1,721,004 research outputs found
Phytoplasma elimination from perennial horticultural crops
No full textThe presence of phytoplasmas is a major threat for plant survival and
production, especially in perennial crop species. The fact that infected plants cannot
be healed emphasizes the importance of strategies for their elimination. Several
methods were exploited and applied to verify their disappearance from plant tissues
in vivo, such as thermotherapy by hot water or hot air of propagation material and
chemotherapy of both propagation material and plants in the field. Numerous in
vitro methods were also tested from meristem tip culture to chemotherapy with
antibiotics or other antimicrobial molecules as well as cryotherapy that showed
some level of phytoplasma elimination. The most promising approach to plant sanitation
from phytoplasma infection still appears to be the combination of in vitro
thermotherapy and shoot-tip culture
European Stone Fruit Yellows (ESFY).
No full textSince the beginning of the twentieth century symptoms of apricot tree decline were observed in France and Italy: Morvan in 1977 named the disease associated with leptonecrosis (Goidanich, 1934) or with new sprouting in winter "apricot chlorotic leaf rolling" (ACLR). Only since the late 1970ies these symptoms were associated with phytoplasma infections, since electron or fluorescence microscopy (by DAPI-staining) allowed to detect phytoplasmas as single cells in sieve tubes (Fig. 1) and transmission experiments to other stone fruit and indicator plants were successfully carried out (Morvan, 1977; Goidanich et al., 1980; Giunchedi et al., 1982, Pastore et al., 1995).
European stone fruit yellows (acronym: ESFY) has been proposed as the common name for phytoplasma-related diseases in European stone fruits (Kison et al., 1997). Among others it includes the French ECA or ACLR, which is a quarantine organism of EPPO (OEPP/EPPO, 1986), included in the EPPO certification scheme for virus tested fruit trees (OEPP/EPPO, 1991/1992).The presence of ESFY disease has been reported in France, Spain, Italy, Greece, and in Hungary, Romania, Switzerland, Germany, former Yugoslavia, the UK and Austria (Nemeth, 1986; Morvan, 1977, Davies and Adams 2000, Laimer da Câmara Machado et al. 2001a) causing decline and death to apricot, Japanese plum, more rarely to peach (Llacer and Medina, 1988) and to almond, flowering cherry and European plum (Seemüller et al. 1998) http://www.boku.ac.at/iam/pbiotech/phytopath/v_esfy.html). An increasing presence of phytoplasma associated diseases such as leptonecrosis on Japanese plum (Prunus salicina) and chlorotic leaf roll on apricot (Prunus armeniaca) has been observed in commercial orchards in several European regions in the last twenty-five years (Giunchedi et al., 1978; Desvignes and Cornaggia, 1982; Dosba et al., 1991; Bertaccini et al., 1993; Laimer et al., 2001; Torres et al., 2004). Prunus rootstocks are also affected by this disease (Dosba et al. 1991, Jarausch et al. 1998). ESFY phytoplasmas have also been detected in wild Prunus species, e.g. Prunus spinosa and P. cerasifera (Carraro et al. 2002) and cherry (Prunus avium) (Paltrinieri et al., 2001). In recent years ESFY phytoplasma has been detected in other wild plants such as Rosa canina, Celtis australis and Fraxinus excelsior (Jarausch et al., 2001) as well as in grapevine in Hungary (Varga et al., 2000) and in Serbia (Duduk et al., 2004)
FAIR CT 97-3889: Health certification of rosaceous species based on disease-indexing of in vitro plants: Validation of diagnostics and diagnostic strategies
No full textAim of the project FAIR CT 97-3889 was to develop and assess broad spectrum and specific assays for detection of filamentous, bacilliform and nematode-transmitted viruses and phytoplasmas to be used in tissue culture laboratories involved in the production of certified elite propagation material. The methodology to be used for broad-spectrum and/or specific detection tests (RT-PCR, PCR-ELISA, NASBA) is based on the amplification of the pathogen genome. Elimination procedures, such as meristem culture, heat therapy, and combinations thereof, were compared to evaluate their efficiency to eliminate recalcitrant pathogens. The release of fruit plant cultivars to fruit plant growers takes several years until all known as well as diseases of unknown etiology related with a plant species are checked by indexing methods currently in use ("base line" tests are carried out in the field with woody indicators). The combination of disease elimination and disease-indexing on in vitro plants, using reliable laboratory diagnostics, would considerably reduce the efforts and contribute to savings of time, money and labour and constitutes a considerable step forward to avoid disease spread and to allow safe commercial transactions of propagating plant material
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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