1,720,981 research outputs found
Influence of soil nutrients on reproduction and pathogenicity of Rotylenchulus reniformis on cotton
No full textAmong the variety of pathogens of cotton (Gossypium hirsutum), nematodes play a major role in reducing yield. Across the U.S. cotton belt, millions of dollars are lost annually due to nematode infestation. In the Mid-South and Southeast United States, root-knot nematode
(Meloidogyne incognita) and reniform nematode (Rotylenchulus reniformis) are responsible for the highest percentage of damage. Crop rotation and nematicides are currently the most commonly used management strategies for nematode management. Soil fertility, which has a direct effect on plant growth, is also known to influence disease severity. Therefore, soil fertility would be an additional factor to consider for management of nematodes. The objectives of these studies were to evaluate the effects of soil nutrients on reniform nematode reproduction and pathogenicity on cotton. Four 60-day-duration greenhouse studies were conducted to evaluate the effect of different soil nutrients on reniform nematode pathogenicity and reproduction. Nutrients
used in greenhouse studies were phosphorus (P), potassium (K) and sulfur (S). For the first study, P and K were used in high (112 kg ha-1
) and low (0 kg ha-1) levels with a soil mixture of 70.1% sand, 25.4% silt, and 2.5% clay. Treatments for the second, third and fourth studies were
five increasing levels of P (10, 20, 35, 60, and 73 mg kg-1), K (44, 70, 106, 123, and 153 mg kg1), and S (3, 12, 20, 40, and 50 mg kg-1) mixed with soil comprised of 68% sand, 30% silt and 2% clay. Application of P produced a significant increase in plant shoot and root dry weights in
studies one and two. Similarly, reproduction of reniform nematodes in these two studies were significantly influenced by levels of P. Studies three and four focused on K and S and did not show any effect on reproduction of reniform nematodes. Treatment with S had a significant
negative influence on shoot height and dry weights. Under field conditions, nematicide application significantly reduced nematode population density at mid-season and at harvest in 2011 and at planting in 2012. In both 2011 and 2012, management of soil nutrients did not
significantly influence nematode reproduction. In both years, seed cotton yield was significantly increased with nematicide, but not with nutrients
Evaluating the densities and distribution of root-lesion nematodes (Pratylenchus spp.) in wheat grown in Canterbury, New Zealand
No full textSpecies of root-lesion nematode (Pratylenchus spp.) are associated with significant reductions in wheat yield in wheat-growing regions around the world. Of these, Pratylenchus thornei and P. neglectus are known to cause the highest damage to the Australasian wheat industry. New Zealand is known to produce high wheat yields on a per-hectare basis yet little research has been conducted to date to determine the effects of Pratylenchus spp. on the production of wheat in New Zealand. Therefore, as the first step towards filling this knowledge gap, the current research focused on conducting surveys to determine the population densities and distribution of Pratylenchus spp. in wheat-growing regions in Canterbury, South Island, New Zealand. Surveys were conducted at ten selected sites that were geographically distinct from each other. At six of the ten sites, lesion nematode populations were reported to be above the recorded Australian threshold of 2000 nematodes per kg of soil. In Australia, it’s been recorded that around 50% yield reductions can occur in intolerant wheat varieties when population densities reaches this number. Differences in population density within each location was also observed indicating the uneven distribution of lesion nematodes within a field. Morphological measurements of the nematodes collected from multiple sites during this study confirmed the presence of P. thornei and P. neglectus in Canterbury wheat-producing areas indicating a potential threat to the New Zealand wheat industry by root-lesion nematodes. Further studies need to be conducted to fully understand the situation and to develop management strategies to mitigate threats from nematodes
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
Pathogenicity and reproduction of isolates of reniform nematode, Rotylenchulus reniformis, from Louisiana on soybean and utility of single nucleotide polymorphisms to evaluate genetic variability
Full text linkExperiments were conducted to evaluate soybean, Glycine max (L.) Merr., responses to indigenous isolates of the reniform nematode
(Rotylenchulus reniformis) in Louisiana and to understand the genetic variability of these native isolates. Microplot and greenhouse experiments
were conducted to evaluate the comparative reproduction and pathogenicity of single egg-mass populations of R. reniformis isolated from West Carroll (WC), Rapides, Tensas and Morehouse
(MOR) parishes of Louisiana. Data from full-season microplot trials, displayed significant differences in reproduction and pathogenicity of the nematode with the commercial soybean cultivars REV 56R63, Pioneer P54T94R, and Dyna-Gro 39RY57. Significantly low population
density was observed in the isolate from the MOR parish compared to that of the least reproducing WC isolate. The MOR isolate was also the most pathogenic and resulted in significantly less soybean plant and pod weights compared to the control. In 60 day greenhouse trials, susceptible cultivar Progeny P4930LL and the resistant germplasm lines PI 90763 and PI 548316 were added together with the same cultivars used in the microplot trials. Similar to the microplot trials, the MOR isolate had the least level of reproduction compared to that of WC and presented the greatest level of pathogenicity. In both microplot and greenhouse trials, the soybean cultivar REV 56R63 had a significant reduction in reniform numbers compared to cultivars Pioneer P54T94R and Dyna-Gro 39RY57. The second set of experiments were conducted to understand the amount of genetic variability present in the 13 reniform nematode
isolates from Louisiana, Mississippi, Arkansas, South Carolina and Georgia with the use of Single Nucleotide Polymorphism (SNP) analysis. Thirty one chosen SNPs were tested against the reniform nematode isolates using kompetitive allele-specific PCR genotyping assay. Out of
the 31 SNPs tested, 26 SNPs amplified genomic DNA of the reniform nematode isolates. Four SNPs out of all tested were able to distinguish genetic differences between and among tested geographic isolates of reniform nematode from Louisiana, Mississippi, and Arkansas. Even with
limited numbers of samples, a genetic variability was observed with 3 SNPs between South Carolina, and Georgia isolates. The results obtained in this study might be extremely useful in resistance breeding programs as well as providing soybean cultivar recommendations for growers in different geographical locations
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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