1,720,980 research outputs found
Figure 11 in Parasenegalia and Pseudosenegalia (Fabaceae): New Genera of the Mimosoideae
No full textFigure 11. Pseudosenegalia riograndensis (Atahuachi & L. Rico) Seigler & Ebinger. —A. Twig with inflorescences and leaves. —B. Fruit. —C. Leaflet, adaxial surface. —D. Flower. —E. Petiolar gland. A–E from Antezana 1325 (NY).Published as part of Seigler, David S., Ebinger, John E., Riggins, Chance W., Terra, Vanessa & Miller, Joseph T., 2017, Parasenegalia and Pseudosenegalia (Fabaceae): New Genera of the Mimosoideae, pp. 180-205 in Novon 25 on page 202, DOI: 10.3417/2015050, http://zenodo.org/record/256146
Phenotypic and biochemical characterization of atrazine and HPPD-resistant waterhemp (amaranthus tuberculatus) populations
Get PDFWaterhemp (Amaranthus tuberculatus) is a dioecious, summer annual, broadleaf species that is native to the Midwest. Two decades ago it was not considered a major agricultural pest, but with the adoption of glyphosate-only postemergence (POST) herbicide programs without soil residual activity combined with no-till practices, it has become one of the most important weeds in Illinois and across the Midwest in regards to corn and soybean production. Research has indicated that multiple herbicide resistances can be found within one waterhemp plant, with one population in Champaign Co., IL exhibiting resistance to five different herbicide sites of action. Concerns exist about how to control waterhemp, especially as more populations are found to be resistant to most herbicides farmers use today.
Chapter 1 of this thesis includes a literature review of waterhemp biology, the history and use of atrazine, a photosystem II inhibitor, and carotenoid biosynthesis inhibitors, as well as the synergistic activity that has been observed when these two classes of herbicides are combined in a tank mixture. Chapter 2 covers previous research indicating that two atrazine-resistant populations of waterhemp (Amaranthus tuberculatus) from Illinois (designated ACR and MCR) displayed enhanced rates of atrazine metabolism via glutathione conjugation. Elevated constitutive expression levels of a single phi-class GST, named AtuGSTF2, correlated with atrazine resistance in ACR and MCR populations. Using this information, a discriminatory rate of 14.4 kg/ha was determined, and a POST study was conducted in the greenhouse to phenotype a segregating F2 population (derived from an MCR x WCS cross). Genotypes falling into three distinct categories (RR, Rr, or rr) were tentatively assigned based on varying phenotypic responses. Basal AtuGSTF2 expression levels were quantified and compared via RT-qPCR. Results indicated that each atrazine-resistant line (RR and Rr) tested displayed high AtuGSTF2 expression levels, ranging from 200- to 1140-fold greater than the low baseline levels detected in atrazine-sensitive lines (rr). Sequence analysis of RT-PCR products revealed several putative allelic variants of the AtuGSTF2 gene among F2 lines and their parent populations. These results demonstrate that constitutive AtuGSTF2 expression correlates strongly with phenotype and may therefore represent the predominant GST that confers atrazine resistance in ACR and MCR.
Chapter 3 provides research that was conducted to explore the options for control of two HPPD- and atrazine-resistant waterhemp populations, SIR and NEB. The first objective was to determine the level of resistance to two HPPD-inhibiting herbicides; one that both populations had been exposed to previously (mesotrione) and another that had not been applied to either population (isoxaflutole). A dose-response experiment was conducted in the greenhouse at two different postemergence (POST) timings. Overall our findings did not indicate a consistent pattern in fold-resistance levels to isoxaflutole in taller plants. However, mesotrione applied POST to SIR showed a clear decrease in fold-resistance levels relative to EPOST. To further investigate potential management strategies of HPPD- and atrazine-resistant waterhemp populations in the field, our second objective was to conduct a POST herbicide interaction study and evaluate combinations of metribuzin and either isoxaflutole or mesotrione. This objective was designed to test two interconnected hypotheses: (1) HPPD-inhibitor activity contributes to synergism in a tank mix with metribuzin, and (2) metabolic atrazine resistance can be overcome by using a different PSII inhibitor (metribuzin). Results indicated that mesotrione at 52.5 g ai ha-1 combined with 191 g ai ha-1 of metribuzin displayed a synergistic effect on biomass reduction in SIR plants. However, all other combinations of either mesotrione or isoxaflutole and metribuzin resulted in an additive effect on biomass reduction in both the SIR and the NEB populations. These results give insight into how the joint activity between HPPD- and PSII-inhibitors can be used to control metabolism-based, multiple herbicide-resistant waterhemp populations.
Chapter 4 summarizes the discussion and conclusions from Chapters 2 and 3 and identifies current limitations and future research goals for utilizing the herbicides we currently have available to control waterhemp, as herbicide resistance continues to evolve and no new modes of action are coming to market.Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2019-12-01The student, Sarah O'brien, accepted the attached license on 2017-11-30 at 14:14.The student, Sarah O'brien, submitted this Thesis for approval on 2017-11-30 at 14:27.This Thesis was approved for publication on 2017-12-01 at 11:03.DSpace SAF Submission Ingestion Package generated from Vireo submission #11795 on 2018-03-13 at 09:56:21Made available in DSpace on 2018-03-13T15:25:18Z (GMT). No. of bitstreams: 2
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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
Molecular Phylogenetic and Biogeographic Study of the Genus Artemisia (Asteraceae), With an Emphasis on Section Absinthium
No full textArtemisia is the largest genus in the tribe Anthemideae and is composed of ecologically, morphologically, and chemically diverse species found primarily throughout the Northern Hemisphere. Delimitation within Artemisia and among allied genera in subtribe Artemisiinae has been difficult, but previous phylogenetic analyses have helped clarify some major lineages and sister relationships. Despite these contributions, many questions remain unanswered regarding the monophyly of certain taxonomic groups, relationships among New and Old World species, and migration history of the genus. The objectives of this investigation were to reexamine the classification and biogeography of Artemisia, with an emphasis on section Absinthium , in greater detail compared to earlier studies and to evaluate the utility of thirteen different chloroplast regions for inferring phylogenetic relationships. Ingroup and outgroup taxon sampling was greatly increased over previous studies and included most New World taxa of Artemisia and Sphaeromeria, more Asian species, and multiple accessions of widespread species and species from the Arctic, Beringia, and islands and archipelagos in the North Pacific. The molecular ITS phylogeny contained 194 accessions of 173 taxa (91 sequences of 73 taxa were new and the remaining from GenBank) and showed that Artemisia and its traditional infrageneric groups are not monophyletic as currently circumscribed. Artemisia is paraphyletic by the exclusion of several small segregate genera from Asia and the North American genus Sphaeromeria. Results from the chloroplast survey showed that the psbA-trnH and rpl32-trnL spacers provided the most parsimony-informative characters. Chloroplast phylogenies using these two markers were constructed with a reduced dataset that included members of Artemisia section Absinthium and exemplars from major clades identified in the ITS-based phylogeny. Plastid sequence data, though less variable and informative, largely corroborated the ITS results. The molecular data suggests that North American Artemisia species have multiple origins, and that western North America has served as a source for some colonizing elements in eastern Asia and South America. This study further identifies Beringia not only as an important migration corridor for the bi-directional exchange of New and Old World species, but also as a secondary center of diversity and source area for the genus Artemisia in the Arctic.Made available in DSpace on 2015-09-28T15:22:56Z (GMT). No. of bitstreams: 2
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Characterization of pigments from cultivated Amaranthus species and assessment of their commercial applications as natural food colorants
Get PDFConsumer demands for healthier foods with simple ingredients have evoked trends in the food industry to replace synthetically produced colorants with naturally derived alternatives. Of these, betalain pigments derived from beets (Beta vulgaris L.) serve as an important alternative to the synthetic dye FD&C Red 40 for many different low-acid food applications. Betalains are a versatile class of colorants, but their application can be undesirably expensive due to the limited production areas and high cost of red beets. Vegetable amaranth (Amaranthus spp.) is a particularly appealing alternative to beets because of its high concentrations of betacyanin pigments and status as a ubiquitous low-maintenance crop that is resilient to many of the environmental stresses that afflict traditional crops. Unlike beets, amaranth can be harvested multiple times per season and provide additional chlorophyll and carotenoid pigments from the same plant material. The work herein surveys a diverse collection of vegetable amaranth cultivars for pigment content, color, and composition and also tests their stability in a model beverage system. The highest average betacyanin content was 479 mg per 100g dry tissue from the accession PI 566897 (A. cruentus L.). No betaxanthins were detected in any of the accessions surveyed. The major betacyanin observed in all extracts was amaranthin (betanidin 5-O-β-glucuronosyl-glucoside). Consistent differences in betacyanin profiles were noted between different species. Color values for highly pigmented accessions indicated that amaranth extracts can provide bluer hues than current commerical options derived from beets. The highest total chlorophyll and carotenoid content was observed from accession PI 608661 (A .graecizans L.), with an average of 5123 μg of chlorophylls a+b per gram DT and 819 μg of carotenoids per gram of dry tissue. Five genotypes from this survey noted for their high betacyanin yields and phenotypic differences were grown under field conditions and used as colorants in a model beverage system to evaluate their real-life performance in comparison to current natural colorant options. In this research, the thermal and pH stability of five different amaranth cultivars along with crude and purified beet-sourced colorants were studied. Significant differences in pigment degradation rates and color parameters were observed between amaranth cultivars, with PI 689689 (A. spp.) showing the greatest stability and highest chroma (C*) values. This accession showed similar stability to beet-colored beverages at pH 3 and 4.5 and produced significantly bluer colors. Overall, beverages showed the best stability at the lowest temperature tested (5 °C) and generally had the slowest pigment degradation at a pH value of 4.5. HPLC-MS is currently being used to identify non-betalain extract components that significantly influence extract color and stability. Results indicate that certain Amaranthus cultivars can match the stability of beet-derived colorants and provide color hues unobtainable with beets alone. Overall, the studies described herein supply valuable baseline data that are necessary for understanding betalain biosynthesis in Amaranthus, implementing the use of Amaranthus pigments as natural food colors in a commercial setting, and informing breeding strategies to optimize pigment yield, stability, and color.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2021-12-01The student, Jay Howard, accepted the attached license on 2019-12-12 at 10:04.The student, Jay Howard, submitted this Thesis for approval on 2019-12-12 at 10:11.This Thesis was approved for publication on 2019-12-12 at 11:24.DSpace SAF Submission Ingestion Package generated from Vireo submission #14709 on 2020-02-28 at 17:37:58Made available in DSpace on 2020-03-02T22:38:57Z (GMT). No. of bitstreams: 2
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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
Characterizing herbicide resistance in Southwestern U.S. and invasive California populations of Amaranthus palmeri
Get PDFPalmer amaranth is a weedy plant species native to the Southwestern U.S. that has invaded California’s Central Valley agricultural areas, impacted crop yields, and evolved resistance to several major herbicide classes. While mechanisms of herbicide resistance in the species have been characterized, little work has been done on the herbicide resistance alleles carried within populations from the native range or the Central Valley. Populations of Palmer amaranth in the Southwestern U.S. and central California may exhibit herbicide resistance due to their proximity to crop fields, as well as general weed control methods near roadsides, or due to introduction of herbicide resistance alleles from other parts of the invasive range of the species. I germinated seedlings from 29 populations of Palmer amaranth that included locations from its native range, plus invasive populations in California, and tested these plants for herbicide resistance using greenhouse assays. I included four herbicides with four different modes of action. I also extracted DNA from sampled populations and conducted DNA-based assays to detect
target-site-based resistance to two widely used herbicide groups: acetolactate synthase inhibitors and glyphosate. Multiple populations exhibited herbicide resistance phenotypes. After extracting and amplifying DNA from the suspected resistant populations, two populations carry herbicide resistance alleles (one population each with ALS-resistance and glyphosate resistance). The data gathered from my experiments can be used in further research on the invasion of this agricultural weed species
Pseudosenegalia Seigler & Ebinger & Riggins & Terra & Miller 2017, gen. nov.
No full textII. Pseudosenegalia Seigler & Ebinger, gen. nov. TYPE: Acacia feddeana Harms, Repert. Spec. Nov. Regni Veg. 16: 450. 1920 [≡ Pseudosenegalia feddeana (Harms) Seigler & Ebinger]. Shrubs or small trees, some to 12 m; twigs terete or nearly so, not flexuous; short shoots present; prickles and stipular spines absent. Leaves alternate or clustered on short shoots, bipinnate; stipules small, linear, symmetrical, herbaceous, tardily deciduous to persistent; petioles adaxially grooved, 0.5–13 mm long; petiolar gland usually present, sessile, solitary; rachis adaxially grooved, usually with glands between some pairs of pinnae; pinnae 1 to 7 pairs/leaf, opposite; paraphyllidia absent; leaflets 11 to 26 pairs/ pinna, linear, 1.2–2.9 X 0.4–0.9 mm, 1 vein from the base, glabrous to lightly pubescent, midrib subcentral. Inflorescences a cylindrical spike, 1 to 2 clustered in leaf axils. Flowers bracteate, sessile, actinomorphic, sympetalous, 5-merous, with a basal copular nectiferous disk; stamens 1 0 0 to 1 5 0, distinct, attached along the side of the nectariferous disk, exserted; anthers small, dorsifixed, dehiscing vertically, anther glands absent; ovary with a stipe to 2.1 mm long; style filiform; stigma filiform. Legumes straight to slightly curved, flattened to elliptic in cross section, oblong, eglandular, dehiscing along both sutures; seeds uniseriate, not surrounded by pulp, ovoid to ellipsoid, flattened; pleurogram present or absent. Habitat and distribution. Pseudosenegalia is known to occur in dry scrub and thorn-scrub vegetation between 1300 and 3300 m in Bolivia. TAXONOMIC KEY TO SPECIES OF PSEUDOSENEGALIA 1. Leaves with a single pair of pinnae............................. P. feddeana (Harms) Seigler & Ebinger 1 '. Leaves with 3 to 7 pairs of pinnae................. P.riograndensis (Atahuachi & L. Rico) Seigler & EbingerPublished as part of Seigler, David S., Ebinger, John E., Riggins, Chance W., Terra, Vanessa & Miller, Joseph T., 2017, Parasenegalia and Pseudosenegalia (Fabaceae): New Genera of the Mimosoideae, pp. 180-205 in Novon 25 on pages 199-200, DOI: 10.3417/2015050, http://zenodo.org/record/256146
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