1,720,985 research outputs found
Resistance of maize varieties to the maize weevil Sitophilus zeamais (Motsch.) (Coleoptera: Curculionidae)
No full textThis study aimed at evaluating commonly used maize varieties, collected from Melkasa and Bako Agricultural Research Centers and Haramaya University, Ethiopia, against the maize weevil Sitophilus zeamais Motsch., one of the most important cosmopolitan stored product pests in maize. A total of 13 improved maize varieties were screened for their relative susceptibility to S. zeamais. The Dobie index of susceptibility was used to group the varieties. The variety, ‘BHQP-542’, had the least index of susceptibility and was regarded as resistant. The varieties, ‘Katumani’, ‘Melkasa-I’, ‘Melkasa-II’, ‘Melkasa-III’, ‘Coree’, ‘BH-541’, ‘BH-660’, ‘BH-540’, ‘Rare-I’, ‘Awasa-511’, ‘ACV3’ and ‘ACV6’, were moderately resistant. Weevils fed with the resistant variety produced low numbers of F1 progeny, had a high median developmental time and a low percentage of seed damage and seed weight loss. Maize varieties with a high F1 progeny tended to have a short median developmental time. An increasing number of F1 progeny resulted in an increasing seed damage and seed weight loss. We found an inverse relationship between the susceptibility index and percent mortality and median developmental time; however, the numbers of F1 progeny, percent seed damage and seed weight loss were positively related with the susceptibility index. The use of resistant varieties should be promoted in managing S. zeamais in stored maize under subsistence farming conditions in Africa
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
Combining Chilo partellus Swinhoe and Sitophilus zeamais Motschulsky insect pest resistance in early maturing maize hybrids.
Full text linkDoctor of Philosophy in Plant Breeding. University of KwaZulu-Natal, Pietermaritzburg, 2016.Abstract available in PDF file
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
Inheritance of post-harvest pest resistance and genetic analysis of combining drought, maize lethal necrosis and maize weevil resistance in tropical maize germplasm.
Full text linkDoctoral degree. University of KwaZulu-Natal, Pietermaritzburg.Drought stress, maize lethal necrosis (MLN) and storage pests, mainly maize weevil (Sitophilus zeamais Motschulsky) and larger grain borer (Prostephanus truncatus Horn), are among the most important maize production constraints and storage problems in tropical and subtropical environments. Drought stress and MLN can cause grain yield losses of up to 90% depending on the severity and stage of growth when they affect the crop, while post-harvest pests can cause 10-60% grain loss. There are no practical agronomic practices that can control these stresses under small-scale farming conditions since investments in irrigation and pesticides are unaffordable for the majority of small-scale farmers in developing African countries. The study was, therefore undertaken to: a) estimate the heritability and gene effects controlling maize weevil and larger grain borer resistance in tropical maize germplasm; b) determine whether resistance to maize lethal necrosis and tolerance to drought can be combined in F1 hybrids developed from tropical maize inbred lines; c) determine the combining ability of tropical maize inbred lines for drought tolerance and resistance to maize weevil and assess the possibility of combining the two traits in one genotype and d) determine gene action controlling the morpho-physiological and agronomic traits of tropical maize under maize lethal necrosis virus infected conditions and maize weevil infestation.
Populations involving six generations; two parents (P1 and P2), F1, F2 and backcrosses (BCP1 and BCP2) were developed from cross one, CKDHL120731 (resistant) × CKDHL120918 (susceptible) and cross two, CKDHL120517 (resistant) × CKDHL120918 (susceptible). The generations were evaluated under artificial infestation of Sitophilus zeamais Motschulsky and Prostephanus truncatus Horn in separate experiments in a post-harvest laboratory at Kiboko, Kenya. Data was recorded for percentage kernel weight loss, kernel damage and the final number of living insects and data were analysed using generation mean analysis. Results revealed that resistance traits for both crosses did not fit a simple additive-dominance model for S. zeamais, suggesting the existence of epistasis effects. However, for P. truncatus resistance, cross one fitted a simple additive-dominance model, but cross two did not, suggesting both simple additive-dominance model and digenic interaction model were important in the inheritance of P. truncatus resistance. Additive, dominance and epistasis gene effects played a role in the inheritance of resistance to both insects in the selected maize genotypes. This was further confirmed by the moderate narrow-sense heritability estimates which suggested the involvement of additive and non-additive gene effects in the expression of resistance to both insect pests.
Three separate half-diallel analyses involving eight inbred lines each were conducted involving (1) lines with varying reactions to drought and maize lethal necrosis (MLN), (2) lines with varying drought tolerance and post-harvest pest resistance backgrounds, and (3) inbred lines with varying reactions to maize lethal necrosis (MLN) resistance and maize weevil resistance. The F1 hybrids from these diallel crosses were evaluated in different locations under optimum conditions and managed drought stress, artificial MLN infestation or artificial infestation with maize weevil depending on the objective. For artificial weevil infestation, grain samples were obtained from sites with optimum conditions.
Hybrids differed significantly (p<0.001) for MLN resistance and drought tolerance traits, including MLN scores, senescence, days to anthesis and anthesis-silking interval. The yield reduction due to MLND was 93% of the optimum mean grain yield of 6.04 t/ha, while reduction due to drought stress was 67% of the same. Genetic analysis detected highly significant mean squares (p< 0.001) due to both general combining ability (GCA) and specific combining ability (SCA) for most of the recorded traits, including grain yield under all environments, suggesting the importance of both additive and non-additive gene effects. However, additive gene action was generally predominant across all evaluation conditions. The results suggest that it is possible to improve tropical maize for combined drought and MLN tolerance and it can be faster when the evaluation is conducted under combined drought and MLN conditions.
Highly significant genotype and genotype × environment interaction mean squares (p<0.001) for grain yield and days to anthesis were observed under drought and optimum conditions for the drought tolerance and weevil resistance. Highly significant genotypic effects (p<0.001) were also observed on the key parameters for maize weevil resistance; Dobie’s Susceptibility Index (SI), living insects, weight loss (WL) and seed damage (SD) revealing different reactions of the tested hybrids. In addition, highly significant mean squares (p<0.001) due to both GCA and SCA for grain yield under drought and significant (p<0.001) under optimum conditions were detected, suggesting the importance of both additive and non-additive effects. Under maize weevil infestation, highly significant mean squares (p<0.001) due to both GCA and SCA for the key parameters were observed except for GCA mean squares for weight loss which was significant (p<0.05). Additive gene action was predominant over non-additive for grain yield under drought, SI, SD and living insects. The cross CKDHL120731 × CKDHL120517 showed tolerance to drought and resistance to maize weevil, while 24 hybrids showed tolerance to drought only.
The maize lethal necrosis (MLN) resistance and maize weevil resistance F1 hybrids showed highly significant (p<0.001) genotype differences for field weight and grain yield under MLN infestation. Highly significant (p<0.001) genotype and genotype × environment interaction effects were also observed for MLN scores at the early and late-stages under artificial MLN infestation, grain yield under optimum conditions, SI, WL and SD under maize weevil infestation. Significant mean squares (p<0.01) due to only GCA for grain yield under MLN and weight loss under maize weevil infestation were detected, while highly significant mean squares (p<0.001) due to both GCA and SCA for MLN scores under MLN infestation and grain yield under optimum growing conditions, SI and SD under weevil infestation were observed suggesting the importance of both additive and non-additive effects.
However, for most of the traits under the three evaluation conditions, additive gene action was predominant. Three hybrids CKDHL120918 × CKSBL10060, CKSBL10060 × CKDHL120731 and CML494 × CKDHL120731 showed good performance under the three evaluation conditions. The observed importance of both additive and non-additive gene action, with predominance of additive gene action, especially under the stressed environments, is an indicator of the feasibility of breeding for resistance to combined stresses, and suggests that recurrent selection can be applied for rapid breeding progress. Furthermore, the improvement of tropical maize for combined stress resistance can be faster when the inbred lines and hybrids are developed and evaluated under the combined stress environments, than under a single stress. The identified superior genotypes across environments in this study can be used immediately in breeding programs, especially in sub-Saharan Africa
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