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Infezioni da DMV su calla bianca in Liguria
No full textLa calla bianca (Zantedeschia aethiopica; Araceae) è una pianta ornamentale che negli ultimi anni ha riscontrato sul mercato europeo un notevole interesse (in Olanda, si è passati dai 24 milioni di “pezzi” del 1998 ai 45 milioni del 2004). Nella provincia di Imperia nell’ultimo ventennio la superficie coltivata a calla bianca è praticamente raddoppiata attestandosi, nel 2004, sui 16 ha.. La tecnica di coltivazione adottata prevede il trapianto dei rizomi (in agosto) partendo da materiale di propagazione recuperato e selezionato nel corso degli anni all’interno delle singole aziende.
Dal punto di vista patologico, la calla bianca è soggetta a numerose malattie batteriche e fungine, a cui si aggiungono alcune virosi. Il virus più frequente e pericoloso, “ubiquitario” nelle coltivazioni di calla di tutto il mondo (anche italiane), è quello del mosaico della colocasia (dasheen mosaic virus: DMV), un Potyvirus specifico delle Araceae. In Italia, nel 1992, è stata diagnosticata l’infezione dal virus dell’avvizzimento maculato del pomodoro (tomato spotted wilt virus: TSWV); successivamente, nel 1993, coltivazioni presenti ad Albenga (Imperia) sono state riscontrate infette dal virus della maculatura necrotica dell’impatiens (impatiens necrotic spot virus: INSV).
Di seguito, vengono riportati i risultati di un’indagine eseguita nella primavera-estate del 2005 in una fra le più importanti coltivazioni di calla bianca sita ad Arma di Taggia (Imperia), specializzata nella produzione del fiore reciso, ove si è verificata una grave malattia virale che ha portato alla perdita della quasi totalità della produzione.
Materiali e metodi
Reperimento dei campioni - I campioni di calla oggetto di studio sono stati reperiti nel corso di sopralluoghi eseguiti nel marzo 2005. Gli impianti esaminati erano costituiti da piante di 1 e 2 anni allestiti utilizzando materiale vegetale prodotto nella stessa azienda nel 2004. La quasi totalità delle piante evidenziava sintomi fogliari: striature clorotiche e/o gialle e malformazioni. Le lamine (anche quelle di foglie apparentemente sane) apparivano più strette del normale e, in alcuni casi, si notavano ondulazioni del margine, enazioni a livello della nervatura principale e vistosi arricciamenti. I fiori, prodotti in numero inferiore alla norma, apparivano malformati; la taglia delle piante era ridotta.
Da un primo esame visivo, i sintomi sono stati diagnosticati quali tipici dell’infezione da DMV. Considerando però che in Letteratura arricciamenti e deformazioni fogliari su calla vengono associati ad infezioni anche da TSWV, e che la diffusione di TSWV ed INSV nelle coltivazioni floricole ed orticole della Liguria è attualmente elevata, sono state effettuate specifiche analisi per rilevarne l’eventuale presenza nei campioni in esame.
Analisi virologiche: Il succo fogliare estratto da calla sintomatica è stato osservato al microscopio elettronico Philips CM10 (tecnica del leaf-dip). Porzioni di tessuto sono state incluse in resina; le sezioni ultrasottili ottenute sono state osservate al microscopio elettronico. Al fine di individuare la presenza di DMV, è stata applicata la tecnica di immunomicroscopia elettronica (IME) decoration.
Per rilevare infezione da Tospovirus e da CMV (virus del mosaico del cetriolo: cucumber mosaic virus) sono state applicate le tecniche DAS- e PAS-ELISA.
Risultati
Le osservazioni dei leaf-dip hanno consentito di rilevare la costante presenza di un virus a particelle filamentose (lunghezza media 750 nm), identificato in IME come un isolato di DMV. Nelle sezioni ultrasottili dei tessuti fogliari di calla inclusa in resina, sono state osservate inclusioni citoplasmatiche (pinwheels) tipiche dei Potyvirus. In alcuni dei preparati ottenuti con succo estratto da foglie con sintomi di arricciamento del lembo, sono state osservate particelle virali sferoidali tipiche dei Tospovirus. Non è stata rilevata infezione, in PAS-ELISA, da CMV.
Discussione
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Recent findings of viruses infecting Ranunculus Hybrids in Liguria (Italy)
No full textRanunculus asiaticus L. an ornamental species grown in many areas of the world ( western Europe, South Africa, California, Israel, Japan) for tuber, potted plants, and cut flowers production. In Italy, the crops of Ranunculus hybrids are located principally in Liguria region, where virus diseases represent a serious problem in cut flower production, even if the impact of virus infections on the crops has not been well studied. For this reason, in 2005-2007, two hundred samples of Ranunculus hybrids collected in Sanremo area (Imperia province) were examined to verify the presence of viruses associated to severe symptoms on leaves (chlorosis, mosaic, “parsely-like” appearance, vein-yellowing, necrotic spots and rings on the lamina; petiol and stem necrosis) and flowers (colour breaking, malformations), stunting and/or prematurely death of plants. By applying virological tests: mechanical inoculations on herbaceous plants, electron microscopy (“leaf-dip”), DAS and PAS-ELISA, IME (“decoration”), and RT-PCR, several virus species of different lengths (from 700 to 800 nm) and sizes (from 30 to 90-100 nm) singly or in mixed infections were detected. Cucumber mosaic virus (CMV) in a few cases alone, much more in combination with Tomato spotted wilt virus (TSWV) infected plants showing leaf mosaic, necrosis, stunting and severe symptoms on flowers. Both TSWV and Impatiens necrotic spots virus (INSV), in some cases with also Potato virus Y-Ranunculus strain (PVY-R), were detected in the foliage characterized by mosaic, stem and petiol necrosis, and “parsely-like” symptoms. Turnip mosaic virus (TuMV) and other unidentified potyvirus-like viruses were found. CMV and all the Potyviruses detected, were much present during Autumn 2006 season as a consequence of the abundance of aphid infestations. Data obtained clearly show not only the high diffusion of different species of viruses in Ranunculus crops in Sanremo area, but also that the correlation between symptom expression and virus presence is very difficult to be explained. Considering the increasing of economic damages to cut flower production recently observed in this area, control measures to prevent virus spreading are required, such as monitoring and virus-testing programs for a rapid removal of inoculum sources and large-scale indexing of propagation materials. In fact, considering that Ranuncuuls is vegetatively propagated, production and distribution of infected tubers can result in an easily virus spread: virus infected tubers rarely show symptoms, and the plantlets obtained usually do not express symptoms until they are rooted. As consequence, Ranunculus viruses (aphid an thrip transmitted) can spread rapidly to other plants before the grower is aware that the pathological problem exists
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
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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