1,720,967 research outputs found
Genetic diversity, phylogenetic and phylogeographic analyses of Oncideres impluviata (Germar, 1823) (Coleoptera: Cerambycidae) in Rio Grande do Sul state, Brazil
Get PDFMachado, Dayanna do Nascimento, Costa, Ervandil Corrêa, Perini, Clérison Régis, Valmorbida, Ivair, Souza, Diego de Santana, Pedron, Leandra, Saldanha, Mateus Alves, Froehlich, Ricardo, Schühli, Guilherme, Greff, Henrique Pinton, Oliveira, Jeferson de, Arnemann, Jonas André (2023): Genetic diversity, phylogenetic and phylogeographic analyses of Oncideres impluviata (Germar, 1823) (Coleoptera: Cerambycidae) in Rio Grande do Sul state, Brazil. Revista Brasileira de Entomologia (e20220092) 67: 1-10, DOI: 10.1590/1806-9665-RBENT-2022-009
Evidence of enhanced reproductive performance and lack-of-fitness costs among soybean aphids, Aphis glycines, with varying levels of pyrethroid resistance
Get PDFBACKGROUND: Foliar application of insecticides is the main strategy to manage soybean aphid, Aphis glycines (Hemiptera: Aphididae), in the northcentral United States. Subpopulations of A. glycines have multiple nonsynonymous mutations in the voltage-gated sodium channel (vgsc) genes that are associated with pyrethroid resistance. We explored if fitness costs are associated with phenotypes conferred by vgsc mutations using life table analyses. We predicted that there would be significant differences between pyrethroid susceptibility and field-collected, parthenogenetic isofemale clones with differing, nonsynonymous mutations in vgsc genes.
RESULTS: Estimated resistance ratios for the pyrethroid-resistant clones ranged from 3.1 to 37.58 and 5.6 to 53.91 for lambdacyhalothrin and bifenthrin, respectively. Although life table analyses revealed some biological and demographic parameters to be significantly different among the clonal lines, there was no association between levels of pyrethroid resistance and a decline in fitness. By contrast, one of themost resistant clonal lines (SBA-MN1-2017) had a significantly higher finite rate of increase, intrinsic rate of increase and greater overall fitness compared to the susceptible control and other pyrethroid-resistant clonal lines.
CONCLUSIONS: Our life history analysis suggests that there are no negative pleotropic effects associated with the pyrethroid resistance in the clonal A. glycines lines used in this study. We discuss the potential impact of these results on efficacies of insecticide resistance management (IRM) and integrated pest management (IPM) plans directed at delaying the spread of
pyrethroid-resistant A. glycines.This article is published as Valmorbida, Ivair, Brad S. Coates, Erin W. Hodgson, Molly Ryan, and Matthew E. O'Neal. "Evidence of enhanced reproductive performance and lack of fitness costs among soybean aphid, Aphis glycines, with varying levels of pyrethroid resistance." Pest Management Science (2022). doi:10.1002/ps.6820.
This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA
Exploring the mechanisms and consequences of soybean aphid (Hemiptera: Aphididae) resistance to pyrethroids
Get PDFSoybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), was first detected in the United States in 2000 and has been actively managed by farmers with foliar insecticide applications. Bifenthrin and lambda-cyhalothrin are insecticides commonly used to control soybean aphid outbreaks. However, control failures were observed and laboratory bioassays confirmed that soybean aphid has evolved resistance to pyrethroids. This research investigated the susceptibility of virulent and avirulent aphids to lambda-cyhalothrin and the mechanisms and fitness costs related with pyrethroid-resistant soybean aphids. Leaf dip bioassays were performed to assess the susceptibility of laboratory and field-collected populations to insecticides. Also, molecular markers were developed to assess the frequency of resistant alleles before and after a foliar insecticide application. Toxicity bioassays revealed that virulent aphids had a higher LC50 compared with virulent aphids, and exposure to the LC25 of lambda-cyhalothrin can trigger hormesis in soybean aphids. These bioassays also confirmed that field-collected aphids have evolved resistance to pyrethroids and sequencing of the voltage-gated sodium channel (vgsc) genes identified non-synonymous mutations associated with resistant aphids. Additionally, molecular markers revealed a high frequency of aphids carrying at least one mutation in the vgsc, and foliar insecticide application significantly increased resistant allele frequency among survivors. Experiments using isofemale lines with varying levels of pyrethroid resistance did not find evidence of fitness cost. Field-evolved soybean aphid resistance to pyrethroids is concerning and will require the development and implementation of integrated pest management (IPM) and insect resistance management (IRM) plans to mitigate the spread of resistant aphids and delay resistance evolution to other management strategies
Soybean aphid (Hemiptera: Aphididae) response to lambda‐cyhalothrin varies with its virulence status to aphid‐resistant soybean
Get PDFBACKGROUND: Soybean aphid, Aphis glycines, is an invasive insect in North America, considered one of the most important pests of soybean. Their management relies heavily on foliar insecticides, but there is growing effort to expand these tools to include aphid-resistant varieties. We explored if the LC50 and LC25 of lambda-cyhalothrin varied between virulent (Resistance to Aphis glycines (Rag) soybeans) and avirulent (susceptible to Rag-genes soybeans) populations of soybean aphid with a leaf-dip bioassay. We also investigated the response to the LC25 of lambda-cyhalothrin on adults (F0) and their progeny (F1) for both avirulent and virulent soybean aphid.
RESULTS: The LC50 of the virulent aphid population was significantly higher compared with the LC50 of the avirulent population. The LC25 significantly reduced fecundity of the F0 generation of avirulent soybean aphid, but no significant effect was observed for virulent aphids. In addition, the LC25 significantly shortened the adult pre-oviposition period (APOP) and lengthened total pre-oviposition period (TPOP) of avirulent aphids, while the mean generation time (T) was significantly increased. For the virulent aphid, sublethal exposure significantly lengthened development time of first and third instars, TPOP, and adult longevity. In addition, all demographic parameters of virulent soybean aphid were significantly affected when they were exposed to the LC25 of lambda-cyhalothrin.
CONCLUSION: Our results demonstrate lambda-cyhalothrin is less toxic to virulent aphids and exposure to the LC25 can trigger hormesis which may have implications for the long-term management of this pest with this insecticide as well as with aphid-resistant varieties of soybean.This is the peer reviewed version of the following article: Valmorbida, Ivair, Dionei S. Muraro, Erin W. Hodgson, and Matthew E. O'Neal. "Soybean aphid (Hemiptera: Aphididae) response to lambda‐cyhalothrin varies with its virulence status to aphid‐resistant soybean." Pest management science (2019), which has been published in final form at doi: 10.1002/ps.5661. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.</p
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
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