Dissertations / Theses: 'Promoting plant growth'

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Hu, Chia-Hui Kloepper Joseph. "Induction of growth promotion and stress tolerance in arabidopsis and tomato by plant growth-promoting." Auburn, Ala., 2005. http://repo.lib.auburn.edu/2005%20Summer/doctoral/HU_CHIA-HUI_54.pdf.

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Davies, Keith Graham. "Studies on plant growth promoting rhizobacteria." Thesis, Bangor University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266612.

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Thomas, N. F. "Synthesis of the plant growth promoting steroid brassinolide." Thesis, Cardiff University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333124.

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Lewis, Ricky W. "TOXICITY OF ENGINEERED NANOMATERIALS TO PLANT GROWTH PROMOTING RHIZOBACTERIA." UKnowledge, 2016. http://uknowledge.uky.edu/pss_etds/77.

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Engineered nanomaterials (ENMs) have become ubiquitous in consumer products and industrial applications, and consequently the environment. Much of the environmentally released ENMs are expected to enter terrestrial ecosystems via land application of nano-enriched biosolids to agricultural fields. Among the organisms most likely to encounter nano-enriched biosolids are the key soil bacteria known as plant growth promoting rhizobacteria (PGPR). I reviewed what is known concerning the toxicological effects of ENMs to PGPR and observed the need for high-throughput methods to evaluate lethal and sublethal toxic responses of aerobic microbes. I addressed this issue by developing high-throughput microplate assays which allowed me to normalize oxygen consumption responses to viable cell estimates. Oxygen consumption is a crucial step in cellular respiration which may be examined relatively easily along with viability and may provide insight into the metabolic/physiological response of bacteria to toxic substances. Because many of the most toxic nanomaterials (i.e. metal containing materials) exhibit some level of ionic dissolution, I first developed my methods by examining metal ion responses in the PGPR, Bacillus amyloliquefaciens GB03. I found this bacterium exhibits differential oxygen consumption responses to Ag+, Zn2+, and Ni2+. Exposure to Ag+ elicited pronounced increases in O2 consumption, particularly when few viable cells were observed. Also, while Ni2+ and Zn2+ are generally thought to induce similar toxic responses, I found O2 consumption per viable cell was much more variable during Ni2+ exposure and that Zn2+ induced increased O2 utilization to a lesser extent than Ag+. Additionally, I showed my method is useful for probing toxicity of traditional antibiotics by observing large increases in O2 utilization in response to streptomycin, which was used as a positive control due to its known effects on bacterial respiration. After showing the utility of my method for examining metal ion responses in a single species of PGPR, I investigated the toxicity of silver ENMs (AgENMs) and ions to three PGPR, B. amyloliquefaciens GB03, Sinorhizobium meliloti 2011, and Pseudomonas putida UW4. The ENM exposures consisted of untransformed, polyvinylpyrrolidone coated silver ENMs (PVP-AgENMs) and 100% sulfidized silver ENMs (sAgENMs), which are representative of environmentally transformed AgENMs. I observed species specific O2 consumption responses to silver ions and PVP-AgENMs. Specifically, P. putida exhibited increased O2 consumption across the observed range of viable cells, while B. amyloliquefaciens exhibited responses similar to those found in my first study. Additionally, S. meliloti exhibited more complex responses to Ag+ and PVP-AgENMs, with decreased O2 consumption when cell viability was ~50-75% of no metal controls and increased O2 consumption when cell viability was <50%. I also found the abiotically dissolved fraction of the PVP-AgENMs was likely responsible for most of the toxic response, while abiotic dissolution did not explain the toxicity of sAgENMs. My work has yielded a straightforward, cost-effective, and high-throughput method of evaluating viability and oxygen consumption in aerobic bacteria. I have used this method to test a broad range of toxic substances, including, metal ions, antibiotics, and untransformed and transformed ENMs. I observed species specific toxic responses to Ag+, PVP-AgENMs, and sAgENMs in PGPR. These results not only show the clear utility of the methodology, but also that it will be crucial to continue examining the responses of specific bacterial strains even as nanotoxicology, as a field, must move toward more complex and environmentally relevant systems.

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Abdul, Mutalib Asilah. "Interactions between plant growth promoting microorganisms (PGPM) and biochar." Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/49082/.

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Rhizobia are frequently used in the agriculture sector to enhance legume growth and improve soil fertility. There is growing interest in utilizing biological nitrogen fixation as a means of increasing the potential for sustainable intensification of food production whilst simultaneously reducing environmental damage caused by overuse of chemical fertilisers. Biochar, a recalcitrant carbon-rich product of pyrolysis which may be added to soil as a fertilizer or as a soil improver, alters soil physico-chemical properties usually by acting as a liming agent, by increasing water holding capacity or by modifying cation exchange capacity. The effects of biochar on the soil microbial community are not fully understood. Therefore, the main aim of this investigation was to evaluate the effects of biochar on the Rhizobium-legume relationship and determine whether biochar could increase legume growth. To achieve this aim, a series of growth experiments were carried out under controlled conditions in which broad bean (Vicia faba) was grown with Rhizobium leguminosarum and the symbiosis tested against three concentrations of biochar applied as a soil amendment and with two different char particle sizes. Beans responded well to Rhizobium under char-free conditions but the effects of biochar on the symbiosis were variable and depended on char particle size, concentration and Rhizobium strain (commercial or indigenous). Powdered char inhibited plant growth when in the presence of the commercial rhizobia, but not with indigenous strains. This is an important finding since commercial inocula are commonly used in agronomic situations. Plant available soil nutrients were modified by biochar and surprisingly by an interaction between char concentration and the two rhizobia strains. When beans were co-cropped with wheat, beans performed better when grown with powdered char than without. This is in contrast to the response of bean plants to powdered char in the absence of any competition. Since wheat was generally the superior competitor, powdered char amendment enabled the bean to take advantage of the N-limiting environment that powdered char created and perform better than in the soils that advantaged the wheat. The investigation highlighted the complexity of the system, but identified the importance of char particle size and Rhizobium strain selection.

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Mulaudzi, Renolda Ipeleng. "Assessment of plant growth promoting rhizobacteria for plant growth enhancement and biocontrol activity against Fusarium pseudograminearum on wheat." Diss., University of Pretoria, 2019. http://hdl.handle.net/2263/77860.

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Plant growth promoting rhizobacteria (PGPR) are those bacteria that colonise the rhizosphere of various plants and promote growth either directly by improving nutrient uptake by the plant roots or indirectly through the control of pathogens. Due to the negative effects associated with the prolonged use of chemical fertilizers and fungicides, a lot of emphasis is now being given to research that investigates an alternative, sustainable and environmentally friendly method of crop production and protection. In the current study, a collection of rhizobacterial isolates from the University of Pretoria- Plant Growth Promoting Rhizobacteria (UP-PGPR) culture collection were screened for plant growth promotion and biocontrol activity against crown rot caused by Fusarium pseudograminearum on wheat (Triticum aestivum). A seedling tray bioassay was utilised as a rapid small-scale method to screen the rhizobacterial isolates for biocontrol activity against wheat crown rot in the greenhouse. The same method was also used to screen the isolates for direct plant growth promotion of wheat. Of all the isolates (113) screened for wheat crown rot control, 52% (59 isolates) significantly increased the shoot dry weight of the seedlings, 41% (46 isolates) increased the root dry weight of the seedlings, and the total seedling dry weight was increased by 32% (36 isolates) of the isolates. A seedling bioassay was also used to screen the isolates for direct plant growth promotion of wheat. Of the 113 isolates screened, 12% (14 isolates) increased the shoot dry weight of the seedlings, 22% (25 isolates) increased the dry weight of the roots; while the total dry weight of the seedlings was increased by 32% (36 isolates) of the isolates. Subsequent to the seedling bioassay in the greenhouse, the isolates were also assessed in vitro for selected traits associated with biocontrol activity and plant growth promotion. To test for a broad spectrum of biocontrol activity, in addition to F. pseudograminearum, the isolates were also screened for inhibition of Rhizoctonia solani, Phytophthora capsici and Macrophomina phaseolina. Almost 50% of the isolates displayed broad-spectrum activity against the pathogens on three different media. Some notable isolates in this regard were Bacillus sp. strain N54 and Pseudomonas sp. strain N59, N67 and N69. All isolates screened displayed multiple traits associated with biocontrol activity such as the production of antibiotic enzymes, volatiles (NH3 and HCN) and the production of siderophores. The isolates also displayed multiple traits associated with direct plant growth promotion (nitrogen fixation, phosphate solubilization, IAA and ACC deaminase). Based on the results obtained from the seedling bioassays in the greenhouse and the in vitro screening, a scoring system was developed, and the isolates were awarded points. Bacillus sp. strain A09AC, A17, A20, N02, N28, N54 Stenotrophomonas sp. strain A45, Pseudomonas sp. strain N04AC, N44 and N59A were selected for pot trials to confirm their F. pseudograminearum biocontrol efficacy (Figure 1.1). Bacillus sp. strain A10AC, Stenotrophomonas sp. strain A33, A43, A45, Paenibacillus sp. strain KBS1F3, Pseudomonas sp. strain N29, N69, N67, N76 and Pantoea sp. strain N34 were selected for use in pot trials in the greenhouse to confirm their efficacy as wheat growth promoters. The selected isolates were further assessed for biocontrol activity and plant growth promotion in greenhouse experiments. KBS1F3 (Paenibacillus alvei) showed the best results for wheat growth promotion while A17 (Bacillus cereus) gave the best results for biocontrol activity. The effect of temperature, pH, NaCl and different carbon sources on the growth of the isolates was also assessed in vitro. The optimum temperature of all isolates was observed to be between 26oC and 35oC while KBS1F3 was able to grow at 47oC and A17 at 50oC. The growth of KBS1F3 decreased with an increase in NaCl concentration while A17 still grew well at 4% NaCl concentration. All isolates grew optimally at pH 7. KBS1F3 still grew well at pH 8 while A17 showed good growth at all pH values except pH 4. All isolates showed the ability to utilise a variety of carbon sources.
Dissertation (MSc (Agric))--University of Pretoria, 2019.
Microbiology and Plant Pathology
MSc (Agric)
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Grandlic, Christopher J. "Plant Growth-Promoting Bacteria Suitable for the Phytostabilization of Mine Tailings." Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/195918.

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Mining activities and their resulting wastes, mine tailings, have created a sizable problem globally. Semiarid lands have been particularly impacted due to intense mining activities in these areas. Growing concerns regarding human health risks and environmental consequences associated with these tailings has created a need for efficient and effective remediation strategies. Phytostabilization, the establishment of a vegetative cover on mine tailings to reduce erosion and dispersion of material, is emerging as a cost-effective remediation technology. However, due to elevated levels of metal contaminants, acidic pH values and poor substrate quality many tailings sites are inhospitable to plant growth. The addition of compost amendments can mitigate the toxic effects of tailings material and facilitate plant growth; however, in many instances the necessary compost amendments may be cost prohibitive. The use of specialized bacterial isolates, known as plant growth-promoting bacteria (PGPB), to enhance plant growth is a developing technology that has a broad range of applications. The use of PGPB to enhance one or more aspect of plant establishment and growth has been demonstrated to be effective in hundreds of previous studies conducted primarily under agricultural settings. To date, very few studies have utilized PGPB in attempts to enhance plant growth in mine tailings. The current study is an investigation into the potential for utilizing PGPB to enhance plant growth during the phytostabilization of semiarid mine tailings. During this investigation a large collection of bacterial isolates was screened for common plant growth-promoting mechanisms such as siderophore and indole-3-acetic acid production, phosphate solubilization and ACC-deaminase activity. Isolates possessing beneficial qualities were utilized in a series of greenhouse screening studies to evaluate their abilities to enhance the growth of native desert plants in various tailings materials. A number of isolates tested have demonstrated the ability to enhance plant growth in composted and non-composted tailings material. Optimization of this technology has now indicated that alginate-encapsulated inoculation of target plants is a beneficial and practical technology.

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Wu, Ruomou. "Identification of candidate plant growth promoting endophytes from Echium plantagineum roots." University of the Western Cape, 2018. http://hdl.handle.net/11394/6288.

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Magister Scientiae - MSc (Biotechnology)
The yearly increase of global population will result in a greater demand for crop production, but with the climates changes and a lack of available agricultural land it will become increasingly more difficult to provide sufficient crops to feed everyone adequately. Application of the PGPE has proven over the past researches to be able enhance growth of plants via various growth promoting mechanisms. To identify suitable growth promoting bacteria candidate, E. plantagineum plant was used to isolate endophytes from the root after surface sterilization. The isolates bacteria were used to inoculate Brassica napus L seeds. The effects of isolate's ability to promote growth were evaluated based on the certain growth parameters after 42 days in the green house. Isolate CP5 produced highest results in all growth parameter. Isolates CP5 was selected as potential candidate as significant improvement was shown by this isolate. This isolate was tested for the ability to produce ACC deaminase, solubilize phosphate, synthesize IAA and siderophore production. Furthermore isolate CP5 growth promotion abilities was tested on Brassica napus L under antimony stress.
2021-08-31

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Adele, Nyekachi Chituru. "Effects of metal speciation on metal plant dynamics in the presence of plant growth promoting bacteria." Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/25414.

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Excessive metal deposition in soil is of major concern to the environment due to the toxicity of metals to animals and plants. Since metals do not degrade, reducing risk of exposure relies in either removing the metals from soil, or changing their speciation which leads to changes in bioavailability, mobility and toxicity. Plants have been shown to provide a cheap alternative to chemical methods for both removing and changing metal speciation, particularly when augmented with plant growth promoting bacteria. The focus of this thesis was to investigate whether the form (speciation) in which a metal contaminant is introduced to soil affects both plant health and the efficiency of metal remediation by the plant, using the well-known hyperaccumulator Brassica juncea (L.) Czern and zinc (Zn) as the metal contaminant. This study also examined the role of plant growth promoting bacteria in changing metal speciation, impact on metal toxicity and phytoremediation efficiency. Brassica juncea was grown in pots containing soil spiked with equal amounts (600 mg Zn kg-1) of soluble Zn (ZnSO4) and nanoparticulate ZnS and ZnO. Plant height, number of leaves, root length, plant biomass and chlorophyll content of Brassica juncea were used to assess Zn toxicity. Zn localisation and speciation in soil and plant tissues was studied using transmission electron microscopy (TEM), synchrotron micro-X-ray fluorescence elemental mapping (μXRF) and synchrotron X-ray absorption spectroscopy (XAS). Growth parameters showed that ZnSO4 was the most toxic form of Zn whilst ZnS and ZnO effects were not statistically different. These differences were linked to differences in Zn content in root and shoot biomass, which was higher in ZnSO4 treatments. Inoculation with Rhizobium leguminosarum and Pseudomonas brassicacearum enhanced plant growth, Zn concentration in plant biomass and translocation of Zn in all Zn treatments. XAS analysis showed that Zn speciation was altered in roots of plants inoculated with bacteria, with Zn cysteine as the most dominant form of Zn in all inoculated Zn treatments, suggesting a role for cysteine in ameliorating Zn toxicity. By also assessing Zn speciation changes across the soilrhizosphere- plant interface, this study established that Rhizobium leguminosarum modified Zn speciation at the rhizosphere. Through this thesis work, metal speciation is a major factor in determining the efficiency of metal phytoremediation and plant tolerance. Hence, this research provides useful information on Zn speciation which will contribute to effective implementation of Zn phytoremediation.

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Stewart, Allan Howard. "Suppression of verticillium wilt in potatoes with a plant growth promoting rhizobacterium." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq24925.pdf.

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Holguin, Zehfuss Gina. "Improving the plant-growth promoting ability of Azospirillum brasilense by genetic manipulation." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/NQ60541.pdf.

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Tchuisseu, Tchakounte Gylaine Vanissa. "Assessing the role of native plant growth-promoting rhizobacteria (PGPR) isolated from Cameroon soil as bio-inoculant in improving plant growth." Doctoral thesis, Humboldt-Universität zu Berlin, 2021. http://dx.doi.org/10.18452/22323.

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Der Mangel an Nährstoffen im Boden, hauptsächlich an Phosphor (P) und Stickstoff (N), verbunden mit einem hohen Salzgehalt und der generellen Verarmung landwirtschaftlicher Böden , sind ein ernstes Problem für die landwirtschaftliche Produktion weltweit. Daher besteht ein dringender Bedarf an Forschung und Entwicklung geeigneter landwirtschaftlicher Praktiken, um ungünstige Bodenbedingungen zu verringern und wenn möglich die Fruchtbarkeit von Kulturland wiederherzustellen. Die Verwendung von Rhizobakterien, die das Pflanzenwachstum (PGPR) fördern, kann sich bei der Entwicklung von Strategien zur Erleichterung des Pflanzenwachstums unter normalen Wachstumsbedingungen sowie unter abiotischen Stress als nützlich erweisen. Diese Bakterien bieten ihren pflanzlichen Wirten Vorteile, indem sie die Aufnahme von Bodenmineralien fördern und Pflanzen vor schädlichen Umwelteinflüssen schützen. Die vorliegende Arbeit bewertet die Rolle von in Kamerun natürlich vorkommenden PGPR an Mais und untersucht deren Potenzial als Bioimpfstoffe zur Steigerung des Pflanzenwachstums in Kamerun. Wir prüfen die Hypothese, dass einheimische Bakteriengemeinschaften aus Kamerun einen hohen Anteil an Bakterien aufweisen, deren Eigenschaften Kulturpflanzen helfen, mit ungünstigen Bedingungen umzugehen. In der vorliegenden Arbeit wurden dazu Bakteriengemeinschaften der Rhizosphäre von in Kamerun angebautem Mais isoliert und untersucht. Zum ersten Mal erfolgte eine umfassende phylogenetische Zuordnung aller kultivierbaren Bakterien, auf Grundlage ihrer potenziellen Fähigkeiten zur Förderung des Pflanzenwachstums.
Nutrient deficiencies in soil, mainly in phosphorus (P) and nitrogen (N), coupled to salinity and the impoverishment of agricultural soils, are a severe problem for agricultural production worldwide. Therefore, there is an urgent need for research and development of more suitable agricultural practices in order to reduce unfavorable conditions, and if possible, to restore the fertility of cultivated lands. The use of rhizobacteria, which promote plant growth (PGPR), can prove useful in developing strategies to facilitate plant growth under normal as well as under abiotic stress conditions. These bacteria offer benefits to plant hosts by promoting the uptake of soil minerals and protecting plants from environmental stresses. The thesis evaluates the role of native PGPR associated with maize as potential bio-inoculants for plants growth in Cameroon. We hypothesized that native bacterial communities from Cameroon include a high potential of bacteria helping the plant cope with unfavorable conditions. Here, we provide for the first time a comprehensive phylogenetic affiliation of cultivable bacterial communities associated with maize rhizosphere grown in Cameroon in relationship to their potential plant growth-promoting abilities.

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Maher, Mary. "Effects of Plant Growth-Promoting Bacteria and Fungi on Strawberry Plant Health, Fruit Yield, and Disease Susceptibility." DigitalCommons@CalPoly, 2021. https://digitalcommons.calpoly.edu/theses/2335.

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Studies on plant growth-promoting rhizobacteria (PGPR) and fungi (PGPF) as biostimulants have shown significant positive effects on plant health, fruit yield, or pest management. However, very few published studies to date have been specific regarding their effects on strawberries (Fragaria × ananassa), particularly on soilborne disease prevalence in organically grown strawberries. Empirical data on the results of using these products in commercial growing applications under various conditions would be highly valuable, especially for organic growers who have limited synthetic chemical pesticides, herbicides and fertilizers registered for use. The objective of this study is to evaluate the efficacy of biostimulant supplementation on strawberries for improving fruit yield, fruit quality, and plant health in both high-tunnel, open-sided ‘hoophouse’ and field conditions. This study consisted of two research projects. The first project investigated the effects of commercially available PGPR-based biostimulant products on strawberry plant health. The three products contained differing proprietary combinations of PGPR, primarily from the Bacillus and Lactobacillus genera. Plants were grown in two different soil types: sandy and clay, in order to investigate the effects of biostimulant supplementation in different soil conditions. In fall of 2018, 160 ‘Monterey’ strawberry plants were grown in an outdoor hoophouse in 3-gallon pots. Plants were either treated monthly with a single bacterial biostimulant product (EM-1, Accomplish LM, or Armory), or left untreated as a control. Plants were grouped into 20 blocks, each block comprised of 8 plants (each of the four treatments replicated in both soil types). Fruit yield (g), fruit sugar content (Brix), and leaf SPAD absorbance levels were measured weekly from January 27 to June 26, 2019. The treatments tested had no significant effects on fruit yield, leaf SPAD absorbance or Brix; soil type, however, did significantly impact fruit yield, with higher yields in sandy soil. The second project was a field trial beginning in spring of 2020, in collaboration with Rutiz Farms in Arroyo Grande, CA, involving a total of 480 ‘Chandler’ strawberry plants. The farm is organically managed and has a history of soilborne diseases, including Verticillium dahliae. These plants were either treated monthly with one of three microbial biostimulant products: a product containing a proprietary strain of Trichoderma harzianum biocontrol fungus (TrichoSym), and two of the same PGPR-based products used the previous year (Accomplish LM and Armory); or left untreated as a control. The experiment was laid out in a randomized complete block design with four blocks, with each block consisting of 4 plots for each of the 4 treatments; each plot contained 30 plants. Fruit yield (g) per plot was measured weekly throughout the 2020 growing season and phenotypic disease incidence was measured biweekly. Soil samples were taken at three different points throughout the season, cultured on selective media, and analyzed to obtain estimates of V. dahliae colony-forming units (CFU) per gram soil. The treatments tested had no significant effect on fruit yield, phenotypic disease incidence, or V. dahliae CFU/g soil. The results are inconclusive as to whether this lack of effect is due to viability of the products themselves, ineffective application techniques resulting in lack of rhizosphere colonization, or some combination of these. Further research is needed to determine whether or not supplementation with microbial biostimulants can produce reliable, beneficial results in strawberries.

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Yusran. "Use of plant growth-promoting rhizobacteria (PGPR) to improve mycorrhization, nutrient acquisition and growth of vegetable plants affected by soilborne pathogens." Göttingen Cuvillier, 2009. http://d-nb.info/997890959/04.

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Daigneault, Luce. "A study of crude and fractionated willow extracts for rooting /." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=63114.

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Timmusk, Salme. "Mechanism of Action of the Plant Growth Promoting Bacterium Paenibacillus polymyxa." Doctoral thesis, Uppsala universitet, Institutionen för cell- och molekylärbiologi, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-3773.

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Paenibacillus polymyxa belongs to the group of plant growth promoting rhizobacteria (PGPR). Activities associated with P. polymyxa-treatment of plants in earlier experiments include, e.g., nitrogen fixation, soil phosphorus solubilization, production of antibiotics, auxin, chitinase, and hydrolytic enzymes, as well as promotion of increased soil porosity. My thesis work showed that, in stationary phase, P. polymyxa released the plant hormone cytokinin isopentenyladenine, in concentrations of about 1.5 nM. In a gnotobiotic system with Arabidopsis thaliana as a model plant, it was shown that P. polymyxa-inoculation protects plants; challenge by either the pathogen Erwinia carotovora (biotic stress) or induction of drought (abiotic stress) showed that pre-inoculated plants were significantly more resistant than control plants. By RNA-differential display on RNA from P. polymyxa-treated or control plants, changes in gene expression were tested. One mRNA, encoding ERD15 (drought stress-responsive gene) showed a strong inoculation-dependent increase in abundance. In addition, several biotic stress-related genes were also activated by P. polymyxa. Antagonism towards the fungal pathogens Phytophthora palmivora and Pythium aphanidermatum was studied. P. polymyxa counteracted the colonization of zoospores of both oomycetes on A. thaliana roots, and survival rates of plants treated with P. polymyxa were much higher when challenged by P. aphanidermatum. Using a green fluorescent protein-tagged isolate of P. polymyxa, colonization of A. thaliana roots was investigated. Two main conclusions can be drawn. Firstly, the bacterium enters the root tissue (but not leaves) and is abundantly present in intercellular spaces. Secondly, the root becomes severely damaged, indicating that – under some conditions – P. polymyxa is a "deleterious bacterium", and in others it promotes growth. Based on work presented in my thesis, I argue that a balance between the activities of a PGPR, the genetic background and physiological state of a plant, and the environmental conditions employed in test systems, ultimately determines the resulting effect.

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Liu, Wing-yee, and 廖泳怡. "Discovery and genome analysis of the plant growth-promoting endophyticbacterium Enterobacter cloacae ENHK." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hub.hku.hk/bib/B49858750.

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Enterobacter cloacae strain ENHK is a Gram-negative endophyte belonging to the family Enterobacteriacae. Initially considered as an unknown bacterium, E. cloacae ENHK was first isolated from a diseased pepper (Capsicum annuum) plant infected by the bacterial plant pathogen Ralstonia solanacearum in Hong Kong in 2010. A pure isolate was obtained for whole genome sequencing. De novo shortgun and paired-end sequencing by 454 GS Junior platform were applied to obtain a draft genome sequence of E. cloacae ENHK containing 36 contigs in one scaffold. Gaps were closed by PCR and primer walking using Sanger sequencing to produce the first complete genome sequence of a plant-associated strain of E. cloacae. The genome size of E. cloacae ENHK consists of a single chromosome of 4,726,582kb, with a GC content of 55.1%. Gene annotation and analysis was performed using NCBI Prokaryotic Genomes Automatic Annotation Pipeline (PGAAP) and further annotation and comparative genome analysis was performed by the SEED-based automated annotation system provided by the RAST server. Comparative genome analysis indicated that E. cloacae ENHK shares major genomic features with Enterobacter sp.638 that is characterized for its plant-growth promoting and endophytic behaviors. Further genome analysis revealed antagonistic potentials of E. cloacae ENHK against other microbes by possessing antagonistic mechanisms which involve microbial competition, production of antimicrobial compounds and induction of plant defense response. Candidates of Chitinases and type VI secretion system associated rhs-related genetic element were identified and their potential antibacterial activity were investigated. E. cloacae ENHK was further demonstrated to suppress the growth of several plant pathogenic fungal species Alternaria sp., Choanephora infundibulifera, Colletotrichum capsici, Didymella bryoniae, Fusarium oxysporum, Sclerotinia sclerotiorum and Sclerotinia rolfsii and a plant pathogenic bacterial species Ralstonia solanacearum. Among the publicly available completed genome sequences of the Enterobacter species complex, E. cloacae ENHK is most closely related to E. cloacae subsp. cloacae ATCC13047, an opportunistic human pathogen. A comparative genome analysis showed that critical factors involving human pathogenesis in terms of virulence and specific adhesion were identified in the variable genomic regions in E. cloacae subsp. cloacae ATCC 13047 and are absent in E. cloacae ENHK. In addition, two microbial competition related type VI secretion systems (T6SS) were found conserved in both E. cloacae strains. Phylogenetic analysis revealed that the two systems were associated with other plant-associated and human/animal-associated species respectively in the Enterobacteriaceae. The results indicated that T6SSs may provide the E. cloacae strains fitness advantages for microbial competition in the microflora of a diverse environment. In short, comparative genome analysis suggested that the conserved chromosomal regions retain the general physiological and survival of the species, while variable genomic regions play a critical role in determining the functional differences of the pathogenic E. cloacae subsp. cloacae ATCC13047 and the endophytic E. cloacae ENHK. Finally, significant findings derived from the current thesis research are summarized and potential applications of E. cloacae ENHK in agricultural, medical and industrial areas, as well as future prospectus are discussed.
published_or_final_version
Biological Sciences
Doctoral
Doctor of Philosophy

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Koumoutsi, Alexandra. "Functional genome analysis of the plant-growth promoting bacterium Bacillus amyloliquefaciens strain FZB42." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2007. http://dx.doi.org/10.18452/15586.

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Bacillus amyloliquefaciens FZB42 ist ein im Boden weit verbreitetes Bakterium. Es kolonisiert Pflanzenwurzeln und werde als Biodünger verwendet, da sie in der Lage sind, Pflanzenwachstum zu fördern. Der domestizierte Stamm B. subtilis 168 ist eng verwand mit B. amyloliquefaciens FZB42, fördert jedoch kein Pflanzenwachstum. Als ein erster Ansatz zur Ermittlung von Gendifferenzen zwischen FZB42 und B. subtilis 168 - wobei zum damaligen Zeitpunkt nur die Genomsequenz letzteren Organismus bekannt war - wurde die Supression Subtractive Hybridisation (SSH) angewandt. Hierdurch wurden mehrere einzigartige Gene in B. amyloliquefaziens identifiziert. Unterdessen beteiligte sich unser Labor in Kollaboration mit dem GenoMik Network in Göttingen an einem Projekt, dessen Ziel die komplette Sequenzierung des Genoms von B. amyloliquefaciens war. Der Hauptanteil der Arbeit, sowie die Koordination des gesamten Projekts wurden von Xiao-Hua Chen und mir selbst durchgeführt. B. amyloliquefaciens FZB42 besitzt die srf, fen, pks1 (bae), bac und dhb Operons, welche für die Synthese von Surfactin, Fengycin, Bacillaene, Bacilysin und Bacillibactin verantwortlich sind und die ebenfalls im Genom von B. subtilis 168 enthalten sind. Das Genom von B. amyloliquefaciens FZB42, beinhaltet die bmy Gencluster, die die Synthese von Bacillomycin D kontrolliert. Ein weiteres in dieser Arbeit verfolgtes Ziel war die Identifizierung der regulatorischen Wege, die die Expression von Bacillomycin D steuern. Es wurde gezeigt, dass globale Regulatoren, wie beispielsweise DegU, DegQ und ComA, die alternativen Sigmafaktoren sigB und sigH und ein neuartiges Rap-Protein die transkriptionale Aktivität des in dieser Arbeit identifizierten Hauptpromotors des bmy-Operons beeinflussen. Es wurde gezeigt, dass DegU seine Effekte nach direkter Bindung an zwei unterschiedliche Regionen im bmy-Promotor ausübt. Es wurde außerdem gezeigt, dass DegU abgesehen von der Aktivierung des Hauptpromoters des bmy-Operons eine zusätzliche, vermutlich eine post-transkriptionale Rolle spielt. Auf ähnliche Weise erwies sich YczE, ein Membranprotein unbekannter Funktion, das neben sfp kodiert liegt, als essentiell für die Bacillomycin D-Produktion. Der Effekt wurde auf einem post-transkriptionalen Level ausgeübt und war unabhängig von DegU.
Bacillus amyloliquefaciens FZB42 is widely distributed in the soil. It colonizes the plant roots and is used as bio-fertilizer, since they can promote plant growth.The domesticated strain of B. subtilis 168 is closely related to B. amyloliquefaciens FZB42, but does not promote plant growth. As a first approach to detect gene differentiation between FZB42 and B. subtilis 168, and since only the genome sequence of the latter was known at that point, Suppression Subtractive Hybridization (SSH) was employed. Thereby, several unique genes of B. amyloliquefaciens FZB42 could be identified. Meanwhile, our laboratory became engaged in a project aiming to define the complete genome sequence of B. amyloliquefaciens FZB42, in collaboration with the GenoMik Network in Göttingen. The major part of the work and the co-ordination of the whole process were performed by Xiao-Hua Chen and myself. B. amyloliquefaciens FZB42 possesses the srf, fen, pks1 (bae), bac and dhb operons, which are also shared by B. subtilis 168. In addition, the genome of B. amyloliquefaciens FZB42 contains the bmy gene clusters, which controls the synthesis of bacillomycin D. A further issue pursued in this work was to identify the regulatory pathways that govern the expression of bacillomycin D. Global regulators, such as DegU, DegQ and ComA, the alternative sigma factors, sigB and sigH, and a novel Rap protein were found to affect the transcriptional activation of the main promoter of the bmy operon identified in this work. In particular, DegU was shown to mediate its effects, after binding directly to two sites at the bmy promoter region. DegU was shown to play an additional role on bacillomycin D production, presumably a post-transcriptional one. Similarly, YczE, a membrane protein of unknown function, encoded adjacently to sfp proved to be essential for bacillomycin D production, but dispensable for the production of the rest peptide antibiotics produced by B. amyloliquefaciens FZB42. The effect was mediated at a post-transcriptional level and was independent of DegU.

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19

Mariappan, Aruljothi. "Molecular mechanisms controlling bacilysin biosynthesis in plant growth promoting rhizobacterium - Bacillus amyloliquefaciens FZB42." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2012. http://dx.doi.org/10.18452/16554.

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Bacillus amyloliquefaciens FZB42 ist ein grampositives Bakterium, das in der Rhizosphäre das Pflanzenwachstum fördert (PGPR - Plant Growth Promotion) und pathogene Organismen hemmt. Abgesehen von dieser Fähigkeit produziert es eine Vielzahl von sekundären Metaboliten, die sowohl ribosomale als auch nicht-ribosomale Peptide umfassen. In dieser Arbeit erfolgte die Untersuchung der transkriptionellen Aktivierung und Regulation der Bacilysin- Biosynthese an den Promotoren der bac- und ywfH- Gene. Durch 5´-Deletionsanalysen wurde der Promotor von Bacilysin identifiziert. Die A (Sigmafaktor A) - abhängige Transkription startet über die konservierten Promotorelemente (-10 und -35) von den bac- und ywfH Genen. Die Untersuchungen der Promotoraktivitäten vom Wildtyp und den erzeugten Regulationsmutanten erfolgten über in vivo ß-Galaktosidase-(Reporter)-Assays. Die Ergebnisse der Reporter-Aktivitäten zeigten, dass Transkriptionsregulatoren die Expression der Bacilysin- Gene aktivieren. Mehrere globale Regulatoren wie DegU, ComA, Hpr und AbrB beeinflussen die Genexpression. In dieser Arbeit wurde mithilfe von DNaseI Footprinting-Analysen die DegU-Bindung an die bac- und ywfH- Promotoren bestätigt.Die negative Regulation der Bacilysin-Biosynthese wird durch den Regulator der transienten Phase Hpr bewerkstelligt. Eine direkte Hpr-Bindung an bac Promotor wurde mit DNaseI Footprint-Analysen gezeigt. Der Promotor des monocistronischen Gens ywfH wurde aber durch Hpr nicht beeinflusst. Die anderen Transkriptionsregulatoren, wie ComA und AbrB, regulieren die Genexpression von Bacilysin indirekt über DegQ und Hpr. In dieser Arbeit konnte demonstriert werden, dass der globale Regulator AbrB den Promotor vom hpr-Gen direkt kontrolliert. Zusammenfassend liefert diese Studie neue Informationen über die genetische Regulation der Bacilysin- Biosynthese in B. amyloliquefaciens FZB42.
Bacillus amyloliquefaciens FZB42 is a Gram-positive, pathogen-suppressing and plant-growth promoting rhizobacterium. Apart from this ability, it produces a vast array of secondary metabolites, which includes both ribosomal and non-ribosomal peptides. In this work, the transcriptional activation and regulation of bacilysin biosynthesis were studied at the promoters of bac and ywfH genes. The promoter of bacilysin was identified using 5''-deletion analysis. Sigma factor A (σA) was found to start transcription via conserved promoter elements (-10 and -35) of bac and ywfH genes. lacZ reporter fusion studies were performed in wild type and regulatory mutants. The results show the involvement of transcriptional regulators to activate the expression of bacilysin genes. Several global regulators such as DegU, ComA, Hpr and AbrB were identified and found to influence gene expression. In particular, I confirmed DegU binding in bac and ywfH promoters using radioactive DNase I footprinting. Furthermore, Hpr, a transition state regulator was found negatively to control bacilysin biosynthesis. Hpr binding to bac promoter was demonstrated using radioactive DNase I footprinting. Remarkably, Hpr does not influence the promoter of the monocistronic gene, ywfH. The other transcriptional regulators, such as ComA and AbrB, were correlated indirectly to affect the gene expression of bacilysin via DegQ and Hpr, respectively. The gene regulation of hpr was studied in this work. It was demonstrated that AbrB, a global regulator, directly controls the promoter of the hpr gene. However, the consensus sequence for AbrB binding was not identified, since it covers the entire promoter region in the DNA-protein interaction study. To conclude, this study provides new information regarding the genetic regulation of bacilysin biosynthesis in B. amyloliquefaciens FZB42.

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Mia, Junaid. "Isolation and characterization of plant growth promoting endophytic bacteria from Eriocephalus africanus roots]." University of the Western Cape, 2018. http://hdl.handle.net/11394/6260.

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Magister Scientiae - MSc (Biotechnology)
Endophytic bacteria are known to have an endosymbiotic relationship with plants and provide them with many beneficial properties. These bacteria stimulate plant hormones, provide protection from pathogens and increase nutrient availability in the environment. In this study some of these potential growth factors were tested. Endophytic bacteria have the potential to be of great value for the increase of crop production. They offer a variety of processes that aid in plant growth promotion in an ecofriendly manner. The use of endophytic bacteria provides a cheaper and cleaner approach compared to industrial made fertilizers. They also have potential uses in bioremediation to clean the environment polluted by industrial processes. Endophytes were isolated and showed significant growth improvement. Each isolate displayed different morphologies. Isolates were tested for classical growth promotion mechanisms such as the ability to solubilize phosphate, Indole-3-acetic acid and siderophore production. Inductively Coupled Plasma Optical Emission Spectrometry was performed to measure the effect of the isolates on the plants nutrient profile. The isolates were then tested again while the plants were under heavy metal stress to determine if they were still capable of growth promotion. The plants were then assayed for cell death using Evans blue and biomass was measured to determine the effect of vanadium stress. Inductively Coupled Plasma Optical Emission Spectrometry was performed again to assess the change in nutrient profile while under vanadium stress.
2021-08-31

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Mdodana, Ntombizanele Thobela. "The effects of the synthetic strigolactone GR24 on Arabidopsis thaliana callus culture." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/71963.

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Thesis (MSc)--Stellenbosch University, 2012.
ENGLISH ABSTRACT: Plant growth promoting substances (PGPS) are emerging as useful tools in the investigation of important plant growth traits. Two PGPS, smoke-water derived from burning plant material and a synthetic strigolactone analogue, GR24, have been reported to regulate a wide variety of developmental and growth processes in plants. These PGPS are beginning to receive considerable attention in the area of improving plant biomass yield and production. Variation in growth between plants is a major impediment towards the complete understanding of the intrinsic processes that control biomass production. Callus cultures of the model plant Arabidopsis thaliana could overcome some of these hindrances. However, the suitability of these callus cultures as a model system for plant biomass production must be established first. This study aimed at using A. thaliana callus cultures as a platform to study the plant growth promoting activities of smoke-water and GR24. The first part of this study was conducted to develop an optimal protocol for inducing A. thaliana callus formation. Wild-type A. thaliana Col-O, as well as strigolactone deficient and insensitive mutants (max1-1, max2-1, max2-2, max3-9 and max4-1) were cultured for callus induction. Hypocotyl and leaf explants were cultured onto MS media supplemented with different hormone concentrations of 2,4-D and kinetin (2:2 mg/L 2,4-D:kinetin and 0.5:0.05 mg/L 2,4-D:kinetin). Both media proved suitable for callus induction of all genotypes, with max1-1 showing the highest efficiency (83.33% and 92.22%) of callus induction. Calli were then used as a platform for future investigations into the effects of smoke-water and GR24. Secondly, this study examined the effects of smoke-water and GR24 on wild-type A. thaliana Col-O callus. Basic physiological studies were conducted to determine if these two compounds would positively affect callus growth, as was shown in previous studies using whole plants. Calli cultivated on MS media containing the two different hormone concentrations were transferred onto the same fresh MS medium, supplemented with either smoke-water or GR24. Growth promotion by smoke-water and GR24 in calli was characterized by a significantly increased mass (biomass). Calli were additionally transferred onto MS medium containing either auxin only or kinetin only and supplemented with GR24 or smoke-water. In the auxin only system, increased mass was recorded for both GR24 and smoke-water treatments, while these two compounds seemed to reduce growth in the kinetin only system. The positive growth stimulatory effect observed for the auxin only system could be attributed to the synergistic relationship between auxin and strigolactones, whilst the reduced mass in the latter system could be due to the antagonistic interaction between strigolactones and cytokinins. Finally, this study has discovered a dual role of strigolactones in biomass accumulation and adventitious root formation for Arabidopsis thaliana callus. On an auxin- and cytokinin-free MS medium supplemented with GR24, calli of Arabidopsis thaliana strigolactone deficient mutants (max1-1 and max4-1) and the wild-type Col- O, but not the strigolactone response mutant (max2-2), showed enhanced biomass accumulation. In addition to this, the max4-1 mutant and wild-type Col-O demonstrated enhanced adventitious rooting, which was not apparent in max2-2. Together these data suggested that the biomass accumulation and the adventitious rooting activities of GR24 in Arabidopsis thaliana calli are controlled in a MAX2- dependent manner. The interaction between strigolactone, auxin and cytokinin signalling pathways in regulating these responses appears to be complex. Gene expression profiling showed regulation of stress-related genes such as B-box transcription factors, CALCINEURIN B-LIKE and RAP4.2 Genes encoding hormones associated with stress (ABA, ethylene) and defence mechanisms (JA) were upregulated. Expression of stress related genes indicated clues on some kind of stress mediation that might be involved during the regulation of the rhizogenic response. Conversely, smoke-water treatment could not enhance the biomass of the calli and nor could it induce adventitious rooting in the absence of auxin and cytokinin. This observation strongly emphasized the distinct roles of these two compounds, as well as the importance of the interaction and ratio of auxin and cytokinin in callus growth. This study has demonstrated a novel role of strigolactones in plant growth and development, i.e. enhancement of biomass production in callus cultures. Secondly the enhanced adventitious rooting ability is in agreement with recently published literature on the role of strigolactones in regulating root architecture. In vitro callus production is advantageous to plant sciences. It creates an opportunity for increasing plant material for cultivation and offers the use of cell cultures that accurately mimic specific growth responses. It could greatly contribute to the study of intricate regulatory and signalling pathways responsible for growth and development in plants. Because the regulation of plant biomass production is very complex and the molecular mechanisms underlying the process remain elusive, it is of paramount importance that further work be done in order to gain more in-depth insights and understanding of this aspect and subsequently improve efficiency and returns when applying biotechnology tools on commercially important crop plants.
AFRIKAANSE OPSOMMING: Verbindings wat plantgroei bevorder (PGBV) het as nuttige alternatief ontstaan om plant groei te ondersoek. Rook-water, afkomstig van verbrande plant material, en ‘n sintetiese strigolaktoon analoog, GR24, wat ‘n α, β-onversadigde furanoon funksionele groep in gemeen het, is vir die regulering van ‘n wye verskeidenheid ontwikkelings- en groei prosesse in plante verantwoordelik. Tans ontvang hierdie PGBVs aansienlik aandag in die area van die verbetering van plant biomassa opbrengs en -produksie. Die variasie in groei tussen plante is ‘n groot hindernis om die intrinsieke prosesse wat biomass produksie beheer, volledige te verstaan. Deur gebruik te maak van kallus kulture van die model plant Arabidopsis thaliana kan van hierdie hindernisse oorkom word. Tog moet die geskiktheid van kallus kulture as ‘n model sisteem vir plant groei biomass produksie eers gevestig word. Die doel van hierdie studie was om A. thaliana kallus kulture as ‘n platform vir die studie van die plantgroei bevorderingsaktiwiteite van rook-water en GR24 te gebruik. Die eerste deel van die studie is uitgevoer ten einde ‘n optimale protokol vir die induksie van A. thaliana kallus produksie te ontwikkel. Wilde tipe Col-0, asook strigolaktoon afwesige en onsensitiewe mutante (max1-1, max2-1, max2-2, max3-9 en max4-1) is vir kallus induksie gekultiveer. Hipokotiel en blaar eksplante is op MS medium wat verskillende hormoon konsentrasies van 2,4-D en kinetien (2:2 mg/L 2,4-D:kinetien en 0.5:0.05 mg/L 2,4-D:kinetien) bevat, oorgedra. Beide media was geskik vir kallus induksie van al die genotipes, met max1-1 wat die hoogste effektiwiteit (83.33% en 92.22%) van kallus induksie getoon het. Kalli is daarna as ‘n platform vir toekomstige navorsing i.v.m die effek van rook-water en GR24 gebruik. Tweedens ondersoek die studie die effek van rook-water en GR24 op wilde tipe Col-0 kallus. Basiese fisiologiese studies is uitgevoer om te bepaal of die twee verbindings ‘n positiewe effek op kallus groei toon soos aangedui in vorige studies waar intakte plante gebruik is. Kallus wat op MS medium wat die twee verskillende hormoon konsentrasies bevat gekultiveer was, is op dieselfde vars MS medium, wat addisioneel óf rook-water óf GR24 bevat, oorgedra. Die stimulering van groei van kalli deur rook-water en GR24 is deur ‘n merkwaardige toename in massa (biomassa) gekenmerk. Kallus is additioneel op MS medium wat slegs óf ouksien óf kinetin bevat (gekombineer met GR24 of rook-water behandeling), oorgedra. In die sisteem waar slegs ouksien toegedien is, is ‘n toename in massa waargeneem vir beide GR24 en rook-water behandelinge. In teenstelling hiermee, het die twee verbindings in die sisteem waar slegs kinetin toegedien is, ‘n vermindering in groei meegebring. Die positiewe groei stimulerende effek wat waargeneem is vir die sisteem waar slegs ouksien toegedien is, kan toegedra word aan die sinergistiese verhouding tussen die ouksien en strigolaktone; terwyl die verlaagde massa in die laasgenoemde sisteem aan die antagonistiese interaksie tussen strigolaktone en sitokiniene toegedra kan word. Laastens het hierdie studie het ‘n gelyktydige rol van strigolaktone vir biomassa akkumulasie en bywortelvorming in Arabidopsis thaliana kallus ontdek. Kallus van A. thaliana strigolaktoon afwesige mutante (max1-1 en max4-1) en die wilde tipe Col-0 (maar nie die strigolaktoon reagerende mutant (max2-2) het op ‘n ouksien en sitokinien vrye MS medium wat GR24 bevat ‘n verhoogde biomassa akkumulasie getoon. Die max4-1 mutant en wilde tipe Col-0 het verhoogde bywortelvorming getoon, wat nie so opmerklik by max2-2 was nie. Hierdie data het tesame voorgestel dat die biomassa akkumulasie en die bywortelvormingsaktiwiteite van GR24 in Arabidopsis thaliana kallus op ‘n MAX2-afhanklike wyse beheer word. Die interaksie tussen strigolaktoon, ouksien en sitokinien sein transduksie paaie vir die regulering van hierdie reaksies blyk kompleks te wees. Die geen uitdrukkingsprofiel het die regulering van stres verwante gene soos B-boks transkripsie faktore, CALCINEURIN B-LIKE en RAP4.2, getoon. Gene wat vir hormone wat aan stres (ABA, etileen) en verdedigingsmeganismes (JA) verwant is, is opgereguleer. Die uitdrukking van stress verwante gene dui op tekens van ‘n ander tipe stres bemiddeling wat dalk by die regulering van die risogeniese reaksie betrokke kan wees. In teenstelling, rook water behandeling kon nie die kallus biomassa verhoog nie en dit kon ook nie die bywortelingvorming in die afwesigheid van ouksien en sitokiniene induseer nie. Hierdie waarneming is ‘n sterk bevestiging vir die uitsonderlike rol van die twee verbindings, asook die belang van die interaksie en verhouding van ouksien en sitokinine vir die groei van kallus. Hierdie studie toon op ‘n nuwe rol van strigolaktoon in plant groei en ontwikkeling, d.w.s die verhoogde biomassa produksie in kallus kulture. Tweedens, die verhoogde bywortelvormingsvermoë is in ooreenstemming met literatuur wat onlangs gepubliseer is i.v.m die rol van strigolaktone in die regulering van wortel argitektuur. Die in vitro produksie van kallus is voordelig in plant wetenskappe. Dit skep ‘n geleentheid vir die vermeerdering van plant materiaal vir kultivering en bied die gebruik van selkulture wat spesifieke groei reaksies op ‘n merkwaardige wyse akkuraat namaak. Dit kan grootliks bydra tot die studie van die delikate regulatoriese en sein transduksie paaie wat vir groei en ontwikkeling van plante verantwoordelik is. Aangesien die regulering van plant biomassa produksie baie kompleks is en die molekulêre meganismes vir die proses onbekend bly is dit van grootskaalse belang dat meer werk gedoen word om ‘n meer in diepte insig en kennis van die aspekte en gevolglike verbetering van effektiwiteit en wins te kry deur die toepassing van biotegnologiese metodes op die gewas plante wat van kommersiêle belang is.

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22

Gouws, Liezel Michelle, and Jens Kossmann. "The molecular analysis of the effects of lumichrome as a plant growth promoting substance." Thesis, Stellenbosch : University Stellenbosch, 2009. http://hdl.handle.net/10019.1/4825.

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PhD
Dissertation presented for the degree of Doctor of Philosophy at Stellenbosch University
Embargo(30)lift date 2009-12-31 plt 2010
ENGLISH ABSTRACT: Through powerful signal molecules, rhizobacteria affect fundamental processes in plants. In recent years, a number of novel rhizobial molecules have been identified that positively affect plant growth and development. Previous studies have shown that Sinorhizobium meliloti, which form symbiotic relationships with leguminous plants, increases CO2 availability by enhancing root respiration in alfalfa. The active compound was identified as lumichrome, a previously unrecognized rhizosphere signal molecule that has been shown to promote plant growth in various studies. Lumichrome is a common breakdown product of riboflavin and produced by both chemical and biological factors. Various studies on lumichrome have proven its growth promoting effect in the interaction with plants. The mechanism through which lumichrome increases plant growth remains to be clarified. This study provides new insight into the molecular effects of the plant growth promoter lumichrome on the root metabolism of plants. The main aim of the work presented in this thesis was to investigate the molecular mechanism of the plant growth promoting substance lumichrome in the roots of the model plants Lotus japonicus and Solanum lycopersicon (tomato). To asses the impact of lumichrome on the root metabolism of Lotus japonicus and tomato and identify key genes involved in the growth stimulation, a comprehensive profile of differentially expressed genes, proteins and metabolites was compiled. As the effects of lumichrome as a plant growth promoter have not previously been tested on Lotus japonicus and tomato, basic growth studies were completed to determine if lumichrome indeed elicits plant growth at nanomolar concentrations, as was proven in numerous previous studies. Both Lotus japonicus and tomato showed significant increases in root biomass when treated with 5 nM of lumichrome. The treatment with lumichrome caused complex changes in gene expression. Generally, transcript profiling showed that the categories that were predominantly affected by lumichrome in both Lotus and tomato, were genes associated with RNA regulation of transcription and signaling, protein synthesis/degradation/modification and stress and defence. Proteomic studies revealed that the majority of the differentially expressed proteins were down-regulated. Lumichrome seems to largely influence proteins involved in protein folding and down-regulate proteins involved in glycolysis. Proteomics studies revealed that GS1 (Lotus) and GAPDH (Lotus and tomato) were present in lower abundance in lumichrome treated roots, therefore targeted analysis utilizing northern blots, western blots and the measurement of enzyme activities were completed to determine and verify their specific role in the lumichrome mediated growth promotion. The results indicated that GAPDH and GS1 seem to be under post-translational modification. The influence of lumichrome on the metabolome of Lotus roots was immense, however minute in tomato roots. The knowledge gained in the parallel analyses of both Lotus japonicus and tomato aided us in finding key genes involved in the growth stimulation. Overall, one of the most significant observations was that for the first time to our knowledge, six genes related to defence and pathogen responses were identified that are concurrently expressed in both Lotus and tomato. Through identifying a small number of genes involved in mediating the growth stimulation, these can be used for their functional analysis in the future, using reverse genetics to provide more insight into the molecular mechanisms that are triggered by lumichrome as a plant growth promoter.
AFRIKAANSE OPSOMMING: Deur kragtige sein-molekules, beïnvloed rhizobakterieë basiese prosesse in plante. In die laaste jare is ŉ aantal nuwe molekules, afkomstig van rhizobakterieë, geidentifiseer wat plantgroei en ontwikkeling positief beïnvloed. Voorafgaande studies het bewys dat Sinorhizobium meliloti, wat simbiotiese verhoudings met peulplante aangaan, die beskikbaarheid van CO2 vermeerder deur wortel respirasie in alfalfa te verhoog. Die aktiewe komponent is as lumikroom geidentifiseer, 'n vroeë onerkenbare risosfeer sein-molekule, wat deur vorige studies bewys is dat dit plantgroei stimuleer. Lumikroom is ŉ algemene afbreekproduk van riboflavin en word geproduseer deur chemiese en biologiese faktore. Verskeie studies op lumikroom het bewys dat dit 'n groei stimuleerende effek het op die groei van plante as dit daarmee in wisselwerking tree. Die meganisme waarmee lumikroom plante groei verhoog, is nog nie opgeklaar nie. Hierdie studie verleen nuwe insigte in die molekulêre effekte van die plantgroei stimuleerende molekuul lumikroom op die wortel metabolisme van plante. Die hoofdoel van die werk wat voorgestel word in hierdie tesis, was om die molekulêre meganisme van die plantgroei stimuleerende stof, genaamd lumikroom, in die wortels van die model plante Lotus japonicus en Solanum lycopersicon (tamatie), te ondersoek. Om die uitwerking van lumikroom op die wortel metabolisme van Lotus japonicus en tamatie te bepaal, asook sleutelgene wat betrokke is by die groei stimulasie te identifiseer, is 'n breedvoerige profiel van differensiële uitgedrukte gene, proteïne en metaboliete saamgestel. Die effekte van lumikroom as 'n plantgroei stimuleerende stof is nog nooit op Lotus japonicus en tamatie getoets nie. Om díe rede is eers basiese plantgroei studies gedoen, om vas te stel of lumikroom inderdaad plantgroei teen nanomolare konsentrasies stimuleer, soos in vele voorafgaande studies bevestig is. Beide Lotus japonicus en tamatie het aansienlike verhogings in wortel biomassa getoon as dit met 5 nM lumikroom behandel is. Die behandeling van plante met lumikroom het komplekse veranderinge in geen-uitdrukking veroorsaak. Oor die algemeen het die transkrip-profiele gewys dat die kategorieë wat die meeste geraak is deur lumikroom behandeling, in beide Lotus en tamatie, gene was wat geassosieer word met RNS regulasie van transkripsie en sein-netwerke, proteïen sintese/degradasie/wysiging en stres en verdedigings prosesse in plante. Proteïen studies het gewys dat daar 'n daling in die meerderheid van die proteïen vlakke was wat differensieël uitgedruk was. Dit blyk dat lumikroom in 'n groot mate proteïene beïnvloed wat betrokke is by proteïen-vouing en veroorsaak dat proteïen vlakke van glikolitiese ensieme daal. Proteïen studies het gewys dat GS1 en GAPDH in laer vlakke teenwoordig was in lumikroom behandelde plante en daarom is 'n meer doelgerigte analiese gedoen deur gebruik te maak van "northern blot", "western blot" en deur die ensiem aktiwiteite te meet om hulle spesifieke rol in die lumikroom bemiddelde groei vas te stel. Die resultate wys daarop dat GAPDH en GS1 mag onder die invloed van na-translasionele verandering wees. Die invloed van lumikroom op die metabolietvlakke was groot in Lotus wortels, maar dit het minder van 'n effek gehad op tamatie wortels. Die kennis wat opgedoen is deur die paralelle analiese van beide Lotus japonicus en tamatie plante help ons om sleutel gene wat betrokke is by groeistimulasie te identifiseer. Een van die betekenisvolste waarnemings van hierdie studie was dat vir die eerste keer, sover ons kennis strek, ses gene wat almal betrekking het tot verdediging en patogene-reaksies, geidentifiseer is wat gelyktydig in beide Lotus en tamatie uitgedruk word. Deur 'n klein aantal gene te identifiseer, wat betrokke is by groeistimulasie, kan die gene in die toekoms vir funksionele analieses gebruik word deur van keerkoppeling-genetika gebruik te maak. Daardeur sal meer insig verkry word in die molekulêre meganisme wat deur lumikroom as 'n plantgroei stof veroorsaak word.

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Vives, Peris Vicente. "Interaction of citrus root exudates with plant growth promoting rhizobacteria under abiotic stress conditions." Doctoral thesis, Universitat Jaume I, 2018. http://hdl.handle.net/10803/461915.

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En la naturaleza las plantas liberan constantemente a la rizosfera una mezcla de metabolitos conocida como exudados radiculares. Su composición puede verse afectada por diferentes estímulos, incluyendo estreses abióticos como la salinidad o elevadas temperaturas. El Capítulo 1 demuestra que los portainjertos de cítricos citrange Carrizo y Citrus macrophylla exudan diferentes concentraciones de prolina y fitohormonas dependiendo del estrés abiótico y del genotipo. El Capítulo 2 estudia el efecto de dichos exudados de plantas de cítricos sometidas a salinidad y calor sobre las rizobacterias Pseudomonas putida KT2440 y Novosphingobium sp. HR1a, los cuales generalmente promueven su crecimiento. Además, se detectó la presencia de prolina y salicilatos en exudados a través del análisis de la expresión de los promotores PputA y PpahA de P. putida KT2442 y Novosphingobium sp. HR1a respectivamente. Finalmente, el Capítulo 3 muestra el efecto beneficioso de ambas bacterias en plantas de C. macrophylla sometidas a salinidad.
In nature, plants are constantly releasing a mixture of metabolites through the roots known as root exudates. Its composition can be affected by different stimuli, including abiotic stress conditions as salinity or high temperatures. Chapter 1 demonstrates that citrus rootstocks Carrizo citrange and Citrus macrophylla exude different concentrations of proline and phytohormones depending on the abiotic stress condition and the genotype. Chapter 2 studies the effect of citrus root exudates from salt- and heat-stressed plants on the rhizobacteria Pseudomonas putida KT2440 and Novosphingobium sp. HR1a, which generally promote their growth. Moreover, the presence of proline and salicylates in root exudates was also tested through the analyses of the expression of the promoters PputA and PpahA of P. putida KT2442 and Novosphingobium sp. HR1a, respectively. Finally, Chapter 3 reveals the beneficial effect of both bacterial strains in C. macrophylla plants subjected to salt stress conditions.

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Shishido, Masahiro. "Plant growth promoting rhizobacteria (PGPR) for interior spruce (Picea engelmannii x P. glauca) seedlings." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq25159.pdf.

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Domfeh, Yayra Ekui. "Variability in Plant Growth Promoting Properties Among Clinical and Environmental Isolates of Stenotrophomonas Maltophilia." Thesis, North Dakota State University, 2015. https://hdl.handle.net/10365/27925.

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Stenotrophomonas maltophilia has both negative and positive attributes by being a human pathogen and plant growth promoting rhizobacterium. This study sought to determine if environmental and clinical isolates of S. maltophilia are phenotypically distinct. A total of 18 S. maltophilia isolates from clinical and environmental sources were investigated. Under normal growing conditions, S. maltophila isolates did not enhance growth of canola seedlings. However, under sodium chloride stress (6 decisiemens per meter or 0.33% NaCl), canola seedlings inoculated with S. maltophilia isolates had significantly (P < 0.05) higher number of root branches (isolate D457), root length (D457, CDC 2004-33-01-01 and CDC 2007-23-08-03) and stem length (D457, CDC 2005-37-11-04 and CDC 2011-01-42) than the ?no bacteria? control. A number of S. maltophilia isolates protected canola plants from the growth limiting effects of Leptosphaeria maculans and Burkholderia cenocepacia. No clear evidence was found between clinical and environmental isolates based on phenotypic data.

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Nava, Diaz Cristian. "Role of plant growth-promoting rhizobacteria in integrated disease management and productivity of tomato." The Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=osu1135888331.

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Dashti, Narjes. "Plant growth promoting rhizobacteria and soybean nodulation, and nitrogen fixation under suboptimal root zone temperatures." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=42011.

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Soybean (Glycine max (L.) Merr.) is a subtropical legume that requires root zone temperatures (RZTs) in the 25 to 30$ sp circ$C range for optimal symbiotic activity. The inability of soybean to adapt to cool soil conditions limits its development and yield in short season areas. In particular, nodulation and N$ sb2$ fixation by this subtropical crop species is sensitive to cool (RZT). The objectives of this thesis were to determine whether or not PGPR could be used to help overcome the low RZT inhibition of soybean nodulation, to improve soybean nitrogen fixation and yield under field conditions and to determine the methods by which such increases occurred. The work reported in this thesis has demonstrated that PGPR can increase early season nodulation and total seasonal nitrogen fixation and yield of soybean growing in an area with cool spring soils. The ability of PGPR to stimulate soybean nodulation and growth was shown to be related to their ability to colonize soybean roots, and this was shown to be related to RZT. All steps in early nodulation were stimulated by the presence of PGPR. The beneficial effects of PGPR are exerted through a diffusible molecule excreted into the growth medium. The addition of genistein, a plant-to-bacteria signal molecule already shown to stimulate soybean N$ sb2$ fixation at low RZT, plus PGPR causes increases in soybean nodulation, N$ sb2$ fixation, and growth that were greater than those caused by the addition of PGPR alone, but only at 25 and 17.5$ sp circ$C, and not at 15$ sp circ$C RZT.

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Finyom, Cyprien William Bopda. "Characterisation of the endophytic bacterial communities associated with South African sorghum plants: looking for potential plant growth-promoting endophytes." Thesis, University of Western Cape, 2012. http://hdl.handle.net/11394/3431.

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>Magister Scientiae - MSc
The term endophyte is used to define all microorganisms that, during a part of their life cycle, colonize the internal tissues of a plant host. Many endophytes have been found to promote plant growth by acting either as biocontrol agents, biofertilizers or phytohormone producers. This study aimed to characterise the endophytic microbial community diversity associated with sorghum farmed in South Africa. Members of any common endophytic bacterial species identified during the study might in future studies be developed to improve sorghum production. Sorghum tissues (roots, shoots, stems) were sampled in three South African provinces (Free State, Limpopo and North West), each site being characterised by the use of different agricultural practices. Denaturing gradient gel electrophoresis (DGGE) and terminal restriction fragment length polymorphism (T-RFLP) analyses were used to characterise the endophytic bacterial communities. The analysis clearly demonstrated that the endophytic bacterial community structure in the three sorghum tissue types differed, suggesting that endophyte colonization is tissue-specific. The endophytic bacterial community structure is quite similar in each tissue when comparing the populations present in the sampling sites. In the sorghum endophytic microbial communities, common bacterial species were identified using molecular tools: The cyanobacterium Synechococcus and Staphylococcus saprophyticus were identified in the root samples. Pantoea sp., Erwinia sp., Enterobacter sp. and Klebsiella sp. were found in all shoot samples. Nocardia fluminea, Bacillus cereus and Microbacterium sp. were isolated as common shoot endophytic bacteria. This study defines, for the first time, the endophytic bacterial species associated with South African sorghum plants. These common endophytic bacterial species can be used to enhance the yield of sorghum crops.

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Cantabella, Velázquez Daniel. "Elucidating the plant growth-promoting effects of three microorganisms on deciduous fruit tree plants using in vitro culture conditions." Doctoral thesis, Universitat de Lleida, 2021. http://hdl.handle.net/10803/672442.

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El cultiu in vitro de teixits vegetals és una tècnica molt utilitzada per a l’obtenció d’importants quantitats de material genèticament idèntic i lliure de malalties. No obstant això, en alguns cultius de fruiters, aquesta tècnica es pot veure limitada per la baixa capacitat d’arrelament i aclimatació d’alguns genotips, així com per las grans pèrdues ocasionades per la presència de contaminacions endòfites. L’ús de microorganismes que milloren el creixement de plantes pot constituir una alternativa interessant gràcies a la seva capacitat de produir hormones vegetals i controlar el creixement de patògens. A més a més, també és important desenvolupar productes basats en aquests microorganismes per a l’escalat de la seva aplicació a camp. En aquesta tesi, els tres microorganismes Pseudomonas oryzihabitans PGP01, Cladosporium ramotenellum PGP02 i Phoma spp. PGP03 es van aïllar de cultius in vitro contaminats de Prunus i Pyrus que mostraven un millor creixement que els no contaminats. En plantes produïdes a partir d’embrions de nectarina rescatats in vitro (Capítol 1), es va demostrar que P. oryzihabitans PGP01 augmentava el desenvolupament radicular que afavoria la seva aclimatació en hivernacle. En portaempelts comercials micropropagats in vitro (Capítol 2), C. ramotenellum PGP02 i Phoma spp. PGP03 milloraven el percentatge d’arrelament in vitro, d’un 56,3% a un 100%, en explants tractats amb IBA del portaempelt difícil d’arrelar Py12. En el mateix capítol, P. oryzihabitans PGP01 també promogué el desenvolupament de les arrels del porta-empelt de Prunus RP-20. Tots aquests resultats podrien estar relacionats amb la producció de IAA per part dels tres microorganismes. Mitjançant l’ús de mutants d’Arabidopsis thaliana, es va suggerir que les modificacions en les arrels induïdes per P. oryzihabitans PGP01 podrien estar mediades per les estrigolactones (SLs) i el glutatió (GSH) (Capítol 3). En un cultiu en medi líquid (Capítol 4), es va observar que els efectes en les arrels produïts per P. oryzihabitans PGP01 podrien estar mediats pel contingut d’auxines en el medi de cultiu. A més a més, utilitzant aquest mateix sistema, en presencia de C. ramotenellum PGP02, es va suggerir un efecte del baix pH en el medi de cultiu sobre el creixement d’endòfits en plantes de RP-20. Aquesta hipòtesi va quedar demostrada al Capítol 5, verificant que un pH àcid, en absència de microorganismes, reduïa la concentració d’endòfits sense afectar la multiplicació in vitro. Finalment, es van provar tres subproductes de la industria de la patata, tomàquet i cereals per a l’elaboració d’ún medi de cultiu barato per la producció de P. oryzihabitans PGP01. El creixement d’aquest bacteri en un medi basat en subproductes de patata es va obtenir un creixement màxim de 4.4x109 UFC mL-1 sense afectar la seva activitat biològica (Capítol 6). Els resultats obtinguts aporten noves aproximacions sobre l’ús de microorganismes beneficiosos com alternatives més sostenibles per a promoure el creixement de plantes in vitro.
El cultivo in vitro de tejidos vegetales es una técnica muy útil para obtener grandes cantidades de material genéticamente idéntico y libre de enfermedades. Sin embargo, esta técnica se ve limitada en algunas plantas frutales por la poca capacidad de enraizamiento y aclimatación de algunos genotipos, o por las pérdidas de material vegetal causadas por la presencia de contaminaciones endófitas. El uso de microorganismos que mejoran el crecimiento de plantas puede ser una alternativa muy interesante debido a su capacidad de producir hormonas vegetales o de controlar el crecimiento de patógenos. Es importante desarrollar productos basados en estos microorganismos para escalar su posible aplicación en campo. Los tres microorganismos Pseudomonas oryzihabitans PGP01, Cladosporium ramotenellum PGP02 y Phoma spp. PGP03 se aislaron de cultivos in vitro contaminados de Prunus y Pyrus que mostraban un mayor crecimiento que los no contaminados. En plántulas obtenidas a partir de embriones de nectarina rescatados in vitro (Capítulo 1), P.oryzihabitans PGP01 indujo mayor desarrollo radicular que favoreció la aclimatación de las plantas en invernadero. En patrones comerciales micropropagados in vitro (Capítulo 2), C. ramotenellum PGP02 y Phoma spp. PGP03 mejoraron el porcentaje de enraizamiento in vitro, de un 56.3 a un 100%, de explantos tratados con IBA del portainjerto Pyrus Py12 difícil de enraizar. En este mismo capítulo, P.oryzihabitans PGP01 también promovió el desarrollo de las raíces del patrón de Prunus RP-20. Todos estos resultados podrían estar relacionados con la producción de IAA por parte de los tres microorganismos. Utilizando mutantes de Arabidopsis thaliana, se sugirió que los efectos en las raíces producidos por P. oryzihabitans PGP01 podrían estar mediados por estrigolactonas (SLs) y glutatión (GSH) (Capítulo 3). En cultivo con medio líquido (Capítulo 4), se observó que los efectos en la raíz producidos por P. oryzihabitans PGP01 podrían estar mediados por el contenido de auxinas en el medio de cultivo. En este mismo sistema de crecimiento en líquido, en presencia de C. ramotenellum PGP02, se sugirió el efecto de un pH bajo en el medio de cultivo sobre el crecimiento de microorganismos endófitos en plantas de RP-20. Esta hipótesis fue finalmente confirmada en el Capítulo 5, demostrando que un pH ácido en ausencia de microorganismos reducía la concentración de endófitos sin afectar la micropropagación in vitro. Finalmente, se probaron tres subproductos de la industria de la patata, tomate y cereales para elaborar un medio barato para la producción de P. oryzihabitans PGP01. El crecimiento de esta bacteria en un medio basado en subproductos de patata proporcionó un crecimiento máximo de 4,4x109 UFC mL-1 sin afectar la actividad biológica del mismo (Capítulo 6). Los resultados presentados en esta tesis proporcionan hallazgos muy novedosos acerca del uso de microoganismos beneficiosos como alternativas más sostenibles para promover el crecimiento de plantas in vitro.
In vitro tissue culture constitutes a very versatile technique to obtain large amounts of true-to-type and disease-free-plant materials. However, in some fruit tree crops, the poor in vitro rooting or acclimatization of some genotypes, or the high losses of plant material associated to endophytic contaminations may limit the effectiveness of the process. The use of microorganisms with plant-growth promoting ability might represent a sustainable alternative to overcome those limitations, knowing their ability to produce plant hormones or control pathogens growth. On the other hand, for the scale-up of the application to field conditions, it is of crucial importance to develop a product based on microorganism showing potential agronomical interest. The three microorganisms Pseudomonas oryzihabitans PGP01, Cladosporium ramotenellum PGP02 and Phoma spp. PGP03 were isolated from Prunus and Pyrus contaminated in vitro cultures showing a greater growth than those non-contaminated. In seedlings obtained from in vitro nectarine rescued embryos (Chapter 1), P. oryzihabitans PGP01 promoted root development, favouring the acclimatization to greenhouse conditions. In in vitro micropropagated commercial rootstocks (Chapter 2), C. ramotenellum PGP02 and Phoma spp. PGP03 increased the in vitro rooting percentage, from 56.3 to 100%, of the hard-to-root Pyrus rootstock Py12 explants treated with 3-indolebutyric acid. An effect of P. oryzihabitans PGP01 on root development of the Prunus rootstock RP-20 was observed. The in vitro ability of the three microorganisms to produce IAA supported these results. Using Arabidopsis thaliana defective mutants, the role of strigolactones (SLs) and glutathione (GSH) in the root events induced by P. oryzihabitans PGP01 was suggested (Chapter 3). In a liquid culture (Chapter 4), it was established a link between auxin levels in the medium and root development in the presence of P. oryzihabitans PGP01. Furthermore and regarding endophytes growth in the culture medium, the role of acidic pH to control their growth in RP-20 cultures was suggested in the presence of C. ramotenellum PGP02, being this assumption finally confirmed in Chapter 5 in the absence of microorganisms. In this chapter, the micropropagation at low pH reduced endophytes population without affecting in vitro micropropagation. Finally, wastes based on potato, tomato and cereals industries were tested for the development of a cheap culture medium for P. oryzihabitans PGP01. The growth of this bacterium in a potato wastes-based medium provided a maximum of 4.4x109 CFU mL-1 without losing the plant growth-promoting activity (Chapter 6). The results obtained in the present thesis provide novel insights regarding the use of beneficial microorganisms as more sustainable alternatives to promote in vitro plant growth.

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Adediran, Gbotemi Abraham. "Role of plant growth promoting bacteria and a leguminous plant in metal sequestration from metal contaminated environments by Brassica juncea." Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/10523.

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The worldwide occurrence of sites contaminated with toxic metals and the associated high costs of remediating them using chemical and mechanical methods have led to calls to develop inexpensive and sustainable approaches based on the use of plants that naturally accumulate large amounts of metals in their tissues. The ability of plants to remediate metals has been rigorously studied and some species have been identified as excellent phytoremediators. However, the growth of phytoremediators is often retarded under high soil metal concentrations, rendering them ineffective. Meanwhile, some plants do not have remediating abilities but are capable of growing in contaminated environments with little or no sign of stress. Despite the volume of research dedicated to the screening and evaluation of phytoremediators, major questions remain about why some plants survive but do not remediate while the growth of phytoremediators is mostly hindered. The growth and metal-remediating efficiency of plants exposed to toxic concentrations of metals can be enhanced by inoculating phytoremediating plants with certain bacteria but the mechanisms behind this process remain unclear. Furthermore, the use of leguminous plants to improve the growth of a target plant under a mixed planting system has long been recognised as an effective yield-enhancing cropping system. However, the possibility of a non-remediating but tolerant leguminous plant conferring metal tolerance to a phytoremediator has not been explored. This thesis reports results from repeated glasshouse and lab-based growth experiments on the phytoremediating plant Brassica juncea exposed to 400 – 600 mg Zn kg-1. The aim was to investigate the abilities of two plant growth promoting bacteria (PGPB) species Pseudomonas brassicacearum and Rhizobium leguminosarum, and a leguminous plant Vicia sativa to promote B. juncea growth and enhance remediation of Zn-contaminated soil. B. juncea plant roots were analysed using synchrotron based micro-focus X-ray Fluorescence (μXRF) imaging and X-ray Absorption Near Edge Structure (μXANES) analysis to probe Zn speciation. P. brassicacearum exhibited the poorest plant growth promoting ability, while R. leguminosarum alone and in combination with P. brassicacearum significantly enhanced B. juncea growth and Zn bioaccumulation. X-ray Absorption Spectroscopy (XAS) analysis showed that reduced plant growth was due to root accumulation of Zn as Zn sulphate, Zn oxalate and Zn polygalacturonic acids. The better growth and increased metal accumulation observed in plants inoculated with R. leguminosarum and its combination with P. brassicacearum was attributed to root storage of Zn in the chelated forms of Zn phytate and Zn cysteine. A subcellular analysis of plant root also showed that the PGPB enhanced tolerance to Zn contamination by enhancing epidermal Zn compartmentalisation depending on the nature of root colonization, and induced changes in Zn speciation to less toxic Zn species in the epidermis and endodermis of plant root. The thesis therefore identifies enhanced Zn compartmentalization at the root epidermis and bacterial mediated changes in Zn toxicity through changes in Zn speciation as key complimentary mechanisms of plant growth promotion and enhanced Zn accumulation in plants by PGPB. Further experiments investigating alternative phytoremediation strategies showed that the use of the leguminous plant V. sativa in a mixed planting system with B. juncea plants completely out performed the effects of bacteria in promoting the growth and remediation potential of B. juncea under Zn contamination. By combining PGPB with mixed planting, B. juncea recovered full growth while also achieving maximum phytoremediation efficiency. The novel legume assistedmicrobial phytoremediation method that is reported in this thesis is the first to demonstrate complete plant growth recovery in plants exposed to 400 – 450 mg kg-1 soil Zn contamination for 5 weeks. Survival of V. sativa was attributed to its root storage of Zn in the chelated forms of Zn histidine and cysteine whereas in the roots of stunted B. juncea plants the majority of Zn was present as Zn oxalate and toxic Zn sulphate. Although the use of natural and synthetic chelates has been reported to enhance phytoremediation, this thesis recommends a legume-assisted-microbialphytoremediation system as a more sustainable method for Zn bioremediation.

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31

Richards, Jeffrey T. "Induced resistance responses in potato inoculated in vitro with a plant growth promoting pseudomonad rhizobacterium." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq24901.pdf.

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Dunbar, Christopher Lloyd. "Utilization of seaweed extract and plant growth promoting rhizobacterium in greenhouse production of potato minitubers." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq24962.pdf.

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Dashti, Narjes. "Plant growth promoting rhizobacteria and soybean nodulation, and nitrogen fixation under suboptimal root zone temperatures." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape15/PQDD_0027/NQ29918.pdf.

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Weishaar, Claudia Regine Verfasser], Nicolaus von [Akademischer Betreuer] [Wirén, Klaus [Akademischer Betreuer] Humbeck, and Joseph [Akademischer Betreuer] Strauss. "Impact of the plant growth-promoting rhizobacterium Raoultella terrigena TFi08N on plant growth and root architecture / Claudia Regine Weishaar. Betreuer: Nicolaus Wirén ; Klaus Humbeck ; Joseph Strauss." Halle, Saale : Universitäts- und Landesbibliothek Sachsen-Anhalt, 2011. http://d-nb.info/1025202600/34.

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Gray, Elizabeth Jean. "Identification of a novel bacteriocin, thuricin 17, produced by Bacillus thuringiensis NEB17." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=84035.

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Bacillus thuringiensis NEB17 is a plant growth promoting rhizobacterium that produces a compound that directly increases plant growth. The compound is a bacteriocin and we propose the name thuricin 17. Thuricin 17 is a novel peptide inhibiting the growth of Bacillus species/strains, displaying both bactericidal and static effects. Its molecular weight, estimated via SDS-PAGE and verified by MALDI-QTOF mass spectroscopy, is 3162 Da. The partial amino acid sequence was determined and is N-term---WTCWSCLVCAACSVELL, C-term-CAS. Heat and pH stability, production and susceptibility to proteolysis were conducted. Thuricin 17 is active in pH 1.00-9.25, stable above 60°C and produced in the late exponential growth phase. This is the first bacteriocin from a Bacillus PGPR and the first reported to increase plant growth. This work presents an original discovery regarding PGPR mechanisms.

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Chen, Chunquan 1958. "Induced systemic resistance against Pythium aphanidermatum by plant growth-promoting rhizobacteria on cucumber (Cucumis sativus L.)." Thesis, McGill University, 1998. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=35862.

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Cucumber root rot caused by Pythium aphanidermatum can be suppressed by introduced plant growth-promoting rhizobacteria (PGPR). Preliminary experiments clarified that this root disease could be suppressed by strains of Pseudomonas aureofaciens, P. corrugata, and P. fluorescens. To determine whether the mechanism was a systemic resistance induced by PGPR, a split root technique was employed on greenhouse cucumbers grown in soilless substrates. On the split roots, bacteria which were introduced into one side of the root were completely separated from pathogen challenged-inoculated roots-on the other side of the roots. Results from the series of experiments conducted with this design demonstrated that (i) the resistance against root rot induced by PGPR was systemic, (ii) germination of P. aphanidermatum zoospores was reduced in extracts from bacterized roots compared to non-treated control, and (iii) spread of Pythium mycelia was delayed and zoospore germination was inhibited on the distant induced root, compared to the non-bacterized control. Furthermore, enzyme analysis indicated that phenylalanine ammonia lyase, peroxidase and polyphenoloxidase increased on cucumber roots two days after they were bacterized with Pseudomonas strains 13 or 63--28. When the bacterized roots were challenged with P. aphanidermatum, these plant defense enzymes increased as the symptoms appeared, but this accumulation of enzymes was not any higher on roots induced with each of the Pseudomonas strains compared to the Pythium inoculated control. This enzyme stimulation was also systemically induced by PGPR or P. aphanidermatum on cucumber roots. The patterns of iso-peroxidase induced with the PGPR and P. aphanidermatum treatments were different. High levels of salicylic acid (SA) accumulated in bacteria-induced roots, as well as in pathogen-infected roots, which suggests that SA may be associated with cucumber resistance response. But exogenous application of SA did not induce any systemi

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Li, Jiping. "Isolation, characterization and regulation of 1-aminocyclopropane-1-carboxylate deaminase genes from plant growth-promoting rhizobacteria." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0007/NQ44773.pdf.

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Chen, Chunquan. "Induced systemic resistance against Pythium aphanidermatum by plant growth-promoting rhizobacteria on cucumber, Cucumis sativus L." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ50129.pdf.

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Steenkamp, Letitia Elizabeth. "Analysis of the effects of the plant growth promoting substances GR24 and smoke water on abiotically stressed Nicotiana benthamiana seedlings." Thesis, Stellenbosch : Stellenbosch University, 2011. http://hdl.handle.net/10019.1/17863.

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Thesis (MSc)--Stellenbosch University, 2012.
ENGLISH ABSTRACT: Almost all processes during the life of a plant are affected by the environment. Changes in phytohormone, metabolite and protein levels follow in response to changes in the environment. Plant growth promoting substances can stimulate changes at these levels to facilitate increased plant growth and yields above what the plant would normally establish. In this study, the effects of two growth promoting substances, smoke water (SW) derived from bubbling smoke from the burning of plant material through water, and a synthetic strigolactone analogue, GR24, on plant growth and architecture, as well as the proteome and metabalome of salt stressed Nicotiana benthamiana seedlings were investigated. Physiological studies were conducted to identify the effects of the growth substances on salt stressed seedlings in a tissue culture system. Under non-stress conditions, SW treatment increased seedling fresh mass, root length and leaf area. Under salt stress conditions (100 mM and 150 mM NaCl), SW increased fresh mass, root length, leaf number and lateral root number significantly. Under non-stress conditions, GR24-treated seedlings showed increased fresh mass, leaf number and area and root length. When GR24-treated seedlings were placed under salt stress, the seedlings showed significant increases in fresh mass, leaf number and lateral root number, but only marginal increases in root length and leaf area. Despite these similarities, slight differences were observed in the metabolomes and proteomes of smoke water and GR24-treated seedlings, both with and without the addition of salt stress. Relatively few of the differentially expressed proteins could be identified with the instruments available. Changes in the metabolome indicated that photoassimilation and photosynthesis could be affected in response to smoke water and GR24 treatment. Our results suggest that smoke water and GR24 both promote growth under salt stress conditions in seedlings and we furthermore conclude that, although there are distinct overlaps between treatments, this is accomplished via slightly different mechanisms.
AFRIKAANSE OPSOMMING: Gedurende ‘n plant se lewe word omtrent alle prosesse deur die omgewing geaffekteer. Veranderinge in die omgewing word gevolg deur veranderinge in hormoon, metaboliet en protein vlakke. Plant groei stimulante affekteer hierdie vlakke om plant groei en -opbrengs na bo normalle vlakke te verhoog. In hierdie studie word die effek van twee groei stimulante, rook water verkry deur rook van plant materiaal deur water te borrel en ‘n sintetiese strigolaktoon, GR24, ondersoek op ‘n morfologiese, metaboliese en ‘n proteomiese vlak in Nicotiana benthamiana saailinge. ’n Studie is onderneem om die veranderinge as gevolg van die onderskeie groei stimulante te ondersoek in ‘n weefsel kultuur sisteem. Rook water het onder normale groei omstandighede vars en droeë massa, blaar aantal asook wortel en blaar lengte verhoog. Rook water het na sout behandeling (100 en 150 mM NaCl) steeds vars massa, wortel lengte, blaai aantal en laterale wortel aantal beduidend verhoog in vergelyking met die sout stres kontrole. Behandeling met GR24 het ook vars massa, wortel lengte, blaar aantal en grootte verhoog en onder sout stres met GR24 is ‘n beduidende vergroting opgemerk in vars massa, blaar grootte en laterale wortel aantal. Ongeag van die veranderinge in groei is klein verskille opgemerk in die metaboliet en protein studies. Net ‘n paar proteine kon positief geidentifiseer word met die apparaat beskikbaar. Verandering in die metaboloom wys na veranderinge in fotoassimilasie en fotosintese in reaksie tot rook water en GR24. Hierdie resultate lei tot die gevolgtrekking dat rook water en GR24 beide groei verbeter in saailing behandel met sout en ook dat alhoewel daar sekere ooreenkomste is tussen die reaksies as gevolg van die plant groei stimulante, dit wel geskiet deur geringe verskillende meganismes.

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Otukpa, Faith Obiye. "Metabolomic analysis of maize (Zea mays&nbsp L.) seedlings treated with selected plant growth promoting rhizobacteria." Diss., University of Pretoria, 2019. http://hdl.handle.net/2263/77875.

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Global food production has significantly increased mainly due to the use of high-yield crop varieties, fertilisers, fungicides and pesticides, and improved irrigation methods. Despite the increase in production, there has been a significant cost to the environment in the form of pollution, and to farmers in the form of rising fertiliser and pesticide costs. The impacts on the environment include but are not limited to groundwater contamination, declining soil health and increased pest and pathogen resistance, all which increase the financial cost to farmers. To reverse or rather salvage the situation, more sustainable agricultural practices need to be employed that will maintain high productivity with little to no damage to the environment, and will reduce agrochemical use, thus, reducing the financial strain on farmers. A potential solution would be to exploit soil dwelling rhizospheric microorganisms to improve plant growth with little to no application of agrochemicals. The rhizosphere refers to the region of soil directly influenced by plant roots and is home to microorganisms known as plant growth promoting rhizobacteria (PGPR). These PGPR have been found to stimulate plant growth via numerous mechanisms, which directly affect the plant metabolome and in turn translates into observable effects in the plant phenotype. The plant metabolome has been described as the bridge between the genotype and phenotype, thus metabolomics acts as a useful tool to evaluate the contribution of external influences on the plant phenotype based on metabolic changes. The effect of PGPR on the plant metabolome is vital in understanding their mode of action, which will further validate their use in farming. The overall aim of this project was to assess the effect of selected PGPR strains with known plant growth promoting activity on the metabolic profile of maize seedlings; and to evaluate if these changes in the metabolic profile directly correlate with the observable effects on the growth of the seedlings. To achieve this aim, firstly, the effect of Lysinibacillus sphaericus (T19), Paenibacillus sp. (T29) and Bacillus megaterium (A07) on early maize growth, i.e., the effects on dry root and shoot biomass, leaf chlorophyll content, stem diameter and shoot length, was assessed. Secondly, the effect of single strain PGPR inoculation on the metabolic profile of maize was evaluated. Finally, metabolomics analysis was conducted on the roots and shoots of the maize seedlings inoculated with strains T29 and T19 respectively. Statistical analysis of the metabolomics results was conducted to find significant pathways and discriminating metabolites between the control and inoculated plants. To assess the effects of the PGPR strains on early maize growth, a greenhouse trial was first conducted. Non-invasive techniques were used to measure the growth parameters that could be recorded prior to harvest. Next an untargeted metabolomics approach was used to analyse the metabolome of harvested roots and shoots. Metabolomics data acquisition was achieved using ultra-performance liquid chromatography hyphenated to quadrupole time of flight mass spectrometry detection (UPLC/QTOF-MS). Finally, to evaluate the effect of single strain inoculation on the maize root and shoot metabolome, univariate and multivariate methods were applied. The results of the greenhouse trial showed a tendency of strains T19 and T29 in stimulating shoot growth and root growth respectively in the maize seedlings. Pathway analysis using results from univariate analysis revealed a number of pathways affected by T19 and T29 in the shoots and roots respectively. Multivariate statistical analysis also showed that the inoculated samples differed from the control samples, albeit with varying trends, which indicates differing metabolic states. Some of the metabolic pathways deemed significant in the inoculated shoots and roots were amino acid, nucleotide metabolism or carbon fixation related. A number of discriminating features were found to be differentially regulated in the inoculated roots and shoots. Overall, the results showed that T19 and T29 inoculation stimulated metabolic responses in maize shoots and roots linked to plant growth and development.
Dissertation (MSc)--University of Pretoria, 2019.
Biochemistry
MSc
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Kuntz, Veronica L. "The relationship between Sarracenia oreophila and an endophytic Burkholderia." Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41094.

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Plant growth-promoting bacteria (PGPB) have been studied in many agriculturally interesting plants, but never in pitcher plants. Sarracenia oreophila (the green pitcher plant) is an endangered species in Georgia, Alabama, and North Carolina (Rice 2010). With the help of Dr. Jim Spain's lab, a previous student in Dr. Gerald Pullman's lab discovered evidence that nitrogen-fixing bacteria (Burkholderia spp.) live within these pitcher plants. This study aims to determine whether these nitrogen-fixing bacteria confer a benefit to their host plants by providing fixed nitrogen. To do this, pitcher plants were inoculated with the Burkholderia and grown on a control medium, a medium without sugar (as the sugar causes the bacteria to grow until they hinder the plants), various media that are missing nitrogen-containing compounds usually provided in growth media, and a medium completely lacking nitrogen. These plants were compared to control plants on the same media that had not been inoculated with Burkholderia. The plants' biomass and root growth were measured. The data suggest that Burkholderia may stimulate plant biomass growth when sufficient nitrogen is present and there may be a nitrogen-threshold that needs to be met in order to sustain the Burkholderia-Sarracenia symbiosis. Also, the Burkholderia has a negative effect on roots grown in high-nitrogen media, possibly due to competition for nutrients.

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Chen, Xiaohua. "Whole genome analysis of the plant growth-promoting Rhizobacteria Bacilllus amyloliquefaciens FZB42 with focus on its secondary metabolites." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2010. http://dx.doi.org/10.18452/16095.

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Bacillus amyloliquefaciens FZB42 besitzt einen beeindruckenden Effekt zur Verbesserung des Pflanzenwachstums. Um die Mechanismen, vor allem auf molekularer Ebene, zu verstehen, wurde das komplette Genom von FZB42 in dieser Arbeit sequenziert. Abwesenheit von der weit verbreiteten Phagen-verwandten Genen im Genom von B. subtilis 168, der in enger Verwandtschaft zum FZB42 steht, ist ein besonderes Merkmal. Dagegen enthält das Genom von FZB42 viele DNA-Inseln, in denen unikale Gene in FZB42 als Cluster gefunden wurden. Viele Gene, die möglicherweise zur Pflanzenwachstumsförderung beitragen, wurden in dieser Arbeit identifiziert. B. amyloliquefaciens FZB42 ist natürlich kompetent. Das kompetente Stadium in FZB42 kommt früher als in B. subtilis 168, nämlich während der späten exponentiellen Wachstumsphase. Das FZB42-Genom enthält den kompletten Satz von Genen, die für die Entwicklung der genetischen Kompetenz nötig sind. Ausgenommen von Gene für Quorum-Sensing-System ist die Mehrzahl der Kompetenz-Gene von FZB42 sehr ähnlich zu denen in B. subtilis 168. Das FZB42 Genom birgt ein enormes Potential zur Produktion von sekundären Metaboliten. Genetische Manipulationen wurden durchgeführt, um die Funktionen der trans-AT Domänen und der Modifikationsdomänen in den PKS-Gen-Clustern zu erklären. Mit Ausnahme von fünf Gen-Clustern in B. subtilis 168 (Surfactin, Fengycin, Bacillibactin, Bacillaene und Bacilysin), sind Bacillomycin D, Difficidin, Macrolactin und ein hypothetisches Tripeptid einzigartig im Genom der FZB42. FZB42 kann kein bekanntes ribosomal synthetisiertes Bacteriocin produzieren kann. Gleichzeitig beinhaltet sein Genom ein Gen-Cluster, das wahrscheinlich für die Produktion eines neuartigen Bacteriocins verantwortlich ist. Die eindrucksvolle genetische Kapazität zur Herstellung von antagonistischen sekundären Metaboliten ermöglicht es FZB42, nicht nur erfolgreich neben konkurrierenden Organismen innerhalb seiner natürlichen Umgebung zu überleben, sondern auch Pflanzen gegen pathogene Bakterien und Pilze zu schützen.
Bacillus amyloliquefaciens FZB42 has an impressive effect to improve plant growth. In order to understand the mechanisms, especially at the molecular biological level, the whole genome of FZB42 was sequenced in this work. The absence of extended phage insertions which are typical for the closely related B. subtilis 168 genome is a particular feature. On the other hand, several DNA islands where unique genes in FZB42 were found clustered. Many candidate genes that may contribute to the plant growth promotion were identified in this works. B. amyloliquefaciens FZB42 is naturally competent. FZB42 exhibited its maximal competence earlier than B. subtilis, during late exponential growth. Not surprisingly, the FZB42 genome harbors the complete set of genes necessary for development of genetic competence. The majority of competence genes are highly homologous to their counterparts in B. subtilis 168, excluded from genes for the quorum-sensing system. The FZB42 genome harbors enormous potential for producing secondary metabolites. Genetic manipulation was carried out to investigate the trans-AT domains and some modification domains in the pks gene clusters. With the exception of five gene clusters in B. subtilis 168 (Surfactin, Fengycin, Bacillibactin, Bacillaene and Bacilysin), Bacillomycin D, Difficidin, Macrolactin and a hypothetical tripeptide are unique in the genome of the FZB42. A remarkable feature of the FZB42 genome is that it does not produce any known ribosomally synthesized bacteriocin, whereas a gene cluster probably responsible for production of a new bacteriocin was identified in this work. The impressive genetic capacity to produce antagonistic acting secondary metabolites not only enables FZB42 to cope successfully with competing organisms within its natural environment, but also to protect plants from pathogenic bacteria and fungi.

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Parkunan, Venkatesan. "Induced disease resistance elicited by acibenzolar-S-methyl and plant growth-promoting rhizobacteria in tobacco (Nicotiana tabacum L.)." Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/29109.

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Active disease resistance in plants is induced during the pathogen infection process that triggers multiple defense-related genes to establish broad-spectrum resistance. Several biotic and abiotic agents can mimic natural induced resistance (IR), categorized as systemic acquired (SAR) or induced systemic resistance (ISR). IR, triggered by acibenzolar-S-methyl (ASM) or plant growth-promoting rhizobacteria (PGPR), was evaluated on two-to-three types of tobacco in greenhouse and field studies. Tobacco mosaic virus (TMV) local lesion assays monitored induction and maintenance of ASM-induced SAR over a 21 day period via proportional reduction in the number of TMV local lesions between an untreated control and ASM-treated plants. Intraspecific variation in SAR was found among tobacco types; burley and flue-cured tobaccos responded by day 3, while oriental tobacco responded between day 3 and 6. The SAR signal was greatest between 6 and 15 days following ASM application, but IR was slightly evident even at 21 days after ASM application in all three tobacco types. Bottom and middle leaves responded similarly on all sample dates, but top leaves showed the weakest SAR response. Tobacco cyst nematode (TCN; Globodera tabacum solanacearum) is one of the most destructive pathogens of tobacco in Virginia. Among four PGPR combinations tested, a mixture of Bacillus amyloliquefaciens IN937a (GB99) and B. subtilis A13 (GB122) most consistently suppressed TCN reproduction in flue-cured and oriental tobacco. Application of ASM similarly reduced final numbers of TCN cysts, but also resulted in chlorosis, stunting, and lower plant fresh weight. GB99+GB122 also suppressed TCN development and reproduction in susceptible and resistant flue-cured cultivars, but reductions by ASM were less consistent. In a split-root trial, soil amendment with GB99+GB122 in one half of an oriental tobacco root system lowered final numbers of TCN more than did ASM. ASM exhibited undesirable effects in phytotoxicity trials in flue-cured and oriental tobacco, but GB99+GB122 was not phytotoxic. When oriental tobacco seedlings were grown in a GB99+GB122-treated soil-less media, a single application of 200 mg ASM/L one week after transplanting significantly suppressed TCN reproduction in the field without phytotoxicity. Further field research is needed to confirm this effect in flue-cured tobacco.
Ph. D.

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Eze, Michael Onyedika [Verfasser]. "The potential of plant growth-promoting bacteria to enhance rhizoremediation of diesel fuel-contaminated sites / Michael Onyedika Eze." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2021. http://d-nb.info/1235756963/34.

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Istain, Brandon. "Isolation and characterization of plant growth promoting endophytic bacteria from Medicago lupulina for enhanced drought tolerance in Maize." University of the Western Cape, 2019. http://hdl.handle.net/11394/7870.

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>Magister Scientiae - MSc
Maize is one of the major staple foods in many African nations however, this crop is sensitive to environmental stressors. Drought is a major environmental stressor affecting maize production. Due to global warming, drought episodes are expected to increase in duration and frequency. Therefore, it is vital to improve maize drought tolerance thereby increasing food security. Many studies have looked at improving maize drought tolerance through genetic engineering techniques which has shown promising results, nonetheless GMOs have been under scrutiny due to public concerns regarding unknown side effects.
2024-02-24

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Mounde, Lenard Gichana [Verfasser], and Joachim [Akademischer Betreuer] Sauerborn. "Understanding the role of plant growth promoting bacteria on sorghum growth and biotic suppression of striga infestation / Lenard Gichana Mounde. Betreuer: Joachim Sauerborn." Hohenheim : Kommunikations-, Informations- und Medienzentrum der Universität Hohenheim, 2015. http://d-nb.info/1068569689/34.

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Mounde, Lenard Gichana Verfasser], and Joachim [Akademischer Betreuer] [Sauerborn. "Understanding the role of plant growth promoting bacteria on sorghum growth and biotic suppression of striga infestation / Lenard Gichana Mounde. Betreuer: Joachim Sauerborn." Hohenheim : Kommunikations-, Informations- und Medienzentrum der Universität Hohenheim, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:100-opus-10495.

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Cadena, Cepeda Marleny Kloepper Joseph. "Assessing soil microbial populations and activity following the use of microbial inoculants effect on disease suppressiveness and soil health /." Auburn, Ala., 2006. http://repo.lib.auburn.edu/2006%20Fall/Theses/CADENA_MARLENY_3.pdf.

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Poupart, Julie. "Analysis of indole-3-butyric acid auxin activity in Arabidopsis." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=84312.

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Auxins are plant hormones involved in virtually all aspects of plant life. Despite long-term commercial and horticultural use of the auxin Indole-3-Butyric Acid (IBA), a full recognition of its natural occurrence in plants was made only recently. I have used multiple approaches to dissect the role of IBA in Arabidopsis thaliana. This thesis includes the first characterization of a mutant with an altered response to IBA that retains wild-type sensitivity to Indole-3-Acetic Acid (IAA), the most studied endogenous auxin. This mutant, named resistant to IBA ( rib1), has modified root architecture and gravitropism and is resistant to auxin transport inhibitors. As these phenotypes are reminiscent of those of characterized auxin transport mutants, movement of IAA and IBA was studied in wild-type and mutant plants. IBA is transported in seedlings in three distinct flows, like IAA, and this transport is saturable, indicating it is carrier mediated. However, unlike IAA, IBA is not polarly transported in inflorescence axes, and IBA transport is not sensitive to IAA transport inhibitors. These results suggest IAA and IBA transport could be mediated or regulated by different mechanisms. In rib1 seedlings, all flows of IBA transport are modified, while IAA transport levels are unchanged. Modifications in IBA transport match phenotypic differences between rib1 and wild-type, and analyses of the physiological effects of IBA also suggest IBA has a role in defining wild-type seedling morphology in Arabidopsis. Though IAA transport levels are not changed in rib1, one flow of IAA transport is rendered insensitive to IAA transport inhibitors, perhaps revealing cross-talk between IAA and IBA transport regulation. Additionally, double mutant analyses reveal that IAA transport and response mutants can suppress some phenotypes of rib1, and some mutant combinations produce novel phenotypes, further suggesting cross-talk between IBA and IAA transport and response p

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Mpanga, Kwadwo Isaac [Verfasser], and Günter [Akademischer Betreuer] Neumann. "Fertilization strategies to improve the plant growth-promoting potential of microbial bio-effectors / Isaac Mpanga Kwadwo ; Betreuer: Günter Neumann." Hohenheim : Kommunikations-, Informations- und Medienzentrum der Universität Hohenheim, 2020. http://d-nb.info/1213348870/34.

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Dissertations / Theses on the topic 'Promoting plant growth'

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