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Morphological and physiological variability of species of Meloidogyne in West Africa and implications of their control
No full textThe extreme morphological and physiological variability of certain rootknot nematodes (Meloidogyne spp.) and its implication on the development of control methods of these parasites, based upon crop rotations and the use of resistant varieties of otherwise susceptible crops are discussed.In a review of the systematics of the genus Meloidogyne reestablished in 1949 by Chitwood to replace the polyphagous species Heterodera marioni Cornu, 1887, the variability of the so-called perineal pattern of the females, the most important character to distinguish species within the genus, is emphasized.The results of the cytological investigations of Triantaphyllou are briefly discussed. It has been shown that most species studied are characterized by a parthenogenetic mode of reproduction. Two types of non-amphimictic reproduction have been observed: mitotic and meiotic parthenogenesis. Meloidogyne incognita, M. javanica and M. arenaria are characterized by mitotic parthenogenesis.An analysis of the number of publications appearing between 1949 and 1976. dealing with identified species of Meloidogyne has revealed that 93% of the articles concern Chitwood's species of 1949, and that 76% refer to M. incognito, M. javanica and M. arenaria.Faunistic studies in West Africa have shown that the most frequently encountered root-knot nematodes belong to the species M. incognita, M. javanica and M. arenaria. Identification of West African populations are complicated by the occurrence of mixtures of species, the great morphological variability and the existance of populations possessing rather large proportions of individuals exhibiting characters intermediate between species.Certain morphometric characters of perineal patterns (width of vulva and distance between phasmids) were measured in a number of clones of Meloidogyne populations. These observations have demonstrated that although these characters are stable within clones, they cannot distinguish M. javanica from M. incognita.The distance of the excretory pore of females from the anterior end, expressed in stylet lengths might possibly be an aid to distinguish M. incognita from M. arenaria and M. javanica.The author is reluctant to describe populations characterized by unusual perineal patterns as new species and suggests inclusion of host-plant and cytological data in the description of new species.Data presented indicate that length of juveniles could not be used to distinguish among M. incognita, M. javanica and M. arenaria.Observations of juveniles from a population of M. incognita acrita have demonstrated that the inflation of the rectum is not an absolute criterium to distinguish M. incognita and M. acrita. A critical evaluation of the data of TERENTEVA (1967) concerning the height of the lip region of males of M.incognita and M. incognita acrita makes the author reject the statement that this character might be useful to distinguish between these two taxa.The author concludes that up till now, no infallible methods have been found to identify naturally occurring populations of Meloidogyne in West Africa.After the splitting of the polyphagous Heterodera marioni into a number of species of Meloidogyne it became possible to assemble host lists for each species. In principal this information should provide a basis for crop rotation recommendations, intended to reduce root-knot nematodes infestation, provided that the Meloidogyne populations could be identified to the species level. Comparison of the host ranges of M. incognita, M. javanica and M. arenaria emphasized that these species have a great number of host plants in common, many of which are important crops. Only a few species could be used as differential plants to distinguish among these three species.Published data and original results presented show that when many populations of the same species of Meloidogyne are studied, resistance/susceptibility of a given plant species cannot be predicted with confidence. Certain populations are able to parasitize a given plant and others are not.The same phenomenon is observed with resistant varieties of otherwise susceptible crops. When several populations of the same species of Meloidogyne are tested against such a variety, those populations capable of parasitizing the resistant varieties are often called 'B races'. Studies concerning development of 'B races' on resistant tomatoes in Senegal have shown that some populations of Meloidogyne are able to parasitize resistant varieties strongly and immediately. others are able to form 'B races' after a selection has taken place, the majority however, is not capable of parasitizing resistant tomatoes.Indications have been obtained that a gene for gene relation exists between nematode populations and resistant tomato varieties and a code indicating nematode and resistant variety genotype is proposed.It is assumed that most plant species are attacked by Meloidogyne populations; the reaction of the plant attacked towards the specific Meloidogyne population concerned, determines if a successful parasitic relation develops.It is proposed to consider as a group the tropical polyphagous species of Meloidogyne, which are characterized by a certain degree of polyploidy and a mitotic parthenogenetic mode of reproduction. This group should comprise M. incognito, M. javanica, M. arenaria, populations intermediate between these species, possibly undescribed species and certain described species for which information on mode of reproduction and physiological characters (host-range) is lacking.On the basis of an actual field trial in Senegal, it is shown that recommendations for crop sequences or rotations should be based on testing different crops and varieties against naturally occurring populations of root-knot nematodes. Incorrect choice of crops may be made if rotations are based upon Meloidogyne identifications only. It is recommended that different populations in an area be tested on cash, food, and cover crops and resistant varieties.Selection of resistant varieties should be based on reactions to as many different populations of Meloidogyne as possible. Using such a technique 'B races' may be detected, and in addition much material not possessing root-knot resistance in the area where the varieties are developed, may be found to have resistance against other populations elsewhere.In order to obtain the maximum value of non-hosts and resistant varieties, it is recommended to use these plants as a preventive measure rather than as a cure. Therefore, their use should be recommended in slightly infested or Meloidogyne- free soils.The author has observed in fact, that non-hosts planted in heavily infested soil may be badly damaged because of a necrotic reaction to invading juveniles. In extreme cases this may give rise to dead patches in the field and a resultant increase of weed growth, accompanied by an increase of Meloidogyne on susceptible weeds. Thus, usefulness of the non-host can be nullified. Moreover the risk of selecting 'B races' is much higher in heavily infested land than in nonor slightly infested fields.Thus it is recommended to use non-hosts and resistant varieties as preventive treatments within an integrated control including the various chemical and physical treatments available
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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