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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Investigating the effects of three herbicides - Kamba, 2,4-D and Roundup on Salmonella enteric serovar Typhimurium growth and antibiotic tolerance phenotypes

Marjoshi, Delphine January 2014 (has links)
Herbicides are a common tool in weed control. With the introduction of genetically modified herbicide-tolerant crops, there has been a dramatic increase in the use of particular herbicides. Herbicides contaminate the environment and food and feed and can come into contact with non-target organisms, especially bacteria. Salmonella enteric serovar Typhimurium, which is a human and animal pathogen, was chosen to investigate if the commercial formulations of three herbicides – Kamba, 2,4-D and Roundup are toxic to bacteria and whether sub-lethal concentrations cause a response to antibiotics. In addition, earlier work demonstrating an effect of salicylic acid on antibiotic response was reconfirmed in this study. The herbicides were toxic to S. typhimurium at concentrations above the manufacturers recommended application rates. A key finding of this study was that when S. typhimurium was grown in sub-lethal concentrations of the herbicides, it demonstrated a change in its susceptibility to various antibiotics. Kamba and 2,4-D caused increased tolerance of chloramphenicol, tetracycline, ampicillin and ciprofloxacin and increased sensitivity to kanamycin. Exposure to Roundup caused increased sensitivity to chloramphenicol and tetracycline and increased tolerance towards kanamycin and ciprofloxacin. Roundup had no measureable affect on ampicillin susceptibility. The minimum concentrations of herbicides that induced an antibiotic response were within the recommended application rates. Furthermore, the minimum 2,4-D concentration that induced tetracycline, chloramphenicol and ampicillin tolerance was at or below the maximum residue limits set for food and feed commodities. Simultaneous exposure to an herbicide and an antibiotic was necessary for the induction of antibiotic tolerance. In addition, the effect of the herbicide on the antibiotic response was faster than the lethal effect of the antibiotics. Kamba induced chloramphenicol, tetracycline, ampicillin and ciprofloxacin tolerance was maintained in the absence of Kamba once tolerance was induced by simultaneous exposure to Kamba and antibiotic. The emergence of antibiotic tolerance is an important health issue that may compromise treatment of serious bacterial infections. The widespread use of herbicides in agricultural, urban and domestic settings increases the number of bacteria that are exposed to herbicides. The tolerance induced by the herbicides may increase the frequency of antibiotic tolerant strains, increase the chance of co-exposure to antibiotics, and increase the potential for failure to treat bacterial infections as a result.


Wiedau, Kayla N 01 August 2017 (has links)
Collinsville, Illinois is the leading producer of horseradish is the nation. The river bottom geography surrounding Collinsville, Illinois near St. Louis, Missouri is a high-production area for horseradish. The development of soybean technologies resistant to dicamba or 2,4-D may allow horseradish growers to gain control of troublesome weeds, such as Palmer amaranth (Amaranthus palmeri) or volunteer horseradish, but could pose risks as well. Drift of these two herbicides or carryover to horseradish could cause severe injury and possible crop loss. While synthetic auxin-tolerant soybean may also allow growers to control volunteer horseradish, herbicide efficacy may differ depending on the volunteer horseradish variety. These risks and benefits could affect the adoption rate of these new soybean technologies in horseradish production areas. A field trial was established in 2015 in Edwardsville, IL and 2016 Medora, IL to simulate drift of both dicamba and 2,4-D onto horseradish. Applications were made in horseradish to mimic drift of a mid-post emergence application in soybean onto the horseradish crop. Plants were monitored for injury and stand, height, and yield reductions throughout the season. Individual roots were evaluated post-harvest. Overall, 2,4-D caused more injury at all rates when compared to dicamba. Horseradish growers may see yield reductions if rates at or greater than 1/1000X of a field rate of 2,4-D drift onto their fields. Not planting horseradish near a 2,4-D-tolerant soybean field, as well as reading the herbicide labels and following application requirements, should help growers prevent serious injury and yield loss. On the other hand, rates of 2,4-D at or above a full field rate offered complete control of all plants; therefore, growers who struggle with persistent volunteer horseradish could rotate to a 2,4-D-tolerant soybean and gain needed control of those plants. Field experiments were conducted in 2014, 2015, and 2016 to investigate the impact of dicamba residues following applications in a dicamba-tolerant soybean crop on horseradish planted the following season. Carryover trials were conducted as two-year rotations of soybean followed by horseradish in Collinsville, Illinois. Multiple rates of dicamba were applied at several timings in dicamba-tolerant soybean and the crop was monitored for injury. The following season horseradish was planted and monitored for injury and stand, height, and yield reductions. No injury or reductions were observed with any treatment in either year, potentially indicating a lack of dicamba remaining in the soil. Horseradish plant stand counts, height as well as yields were not reduced when compared to the nontreated. Results from this experiment suggest that rotating from dicamba-tolerant soybean to horseradish should pose no threat to horseradish. Greenhouse experiments were carried out in 2016 in three separate runs. Each run consisted of three replications of five varieties of horseradish, 604, 788, 9705, Hungarian, and V7E3, and two rates of dicamba, glyphosate, and dicamba plus glyphosate . Plants were sprayed when at least one plant in each pot had reached a height of 17 to 23 cm. Horseradish was then rated for injury at 3, 7, 14, 21, and 28 days after treatment (DAT). Heights were also taken at 0, 14, and 28 DAT. At 28 DAT plants were harvested, weighed and place in a dryer for 72 hours and weighed again. The lowest level of injury at 28 DAT was with variety 604. The control of horseradish roots is critical to ensure the plant is killed completely and does not return the following season as a volunteer. The concerns associated with auxin-tolerant crops can be mitigated with proper management of herbicides and crop locations. While off target movement of 2,4-D may cause damage to a horseradish crop, it could be used as a herbicide to control volunteer horseradish. Additionally, if a grower chooses to use a dicamba-tolerant soybean variety, they may have the choice to use a dicamba plus glyphosate premix which will also give good control of volunteer horseradish with little concerns of dicamba carryover to the subsequent horseradish crop. Capitalizing on the strengths and weaknesses of each technology will help horseradish growers manage many weeds and facilitate the production of this important specialty crop.

Determining the Effect of Auxin Herbicide Concentration and Application Timing on Soybean (Glycine Max) Growth and Yield

Scholtes, Alanna Blaine 13 December 2014 (has links)
Auxin resistant cropping systems will provide producers with an alternative option for weed management, but with this new technology also comes the concern of off target movement of dicamba and/or 2,4-D to susceptible crops. Research was conducted over multiple site years in order to determine the effect of soybean response to different application timings and rates of 2,4-D and dicamba. 2,4-D was applied at 1X (0.56 kg ae/ha), 1/4X, 1/16X, 1/64X, and 1/256X rates, and dicamba was applied in a separate study at 1X (0.56 kg ae/ha), 1/4X, 1/16X, 1/64X, 1/256 and 1/1024X. All rates were applied at the V3 and R1 growth stages. Greatest yield losses occurred from dicamba applied at the R1 growth stage. Additional studies were conducted to determine at which growth stage soybeans are most sensitive to 2,4-D and dicamba. Greatest yield losses occurred at the late vegetative and early reproductive growth stages for both herbicides.

4-D Modeling of Displacement Vector Fields for Improved Radiation Therapy

Zachariah, Elizabeth 10 December 2010 (has links)
In radiation therapy, it is imperative to deliver high doses of radiation to the tumor while reducing radiation to the healthy tissue. Respiratory motion is the most significant source of errors during treatment. Therefore, it is essential to accurately model respiratory motion for precise and effective radiation delivery. Many approaches exist to account for respiratory motion, such as controlled breath hold and respiratory gating, and they have been relatively successful. They still present many drawbacks. Thus, research has been expanded to tumor tracking. This paper presents a spatio-temporal model for four dimensional CT reconstruction. The method begins with a set of initial CT projections and a simultaneously acquired breathing trace. Two methods are explored to model the spatial components: principal component analysis and a pseudoinverse matrix method. An iterative approach is used to match the simulated projections to the actual projections. The simulated projections and the initial projections are evaluated using Normalized Root Mean Square Error (NRMSE). The proposed method shows simulated projections and actual projections match, and as such the model is able to accurately predict the deformation.


Tolson, Joshua Allen 01 January 2012 (has links)
Field studies examined the strategies of mowing, herbicide, fertility, and all combinations on tall ironweed populations, weed biomass, pasture yield, grazing, economics, and forage quality at three Kentucky locations. Mowing was performed in July 2008 and 2009, herbicide applied in August 2008, and fertilizer applied in September 2008 and 2009 at all locations. Weed populations were measured in 2008, 2009, and 2010, and forage and weed biomass collected in May or June of 2009 and 2010. Herbicide treatments reduced weed biomass at all locations, and reduced tall ironweed stems by 64% or greater in 2009 at all locations. Weed biomass did not differ when comparing all treatments with and without mowing or treatments with or without fertilizer. Forage grass biomass produced was greatest with herbicide plus fertilizer and with the combination of mowing plus herbicide plus fertilizer at all locations in both years. Two years of grazing did not reduce weed populations. Grazing did reduce forage grass and clover biomass at one location, and weed biomass at two locations. Two locations had positive economic returns based on herbicide treatment for weed control and forge yield. Herbicide treatments reduced crude protein at one location and in-vitro true digestibility at two locations.

Avaliação da Adsorção do Herbicida 2,4-d em Carvão Ativado em Pó Utilizando Água Com Diferentes Qualidades

MARSOLLA, L. D. 02 March 2015 (has links)
Made available in DSpace on 2018-08-24T22:53:37Z (GMT). No. of bitstreams: 1 tese_8867_Dissertação - Lorena Dornelas Marsolla.pdf: 1488919 bytes, checksum: c1ce2244e415d48fd49ab78d33197993 (MD5) Previous issue date: 2015-03-02 / O 2,4-diclorofenoxiacético (2,4-D) é um dos herbicidas mais consumidos no Brasil e é preferencialmente usado devido a sua boa seletividade e baixo custo. Possui alta toxidade e baixa biodegradabilidade, oferecendo risco à saúde humana e ao meio ambiente, podendo ser encontrado em solos, águas superficiais e subterrâneas. Estudos mostram que o tratamento convencional da água possui baixa eficácia na remoção de microcontaminantes, com isso várias técnicas têm sido utilizadas na remoção de compostos em água, como a adsorção por carvão ativado. Apresenta-se a adsorção em carvão ativado tem se demonstrado como tecnologia eficiente na remoção de diversos contaminantes, dentre eles os agrotóxicos. Assim, o presente trabalho objetivou avaliar a adsorção do 2,4-D por três carvões ativados em pó (CAP) em água ultrapura e em água bruta do Rio Santa Maria da Vitória. A quantificação do herbicida foi analisada por cromatografia líquida de alta eficiência, após concentração da amostra pelo método de extração em fase sólida. Os ensaios de adsorção foram realizados com carvões ativados derivados da casca de coco (CAP-01), pinus (CAP-02) e palha de café (CAP-03), que foram caracterizados e avaliados na sua capacidade de remoção do 2,4-D nas duas matrizes de água. Dois modelos de isoterma de adsorção, Langmuir e Freundlich, foram aplicados para descrever os dados de adsorção, que indicaram o CAP-02 como o carvão que apresentou a melhor capacidade de adsorção do 2,4-D entre os carvões estudados, tanto em água ultrapura quanto em água bruta. Nos ensaios realizados em água bruta, houve redução da adsorção do 2,4-D para as três amostras de CAP, quando comparado com os ensaios realizados em água ultrapura, indicando interferência de compostos, como a matéria orgânica, no processo de adsorção.

Evaluation of a Cultural Practice and 2,4-D-Based Herbicide Programs for Glyphosate-Resistant Palmer Amaranth Management

Lawrence, Benjamin Haynes 11 December 2015 (has links)
Glyphosate-resistant Palmer amaranth (Amaranthus palmeri [S.] Wats) is an economically troublesome weed to southeastern United States soybean (Glycine max [L.] Merr.) growers. Palmer amaranth is troublesome due to its evolution of resistance to multiple herbicide modes of action, competiveness, and prolific seed production. Greenhouse studies were conducted at the Delta Research and Extension Center in Stoneville, MS to evaluate different rates of 2,4- dichlorophenoxyacetic acid (2,4-D) for control of Palmer amaranth. Field experiments were conducted at the Delta Research and Extension Center in Stoneville, MS in 2013 and 2014 to evaluate Palmer amaranth emergence using a cultural practice and a residual herbicide. Field experiments were also conducted at the Delta Research and Extension Center in Stoneville, MS in 2013 and 2014 to evaluate Palmer amaranth control with applications of glyphosate, glufosinate, and 2,4-D alone and in mixtures.

Evaluation of pesticide application technology in cotton production

Samples, Chase 01 May 2020 (has links)
There have been many changes in production agriculture over the last 20 years. The use of herbicide resistant crops has become common place in production agriculture. However, the release of crops resistant to auxin herbicides has brought more attention to the pesticide application process regardless of the type of pesticide applied. Moreover, controlling off-target movement of pesticides has become an integral part of the day to day farming tasks. The use of deposition aids when applied with water has been documented; however, the effect of deposition aids on pesticide application is not well understood. Based on these findings, selecting a deposition aid not only can be affected by the pesticide used but also the crop in question. Additionally, label restrictions on auxin herbicide application in auxin tolerant crops brings an additional problem to cotton growers. The use of insecticides in conjuction with herbicide applications has been commonplace for many growers across the cotton belt. However, smaller droplets have been utilized to increase coverage of these insecticides. Data presented in these findings suggest that larger droplets can still have good levels of efficacy and in some instances increase yield. The use of auxin tolerant crops allows for usage of addition POST herbicides to cotton; however, the effect of these tank mix applications on ctrop injury is not well understood. In both EnlistTM and Xtend® Flex cotton levels of injury were increased when glufosinate and S-metolachlor were applied in a tank mix. However, yield was not negatively impacted in either study.

Molecular And Biochemical Role Of Auxin And Cytokinin In Dedifferentiation And Organogenesis Of Arabidopsis

Kakani, Aparna 11 December 2009 (has links)
Cell dedifferentiation is a cell fate regression process in which the cell fate memory of a differentiated cell is erased, leading to regain stem cell characteristics. Auxin regulates both cell dedifferentiation and differentiation in plants. It is unknown how auxin controls the two opposite processes. Here the minimal auxin requirements for cell dedifferentiation were found, molecular markers associated with the cell dedifferentiation event were identified. When cellular auxin concentration exceeds the level of meristem cell, most differentiated cells undergo dedifferentiation. In differentiated cells, the polar auxin efflux system prevents cell dedifferentiation by reducing auxin accumulation, particularly in the presence of exogenous auxin. Classic plant tissue culture experiments have shown that exposure of cell culture to a high auxin to cytokinin ratio promotes root formation and a low auxin to cytokinin ratio leads to shoot regeneration. Since the auxin level is highly elevated in the shoot meristem tissues, it is unclear how a low auxin to cytokinin ratio promotes the regeneration of shoots. To identify genes mediating the cytokinin and auxin interaction during organogenesis in vitro, three allelic mutants that display root instead of shoot regeneration in response to a low auxin to cytokinin ratio are identified using a forward genetic approach in Arabidopsis. Molecular characterization shows that the mutations disrupt the AUX1 gene, which has been reported to regulate auxin influx in plants. Meanwhile, it was found that cytokinin substantially stimulates auxin accumulation and redistribution in calli and some specific tissues of Arabidopsis seedlings. In the aux1 mutants, the cytokinin regulated auxin accumulation and redistribution is substantially reduced. These results suggest that auxin elevation and other changes stimulated by cytokinin, instead of low auxin or exogenous auxin directly applied, is essential for shoot regeneration. In this study, as a part of interaction between auxin and cytokinin it was identified that the induction of ARR5 and ARR6 expression by cytokinin is subjected to the regulation of auxin. The expression of ARR5 and ARR6 follows a mutual exclusive pattern in response to the induction of exogenous auxin in Arabidopsis seedlings and calli. The results suggest that auxin interacts with the cytokinin via a gene and tissue specific induction of the negative regulators in the cytokinin signaling pathway.

Stewarding 2,4-D- and dicamba- based weed control technologies in cotton and soybean production systems

Buol, John Tyler 03 May 2019 (has links)
Distinguishing 2,4-D and dicamba herbicide formulations in cotton and soybean tissue is challenging in regulation of crop injury from these herbicides. Additionally, stewardship of 2,4-D and dicamba technologies is important to maximize their longevity and efficacy. Research was conducted to (1) characterize cotton and soybean response to various formulations of 2,4-D or dicamba with or without glyphosate, (2) develop a method for classifying these formulations in crop tissue, and (3) optimize use of chloroacetamide herbicides in dicamba systems for mitigation of selection pressure on dicamba. Formulations evaluated include dicamba diglycolamine (DGA), dimethylamine (DMA), N,N-Bis-(3-aminopropyl) methylamine (BAPMA), and DGA plus potassium acetate (KAc); and 2,4-D DMA, acid, isooctyl ester (ESTER), and choline. Weed management by the chloroacetamides s-metolachlor and acetochlor was evaluated with applications preemergence (PRE), early postemergence (EP), late postemergence (LP), PRE followed by (fb) EP, PRE fb LP, and EP fb LP. Cotton and soybean response differed by 2,4-D and dicamba formulation, and glyphosate presence. Cotton yield was reduced by 200 to 500 kg ha-1 following exposure to 2,4-D choline or DMA relative to acid or ESTER. Glyphosate presence led to a reduction in cotton and soybean yield of 377 and 572 kg ha-1, respectively. Exposure to dicamba DMA resulted in a 263 kg ha-1 reduction in soybean yield relative to dicamba DGA, and glyphosate presence reduced yield by 439 and 246 kg ha-1 in cotton and soybeans, respectively. Chemometric analyses generated models capable of up to 85% accuracy in identifying dicamba formulation in cotton and soybean tissue, and up to 80% accuracy in identifying 2,4-D formulation. Split chloroacetamide applications improved cotton yield up to 60%, reduced weed densities up to 90%, and improved control up to 56% relative to single applications. Cotton height was reduced up to 23% if a single chloroacetamide application was made. Soybean yield was maximized following any chloroacetamide application timing except PRE alone, and weed control was reduced up to 31% following single chloroacetamide application relative to split applications. These results will aid regulatory bodies in managing use of new weed control technologies and will assist producers in stewarding these new technologies.

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