derived oxylipin 10-HPOME; and diacylglyceride DAG36:4(18:1/18:3)
In vitro antimicrobial activity of plant extracts against Pseudomonas syringae pv. actinidiae causal agent of bacterial canker in kiwifruit
No full textPseudomonas syringae pv. actinidiae (Psa), the causal agent of bacterial canker of kiwifruit, is considered the main pathogen of yellow-, green- and red-fleshed kiwifruit. All major kiwifruit producing countries in the world have been affected by this bacterial pathogen, leading to substantial economic losses. The control of bacterial canker of kiwifruit is based only on preventive methods or on the use of copper compounds that can cause phytotoxicity problems. In this study, the in vitro antibacterial activity of seven different plant extracts against eight Psa strains has been evaluated. The inhibition of 100% of the Psa growth was observed, after 24 h, for the extracts of Polygonum cuspidatum roots (POL-roots), Hypericum perforatum roots elicited with chitosan oligosaccharides (HYP-COS roots) and non-fermented grape pomace (ITA-pomace). The strongest antibacterial activity was exhibited by POL-roots, with a geometric mean of minimum inhibitory concentration of 100% of growth (GMMIC100) of 105.11 μg/mL after 24 h, and with a GMMIC100 value of 148.65 μg/mL after 48 h. Moreover, POL-roots extract showed the best bactericidal activity with a GMMBC of 210.22 μg/mL. No phytotoxic activity was observed up to 15 days in the leaves of Actinidia chinensis “Belen” treated with plant extracts at 500 μg/mL
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
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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