1,720,958 research outputs found
Haplaxius crudus transmission of ‘Candidatus Phytoplasma palmae’ to coconut seedlings in Cuba
No full textLethal yellowing comprises the coconut lethal yellowing as one of the most important diseases affecting coconut
plantations worldwide. In Cuba, it was associated predominantly with phytoplasmas of the group 16SrIV
detected in symptomatic coconut palms but in some cases, these phytoplasmas were in mixed infection with
phytoplasmas from other ribosomal groups. During recent surveys to verify the phytoplasma presence, Haplaxius
crudus leafhoppers were predominantly found in the coconut agrosystems of the western region of Cuba, where
coconut plantations are mainly located. Two transmission tests were carried out to determine the phytoplasma
transmission by H. crudus under Cuba conditions. Coconut seedlings showed leaf yellowing 10 month after the
insect inoculation and their associated pool of insects tested positive for ‘Candidatus Phytoplasma palmae’
presence. Virtual RFLP, sequencing and phylogenetic analyses confirmed the phytoplasma identity and the first
experimental H. crudus transmission of ‘Ca. P. palmae’ to coconut seedlings in Cuba
Genetic diversity among phytoplasma strains infecting Citrus and coconut in Cuba
No full textLethal yellowing diseases are among the most important diseases affecting palms worldwide. The lethal
yellowing phytoplasmas affecting coconut in Cuba were enclosed in the 16SrIV group and the presence of
phytoplasmas in this ribosomal group was detected also in coinfection with phytoplasmas belonging to other
ribosomal groups. Recently a mixed infection of ‘Candidatus Liberibacter asiaticus’ with several phytoplasmas
(including the 16SrIV phytoplasmas) was reported also in citrus in Cuba. The objective of this study was to
determine the genetic diversity of the strains of ‘Ca. Phytoplasma palmae’ detected in citrus and in coconuts.
HLB-symptomatic leaf samples of citrus were collected from Jaguey Grande, Matanzas province. The 58 samples
were tested to detect ‘Ca. L. asiaticus’ and phytoplasmas using the 16S ribosomal and the groEl genes. The
characterization of citrus infecting phytoplasma strains confirmed the relationship with some of the strains
detected previously in coconut. This finding is suggesting the lack of specificity in ‘Ca. P. palmae’ strains
indicating that their presence in the agroecosystems could represent a threat also to citriculture. Additionally,
the presence of phytoplasma strains in group 16SrIX was detected for the first time in Cuba in some of the
sampled citrus. All these elements makes it necessary to perform deeper and accurate surveys on phytoplasma
presence in Cuba as basis to understand epidemiology of these bacteria associated diseases in the different
agroecosystems and to devise the best management practices
Multigene characterization of ‘Candidatus Phytoplasma palmae’ strains infecting citrus species in Cuba
No full textSurveys for the presence of ‘Candidatus Liberibacter asiaticus’ in citrus showing “huanglongbing” symptoms in Cuba allowed
the detection of citrus plants coinfected with ‘Candidatus Phytoplasma palmae’. The molecular characterization of these citrus
infecting phytoplasmas confirmed that they are indistinguishable from phytoplasma strains previously detected in coconut
during the lethal yellowing outbreak in the island in 2000. This finding suggests the possible loss of specificity in some ‘Ca. P.
palmae’ strains confirming that their presence could represent a further threat to the Cuban citriculture
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
Identification of ‘Candidatus Phytoplasma’ species in “huanglongbing” infected citrus orchards in the Caribbean
Full text link“Huanglongbing” (HLB) is one of the most devastating diseases of citrus orchards worldwide. Samples from 183 citrus plants of different cultivars and rootstock/cultivar combinations, showing HLB symptoms in three Caribbean countries (Cuba, Jamaica, and Guadeloupe-France), were collected to verify the possible co-infection of ‘Candidatus Phytoplasma’ and ‘Candidatus Liberibacter’ species. The 64% of the samples resulted positive to the ‘Ca. L. asiaticus’ and the 27% to diverse ‘Ca. Phytoplasma’-related species, moreover about the 14% of the samples infected with ‘Ca. Liberibacter’ were also found positive to phytoplasmas, indicating the presence of mixed infection especially in the orchards located in Cuba. Moreover, in one of the samples from Jamaica mixed phytoplasma infection was detected. Moreover the detection of only phytoplasmas in 11 symptomatic citrus samples collected from Cuba and Guadeloupe without ‘Ca. Liberibacter’ detection, confirmed that the symptomatology cannot be the sole criterium to discriminate between the presence of the two pathogens, and molecular detection is necessary to identify single or mixed infections. Diaphorina citri insects collected from Cuba and Guadeloupe resulted infected with ‘Ca. L. asiaticus’ confirming its active role in the dissemination of the pathogen. Only one insect of the Cicadidae family, collected in Guadeloupe, was found positive for phytoplasma presence. Considering that the phytoplasmas belonging to some ‘Candidatus species’ were detected in the three countries in different citrus varieties, a relevant role as phytoplasma reservoir can be attribute to citrus orchards
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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