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Genetic analysis of sweetpotato resistance to the African sweetpotato weevils (Cylas spp.)
No full textA thesis submitted to the Directorate of Research and Graduate Training for the award of a Doctorate of Philosophy in Plant Breeding and Biotechnology of Makerere UniversitySweetpotato weevils (Cylas spp.) are the major pests of sweetpotatoes in Uganda and sub Saharan Africa. They cause losses ranging from 60-100% particularly during dry periods and in drought prone areas. Host plant resistance is currently considered as one of the most viable control options for these pests given their obscure feeding habits. However, breeding for resistance to Cylas spp. requires a clear understanding of the genetics underlying this trait. The genetic basis for sweetpotato weevil (SPW) resistance though, has never been fully elucidated despite years of research on this trait. Genetic analyses in this crop are typically challenging due to the crop's polyploid, highly heterozygous, and outcrossing nature. This study was aimed at improving our understanding about the genetics underlying resistance to the African sweetpotato weevils, Cylas puncticollis and Cylas brunneus, using a population developed from an 8 x 8 partial diallel cross of sweetpotato, known as the Mwanga Diversity Panel (MDP). The test population was initially phenotyped in field trials with the aim quantifying the heterotic gains, transgressive segregation and fitness costs associated with sweetpotato weevil resistance expression in sweetpotato. A total of 1,896 clones were tested together with their parental genotypes at two field sites located in Lira and Arua districts within Uganda for two seasons each, using an augmented design. Data on weevil severity (WED), weevil incidence (WI), storage root yield (SRY) and dry matter content (DM) were obtained and thereafter analyzed using R statistics software. Best linear unbiased predictors (BLUPs) for each genotype across environments were used to estimate heterotic gains and for regression analyses to establish fitness costs related to sweetpotato weevil resistance expression in sweetpotato. In general, relatively low mid-parent heterotic gains were detected, with the highest favorable levels recorded for SRY (14.7%) and WED (-7.9%). About 25% of the crosses exhibited desirable and significant mid-parent heterosis for weevil resistance. Over 16% of the clones displayed superior transgressive segregation, with the highest percentages recorded for SRY (21%) and WED (18%). The best performing clones across all traits were MDP449, MDP1514 and MDP920. Transgressive segregation was observed in all traits although crosses ‗Wagabolige‘ x NASPOT 10 O and ―New Kawogo‖ x ―Ejumula‖, particularly produced the highest number of superior segregants with regards to weevil resistance. Out of the 64 crosses, only NASPOT 11 x NASPOT 7 demonstrated desirable heterosis and had superior transgressive segregants for all the traits examined. A yield penalty of 10% was observed to be associated with SPW resistance whereas no decline in DM was detected in relation to the same. The yield penalty detected due to SPW resistance suggests that a trade-off may be necessary between maximizing yields and developing weevil-resistant cultivars if the current needs for this crop are to be met in weevil-prone areas. To study the inheritance of SPW resistance and other test traits, general combining ability (GCA), specific combining ability (SCA) and heritability analyses were conducted in the MDP population. To achieve this, 1,360 clones that survived in the field were further evaluated in three rounds of a no-choice feeding laboratory bioassay using a randomized complete block design with three replications. This was done at the sweetpotato Entomology Laboratory at NaCRRI. In the no-choice bioassay, three clean, healthy storage roots of each genotype were placed in separate plastic jars and artificially inoculated with 2-week-old gravid female adult weevils (C. puncticollis). The weevils were allowed to feed and oviposit for 24 hours, after which they were removed from each jar and the number of feeding holes on the roots counted and recorded. The eggs that were laid were left to incubate until emergence at room temperature, and thereafter, the number of adults that emerged from the roots was counted on a weekly basis. Data from this experiment was combined with field data to perform subsequent analyses. Results revealed significant GCA effects for parents and SCA effects for families for most traits. All variance components were highly significant (P ≤ 0.001). Narrow-sense heritability estimates for WED, SRY and DM were 0.35, 0.36 and 0.45, respectively. Parental genotypes with superior GCA for weevil resistance included ‗Mugande‘, NASPOT 5, ‗Dimbuka-bukulula‘, and ‗Wagabolige‘. On the other hand, families that displayed the highest levels of resistance to weevils were derived from crosses, ‗Wagabolige‘ × NASPOT 10 O, NASPOT 5 × ‗Dimbukabukulula‘, ‗Mugande‘ × ‗Dimbuka-bukulula‘, and NASPOT 11 × NASPOT 7. Superior parents and families identified through this study could be deployed in further research involving the genetic improvement of these traits. The moderate levels of narrow-sense heritability observed for the traits, coupled with the significant GCA and SCA effects, suggest that there is potential for their improvement through breeding via hybridization and progeny selection and advancement. Finally, genome-wide association (GWAS) studies were conducted with the aim of identifying single nucleotide polymorphisms (SNPs) and quantitative trait loci (QTL) and associated with SPW resistance, storage root yield and dry matter content in sweetpotato. A subset of the MDP population consisting of 822 clones was sequenced via a high throughput sequencing platform, OmeSeq. Quality filtering and allele calling were done using bioinformatic pipelines, ngsComposer and GBSapp respectively. The quality SNPs together with BLUPS from the phenotypic data were used to test for significant marker-trait associations via GWASpoly, while modeling different types of polyploid gene action including additive and all hexaploid dosagebased dominance SNP effects. GWASPoly identified 18 significant SNPs associated with sweetpotato weevil resistance, located on chromosomes 4, 7, 10 and 12. The additive model and the simplex dominant gene action model (1-dom-alt) were found to be most important for SPW resistance signifying the importance of both additive and non-additive gene action in the control of SPW resistance. Through this GWAS study, significant SNPs and QTL associated with sweetpotato weevil resistance were idntified. These could be quite resourceful in next-generation genomics and/or marker-assisted breeding in the genetically complex hexaploid sweetpotato and will expedite the development of high yielding, weevil resistant varieties. From this study, the following are recommended: 1) Further tests and selection of the best performing clones for potential variety release or deployment in research as parental genotypes; 2) Further investigations to confirm the yield penalty due to sweetpotato weevil resistance followed by strategic decisions such as developing targeted weevil resistant genotypes for the drier weevil-prone areas; 3)Validate the genomic regions detected to be controlling sweetpotato weevil resistance in another sweetpotato population to confirm their usefulness before they are deployed in genomic and/or marker assisted selection, and 4) Identifiy specific genes controlling sweetpotato weevil resistance using a higher marker density, to facilitate future molecular or genomics-related research
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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