1,722,228 research outputs found
First report of downy mildew (Plasmopara obducens) on impatiens walleriana in Italy
No full textDuring summer 2012, potted plants of impatiens (Impatiens
walleriana) grown in gardens near Biella (northern
Italy) showed symptoms of downy mildew. Infected leaves
were paler green than normal and showed white, downy
growth on the lower surface. Plants collapsed very rapidly,
especially at high relative humidity (RH). Microscopical
observations of infected leaves, maintained for 24 h at high
RH, disclosed the presence of hyaline, tree-like, straight,
120-350×5.8-10 μm sporangiophores, with three sterigma.
Sporangia were ovoid, hyaline and 10.7-15.4×11.7-16.6
(average 13.2×14.5) μm in size. Oospores were not observed
in leaf tissue. The DNA region encoding the large
ribosomal subunit (LSU rDNA) was amplified using
primers NL1 and NL4 (Maier et al., 2003) and sequenced
(GenBank accession No. JX880252LSU). BLAST analysis
of the 729 bp product obtained showed a similarity of
99% (E-value=0) with Plasmopara obducens from the USA
(GenBank accession No. JX217746). To confirm pathogenicity,
60-day-old impatiens plants, grown singly in 15
litre pots in a growth chamber at 20±1°C, were inoculated
by spraying leaves with a suspension of 1×105 sporangia/
ml. Control plants were sprayed with distilled water. Plants
were covered with plastic bags for 4 days. The first symptoms
(chlorosis) developed 8 days post inoculation. Control
plants remained healthy. This is the first report of P.
obducens in Italy. The disease has been reported in several
countries, including the USA (Wegulo et al., 2004), UK
(Lane et al., 2005) and Serbia (Bulajic et al., 2011). Currently,
this disease is present in several gardens in northern
Italy, where its importance may increase rapidly due to
the widespread cultivation of impatiens
Antagonistic yeasts and thermotherapy as seed treatments to control Fusarium fujikuroi on rice
No full textBakanae disease, caused by Fusarium fujikuroi, is the most important seedborne disease of rice. Biological
control and physical treatments can be effective tools to control seedborne diseases. Sixty-two isolates of
yeasts and yeast-like fungi were obtained from different rice seeds. Four yeast isolates were selected in
dual culture assays for mycelial growth inhibition, and in seed tests for reduction of infection rate. The
isolates R23 and R26 were identified as Metschnikowia pulcherrima, the isolate R9 as Pichia guilliermondii,
and the isolate SB1 as Sporidiobolus pararoseus. Rice seeds treated with P. guilliermondii R9, M. pulcherrima
R23 and R26 significantly reduced the infection rate of F. fujikuroi, compared to some commercial biofungicides.
The four selected yeasts reduced the bakanae disease severity in rice plants grown in greenhouse
trials. Antagonist seed dressing resulted in reduction of the disease index from 93.0% in the untreated
control to 20.0% in P. guilliermondii R9 treated seeds, and to 28.5% in M. pulcherrima R23 treated seeds.
Selected antagonists were also used in combination with thermotherapy, which contributed to increase
their efficacy. Thus, P. guilliermondii R9 and M. pulcherrima R23 combined with thermotherapy at 60 C for
10 min decreased the bakanae disease index below 5%, and improved the seed germination rate compared
to the single treatments, showing a seed priming effect. This is the first report about the use of
antagonistic yeasts for seed dressing of rice to control F. fujikuroi on rice seeds, and biological treatment
may be improved through combination with thermotherapy
PCR detection of Fusarium oxysporum f. sp. basilici on basil
No full textSixty-nine amplified DNA fragments, generated from different isolates of Fusarium oxysporum
f. sp. basilici, were tested for F. oxysporum f. sp. basilici–specificity in a dot blot assay. One
1,038-bp fragment hybridized to DNA from all F. oxysporum f. sp. basilici isolates but not to
DNA obtained from F. oxysporum isolates nonpathogenic to basil or representatives of other
formae speciales of F. oxysporum, or from isolates of F. redolens, F. tabacinum, Rhizoctonia
solani, Sclerotinia sclerotiorum, S. minor, and Pythium ultimum obtained from diseased basil.
This fragment was cloned and sequenced, and three pairs of F. oxysporum f. sp. basilici–
specific primers were designed, giving rise to amplification products of 943, 382, and 330 bp. A
nested PCR assay allowed detection of F. oxysporum f. sp. basilici in diseased seedlings and in
artificially and naturally contaminated seeds. The theoretical detection limit of this system was
102 fungal propagules per 100 seeds on artificially contaminated samples, while on naturally
contaminated commercial seed lots, 32 propagules per 100 seeds were detected
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
Detection of Fusarium oxysporum f. sp. dianthi in carnation tissue by PCR amplification of transposon insertions
Full text linkStrains of the carnation wilt pathogen, Fusarium oxysporum f. sp. dianthi, can be distinguished by DNA fingerprint patterns, using the fungal transposable elements Fot1 and impala as probes for Southern hybridization. The DNA fingerprints correspond to three groups of F. oxysporum f. sp. dianthi strains: the first group includes isolates of races 1 and 8; the second group includes isolates of races 2, 5 and 6; and the third group includes isolates of race 4. Genomic DNAs flanking race-associated insertion sites of Fot1 (from races 1, 2, and 8) or impala (from race 4) were amplified by the inverse polymerase chain reaction (PCR) technique. These regions were cloned and sequenced, and three sets of primers overlapping the 3' or 5' end of the transposon and its genomic insertion were designed. Using fungal genomic DNA as template in PCR experiments, primer pairs generated amplification products of 295, 564 and 1,315 bp, corresponding to races 1 and 8; races 2, 5, and 6; and race 4, respectively. When multiplex PCR was performed with genomic DNA belonging to races 1 and 8, 2, or 4, single amplimers were generated, allowing clear race determination of the isolate tested. PCR was successfully performed on DNA extracted from susceptible carnation cv. Indios infected with isolates representative of races 1, 2, 4, and 8
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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