1,720,967 research outputs found
Le batteriosi delle drupacee, un problema di non facile soluzione
No full textDa diversi anni, però, i frutticoltori italiani lamentano serie difficoltà nel mantenere la produttività degli impianti a causa di frequenti scoppi epidemici di alcune malattie batteriche che sono responsabili della comparsa di sintomi a carico dei frutti, foglie e parti legnose degli alberi
Attuazione di strategie IPM per controllare le malattie batteriche di drupacee e noci causate da pseudomonadi e xantomonadi resistenti/tolleranti al rame
No full textIl cancro batterico delle drupacee causato da Pseudomonas syringae pv. syringae e Pseudomonas syringae pv. morsprunorum e il mal secco del noce causato da Xanthomonas arboricola pv. juglandis, sono stati studiati per oltre un secolo e hanno portato a significativi progressi nella nostra comprensione dell'epidemiologia delle malattie batteriche fogliari e del ciclo di vita epifita di questi agenti patogeni. Recenti studi sull'ecologia, la caratterizzazione e l'identificazione dei patogeni sono stati stimolati dall'importanza economica delle malattie e dalla mancanza di misure di controllo efficaci. Una collezione di 54 isolati di P. syringae spp. da albicocco e 47 isolati di X. a. pv. juglandis da noce sono stati studiati utilizzando il fingerprinting genomico mediante reazione a catena della polimerasi ripetitiva (PCR), utilizzando i set di primer ERIC, BOX e REP e l'analisi della sequenza multi-locus (MLSA). La tolleranza al rame di tutti i ceppi è stata valutata osservando la crescita batterica su terreni con aggiunta di solfato di rame e i risultati sono stati confrontati con quelli di uno studio di cinque anni nella stessa area. Questa tesi ha mostrato che la frequenza dei batteri resistenti al rame aumenta dopo ripetuti trattamenti con composti a base di rame. Questi risultati suggeriscono che la selezione di ceppi resistenti al rame può essere una delle principali cause di fallimento nel controllo dopo il trattamento con composti rameici. I batteriofagi, in quanto elementi naturalmente presenti nell’ambiente, potrebbero essere un'opzione praticabile per il controllo di queste malattie batteriche. In questa tesi, dieci nuovi fagi che lisano P. s. pv. syringae e dieci nuovi fagi che lisano X. a. pv. juglandis sono stati isolati da frutti, foglie, suolo e acqua di irrigazione di albicocche e noci nel nord Italia. La digestione con endonucleasi di restrizione dei fagi ha rivelato che esistono tre gruppi fagici distinti, designati come gruppi 1, 2 e 3. Nonostante il fatto che tutti i fagi isolati fossero specifici per X. a. pv. juglandis, un'analisi della gamma ospite di fagi che coinvolge 25 diversi X. a. pv. juglandis ha rivelato che i fagi possono essere suddivisi in quattro classi in base alla loro capacità di lisare i 25 ceppi considerati. Nei test di laboratorio, tutti i fagi hanno avuto un promettente effetto litico su P. s. pv. syringae e X. a. pv. juglandis.Bacterial canker of stone fruits caused by Pseudomonas syringae pv. syringae and Pseudomonas syringae pv. morsprunorum, and bacterial blight of walnut caused by Xanthomonas arboricola pv. juglandis, have been studied for over a century and have resulted in significant advances in our understanding of the epidemiology of foliar bacterial diseases and epiphytic life cycle of these pathogens. Recent studies on the ecology, characterization, and identification of pathogens have been prompted by the economic importance of the diseases and the lack of effective control measures. A collection of 54 P. syringae spp. on apricot and 47 X. a.pv. juglandis strains on walnut were studied using repetitive polymerase chain reaction (PCR) genomic fingerprinting using ERIC, BOX, and REP primer sets, and Multi-Locus Sequence Analysis (MLSA). Copper tolerance of all strains were assessed by observing bacterial growth on copper sulphate-added media, and the results were compared to those of a five-year-old study in the same area. This thesis showed that the frequency of copper resistant bacteria increased after repeated treatments with copper-based compounds. These findings suggest that the selection of copper-resistant strains may be a major cause of control failures after copper bactericide treatment. Bacteriophages, as realistic and environmentally friendly microorganisms, could be a viable option for controlling these bacterial diseases. In this thesis, ten novel phages that lyse P. s. pv. syringae and ten novel phages that lyse X. a. pv. juglandis were isolated from apricot and walnut fruits, leaves, soil, and irrigation water in Northern Italy. The restriction endonuclease digestion of phages revealed that there are three distinct phage groups, designated as groups 1, 2, and 3. Despite the fact that all isolated phages were specific to X. a. pv. juglandis, an analysis of the host range of phages involving 25 different X. a. pv. juglandis strains revealed that the phages can be divided into four classes based on their ability to lyse the 25 strains considered. In laboratory tests, all phages had a promising lytic effect on P. s. pv. syringae and X. a. pv. juglandis. P. s. pv. syringae and X. a. pv. juglandis showed promising lytic effect in laboratory trials
Le principali malattie del noce da frutto: aspetti epidemiologici e tecniche di controllo
No full textWell-known bacterial and fungal diseases affecting walnut trees represent a limiting factor in intensively cultivated areas. Nowadays, the most important bacterial and fungal diseases are: the bacterial blight, caused by Xanthomonas arboricola pv juglandis, and the anthracnose, caused by the ascomycete Marssonina juglandis (teleomorph: Gnomonia leptostyla). Other well-known diseases, although of minor impact, are the shallow bark necrosis caused by the Gram-negative rod Brenneria nigrifluens, the Armillaria root rot, caused by the basidiomycete Armillaria mellea and the crown and root rot, caused by a few oomycetes belonging to the genus Phytophthora. Two more diseases appear to be a possible future threat in walnut production: the blackline disease, caused by the Cherry Leaf Roll Virus (CLRV) and the thousand cankers disease, caused by Geosmithia morbida, a fungus that is disseminated by the walnut twig beetle, Pityophthorus juglandis
Biological control of plant bacterial pathogens by a beneficial Streptomyces sp.
No full textIn the present study a set of beneficial microorganisms were evaluated for
their in vitro antimicrobial activity on various phytopathogenic bacteria,
like Xanthomonas vesicatoria, Clavibacter michiganensis subsp.
michiganensis (Cmm), Clavibacter michiganensis subsp. sepedonicus
(Cms), Acidovorax citrulli and Ralstonia solanacearum. A prospective
antagonist, strain SA51 (Streptomyces sp.) was selected based on its remarkable
in vitro antibacterial activity and was further studied under
greenhouse conditions on tomato (Solanum lycopersicum) seedlings as
a model plant against X. vesicatoria. Fromin vitro results, it was clearly
evident that SA51 was very active against bacteria like Cmm, Cms, R.
solanacearum and X. vesicatoria compared to other antagonists. Tomato
plantlets were inoculated with SA51 at the roots and, thereafter, they were
sprayed with X. vesicatoria. Protection against X. vesicatoria by the bacterized
tomato plants was confirmed in the greenhouse: disease was reduced
by approximately 96%. Additionally, plants bacterized by strain SA51
showed significant plant growth, particularly in aerial parts as compared
to un-bacterized controls. Finally, benefit was seen in inoculated
healthy plants in terms of a significant increase in dry weight and length
of roots and shoots, as compared to the uninoculated controls. A GFP
mutant of strain SA51 was produced to study its endophytic colonisation
in tomato plants: results confirmed that SA51 was able to efficiently
colonise tomato endophytically, from the roots to the leaves. Field experiments
confirmed the ability of strain SA51 to act as plant growth promoting
agent: such promoting activity was also reflected into an increase
of fruit production by approximately 7%
First report of bacterial spot caused by Xanthomonas cucurbitae on pumpkin in Italy
Full text linkIn 2018, a disease outbreak was observed on pumpkin (Cucurbita moschata cv. Violina) in the municipality of Reggio Emilia (Northern Italy). Symptoms were observed on leaves and fruits
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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