1,720,956 research outputs found
Genetic variation of wheat seedling root angle
No full textPhenotyping wheat seedling’s root angle variation to highlight correlations with water stress
Clothilde Collet, Xavier Draye.
An increasing diversity of water limited scenarios is predicted by climate research. Because roots determine soil-root conductance and water extraction[1], root traits have been proposed as a priority target to breed for drought tolerant yielding crops. There are many reports that the seminal root angle of cereal seedlings is a good predictor of several aspects of field root architecture[2], including deep root distribution[3],[4], which is considered as a positive adaptation to drought scenarios[5]. We have carried out an experiment under controlled conditions to analyse the genetic determinism of seminal root angles of wheat seedlings. Two diversity panels have been studied: a bread wheat diversity panel (250 varieties) and a durum wheat diversity panel (250 varieties). Seedlings (12 per genotype) were disposed at six different heights on a vertical germination paper plate whose moisture was maintained by capillary rise of water from the bottom of the plate. Daily pictures of the root systems have been captured during a 4-day long experiment and have been vectorized with the SmartRoot program. We observed a weak but significant correlation between the metric potential of water in the filter paper and the seedling seminal root angle. We also confirm that there is a very high broad-sense heritability for the root angle within each panel. This experiment is part of the EU project SolACE (http://www.solace-eu.net).
[1] Xavier Draye et al., ‘Model-Assisted Integration of Physiological and Environmental Constraints Affecting the Dynamic and Spatial Patterns of Root Water Uptake from Soils’, Journal of Experimental Botany 61, no. 8 (May 2010): 2145–55, https://doi.org/10.1093/jxb/erq077.
[2] Ahmad M. Manschadi et al., ‘The Role of Root Architectural Traits in Adaptation of Wheat to Water-Limited Environments’, Functional Plant Biology 33, no. 9 (22 September 2006): 823–37, https://doi.org/10.1071/FP06055; Manschadi et al.
[3] A. Oyanagi, ‘Gravitropic Response Growth Angle and Vertical Distribution of Roots of Wheat (Triticum Aestivum L.)’, Plant and Soil165, no. 2 (1994): 323–26.
[4] A. M. Manschadi et al., ‘Experimental and Modelling Studies of Drought‐adaptive Root Architectural Traits in Wheat (Triticum Aestivum L.)’, Plant Biosystems - An International Journal Dealing with All Aspects of Plant Biology 144, no. 2 (1 June 2010): 458–62, https://doi.org/10.1080/11263501003731805.
[5] Ahmad M. Manschadi et al., ‘Genotypic Variation in Seedling Root Architectural Traits and Implications for Drought Adaptation in Wheat (Triticum Aestivum L.)’, Plant and Soil 303, no. 1 (1 February 2008): 115–29, https://doi.org/10.1007/s11104-007-9492-1.</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
Root architecture phenotyping in aeroponics: a critical review
No full textGenetic Analysis of Dynamic Root Traits using Wheat Diversity Panels
Clothilde Collet*, Patrick Thaon*, Karine Chenu, Jack Christopher, Xavier Draye.
*These authors contributed equally to the work.
Understanding drought tolerance mechanisms has never been so relevant, especially in view of the increasing diversity of water limited scenarios predicted by climate research. Classically, breeders target above ground traits to improve drought tolerance and a rather limited interest has been given to the root system architecture. Root traits should be considered because roots are key players of soil water extraction. In particular, special attention should be devoted to dynamic root traits in order to shift the focus towards a better understanding of drought resilience. Using time-lapse image sequences of whole root systems over three weeks, we captured dynamic information on root architecture of wheat seedlings growing in aeroponics. Three wheat diversity panels have been phenotyped: a MR-NAM bread wheat population (521 lines), a bread wheat diversity panel (250 varieties) and a durum wheat diversity panel (250 varieties). Data extraction, based on the identification and tracking of root tips in image sequences, has allowed the determination of the root growth rate, emergence, maximum length and apical diameter of primary and seminal roots. For the MR-NAM panel, a high heritability of seminal root emergence has been estimated, despite important environmental and genotype by environment variances. However, for the others seminal traits, heritability tended to be low. Efforts are ongoing to analyse lateral root traits, yet their extraction from images is challenging due the high density of lateral roots. A genome wide association study (GWAS) has been carried out with the MR-NAM population data and has led to the identification of three QTLs, related to seminal root growth rate and maximum root length. Phenotyping of the other panels are still ongoing and a meta-analysis will be conducted using GWAS results from the three panels. These experiments are part of the EU project SolACE (http://www.solace-eu.net).
References:
Burton, Amy L., James Johnson, Jillian Foerster, Meredith T. Hanlon, Shawn M. Kaeppler, Jonathan P. Lynch, et Kathleen M. Brown. 2015. « QTL Mapping and Phenotypic Variation of Root Anatomical Traits in Maize (Zea Mays L.) ». Theoretical and Applied Genetics 128 (1): 93‑106. https://doi.org/10.1007/s00122-014-2414-8.
de Dorlodot, S., 2007. Root system architecture: a genetic analysis in rice (PhD Thesis). Université catholique de Louvain.
de Dorlodot, S., Forster, B., Pagès, L., Price, A., Tuberosa, R., Draye, X., 2007. Root system architecture: opportunities and constraints for genetic improvement of crops. Trends in Plant Science 12, 474–481. https://doi.org/10.1016/j.tplants.2007.08.012
Lynch, J. 1995. « Root Architecture and Plant Productivity ». Plant Physiology 109 (1): 7‑13. https://doi.org/10.1104/pp.109.1.7.
Thaon, P., 2017. Genetic analysis of wheat root architecture in aeroponics.
Tuberosa, R., Sanguineti, M.C., Landi, P., Michela Giuliani, M., Salvi, S., Conti, S., 2002. Identification of QTLs for root characteristics in maize grown in hydroponics and analysis of their overlap with QTLs for grain yield in the field at two water regimes. Plant Mol Biol 48, 697–712. https://doi.org/10.1023/A:1014897607670
Wasson, A. P., R. A. Richards, R. Chatrath, S. C. Misra, S. V. Sai Prasad, G. J. Rebetzke, J. A. Kirkegaard, J. Christopher, et M. Watt. 2012. « Traits and selection strategies to improve root systems and water uptake in water-limited wheat crops ». Journal of Experimental Botany 63 (9): 3485‑98. https://doi.org/10.1093/jxb/ers111.
Welcker, C., Sadok, W., Dignat, G., Renault, M., Salvi, S., Charcosset, A., Tardieu, F., 2011. A Common Genetic Determinism for Sensitivities to Soil Water Deficit and Evaporative Demand: Meta-Analysis of Quantitative Trait Loci and Introgression Lines of Maize. Plant Physiology 157, 718–729. https://doi.org/10.1104/pp.111.176479</p
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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