1,720,957 research outputs found
Unlocking the genetic diversity of the undomesticated rice relative Oryza longistaminata
Full text linkRice (Oryza sativa) is a crucial part of the global food supply. Meeting projected increases in demand, which are rising fastest in sub-Saharan Africa, while using resources efficiently and adapting to a changing climate will require new sources of variation for trait improvement. The genetically diverse undomesticated African rice, Oryza longistaminata, which is native to a broad range of habitats throughout sub-Saharan Africa, is a valuable resource improving O. sativa with genes conferring biotic and abiotic stress tolerances, increased yield, super-ratooning ability, and floral traits conducive to hybrid rice production. The major obstacle to utilization of O. longistaminata in breeding programs is a breeding barrier which complicates interspecific hybridization with O. sativa, as well as the expense and difficulty of identifying which O. longistaminata accessions carrying useful genes. Breeding programs also rely on thorough ex-situ conservation of O. longistaminata, which enables long-term access to germplasm for breeders and other stakeholders. In this work, three genetic subpopulations were identified in O. longistaminata using individuals representing most of the species’ range genotyped with densely-spaced, genome-wide molecular markers. Spontaneous interspecific hybrids of O. longistaminata and O. sativa were discovered in germplasm from the International Rice Research Institute’s genebank, which can be used to accelerate introgression from O. longistaminata to O. sativa. A species distribution model of O. longistaminata was generated to identify sampling gaps in ex-situ collections, and environmental data was used to predict likely locations of O. longistaminata tolerant to abiotic stresses.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2019-08-01The student, Marlee Labroo, accepted the attached license on 2017-07-20 at 15:00.The student, Marlee Labroo, submitted this Thesis for approval on 2017-07-20 at 15:04.This Thesis was approved for publication on 2017-07-20 at 17:55.DSpace SAF Submission Ingestion Package generated from Vireo submission #11557 on 2017-09-29 at 11:20:02Made available in DSpace on 2017-09-29T17:52:31Z (GMT). No. of bitstreams: 2
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Previous issue date: 2017-07-20Embargo set by: Colleen Fallaw for item 103516
Lift date: 2019-09-29T17:52:45Z
Reason: Author requested closed access (OA after 2yrs) in Vireo ETD systemLimited Restriction Lifted for Item 103516 on 2019-09-30T09:15:23Z
Three studies in marker-assisted plant breeding
Full text linkEffective breeding for crop improvement has the potential to increase food security, improve environmental health, and contribute to economic development. Here, we present three studies which further our understanding of marker-assisted plant breeding and plant genetics.
First, we fine-map a recessive Mendelian mutation in maize which confers reduced leaf area, rdla, to a 153-Kb region on chromosome 4 with a mapping-by-sequencing approach. We find that the rdla mutation reduces total leaf area and per-leaf area in terms of both leaf length and leaf width, and has further pleiotropic effects of reduced plant height and reduced basal stem circumference. We find no evidence of changes in specific leaf weight, a proxy for leaf thickness. Characterization and mapping of the rdla gene is of basic interest in understanding the genetic control of maize leaf traits. We also speculate that rdla may useful in breeding maize varieties tolerant of high planting densities and initiate a marker-assisted backcrossing program of rdla into modern Expired Plant Variety Protection maize cultivars.
Second, we phenotype F1 rice hybrids of existing male-sterile lines at the International Rice Research Institute and highly stress-tolerant male lines used in development of Green Super Rice varieties. We select the F1 hybrids for yield performance and their parents with outstanding general combining ability for yield by genomic best linear unbiased prediction. We also find that parental genetic distance is negatively correlated with mid-parent heterosis and performance of progeny for most traits, including yield, in the population of study, which supports other bodies of evidence that increased parental genetic distance does not always result in improved progeny performance. We hypothesize that the outstanding F1 hybrids identified are likely to be highly stress-tolerant. However, based on the prediction accuracies observed in our study, we recommend obtaining better estimates of parental general combining ability by expanding the training set before relying on genomic prediction to conduct reciprocal recurrent genomic selection for stress-tolerant hybrid rice.
Third, we compare the effects of using overlapping and discrete selection generations in recurrent mass phenotypic, genomic, and genomic optimum contribution selection by simulation of fifty breeding cycles. We find that discrete generations outperform overlapping generations in terms of mean genetic value under phenotypic selection. This is because selected plants are more likely to have positive error variances if phenotyped only once, and overlapping selection generations allow error to propagate as individuals erroneously believed to have exceptional breeding values are repeatedly selected. In genomic selection, estimates of genetic value are updated even if individuals are phenotyped once as relatives in the population are phenotyped, and overlapping and discrete selections perform similarly with genomic and genomic optimum contribution selection. However, it appears that overlapping selection might allow slightly better optimization of inbreeding and mean genetic value in optimum contribution selection. As such, we recommend maintaining discrete generations in phenotypic mass selection programs in which individuals are only phenotyped once. In genomic mass selection, we observed no clear benefit to allowing generations to overlap.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2022-08-01The student, Marlee Labroo, accepted the attached license on 2020-07-17 at 15:23.The student, Marlee Labroo, submitted this Dissertation for approval on 2020-07-17 at 15:29.This Dissertation was approved for publication on 2020-07-17 at 15:45.DSpace SAF Submission Ingestion Package generated from Vireo submission #15685 on 2020-10-02 at 15:51:29Made available in DSpace on 2020-10-07T22:50:03Z (GMT). No. of bitstreams: 2
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Previous issue date: 2020-07-17Embargo set by: Seth Robbins for item 116348
Lift date: 2022-10-07T22:50:13Z
Reason: Author requested closed access (OA after 2yrs) in Vireo ETD systemAuthor requested closed access (OA after 2yrs) in Vireo ETD systemLimite
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
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
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