1,720,970 research outputs found
Does root complexity affect the response of maize (Zea mays spp. mays) to abiotic stresses?
Full text linkAs concerns of climate change grow and the world population increases the demands on agricultural production, developing stress tolerant cultivars is a key step towards feeding the world in 2050. The mechanisms of response that cause plants to tolerate abiotic stresses like drought, high temperature, or low nutrient availability are often not well understood; however, abiotic stresses are some of the most influential factors affecting maize yields. Two of the most relevant stresses faced by growers are drought stress and low nitrogen fertility. Furthermore, production in the U.S. Corn Belt will likely continue to be significantly affected by the more frequent occurrence of hot, dry growing seasons. In the cases of nutrient and water acquisition, it is obvious that the root system of the maize plant is essential. Given the importance of the root system in plant performance, it is intuitive that differences in root characteristics would impact the performance of maize under water and nutrient limited conditions.
Despite its importance, maize root architecture and its involvement in plant performance is a relatively unexplored area; however, it is possible to accurately and quantitatively describe the root system of maize. A new and valuable tool in this effort is the use of fractal geometry and high-throughput phenotyping to assign a value to the complexity of the root system. Significant genetic variation exists for root system complexity in maize, making it a possible breeding target. Prior to the initiation of this study, fractal geometry was used to phenotype the root systems of maize hybrids selected for this study and to classify them as either high- or low-complexity root systems. The impact of varying root characteristics on agronomic performance and overall yield still needs to be investigated. In stressed environments, the root system is likely critical in maintaining function and thus protecting yield.
In this study we investigated the relationship between root complexity and biomass partitioning when maize plants are subjected to the abiotic stresses of low nitrogen availability and drought stress. These represent two of the primary stresses growers face and it has been suggested that the adaptability of maize to low nitrogen stress confers drought tolerance. By growing trials in both field and greenhouse environments, a comprehensive set of information was collected allowing us to better describe the role of root system complexity in creating stress tolerant cultivars. We anticipate that the findings of this study will be critical in understanding the relationship between root complexity and key abiotic stresses and will guide breeding efforts to develop maize cultivars with improved stress tolerance.Item withdrawn by Laura Spradlin ([email protected]) on 2014-04-29T19:22:44Z
Item was in collections:
University of Illinois Theses & Dissertations (ID: 1)
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Item is restricted until 2016-05-30T17:09:03ZRestriction data tranferred 2014-07-01T11:38:12-05:00
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Release Date: 2016-05-30 12:09:03 UTC
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Adaptation and Invasiveness of Western Corn Rootworm: Intensifying Research on a Worsening Pest
Full text linkThe western corn rootworm, Diabrotica virgifera virgifera LeConte, is an established insect pest of maize (Zea mays L.) in North America. The rotation of maize with another crop, principally soybeans, Glycine max (L.), was the primary management strategy utilized by North American producers and remained highly effective until the mid-1990s. In 1995, widespread and severe root injury occurred in east-central Illinois and northern Indiana maize fields that had been annually rotated with soybeans on a regular basis for several decades. The failure of this cultural tactic from a pest management perspective was attributed to a behavioral adaptation by a variant western corn rootworm that had lost fidelity to maize for egg laying. In 1992, an infestation of western corn rootworm was found within a small maize field near the Belgrade Airport. By 2007, the presence of this insect pest had been confirmed in 20 European countries. More recent molecular studies have confirmed that at least three separate invasions (until 2004) of western corn rootworms have occurred in Europe, increasing the risk that rotation-resistant western corn rootworms will be introduced into a new continent. Although biological control and use of conventional resistant maize hybrids have not achieved widespread success in the management of western corn rootworms in North America, these tactics are being evaluated in Europe
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
Characterization of the effect of nitrogen deficiency on above-ground plant phenotypes in relation to root complexity in maize
No full textNitrogen (N) is an essential plant nutrient in maize production, and if considering only natural sources, is often the limiting factor world-wide in terms of a plant’s grain yield. For this reason, many farmers around the world supplement available soil N with synthetic man-made forms. Years of over-application of N fertilizer have led to increased N in groundwater and streams due to leaching and run-off from agricultural sites. In the Midwest Corn Belt much of this excess N eventually makes its way to the Gulf of Mexico leading to eutrophication (increase of phytoplankton) and a hypoxic (reduced oxygen) dead zone. Growing concerns about these types of problems and desire for greater input use efficiency have led to demand for crops with improved N use efficiency (NUE) to allow reduced N fertilizer application rates and subsequently lower N pollution. It is well known that roots are responsible for N uptake by plants, but it is relatively unknown how root architecture affects this ability. This research was conducted to better understand the influence of root complexity (RC) in maize on a plant’s response to N stress as well as the influence of RC on other above-ground plant traits. Thirty-one above-ground plant traits were measured for 64 recombinant inbred lines (RILs) from the intermated B73 & Mo17 (IBM) population and their backcrosses (BCs) to either parent, B73 and Mo17, under normal (182 kg N ha-1) and N deficient (0 kg N ha-1) conditions. The RILs were selected based on results from an earlier experiment by Novais et al. (2011) which screened 232 RILs from the IBM to obtain their root complexity measurements. The 64 selected RILs were comprised of 31 of the lowest complexity RILs (RC1) and 33 of the highest complexity RILs (RC2) in terms of root architecture (characterized as fractal dimensions). The use of the parental BCs classifies the experiment as Design III, an experimental design developed by Comstock and Robinson (1952) which allows for estimation of dominance significance and level. Of the 31 traits measured, 12 were whole plant traits chosen due to their documented response to N stress. The other 19 traits were ear traits commonly measured for their influence on yield. Results showed that genotypes from RC1 and RC2 significantly differ for several above-ground phenotypes. We also observed a difference in the number and magnitude of N treatment responses between the two RC classes. Differences in phenotypic trait correlations and their change in response to N were also observed between the RC classes. RC did not seem to have a strong correlation with calculated NUE (ΔYield/ΔN). Quantitative genetic analysis utilizing the Design III experimental design revealed significant dominance effects acting on several traits as well as changes in significance and dominance level between N treatments. Several QTL were mapped for 26 of the 31 traits and significant N effects were observed across the majority of the genome for some N stress indicative traits (e.g. stay-green). This research and related projects are essential to a better understanding of plant N uptake and metabolism. Understanding these processes is a necessary step in the progress towards the goal of breeding for better NUE crops.Item withdrawn by Mark Zulauf ([email protected]) on 2011-10-13T15:04:26Z
Item was in collections:
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Item is restricted until 2014-02-01T00:50:07ZItem reinstated by Sarah Shreeves ([email protected]) on 2014-02-01T11:00:24Z
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Theses and Dissertations - Crop Sciences (ID: 681)
Graduate Theses and Dissertations at Illinois (ID: 204)
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Genetics underlying flaking grit yield from dry milled maize grain
Full text linkA survey of U.S. corn germplasm was conducted to explore genetics underlying flaking grit yield (FGY) and evaluate the relationship between FGY and agronomic performance, with an aim to devise breeding strategies to simultaneously improve FGY and agronomic performance in the future. The survey used a broad-based set of inbreds that represent parentage of heterotic subgroups utilized in current commercial maize hybrids. The 12 inbreds were crossed in a diallel design without reciprocals to create 66 test hybrids which were evaluated for agronomic, dry milling, ear, and kernel properties over 3 years. The overall mean among test hybrids for FGY was 29.4 g grits/100g corn dry basis with a range from 24.0 to 36.0 g grits/100g corn dry basis. Narrow and broad sense heritability estimates for FGY were 0.53 and 0.65, respectively, indicating the importance of additive gene action for this trait. The general combining ability (GCA) variance for FGY was twice the size of the specific combining ability variance, indicating the importance of GCA. Heterosis is not a factor in expression of FGY. In most cases, FGY was not correlated with agronomic, ear, and kernel traits, but FGY was phenotypically correlated (p < 0.05) with both grain yield (r = -0.50) and test weight (r = 0.52). Grain yield and FGY were genetically correlated with an r = -0.43. A moderate amount (31%) of the variation in flaking grits per acre (FGA) was explained by multiple regression of several traits including grain yield as well as simple physical kernel characters: test weight, kernel depth, 100 kernel volume.
Overall, the results of this study indicated presence of genetic variation for FGY in U.S. maize germplasm which could be exploited to develop new corn hybrids with improved FGY and FGA. Furthermore, performance for FGA may be predicted to some extent based on performance for some select agronomic and kernel characteristics. However, there is a need to explore additional options for improving predictions of FGA. Kernel characteristics such as kernel density and breakage susceptibility, implicated in previous reports to be highly correlated with FGY, may represent potential candidate traits for such a study.Item withdrawn by Mark Zulauf ([email protected]) on 2012-07-16T17:49:47Z
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Release Date: 2014-09-18 16:27:16 UTC
Reason: Author requested closed access (OA after 2yrs) in Vireo ETD systemLimited Restriction Lifted for Item 34846 on 2014-09-18T10:00:37Z
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
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