Thèses : « Promoting rhizobacteria »

1

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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Noh, Medina José Alfredo. « Rhizobacteria promoting the growth of plants infected with viruses ». Thesis, Université Laval, 2007. http://www.theses.ulaval.ca/2007/24319/24319.pdf.

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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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Swift, Rebecca Gaye. « Novel plant growth promoting rhizobacteria (PGPR) isolated from Western Australian soils ». Thesis, Swift, Rebecca Gaye (2006) Novel plant growth promoting rhizobacteria (PGPR) isolated from Western Australian soils. Honours thesis, Murdoch University, 2006. https://researchrepository.murdoch.edu.au/id/eprint/32755/.

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Plant growth promoting rhizobacteria (PGPR) colonise plant roots and exert beneficial effects on plant growth and development. The mechanisms of action of these PGPR are not conclusively known, however, there is evidence for the role of indole-3-acetic acid (IAA) and 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase production by rhizobacteria in plant growth promotion. In this study, novel-PGPR were isolated from the rhizosphere of native species as well as agricultural crop species, as opposed to other work in this field in which potential PGPR are isolated from the rhizosphere of the target plant species. One hundred and sixty six bacteria were isolated from four rhizosphere soils in Western Australia and 72 isolates were assayed for the production of IAA. In the presence of the auxin precursor L-tryptophan (L-TRP) IAA production ranged from 0-37 1-Lg/ml. Five rhizosphere soils were screened for bacteria capable of utilizing ACC as a sole nitrogen source and 13 isolates were obtained. To ensure that the isolates were not potentially deleterious to host plants, 14 IAA producing (IAA-PGPR) and all rhizobacteria capable of using ACC as a sole nitrogen source (ACC-PGPR) were tested for their effects on germinating clover and wheat seedlings. Two IAA-PGPR isolates, NCH7 and PMK4, were inhibitory to wheat seedling germination and one ACC-PGPR isolate was inhibitory to clover seedlings. Based on these findings, 6 IAA-PGPR and 4 ACC-PGPR were screened for their effects on germinating wheat seedlings in gnotobiotic growth pouch assays. Prior to these tests, spontaneous rifampicin resistant mutants were generated for 6 isolates. The mutants, or the wild type isolates where rifampicin mutants were not generated, were (re)tested for their ability to produce IAA and utilize ACC. All 10 isolates produced IAA in the presence of L-TRP ranging from 0.11-2.97 1-Lg IAA/ 1-Lg cellular protein and 7 of the isolates grew on ACC amended medium. Bacterial growth was greatly increased in some isolates in the L-TRP amended media used in the auxin assay, suggesting some of the isolates have a requirement for tryptophan for optimal growth. The largest increases in root lengths in the gnotobiotic growth pouch assays were observed for seed treated with thhe ACC-PGPR, AWMK3 (81% increase). The IAA-PGPR treatments that increased root lengths were PMK4R (76%), WMK10R (66%) and NCH45 (33%). Increases in shoot lengths were recorded for seed treated with isolates WMK10R (42%), AWMK3 (11%), APMK2R (9%) and PMK9 (9%). A reduction in germination was observed in seed treated with some isolates, particularly PMK4R and WMK10R, which reduced germination by 34% and 20%, respectively. Five of the PGPR isolated in this study were tested in the field on 2 wheat cultivars at 3 locations in Konjonup and Wongan Hills and as a co-inoculant with a commercial rhizobial strain on peas at Kojonup. All the PGPR were delivered in the field using the clay based A1osca™ carrier technology. The increases in yields in response to the inoculation with the PGPR on peas and wheat were small and not significantly different from the controls. However, the yield of wheat was improved by four of the PGPR (NCH45, NCH54, PMK9, WMK10) at the Wongan Hills heavy soil site by 2 to 23% and by NCH54 and PMK9 at the Wongan Hills light soil site by 4% and 3%, respectively compared with the uninoculated controls. On the peas at Kojonup, nodulation was improved with the isolate PMK4 and these plots were visually more vigorous than the other treatments, however this growth was not significant. At harvest, four of the PGPR (NCH45, PMK4, PMK9 WMK1 0) improved pea yields compared to the Alosca™ control by 6-13%. These results suggest that further testing is warranted. Improvements to experimental design and sampling have been recommended to allow for the detection of statistically significant small percentage increases if they occur. The findings in this study demonstrate that novel PGPR can be isolated from non-target as well as target plant species and that the screening of rhizobacteria based on their in vitro auxin production and growth promoting effects in growth pouch assays is valid for the selection of effective PGPR.

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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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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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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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MINAZZATO, GABRIELE. « Characterization of a transcription factor controlling vitamin B3 metabolism in plant growth promoting rhizobacteria ». Doctoral thesis, Università Politecnica delle Marche, 2020. http://hdl.handle.net/11566/274533.

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I rizobatteri sono in grado di colonizzare le radici delle piante in tutte le sue fasi di crescita, in presenza di una microflora competitiva. All'interno di questo gruppo di batteri, le specie che promuovono la crescita delle piante (PGPR) stabiliscono un'interazione benefica con le radici, migliorando la crescita e lo sviluppo dell'ospite. Evidenze sperimentali hanno dimostrato che la sintesi della forma biologicamente attiva della vitamina B3, cioè il coenzima NAD, è direttamente coinvolta negli effetti benefici mediati dai PGPR. Infatti, in Burkolderia sp. ceppo PsJN, un PGPR simbiotico della patata, l’attività dell’enzima chinolinato fosforibosiltransferasi che catalizza una reazione chiave nella via biosintetica de novo del NAD, è essenziale per promuovere la crescita della piantea. Il lavoro di questa tesi si è concentrato sullo studio della regolazione della via biosintetica de novo del NAD nei PGPR, con l'obiettivo di migliorare le nostre conoscenze sull'interazione PGPR-ospite e di ottenere nuovi strumenti in grado di migliorare lo sviluppo e il benessere delle piante. Analisi bioinformatiche hanno mostrato che nei PGPR la via de novo è controllata dal regolatore trascrizionale NadQ. Per caratterizzare questo regolatore abbiamo prodotto la proteina da Agrobacterium tumefaciens in forma ricombinante e, attraverso saggi di mobility shift, abbiamo verificato il suo legame con il DNA, in una regione situata a monte dell'operone coinvolto nelle prime fasi della biosintesi de novo del NAD. Abbiamo scoperto che NadQ lega il DNA in modo ATP e NAD-dipendente. In seguito, la risoluzione delle strutture cristallografiche del regolatore nella sua forma apo e in complesso con ATP e DNA, ha rivelato il meccanismo strutturale alla base della dissociazione della proteina dal DNA. Infine, abbiamo dimostrato che in alcune specie del genere Bordetella, NadQ regola la biosintesi de novo del NAD controllando anche il trasporto attraverso la membrana cellulare dell’acido chinolinico, precursore del NAD stesso. Abbiamo caratterizzato questo trasportatore mediante analisi di thermal shift, dimostrando la sua capacità di legare l'acido chinolinico con un’elevata affinità.
Rhizobacteria are able to colonize plant roots at all stages of plant growth, in the presence of a competing microflora. Within this group, plant growth promoting rhizobacteria (PGPRs) establish a beneficial interaction with roots, enhancing host growth and development. Experimental evidence shows that the synthesis of the biologically active form of vitamin B3, i.e. the coenzyme NAD, is directly involved in PGPRs mediated plant growth. Indeed, in Burkolderia sp. strain PsJN, a potato symbiotic PGPR, the enzyme quinolinate phosphoribosyltransferase, which catalyzes a key step in the de novo NAD biosynthetic pathway, is fundamental to promote the plant growth. Based on this evidence, this work focused on the study of the regulation of the de novo NAD biosynthetic pathway in PGPRs with the aim to enhance our knowledge on PGPR-plant interaction and to disclose novel tools to improve plant growth. Bioinformatic analyses showed that in PGPRs the pathway is controlled by the transcriptional regulator NadQ. To fully characterize this regulator, we produced the recombinant protein from A. tumefaciens and through mobility shift assays, we validated its binding to DNA, in a region upstream of the operon involved in the first steps of the de novo NAD biosynthesis. We found that NadQ binds DNA in ATP- and NAD- dependent manner. The resolution of the crystal structures of the regulator in its apo-form and in complex with ATP and DNA provided a first view of the structural mechanism of the release of the protein from DNA. Finally, we showed that in Bordetella species, NadQ regulates the de novo NAD biosynthesis by also controlling the transport of the NAD precursor quinolinic acid across the cellular membrane. We characterized the transporter by thermal shift assay, revealing its ability to bind quinolinic acid with high affinity.

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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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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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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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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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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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Raudales, Banegas Rosa Emilia. « Studies In Biocontrol : Enumeration, Characterization, And Screening Of Rhizobacteria ». Columbus, Ohio : Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1218207906.

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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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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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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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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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Teijeiro, Rosalia Isabel Garcia. « Using plant growth promoting rhizobacteria to mitigate effects of soil drying in pea ( Pisum sativum ) and lettuce (Lactuca sativa ) ». Thesis, Lancaster University, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.661127.

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The early stages of drought affect plant hormonal homeostasis, including root to shoot signalling. This thesis focuses on manipulating this signalling (to enhance plant drought tolerance) by adding bacterial inocula (Variovorax paradoxus 5C-2 or Bacillus subtilis IR15) to the rhizosphere of pea and lettuce plants. These bacteria can decrease plant ACC (ethylene) or increase cytokinin status, respectively. Firstly, characterising V. paradoxus 5C-2. indicated that it tolerates drought conditions, and colonises the roots of different plant species with different specificity. In the highly specific V. paradoxus 5C-2 / Pisum sativum interaction, bacterial genes of attraction (chemotaxis) are switched on. Secondly, V. paradoxus 5C-2 was applied to pea plants under field conditions and soil drying imposed. V. paradoxus 5C-2 did not alter rhizospheric microorganism community structure and activity, but pea biomass and nodule numbers increased, even in drying soil. Thirdly, root samples from the field were further studied using molecular biology techniques to find rhizobium candidate strains interacting with V. paradoxus 5C-2. The detection of specific RFLP patterns lead to the identification of a specific Rhizobium leguminosarum strain, which physically interacts with V. paradoxus 5C-2 as seen in LAMP-FISH (loop mediated isothermal amplification - fluorescence in situ hydridisation) by confocal microscopy. V. paradoxus 5C-2 increased rhizobium recruitment on root hairs by stimulating rhizobium expression of nodC genes needed for attachment to the roots. Finally, B. subtilis IR15 applied to the rhizosphere of lettuce plants increased foliar cytokinin concentration, and shoot biomass of plants grown in drying soil. Since cytokinins can inhibit root elongation, B. subtilis IR15 was transformed to express the ACC deaminase gene of V. paradoxus 5C-2: ~This increased root elongaljon of lettuce seedlings in in vitro experiments. Further studies to allow the practical transfer of these inocula to farming systems were discussed.

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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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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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Patrick, Melanie. « Characterisation of rhizobacterial communities of Eucalyptus species and hybrids ». Thesis, Bloemfontein : Central University of Technology, Free State, 2013. http://hdl.handle.net/11462/244.

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Thesis (M. Tech. (Agriculture)) -- Central University of Technology, Free State, 2013
ntroduction: Good quality Eucalyptus is of importance to South Africa’s pulp and paper industry. Limited land is available for forestry, therefore Eucalyptus with genotypes for good pulp and paper qualities, particularly hybrids, are bred and cloned via cuttings. Although these Eucalyptus clones keep the favourable genotypes in the population, many have difficulty with rooting. Research has shown that rhizobacteria can improve rooting. Thus, one strategy to enhance the rooting of cuttings is to use rhizobacterial preparations. The aim of this study was to characterise rhizobacterial communities of Eucalyptus hybrid and species and identify possible plant-growth promoting rhizobacteria (PGPR). Materials and methods: Rhizospheric samples were collected from Eucalyptus hybrids and species. The rhizobacterial communities were characterised using fatty acid methyl esters (FAME) analysis and denaturing gradient gel electrophoresis (DGGE). DGGE fragments were further sequenced to identify rhizobacteria. Results and discussion: FAME analysis successfully achieved a broad characterisation of the Eucalyptus hybrid and species rhizobacterial communities based on their fatty acid composition. Myristic acid (C14:0) was the most abundant fatty acid. DGGE profiles gave a molecular profile of the Eucalyptus hybrid and species rhizobacterial communities based on their DNA composition. Nitrosomona eutropha was present in all samples which illustrates a nitrogen-rich environment. Adhaenbacter aquaticus was unique to the better rooting Eucalyptus hybrid GU111. Conclusion: This study provided some insight into the diversity of rhizobacterial communities of Eucalyptus hybrids and species. Possible PGPR were identified and the observation made that the nature of the soil environment changes with the aging of the associated host. These findings allow further investigation into the formulation of potential rhizobacterial preparations for rooting enhancement of Eucalyptus cuttings.

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Valette, Marine. « Gènes et métabolites végétaux marqueurs de l'association riz-bactérie phytobénéfique ». Thesis, Lyon, 2019. http://www.theses.fr/2019LYSE1064.

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Ce projet explore l’hypothèse selon laquelle les gènes et les métabolites végétaux communément régulés joueraient un rôle majeur dans l’interaction riz-PGPR et constituerait une signature moléculaire de la perception des PGPR par le riz. Dans cet objectif, une analyse intégrant le suivi de l’expression d’une sélection de gènes ainsi que le profilage des métabolites secondaires a été conduite sur les racines d’un unique cultivar de riz (Nipponbare) en réponse à l’inoculation de dix souches de PGPR appartenant à divers genres bactériens (Azospirillum, Herbaspirillum, Paraburkholderia). Nos résultats ont permis l’identification de quatre gènes de riz pouvant être considérés comme marqueurs de l’association riz-PGPR, avec notamment deux gènes impliqués dans la biosynthèse de phytoalexines et un gène codant pour une protéine PR (pathogenesis-related). De plus, une signature métabolique commune, constituée de neuf composés, a été mise en évidence, dont la réduction de l’accumulation de trois alkylrésorcinols et l’augmentation de l’accumulation de deux amides d’acides hydroxycinnamiques (HCAA) : la N-p-coumaroylputrescine et la N-féruloylputrescine. Cette signature métabolique a été corrélée avec l’augmentation de l’expression de deux gènes impliqués dans la biosynthèse de la N-féruloylputrescine. Il est intéressant d’observer que la confrontation du riz à un pathogène bactérien entraine une réduction de l’accumulation de ces HCAA dans les racines. Cette accumulation d’HCAA, qui sont des composés antimicrobiens potentiels, pourrait être considérée comme une réaction primaire de la perception de bactéries par le riz
Besides, a common metabolomic signature of nine compounds was highlighted, with the reduced accumulation of three alkylresorcinols and increased accumulation of two hydroxycinnamic acid amides (HCAA), identified as N-p-coumaroylputrescine and N-feruloylputrescine. This coincided with the increased transcription of two genes involved in the N-feruloylputrescine biosynthetic pathway. Interestingly, exposure to a rice bacterial pathogen triggered a reduced accumulation of these HCAA in roots. Accumulation of HCAA, that are potential antimicrobial compounds, might be considered as a primary reaction of rice to bacterial perception

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Mengual, Navarro-Soto Carmen María. « Aplicación de rizobacterias promotoras del crecimiento vegetal (RPCV) en la reforestación de zonas semiáridas = Application of plant growth promoting rhizobacteria (PGPR) in the revegatation of semiarid areas ». Doctoral thesis, Universidad de Murcia, 2015. http://hdl.handle.net/10803/294264.

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En las zonas semiáridas mediterráneas del sureste de España, las escasas e irregulares precipitaciones, y un largo y seco periodo de verano han contribuido drásticamente a la aceleración de los procesos de degradación del suelo. Los cambios ambientales como consecuencia de la pérdida de las comunidades naturales de plantas, vienen a menudo acompañados o precedidos por la degeneración de las propiedades físicas y químicas del suelo, además de por una pérdida o reducción de la actividad microbiana. Actualmente se acepta que la diversidad y actividad de la microbiota del suelo es la base de uno de los mecanismos que más contribuyen a la conservación del suelo, al desarrollo y mantenimiento de la cubierta vegetal y por ende, a la estabilidad y funcionamiento del ecosistema. Así pues, el objetivo principal de este trabajo fue evaluar, en áreas degradas, la eficacia de diversas cepas de rizobacterias promotoras del crecimiento vegetal (RPCV) junto a la aplicación de enmiendas orgánicas sobre el desarrollo de la cubierta vegetal y la calidad de las propiedades del suelo, así como verificar la efectividad como RPCV de varias cepas de actinobacterias, previamente aisladas de diferentes suelos de la Región de Murcia. Con este fin, se llevaron a cabo cinco ensayos diferentes: tres de ellos en condiciones de campo, utilizando diferentes enmiendas orgánicas y RPCV, un cuarto ensayo consistente en el aislamiento de cepas de actinobacterias de la rizosfera de un arbusto autóctono presente en dos localidades diferentes de la Región de Murcia, Rhamnus lycioides L. y un quinto y último ensayo focalizado en la verificación como RPCV de las cepas de actinobacterias previamente aisladas así como el estudio de la incidencia relativa del de origen de las cepas y el suelo sujeto a plantación en la efectividad de las mismas. En todos los experimentos desarrollados en condiciones de campo, se evaluaron tanto el crecimiento y la absorción de nutrientes por parte de la planta, así como las respuestas al estrés originado por la escasez de agua. Del mismo modo, se determinaron las propiedades físico-químicas, químicas y biológicas del suelo. Con respecto al ensayo de aislamiento de actinobacterias de suelo rizosférico, se llevaron a cabo diversas técnicas que permitieron aislar y purificar diferentes cepas, así como caracterizarlas e identificarlas. Como resultados principales del trabajo, se puede destacar que en los tres primeros ensayos, las rizobacterias empleadas promovieron, satisfactoriamente, el crecimiento de las plantas así como la absorción de nutrientes y su tolerancia al estrés. En el primer experimento, en el que se ensayó sobre Cistus albidus L. una mezcla de dos rizobacterias inmovilizadas en arcilla (Azospirillum brasilense y Pantoea dispersa) como inoculante microbiano y residuo de oliva como enmienda, se observó un efecto aditivo en el tratamiento combinado, consistente en la inoculación microbiana y la adición del residuo orgánico al mismo tiempo, que permitió acrecentar las propiedades bioquímicas y microbiológicas del suelo. En el segundo ensayo en campo, en el que se probaron las mismas rizobacterias y la misma enmienda sobre Pinus halepensis Mill., se determinó que la eficacia de la inoculación microbiana fue el tratamiento más efectivo sobre el desarrollo de la planta y sobre las propiedades del suelo. El tercer ensayo se desarrolló para verificar la eficacia de diferentes cepas libres de RPCV (Bacillus megaterium, Enterobacter sp., Bacillus thuringiensis y Bacillus sp.) y la adición de residuo de remolacha azucarera compostado como enmienda orgánica sobre Lavandula dentata L. En este caso, la selección de las rizobacterias efectivas y la combinación de su inoculación junto con la aplicación de la enmienda orgánica se consideró el punto crucial del que dependería la eficacia de esta técnica de revegetación. Con respecto al cuarto ensayo, desarrollado en condiciones de laboratorio, la metodologías utilizadas para el aislamiento caracterización e identificación de diferentes especies de actinobacterias se consideraron las adecuadas, obteniéndose cuatro cepas pertenecientes al género Streptomyces que reunían las condiciones necesarias para ser consideradas potenciales RPCV. En el quinto y último ensayo, en condiciones de campo, se determinó que las bacterias previamente aisladas preservaban las habilidades descritas en condiciones de laboratorio, verificándose su rol como RPCV. Sin embargo, deberían considerarse tanto el origen de la cepa como la fertilidad biológica del suelo sujeto a plantación como factores fundamentales para la selección de cepas de actinobacterias destinadas a uso en revegetación en ambientes semiáridos.
In Mediterranean semiarid zones of Southeast Spain, limited and irregular rainfalls and a long and dry summer periods have contributed drastically to the acceleration of soil degradation processes. Environmental changes as a consequence of loss of natural plant cover are often accompanied by the physical and chemical soil properties degeneration, and by a loss or reduction of microbial activity. It is a corroborated fact that the proper functioning and stability of terrestrial ecosystems depends, to a large extent, of the diversity and composition of their vegetal cover. However, the ecological mechanisms that adjust and maintain the peculiar diversity of plant species in an ecosystem throughout the time are only known in a fragmentary way. Nowadays, it is permissible to think that the soil microbiota diversity and activity constitute the basis of one of the mechanisms that influences on soil preservation, on the development and maintenance of the vegetal cover and, consequently, on the ecosystem stability and functioning. The main objective in this Thesis was to evaluate, in degraded areas, the effectiveness of diverse plant growth promoting rhizobacteria (PGPR) strains and the addition of an organic waste on plant performance and on the soil quality properties, as well as to verify the efficacy of some actinobacteria strains as PGPR, previously isolated from different soils of Murcia. So, five different assays were developed: three field experiments involved the use of different organic amendments and PGPR strains; a fourth assay based on the isolation of different actinobacterial strains from the rhizosphere of an autochthonous shrub, that occurs naturally in two distinct sites of Murcia, Rhamnus lycioides L. and a fifth and last experiment focused on the verification as PGPR of the previously isolated actinobacteria strains as well as the study of the relative incidence of both the strain origin and the characteristics of soil subjected to plantation. In the entire field assays it was evaluated the plants growth, nutrients uptake and the biochemical and/or physiological responses of the plants. The physical, physico-chemical and biological soil properties were also determined. With regard to the experiment focused to the actinobacteria isolation from rhizosphere soil, diverse techniques were carried out allowing isolating and purifying different strains as well as to characterise and identify them. The main results obtained in this Thesis can be summarised as follows: in the assays developed under field conditions, the assayed PGPR satisfactory promoted the plant growth, the nutrients uptake and the tolerance to water stress. In the first assay, it was tested the addition of a mixture of two immobilised PGPR in clay pellets (Azospirillum brasilense and Pantoea dispersa) as microbial inoculant and olive mill residue as organic amendment on the target plant Cistus albidus L., it was observed an additive effect in the combined treatment consisting of the microbial inoculation and the organic amendment applied jointly, allowing to enhance biochemical and microbiological soil properties. In the second field experiment, developed by using the same PGPR and organic residue than in the previous assay, it was determined that the most effective treatment to improve Pinus halepensis Mill. plant performance and soil conditions was the microbial inoculation. The third experiment was developed to verify the effectiveness of diverse PGPR free strains (Bacillus megaterium, Enterobacter sp., Bacillus thuringiensis and Bacillus sp.) and the application of sugar beet residue as organic amendment Lavandula dentata L. performance as target plant. The selection of the most efﬁcient rhizobacteria strains and their combined effect with organic residue seems to be a critical point that drives the effectiveness of using these biotechnological tools in revegetation tasks. Regarding the fourth experiment, developed under laboratory conditions, the methodologies used to the actinobacteria isolation, characterisation and identification were successful. Four strains belonging to genus Streptomyces were obtained and they met the required abilities to consider them PGPR. The actinobacteria strains were tested in a fifth assay developed under field conditions being observed that the PGPR capacities were preserved. However, the strain origin and the biological fertility of plantation soil must be considered to an adequate actinobacteria strain selection to be used in restoration programs under semiarid conditions.

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Rankin, Lynda. « Evaluation of native rhizosphere bacteria for use as biological control agents against Pythium aphanidermatum root rot of European greenhouse cucumbers ». Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=56660.

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Thirty-two isolates of rhizosphere bacteria, selected for their ability to inhibit zoospore germination and/or mycelial growth of Pythium aphanidermatum (Pa) in vitro, were evaluated in a test tube bioassay using cucumber c.v. 'Straight 8'. These isolates were identified as Psedudomonas corrugata (Pc13 or 35) and P. fluorescens (Pf15, 16 or 27). All but one of the five isolates effectively colonised the roots of cucumber plants in short term studies. Isolates 15 and 35 were found to maintain high population densities throughout the time period. Pa-inoculated plants treated with the Pc13 or Pf15 produced fruit yields equal to 92 and 74% respectively of the control (no Pa, no bacteria). Pa-inoculated plants without bacteria yielded only 46% of the control. In the fall crop, Pa-inoculated plants treated with Pc13 or Pf15 yielded 52 and 47% of the control compared to Pa-only treatment, which yielded 12.5% of the control. In both crops, treatment with any of the bacterial isolates resulted in significantly reduced cull rates compared to the Pa-only treatment.

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Mwafulirwa, Lumbani. « The potential for root trait selection to enhance soil carbon storage and sustainable nutrient supply ». Thesis, University of Aberdeen, 2017. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=231426.

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Plant roots are central to C- and N-cycling in soil. However, (i) plants differ strongly in tissue recalcitrance (e.g. lignin content) affecting their mineralization in soil, and (ii) rhizodeposits also vary strongly in terms of the metabolites that they contain. Therefore, (i) we used 13C labelled ryegrass root and shoot residues as substrates to investigate the impact of tissue recalcitrance on soil processes through controlled incubation of soil, (ii) we assessed variations in root C-deposition between barley genotypes and their respective impacts on soil processes using 13CO2 labelled plants, (iii) using 13C/15N enriched ryegrass root residues as tracer material, we investigated the impacts of barley genotypes on mineralization of recently incorporated plant residues in soil and plant uptake of the residue-derived N, and (iv) we applied a quantitative trait loci analysis approach to identify barley chromosome regions affecting soil microbial biomass and other soil and root related traits. In the first study, addition of root residues resulted in reduced C-mineralization rates, soil microbial activity and soil organic matter (SOM) priming relative to shoot residues. Planted experiments revealed (i) genotype effects on plant-, SOM- and residuederived surface soil CO2-C efflux and showed that incorporation of plant derived-C to the silt-and-clay soil fraction varied between genotypes, indicating relative stabilization of root derived-C as a result of barley genotype, (ii) that plant uptake of residue released N between genotypes was linked to genotype impacts on residue mineralization, and (iii) barley chromosome regions that influence plant-derived microbial biomass C. These results (i) suggest that greater plant tissue recalcitrance can lower soil C-emissions and increase C-storage in soil, and (ii) demonstrate the barley genetic influence on soil microbial communities and C- and N-cycling, which could be useful in crop breeding to improve soil microbial interactions, and thus promote sustainable crop production systems.

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Laudick, Julia Ann. « Microbial Biostimulants in Organic Farming Systems : Patterns of Current Use and an Investigation of Their Efficacy in Different Soil Environments ». The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1483689529339271.

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Planchon, Aline. « Le pathosystème Lin (Linum usitatissimum) - Fusarium oxysporum : Impact du champignon et d'un agent de biocontrôle sur des réponses moléculaires de la plante et le développement de la fusariose ». Thesis, Normandie, 2018. http://www.theses.fr/2018NORMR122.

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Le lin, principale plante à fibres cultivée en France possède un intérêt industriel pour la qualité de ses fibres. Les cultures de lin sont régulièrement attaquées par un champignon tellurique, Fusarium oxysporum f. sp. lini (Fol), responsable des plus grandes pertes dans les cultures de lin. Les PGPR (Plant Growth Promoting Rhizobacteria) sont des bactéries réputées pour leurs capacités à améliorer la croissance et le développement des plantes, mais également pour leur pouvoir compétiteur au sein de la rhizosphère et leur aptitude à induire une réponse immunitaire chez les plantes. Parallèlement, l’utilisation de SDP (Stimulateur des Défenses des Plantes), molécules capables d’éliciter les mécanismes de défenses des plantes est une autre alternative pour limiter l’utilisation des pesticides. Dans le cadre de ce projet mené sur deux variétés de lin, Aramis et Mélina, il a pu être montré que Fol induisait un remodelage de la paroi au niveau des racines et des tiges, impliquant les hémicelluloses et les pectines, seulement deux jours après inoculation avec le champignon. L’utilisation de la souche ATCC 6633 de Bacillus subtilis comme agent de biocontrôle a permis de réduire de façon significative l’apparition des symptômes de la fusariose. Il a également été montré qu’en plus d’avoir un effet fongicide sur Fol, cette bactérie est capable d’induire l’expression de deux gènes de défense (Pathogenesis-Related) codant pour une β-(1,3)-glucanase (PR-2) et codant pour une chitinase-like (CTL-10), de gènes impliqués dans la voie des phénylpropanoïdes (PHENYLALANINE AMONIA LYASES, PAL-3 et PAL-4) et dans le remodelage pariétal (PECTIN METHYLESTERASE-3, PME-3) au niveau racinaire. Des analyses biochimiques ont également permis de montrer que B. subtilis provoque des modifications se traduisant par un renforcement pariétal au niveau des tiges chez les deux variétés. Enfin, l’association de la PGPR avec une molécule élicitrice (pregnénolone sulfate) a eu un effet synergique sur l’expression de gènes de défense
In France, flax (Linum usitatissumum) is a principal fibers crop. Fusarium oxysporum f sp lini (Fol), a soil-borne fungus, is responsible for the major losses in crop yield. PGPR (Plant Growth Promoting Rhizobacteria) are known for their abilities to promote plant growth and health. These bacteria are also good competitors in the rhizosphere and can induce a plant defense response. The use of compounds able to elicit plant defense mechanisms is also an alternative to limit the use of pesticides. In this project, it has been shown that F. oxysporum f. sp. lini induces only two days after inoculation cell wall remodeling in the root and the stem involving hemicelluloses and pectins on two flax varieties, Aramis and Mélina, . The use of the Bacillus subtilis strain ATCC 6633 as biocontrol agent significantly reduced fusarium wilt appearance. In addition to its antifungal effect against Fol, this bacteria is able to induce the expression of two Pathogenesis-Related genes coding for a β-(1,3)-glucanase (PR-2) and a chitinase-like (CTL-10), genes involved in the phenylpropanoid pathway (PHENYLALANINE AMONIA LYASES, PAL-3 and PAL-4) and also in cell wall remodeling (PECTIN METHYLESTERASE-3, PME-3) in the root. Biochemical analyses show that B. subtilis causes modifications resulting in cell wall reinforcement in the stem in both varieties. Finally, the association of B. subtilis with an elicitor (pregnenolone sulfate) had a synergistic effect on the expression of defense-related genes

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Zappelini, Cyril. « Étude des communautés microbiennes rhizosphériques de ligneux indigènes de sols anthropogéniques, issus d’effluents industriels ». Thesis, Bourgogne Franche-Comté, 2018. http://www.theses.fr/2018UBFCD057/document.

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Mon sujet de thèse intègre l’un des projets globaux de l’UMR UFC/CNRS 6249 Chrono-Environnement intitule « stratégies de phytoremédiation basées sur l’utilisation d’arbres et de microorganismes associés », qui s’appuie, entre autre, sur 2 projets de recherche :• le projet PROLIPHYT (programme Eco-Industrie, 2013-2018, ADEME) intitulé « PROduction de LIgneux PHYtoremédiants»,• le projet PHYTOCHEM (ANR CD2i, 2013-2018) intitulé « Développement de procédés chimiques éco-innovants pour valoriser les biomasses issues des phytotechnologies ».Les objectifs généraux sont d’améliorer le potentiel de phytoremédiation d’un panel d’espèces ligneuses et de développer le potentiel microbien pour une phytoremédiation aidée sur sol contaminé. En plus de limiter l’impact des polluants, cette stratégie vise à promouvoir la production de biomasse sur sols délaissés et non exploitables par l’agriculture, tout en assurant la biodiversité nécessaire à la restauration d’un écosystème anthropogénique.Mon travail de thèse est financé au travers un contrat doctoral ministériel handicap (dyslexie). Il s’appuie sur la réhabilitation de deux zones de stockage de sédiments industriels, utilisés jusque dans les années 2000. Ces deux sites expérimentaux (site INOVYN de St Symphorien-sur-Saône en Côte d’Or, site CRISTAL de l’Ochsenfeld en Alsace) présentent des caractéristiques physico-chimiques très particulières qui en font des lieux d’étude privilégiés. Le premier est une ancienne lagune de décantation dont les sédiments enrichis en Hg, Ba et As proviennent du traitement des eaux usées issues du procédé d’électrolyse à Hg de l’entreprise SOLVAY. Le second est une lagune constituée d’un remblai dans lequel ont été stockés depuis les années 1930, les résidus d’extraction du dioxyde de titane de l’Usine CRISTAL de Thann. A l’inverse du premier site expérimental, on observe une flore peu abondante qui se traduit par un développement hétérogène d’une espèce ligneuse principale, le bouleau.La recolonisation naturelle et spontanée de végétaux, plus particulièrement d’espèces ligneuses sur les deux sites est sans doute le résultat d’étroites collaborations avec des microorganismes telluriques situés aux abords de leur système racinaire. Nous avons ainsi choisi de travailler sur 3 espèces pionnières qui se sont naturellement réimplantées sur les deux sites d’études : le saule et le peuplier pour la friche industrielle de Tavaux et le bouleau pour l’unité de traitement des effluents du site de l’Ochsenfeld
AbstractMy thesis subject includes one of the global projects of the UMR UFC/CNRS 6249 Chrono-Environnement entitled "phytoremediation strategies based on the use of trees and associated microorganisms", which is based, among other things, on 2 research projects:• the PROLIPHYT project (Eco-Industry programme, 2013-2018, ADEME) entitled "Production of woody phytoremediants",• the PHYTOCHEM project (ANR CD2i, 2013-2018) entitled "Development of eco-innovative chemical processes to exploit biomasses from phytotechnologies".The general objectives are to improve the phytoremediation potential of a panel of woody species and to develop the microbial potential for assisted phytoremediation on contaminated soil. In addition to limiting the impact of pollutants, this strategy aims to promote the production of biomass on land abandoned and not exploitable by agriculture, while ensuring the biodiversity needed to restore an anthropogenic ecosystem.My thesis work is financed through a ministerial doctoral contract for disability (dyslexia). It is based on the rehabilitation of two industrial sediment storage areas, used until the 2000s. These two experimental sites (INOVYN site of Saint-Symphorien-sur-Saône in Côte-d'Or, CRISTAL site of Ochsenfeld in Alsace) present very particular physico-chemical characteristics which make them privileged places of study. The first is a former settling lagoon whose sediments enriched in Hg, Ba and As come from the treatment of wastewater from SOLVAY's Hg electrolysis process. The second is a lagoon consisting of a backfill in which the titanium dioxide extraction residues from the CRISTAL Thann Plant have been stored since the 1930s. In contrast to the first experimental site, there is a low abundance of flora which results in heterogeneous development of a main woody species, the birch.The natural and spontaneous recolonisation of plants, more particularly woody species on both sites, is undoubtedly the result of close collaboration with telluric microorganisms located near their root systems. We have thus chosen to work on 3 pioneer species that have naturally relocated to the two study sites: willow and poplar for the industrial wasteland of Tavaux and birch for the effluent treatment unit at the Ochsenfeld site

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South, Kaylee. « Improving abiotic and biotic stress tolerance in floriculture crops ». The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1595499762154056.

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GUERRIERI, MARIA CHIARA. « Bioprospecting di simbionti vegetali con proprietà PBS per lo sviluppo di nuovi prodotti biostimolanti : bridging tra i risultati della ricerca e gli aspetti normativi ». Doctoral thesis, Università Cattolica del Sacro Cuore, 2021. http://hdl.handle.net/10280/95717.

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L'agricoltura moderna sta affrontando sfide come la perdita di fertilità del suolo, la variabilità climatica e gli attacchi di agenti patogeni in continuo aumento. Le pratiche agricole si stanno evolvendo verso sistemi sostenibili e rispettosi dell'ambiente. L'uso di biostimolanti (PBS, plant biostimulant) è una soluzione innovativa per affrontare le sfide di un’agricoltura sostenibile che garantisce un assorbimento ottimale dei nutrienti, una resa delle colture e tolleranza agli stress abiotici. In particolare, tra i diversi tipi di biostimolanti presenti sul mercato, i rizobatteri, classificati come Plant Growth Promoting Rhizobacteria (PGPR), offrono un nuovo approccio per promuovere la crescita delle piante, la mitigazione degli stress e l’aumento della resa colturale. Pertanto i PGPR sono considerati come una sorta di "probiotici" vegetali, poiché contribuiscono in modo efficiente alla nutrizione e all'immunità delle piante. L'obiettivo principale di questa tesi è isolare e identificare batteri presenti nella rizosfera di pomodoro (Solanum lycopersicum L.) che mostrano proprietà PBS, nonché valutare i meccanismi coinvolti nell'azione di promozione della crescita delle piante (Capitolo 2) e la genetica alla base di questi meccanismi (Capitolo 3 e 4). Infatti, una profonda comprensione dei meccanismi d’azione dei PGPR potrebbe colmare la mancanza di coerenza del dato di efficacia tra gli studi di laboratorio e gli studi in campo e stimolare la ricerca per la produzione e la commercializzazione di nuovi prodotti biostimolanti microbici.
Modern agriculture faces challenges such as loss of soil fertility, ﬂuctuating climatic factors and increasing pathogen and pest attacks. Agricultural practices have been evolving towards organic, sustainable and environmentally friendly systems. The use of natural plant biostimulants (PBS) is an innovative solution to address the challenges in sustainable agriculture, to ensure optimal nutrient uptake, crop yield, quality and tolerance to abiotic stress. In particular, among different types of biostimulants present on the market, plant growth promoting rhizobacteria (PGPR) offer a novel approach for promoting plant growth, mitigate stress and increase crop yield. Hence, PGPR inoculants are now considered as a kind of plant ‘probiotics’, since they efficiently contribute to plant nutrition and immunity. The main goal of this thesis was to isolate and identify bacteria symbionts of tomato (Solanum lycopersicum L.) rhizosphere, which showed PBS properties and evaluate mechanism involved in the action of PGPR (Chapter 2), underlying genetics and physiological pathways (Chapter 3 and 4). Indeed, a deeply understanding of the mechanisms of plant growth promotion, could fulfill the lack of consistency between lab, greenhouse and field studies, and support commercialization of novel plant biostimulant products.

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GUERRIERI, MARIA CHIARA. « Bioprospecting di simbionti vegetali con proprietà PBS per lo sviluppo di nuovi prodotti biostimolanti : bridging tra i risultati della ricerca e gli aspetti normativi ». Doctoral thesis, Università Cattolica del Sacro Cuore, 2021. http://hdl.handle.net/10280/95717.

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L'agricoltura moderna sta affrontando sfide come la perdita di fertilità del suolo, la variabilità climatica e gli attacchi di agenti patogeni in continuo aumento. Le pratiche agricole si stanno evolvendo verso sistemi sostenibili e rispettosi dell'ambiente. L'uso di biostimolanti (PBS, plant biostimulant) è una soluzione innovativa per affrontare le sfide di un’agricoltura sostenibile che garantisce un assorbimento ottimale dei nutrienti, una resa delle colture e tolleranza agli stress abiotici. In particolare, tra i diversi tipi di biostimolanti presenti sul mercato, i rizobatteri, classificati come Plant Growth Promoting Rhizobacteria (PGPR), offrono un nuovo approccio per promuovere la crescita delle piante, la mitigazione degli stress e l’aumento della resa colturale. Pertanto i PGPR sono considerati come una sorta di "probiotici" vegetali, poiché contribuiscono in modo efficiente alla nutrizione e all'immunità delle piante. L'obiettivo principale di questa tesi è isolare e identificare batteri presenti nella rizosfera di pomodoro (Solanum lycopersicum L.) che mostrano proprietà PBS, nonché valutare i meccanismi coinvolti nell'azione di promozione della crescita delle piante (Capitolo 2) e la genetica alla base di questi meccanismi (Capitolo 3 e 4). Infatti, una profonda comprensione dei meccanismi d’azione dei PGPR potrebbe colmare la mancanza di coerenza del dato di efficacia tra gli studi di laboratorio e gli studi in campo e stimolare la ricerca per la produzione e la commercializzazione di nuovi prodotti biostimolanti microbici.
Modern agriculture faces challenges such as loss of soil fertility, ﬂuctuating climatic factors and increasing pathogen and pest attacks. Agricultural practices have been evolving towards organic, sustainable and environmentally friendly systems. The use of natural plant biostimulants (PBS) is an innovative solution to address the challenges in sustainable agriculture, to ensure optimal nutrient uptake, crop yield, quality and tolerance to abiotic stress. In particular, among different types of biostimulants present on the market, plant growth promoting rhizobacteria (PGPR) offer a novel approach for promoting plant growth, mitigate stress and increase crop yield. Hence, PGPR inoculants are now considered as a kind of plant ‘probiotics’, since they efficiently contribute to plant nutrition and immunity. The main goal of this thesis was to isolate and identify bacteria symbionts of tomato (Solanum lycopersicum L.) rhizosphere, which showed PBS properties and evaluate mechanism involved in the action of PGPR (Chapter 2), underlying genetics and physiological pathways (Chapter 3 and 4). Indeed, a deeply understanding of the mechanisms of plant growth promotion, could fulfill the lack of consistency between lab, greenhouse and field studies, and support commercialization of novel plant biostimulant products.

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Mangmang, Jonathan S. « Plant growth promotion by rhizobacteria in aquaponics ». Thesis, The University of Sydney, 2015. http://hdl.handle.net/2123/14863.

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Wastewater or fish effluent (FE) from freshwater aquaculture can be a good and cheap liquid fertiliser for plants. However, while it represents a good source of nutrients to support plant growth in a system called aquaponics, it appears that its use needs to be optimised to take full advantage of the potential benefits. Apart from mineral amendments, the use of beneficial microorganisms that can have a direct impact on plant growth and nutrient utilisation could be a promising option. Plant growth promoting rhizobacteria (PGPR) are a group of rhizospheric bacteria, when introduced in association with the host plant at optimum density, can enhance plant growth and health. One well-known and versatile PGPR is Azospirillum brasilense that has numerous beneficial effects on plants. The production of phytohormones by the bacterium has been proposed as one of the major mechanisms responsible for the plant growth promoting effects observed in plants inoculated with Azospirillum. Hence, this PGPR could be a valuable input in vegetable production under an aquaponics system. In addition, despite the widespread studies conducted with this PGPR in various crops, there is no published report on vegetables fertilised with fish effluent or under an aquaponics system. This study focuses on evaluating the role of PGPR, particularly A. brasilense, on the growth and development of selected vegetable crops fertilised with fish effluent and using an aquaponics system. Strains of A. brasilense Sp7, Sp7-S and Sp245, Herbaspirillum seropedicea and Burkholderia phytofirmans PsJNT were used to inoculate seeds and/or seedlings by soaking and/or drenching. Inoculated and uninoculated seeds and seedlings were germinated and raised in controlled growing cabinets and a greenhouse, respectively. PGPR-inoculated vegetable seeds generally germinated faster and had better early seedling growth than uninoculated controls. Cucumber seeds inoculated with strains Sp7, Sp245 and H. seropedicea exhibited increase in germination percentage and shoot length by 9 and 20%, respectively, while all PGPR improved the germination vigour index, and enhanced length and weight of seedling roots by 25 and 23%, respectively. In tomato, Sp7-S enhanced the germination value, while most PGPR, except Sp7, significantly improved the germination vigour, root length (28%) and weight (37%) with superior vigor. In lettuce, Sp7-S, Sp245 and H. seropedicea inoculation resulted in longer roots (26%). Germination vigour was also improved by inoculation, except for B. phytofirmans. This improved germination and early seedling growth characteristics may influence future crop establishment and production. Of the two laboratory-based inoculation methods used, soaking appeared to be a better technique for enhanced early seedling growth by strains of A. brasilense. This effect could be related to their unique metabolic characteristics of the strains. The growth promoting effects of A. brasilense strains on the early seedling growth of vegetables varied between the bacterial strains and crop species, In particular, strains Sp7-S and Sp245 strongly enhanced root (85%) and shoot (75%) growth, germination value and vigour in tomato when inoculated by soaking. Sp245 increased endogenous plant IAA (indole-3-acetic acid) content of cucumber and lettuce by up to 100%, irrespective of inoculation method. This work demonstrates that the strains can be used for inoculation within the studied range of cell concentrations with or without plant growth promoting (PGP) effects. However, strain Sp7 appeared to be more influential at lower inoculum concentrations (about log10 6), while Sp7-S and Sp245 at log10 7 cfu mL-1 or higher. For instance, cucumber seeds inoculated with Sp7 log10 8 and 6, Sp7-S and Sp245 log10 8 and 7 cfu mL-1 increased seedling growth, vigour index and endogenous plant IAA by up to 55%. In lettuce, the inoculation with log10 6 of Sp7, log10 7 and 6 of Sp7-S, and log10 8 and 7 of Sp245 yielded superior seedling growth with improved seedling vigour, while log10 7 and 8 of Sp7 and Sp7-S, respectively, increased plant IAA concentration by more than 20%. In tomato, Sp7 at log10 6, Sp7-S and Sp245 at log10 7 enhanced the root biomass, while inoculation with all concentrations of Sp7 and Sp7-S, and log10 8 of Sp245 significantly increased plant IAA content by up to 300%. The inoculation with the bacterial cell suspension exerted more beneficial effects on the early seedling growth, vigor and endogenous plant IAA. In cucumber, seeds inoculated with bacterial cell and those treated with IAA solutions produced longer roots and shoots by 163 and 60%, respectively. Seedlings also exhibited superior vigor. These treatments, together with culture supernatant, and combined cell and supernatant, also increased endogenous plant IAA content, in which the combined cell and supernatant produced up to four-fold greater plant IAA concentrations. In lettuce, seeds inoculated with cell suspension produced longer roots (86%) with superior seedling vigour and elevated plant IAA. In tomato, inoculation with cell suspension and treatment with IAA solutions enhanced length of roots length by up to 52 and 188%, respectively, while all treatments significantly increased the plant IAA content by 70%. These results also demonstrate that bacterial cell suspension and combined cell and supernatant showed consistent effects on the expression of plant IAA. This work suggests that the endogenous IAA levels in the seeds during germination have been altered by the activity of live bacteria and phytohormones present in the supernatant. The altered root morphology of the seedlings due to A. brasilense inoculation might have enhanced the capacity of roots to absorb water and essential minerals leading to enhanced plant growth and metabolic activity. For instance, inoculated cucumber seedlings produced longer roots (23%), greater root biomass (19%), higher total phosphorus (15%), endogenous plant IAA (101%) and peroxidase activity (134%). In lettuce, inoculation increased root length (22%), peroxidase activity (53%) and plant IAA (38%). In addition, strain Sp7 enhanced the chlorophyll and protein contents by 25 and 42%, respectively. In tomato, inoculation resulted in longer roots (67%), larger leaves (22%), higher dry matter accumulation (33%), protein (15%) and endogenous plant IAA (94%) contents. Taller seedlings (12%) with larger stems (15%) and more developed leaves (9%) with greater fresh biomass (18%) were observed with Sp7 inoculation, while two-fold increase in peroxidase activity due to strain Sp245 was detected. On the other hand, inoculated basil seedlings grown in soil produced longer roots (90%), taller seedlings (19%) with more (25%) and larger (61%) leaves, which resulted in greater seedling biomass (61%) and phosphorus content (3%), and higher peroxidase activity (122%) particularly for those inoculated with Sp245 and Sp7, respectively. These plant growth promoting effects were also observed in basil grown in an aquaponics system. These include larger stems and leaves (25%), fresh weight yield (17%), peroxidase activity (73%), phosphorus (5%) and protein (23%) contents due to inoculation. The amount of endogenous plant IAA (27%) and chlorophyll (13%) contents were also increased by Sp7 and Sp7-S inoculation, respectively. This further suggests that A. brasilense could be a valuable agent to help maximize the usefulness of fish effluent or wastewater from freshwater aquaculture for vegetable seedling production. The 16S rDNA terminal restriction fragment length polymorphism (T-RFLP) analysis revealed that inoculation with A. brasilense has no adverse effect to the existing rhizobacterial communities (measured by the changes in the distribution of detectable operational taxonomic unit (OTU) (represented by TRF)) in the root rhizosphere of vegetables (i.e. lettuce, cucumber and basil) grown under different systems (i.e. sterile artificial substrate, soil and aquaponics). This highlights that this PGPR did not cause disturbance to the resident microbial communities or imbalance of the normal functioning of the system. In aquaponics, the presence of a substantial density of A. brasilense strains in the root rhizosphere of basil and the enhanced plant growth and physiological parameters of inoculated basil may imply that Azospirillum have successfully established a beneficial association with the existing bacterial populations. Moreover, this study demonstrates the potential of Azospirillum to be a practical agent for enhancing plant growth and development of vegetables fertilised with fish effluent and under aquaponics system. Directing future research endeavors to better understand the basic mechanisms occurring in the Azospirillum-plant interaction rather than exploring large scale application of this PGPR would support further development of the bioinoculant technology.

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Meneghin, Silvana Perissatto [UNESP]. « Efeito da aplicação de fitorreguladores em rizobactérias isoladas de diferentes variedades de cana-de-açúcar (Saccharum spp.), no município de Araras - SP ». Universidade Estadual Paulista (UNESP), 2008. http://hdl.handle.net/11449/103966.

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Made available in DSpace on 2014-06-11T19:32:55Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-04-29Bitstream added on 2014-06-13T19:43:45Z : No. of bitstreams: 1 meneghin_sp_dr_rcla.pdf: 500401 bytes, checksum: 1dbb48df89774c8c8a05446c822888e1 (MD5)
Universidade Estadual Paulista (UNESP)
Nas usinas, no início da safra, a obtenção de matéria-prima de boa qualidade é maximizada com a aplicação de fitorreguladores, os quais aumentam o teor de sacarose da cana-de-açúcar. Em áreas onde eles são aplicados, tem se observado melhor desenvolvimento e perfilhamento das plantas. Avaliou-se aqui o efeito da aplicação dos fitorreguladores Ethrel e Moddus sobre o crescimento da cana-de-açúcar, de forma direta e indiretamente, através da modificação da microbiota rizosférica. Além disso, objetivou-se também avaliar o uso de rizobactérias, isoladas dos experimentos com fitorreguladores, para o biocontrole de doenças e seus possíveis mecanismos de ação. Os efeitos dos fitorreguladores sobre os microrganismos do solo foram avaliados em meios de cultura acrescidos de Ethrel e Moddus em concentrações de 0 a 1000 ppm. Estes fitorreguladores foram aplicados via foliar e via solo para análise do desenvolvimento da cana-de-açúcar (variedades RB72454, RB835486 e RB855156) em casa-de-vegetação, utilizando-se solo sem tratamento e tratado com brometo de metila. Após dez meses, foram avaliadas a brotação, altura e matéria seca da parte aérea e das raízes das plantas cultivadas. Rizobactérias foram isoladas dos solos contidos nos vasos e avaliadas in vitro quanto à capacidade de controle de fungos fitopatogênicos (Thielaviopsis paradoxa, Fusarium spp. e Hendersonina sacchari), e in vivo, quanto à capacidade de promoção de crescimento de plântulas de cana-de-açúcar. Alguns mecanismos de ação das rizobactérias foram também estudados, como produção de ácido indol acético, ácido cianídrico, sideróforos e solubilização de fosfato inorgânico. Constatou-se que as populações de fungos foram mais sensíveis à adição dos fitorreguladores do que outros grupos de microrganismos, com redução...
For sugar and alcohol industries, at the start of harvesting, to obtain good quality raw material is potentially possible with the application of plant regulators, which have a role in natural sugar cane maturation, increasing sucrose content. In areas where they have been applied, better plant development and shooting have been observed. The aim here was to evaluate the application of plant regulators Ethrel and Moddus on sugar cane growth, not only in a direct way, but also indirectly, through the modification of rhizosphere microorganisms. Besides, this work also aimed the evaluation of rhizobacteria isolated from the experiments using plant regulators upon the disease biocontrol and their action mechanisms in this respect. The effects of plant regulators upon the soil microorganisms were verified in culture media where Ethrel and Moddus were added in concentrations ranging from 0 to 1000 ppm, while the effects of these substances (applied in leaves and in soil) upon the sugar cane development (varieties RB72454, RB835486 and RB855156) were surveyed in greenhouse, using soil without treatment and treated with methyl bromide. After a ten-month period, the experiments were finished, and sprouting, height and aerial part and root dry matter were analyzed. Soil samples were taken from the pots for rhizobacteria isolation, which were evaluated initially in vitro regarding their ability to control plant pathogenic fungi (Thielaviopsis paradoxa, Fusarium spp. and Hendersonina sacchari), and in vivo, regarding their ability to promote sugar cane growth. Some action mechanisms were also studied, as indol acetic acid, cyanide acid and siderophore production and inorganic phosphate solubilization. It was verified that the fungi populations were more sensitive to the addition of plant regulators than other microorganisms, reducing their colony-forming unit (CFU)...(Complete abstract, click electronic access below)

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Meneghin, Silvana Perissatto. « Efeito da aplicação de fitorreguladores em rizobactérias isoladas de diferentes variedades de cana-de-açúcar (Saccharum spp.), no município de Araras - SP / ». Rio Claro : [s.n.], 2008. http://hdl.handle.net/11449/103966.

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Orientador: Samia Maria Tauk-Tornisielo
Banca: Sandra Regina Ceccato Antonini
Banca: Regina Teresa Rosim Monteiro
Banca: Antonio Ismael Bassinelo
Banca: Carlos Renato Corso
Resumo: Nas usinas, no início da safra, a obtenção de matéria-prima de boa qualidade é maximizada com a aplicação de fitorreguladores, os quais aumentam o teor de sacarose da cana-de-açúcar. Em áreas onde eles são aplicados, tem se observado melhor desenvolvimento e perfilhamento das plantas. Avaliou-se aqui o efeito da aplicação dos fitorreguladores Ethrel e Moddus sobre o crescimento da cana-de-açúcar, de forma direta e indiretamente, através da modificação da microbiota rizosférica. Além disso, objetivou-se também avaliar o uso de rizobactérias, isoladas dos experimentos com fitorreguladores, para o biocontrole de doenças e seus possíveis mecanismos de ação. Os efeitos dos fitorreguladores sobre os microrganismos do solo foram avaliados em meios de cultura acrescidos de Ethrel e Moddus em concentrações de 0 a 1000 ppm. Estes fitorreguladores foram aplicados via foliar e via solo para análise do desenvolvimento da cana-de-açúcar (variedades RB72454, RB835486 e RB855156) em casa-de-vegetação, utilizando-se solo sem tratamento e tratado com brometo de metila. Após dez meses, foram avaliadas a brotação, altura e matéria seca da parte aérea e das raízes das plantas cultivadas. Rizobactérias foram isoladas dos solos contidos nos vasos e avaliadas in vitro quanto à capacidade de controle de fungos fitopatogênicos (Thielaviopsis paradoxa, Fusarium spp. e Hendersonina sacchari), e in vivo, quanto à capacidade de promoção de crescimento de plântulas de cana-de-açúcar. Alguns mecanismos de ação das rizobactérias foram também estudados, como produção de ácido indol acético, ácido cianídrico, sideróforos e solubilização de fosfato inorgânico. Constatou-se que as populações de fungos foram mais sensíveis à adição dos fitorreguladores do que outros grupos de microrganismos, com redução...(Resumo completo, clicar acesso eletrônico abaixo)
Abstract: For sugar and alcohol industries, at the start of harvesting, to obtain good quality raw material is potentially possible with the application of plant regulators, which have a role in natural sugar cane maturation, increasing sucrose content. In areas where they have been applied, better plant development and shooting have been observed. The aim here was to evaluate the application of plant regulators Ethrel and Moddus on sugar cane growth, not only in a direct way, but also indirectly, through the modification of rhizosphere microorganisms. Besides, this work also aimed the evaluation of rhizobacteria isolated from the experiments using plant regulators upon the disease biocontrol and their action mechanisms in this respect. The effects of plant regulators upon the soil microorganisms were verified in culture media where Ethrel and Moddus were added in concentrations ranging from 0 to 1000 ppm, while the effects of these substances (applied in leaves and in soil) upon the sugar cane development (varieties RB72454, RB835486 and RB855156) were surveyed in greenhouse, using soil without treatment and treated with methyl bromide. After a ten-month period, the experiments were finished, and sprouting, height and aerial part and root dry matter were analyzed. Soil samples were taken from the pots for rhizobacteria isolation, which were evaluated initially in vitro regarding their ability to control plant pathogenic fungi (Thielaviopsis paradoxa, Fusarium spp. and Hendersonina sacchari), and in vivo, regarding their ability to promote sugar cane growth. Some action mechanisms were also studied, as indol acetic acid, cyanide acid and siderophore production and inorganic phosphate solubilization. It was verified that the fungi populations were more sensitive to the addition of plant regulators than other microorganisms, reducing their colony-forming unit (CFU)...(Complete abstract, click electronic access below)
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Griggs, Roland Stephen. « Pseudomonas spp. Isolated from Soybean Nodules Promote Soybean Growth and Nitrogen Fixation ». Thesis, Virginia Tech, 2020. http://hdl.handle.net/10919/98790.

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Nitrogen-fixing bacteria in soybean nodules convert atmospheric nitrogen to plant-available forms in exchange for carbon from the plant, but other non-nitrogen-fixing bacteria also reside in nodules, and their role in the nodule is not well understood. This study was conducted to determine the effect of three non-nitrogen-fixing Pseudomonas spp. strains isolated from nodules on soybean, and we hypothesized these strains benefit soybean. A greenhouse study in which two cultivars of soybean (Asgrow AG46X6 and Pioneer P48A60X) were treated with three fluorescent Pseudomonas spp. strains (referred to in this study as Bullseye, Pancake, and Starfish) and an uninoculated control. Soybeans were harvested at two time points: the R2/R3 growth stage and the R6 growth stage. Following each harvest, measures of growth, yield, and nitrogen fixation were taken, and data were analyzed using two non-parametric, multivariate analyses: multiple response permutation procedure (MRPP) and permutational multivariate analysis of variance (PERMANOVA). Both analyses showed soybeans of both cultivars treated with Pancake differed from controls following the first harvest but not the second. When analyzed individually, most metrics for growth, yield, and nitrogen fixation following the first harvest were not significantly different between Pancake and control treatments, but Pancake treatment means were still generally higher than controls. If metrics are considered collectively in conjunction with the results of the multivariate analyses, the results show Pancake generally increased soybean growth and nitrogen fixation. These findings support the hypothesis that non-nitrogen-fixing bacteria from nodules benefit plants, and such bacteria have the potential to serve as biofertilizers.
Master of Science in Life Sciences
Soybeans are one of the most commonly grown crops in the world, and nitrogen-fixing bacteria colonize the roots of soybeans and initiate the formation of spherical nodules attached to the roots. Inside the nodules, these bacteria convert atmospheric nitrogen to plant-available forms in exchange for sugar from the plant, and such bacteria reduce the need to add nitrogen fertilizer to agricultural fields. Other non-nitrogen-fixing bacteria also reside in nodules, but their role in the nodule is not well understood. If these bacteria benefit soybeans, they have the potential to serve as biofertilizers (microbial inoculants that promote plant growth). This study was conducted to determine whether non-nitrogen-fixing bacteria isolated from nodules benefit soybean. A greenhouse study in which two cultivars of soybean (Asgrow AG46X6 and Pioneer P48A60X) were grown in soil and were either left uninoculated or were inoculated with one of three strains of bacteria from the genus, Pseudomonas (referred to in this study as Bullseye, Pancake, and Starfish). Following harvest, measures of growth, yield, and nitrogen fixation were taken, and data showed the bacteria generally benefited the soybean plants. Although, these results showed the bacteria benefitted the plants, field trials and further testing in the greenhouse should be conducted before using these bacteria as commercial biofertilizers. Additionally, the effects of other non-nitrogen-fixing nodule bacteria on soybeans should also be tested to identify other beneficial strains, and the cost of production should be compared to the potential gains of using such bacteria before they are developed into biofertilizers.

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Lord, Fritz. « Untersuchungen zum Einfluss spezieller Rhizosphärenbakterien auf Pflanzenwachstum und Fusarium spp.-Toleranz bei Spargel (Asparagus officinalis L.) ». Doctoral thesis, Humboldt-Universität zu Berlin, Landwirtschaftlich-Gärtnerische Fakultät, 2002. http://dx.doi.org/10.18452/14979.

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Der Einfluss der Rhizosphärenbakterien Bacillus subtilis FZB 24, FZB 37, FZB 42, Bacillus pumilus RK 13 und Streptomyces graminofaciens und des Algenpräparates Goemar Fruton Spezial® (Ascophyllum nodosum) auf Wachstum, Ertrag und Toleranz gegenüber Fusarium spp. bei Spargel wurde untersucht. Es wurden mehrjährige Parzellenfeldversuche und Modellversuche unter kontrollierten Bedingungen mit natürlich Fusarium spp. belasteten Böden und mit speziellen Fusarium Erregern inokulierten Substraten durchgeführt. Die Analyse des verwendeten Nachbaubodens ergab eine wesentlich höhere Kontamination mit Fusarium spp. (56%) in Relation zum Fruchtfolgeboden (14%). F. oxysporum war die dominante Fusariumart. Desweiteren wurde eine ganze Reihe anderer Arten, wie z.B. F. acuminatum, F. culmorum, F. proliferatum und F. culmorum bestimmt, was die Komplexität der Wurzel- und Stängelfäuleerkrankung belegt. Analog zu diesem Ergebnis konnten im Vergleich zur Fruchtfolgevariante von den in dem Nachbauboden kultivierten Spargelpflanzen signifikant mehr Fusarium spp. (80%) isoliert werden. Das Wurzelwachstum war hier extrem reduziert. Unter diesen konduktiven Bedingungen gelang es durch Rhizombakterisierung (107 cfu/ml) mit B. subtilis FZB 42, eine signifikante Förderung des Wurzelwachstums relativ zur unbehandelten Kontrolle und zur B. subtilis FZB 37 Variante zu erzielen. In Pathogenitätstests konnten F. culmorum, F. oxysporum und F. proliferatum als bedeutende Spargelpathogene mit signifikant reduzierter Trieb- und Wurzelmasse nachgewiesen werden, während F. acuminatum nur geringe Symptome verursachte. Eine bakterielle Saatgutbeizung (108 cfu/ml) und zusätzliche präinfektionelle Gießapplikation (107 cfu/ml) konnte eine Infektion mit F. oxysporum f.sp. asparagi nicht verhindern. Dennoch waren die negativen Effekte im Vergleich mit der nicht bakterisierten Kontrolle in den B. subtilis Varianten FZB 24 und vor allem bei FZB 42 deutlich kompensiert. Diese Ergebnisse lassen vermuten, dass eine Resistenz- bzw. Toleranzinduktion ein potentieller Wirkmechanismus der Bakterien ist. In den Feldversuchen erbrachte eine Bakterisierung einjähriger Rhizome (107 cfu/ml) zur Pflanzung und ergänzende Gießbehandlungen (108 cfu/ml/1l/m) in den folgenden 2 Jahren eine tendenzielle Reduzierung der Trieblänge und des Triebdurchmessers, insbesondere in Kombination mit dem Algenpräparat. Einen eindeutigen Einfluss auf das Sortierungsergebnis konnte nicht nachgewiesen werden. Im Gegensatz hierzu resultierte eine Saatgutbakterisierung mit B. subtilis FZB 24 in einem generell geförderten Triebwachstum und einer signifikant gesteigerten Wurzelentwicklung. Auch die anderen Mikroorganismen erbrachten eine tendenzielle Wuchsförderung. Es konnte eine gesicherte Korrelation zwischen Wurzelmasse und Knospenanzahl ermittelt werden. Blattapplikationen mit Goemar Fruton Spezial® während der Hauptvegetationsphase hatten keinen Einfluss auf das Pflanzenwachstum.
The effects of the rhizobacteria Bacillus subtilis, Strain FZB 24, FZB 37and FZB 42, Bacillus pumilus RK 13, Streptomyces graminofaciens N6 and the alga Ascophyllum nodosum (Goemar Fruton Spezial®) on plant growth, yield and Fusarium spp. tolerance of Asparagus officinalis (L.) were investigated. The trials were carried out under field conditions over sev-eral years by sawing and planting and as pot trials in the greenhouse and climate chamber with soil naturally infested with Fusarium spp. and with steamed substrates inoculated with particularly Fusarium species. Asparagus replant soil was considerable higher infested with Fusarium spp. (56 %) than fresh soil without asparagus history (14 %). F. oxysporum was the most determined Fusarium species followed by F. redolens, F. acuminatum, F. culmorum, F. proliferatum, F. solani a.o.. That indicates the complex character of root and crown rot of asparagus. From asparagus plants cultivated in replant soil a significant higher rate of Fusarium isolations (80 %) could be worked out compared to the fresh soil treatment. The root growth in the contaminated soil was extremely reduced. In these conductive situation bacterial treatments with B. subtilis FZB 42 done as rhizom soaking (107cfu/ml) resulted in significantly increased root growth up to 32, 9 % related to the non treated control. B. subtilis FZB 37 was ineffective. F. oxysporum, F. culmorum and F. proliferatum showed a high pathogenicity to asparagus seedlings, manifested in significantly reduced fresh and dry weights of shoots and roots, while F. acuminatum caused only slight symptoms. None of the tested microorganisms applicated as seed coating (108 cfu/ml) and substrate drenching before pathogen inoculation (107 cfu/ml) could prevent seedlings from being infected by F. oxysporum f. sp. asparagi. The negative effects of infection are significantly compensated by Bacillus subtilis FZB 42 and FZB 24. The results support the conclusion, that induced tolerance is a potential mechanism of bacterial mode of action. Under field conditions rhizom bacterization of one year old asparagus plants (107 cfu/ml) before planting and additional soil drenching (108 cfu/ml/1,5l/m) during the following two years reduced shoot length, shoot diameter and yield, especially in combination with Goemar Fruton Spezial®. There was no remarkable influence on spear quality. Seed coating with B. subtilis FZB 24 (108 cfu/ml) and a soil drenching (108 cfu/ml/1l/m) in summer however re-sulted in higher shoots and significantly increased fresh weight and dry substance of roots. But also the other tested microorganisms showed a plant growth promoting trend. There was a significant positive correlation between root fresh weight and number of buds. By spraying the phylloclads four times during the main vegetation season the alga application only gave a slight improvement of plant growth in the field trials.

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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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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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Kierul, Kinga. « Comprehensive proteomic study of Bacillus amyloliquefaciens strain FZB42 and its response to plant root exudates ». Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2013. http://dx.doi.org/10.18452/16805.

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Bacillus amyloliquefaciens FZB42 ist ein frei lebendes Bakterium, das Pflanzenwurzeln besiedelt und das Pflanzenwachstum durch viele verschiedene Wirkmechanismen anregt. In dieser Arbeit wurden die molekularen Grundlagen dieser positiven Wirkungen, die dieses „Pflanzenwachstum fördernde Rhizobakterium“ (PGPR) auf seine Wirte ausübt, untersucht. Um den gegenseitigen Austausch von B. amyloliquefaciens und seinen Wirtspflanzen zu entschlüsseln, wurden umfangreiche Proteomstudien durchgeführt. Es wurden Referenzkarten der extrazellulären und zytosolischen Proteinfraktionen erstellt. Die größte Anzahl an ausgeschiedenen Proteinen konnte während der stationären Phase beobachtet werden. Die identifizierten extrazellulären Proteine gehören verschiedenen Funktionsklassen an, wobei die prominentesten Klassen am Kohlenhydrat-Abbau und den Transport von Molekülen durch die Zellwand beteiligt sind. Die zytosolischen Extrakte von Kulturen, die in 1C-Medium bzw. Mineralmedium angezogen wurden, und in der zweidimensionalen Gelelektrophorese (2 DE) aufgetrennt wurden, ergaben 461 und 245 verschiedene Protein-Einträge. Die erstellten Referenz-Karten wurden anschließend verwendet, um Proteine und Prozesse, in an der Interaktion mit Pflanzen beteiligt sind, zu identifizieren. Dafür wurden die Bakterien Wurzelexudaten von Mais (Zea mays L.) ausgesetzt. Die Proteine aus zwei Stämmen, denen die globalen Transkriptionsregulatoren (Degu, AbrB) und vier Sigma-Faktoren (SigB, SigM, SigV, und SigX) fehlen, wurden ebenfalls untersucht, um ihre Beteiligung an den bakteriellen Reaktionen auf die Wurzelausscheidungen zu analysieren. Zusammenfassend ist dies die erste Studie, die umfangreiche Proteomdaten von Gram-positiven PGPR präsentiert, wobei gleichzeitig die Veränderung der Expression von extrazellulären und zytoplasmatischen Proteinen, nach Zugabe von Wurzelexudaten, ausgewertet wurde.
Bacillus amyloliquefaciens strain FZB42 is a free-living bacterium that competitively colonizes plant roots and stimulates plant growth by many different modes of action. The molecular basis of singular beneficial effects that this Plant Growth-Promoting Rhizobacteria (PGPR) exert on their hosts have been studied. To decipher the molecular cross-talk of B. amyloliquefaciens and its’ host plants as a whole system, an extensive proteomic approach was performed. Reference maps of the extracellular and cytosolic protein fractions were established. The highest number of secreted proteins was observed during stationary growth phase. Identified extracellular proteins belong to different functional classes, with the most prominent classes involved in carbohydrate degradation and transportation of molecules across the cell wall. Cytosolic extracts obtained from cultures grown in 1C and minimal media subjected to the 2 Dimensional Electrophoresis (2 DE), revealed 461 and 245 different protein entries, respectively. Created reference maps were subsequently used to identify proteins and processes involved in the interaction with plants, prior to exposure of bacteria to maize (Zea mays L.) root exudates. The proteomics of two strains lacking expression of genes coding for global transcriptional regulators (degU, abrB) and four sigma factors (sigB, sigM, sigV, and sigX) were also inves-tigated, in order to analyse their involvement in bacterial responses to root exudates. In summary, this is the first study presenting comprehensive proteomics of Gram-positive PGPR, evaluating at the same time changes in protein expression caused by addition of root exudates at the extracellular and cytosolic level.

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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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Ashraf, Zakira Naureen. « Identification of rhizobacteria from rice and maize for plant growth promotion and biological control of rice diseases ». Thesis, Lancaster University, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.578244.

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The scope of this study was the selection of bacterial strains from rice and maize and evaluation of their potential for plant growth promotion and biological control of rice diseases. 103 bacterial strains isolated from roots, rhizosphere and soil of rice and maize were assayed for production of siderophores, antibiotics, hydrolytic enzymes and HCN. From these, 33 strains were found to produce siderophores, eight were capable of producing diffusible antibiotics and four produced volatile antibiotics, while only one strain was found to produce HCN. Dual culture antagonistic assays were used to select strains capable of inhibiting growth of three major rice pathogens, Xanthomonas oryzae pv. oryzae (bacterial blight), Rhizoctonia solani (sheath blight) and Magnaporthe grisea (rice blast). When inoculated into soils, a number of strains suppressed the incidence of rice blast and sheath blight diseases in two different rice varieties. A strong correlation between siderophore production and in vitro antagonism was found, which extended to biocontrol assays for rice blast disease in the variety Super Basmati, but not Azucena, suggesting that bacterial strains use different mechanisms in suppressing the same pathogen in different rice varieties. As there was no direct contact between the pathogen and bacterial strains, the proposed mechanism for disease suppreSSIOn is induced systemic resistance (ISR). Gene expression analysis for sheath blight experiments confirmed the enhanced induction of chitinase IIb and the peroxidase P0X22.3 by selected bacterial strains. Selected bacterial strains from rice were also observed to enhance plant growth and yield, and this may be related to their ability to fix nitrogen (detected by acetylene reduction assay), solubilize phosphates and/or produce auxin. This study led to the isolation, selection and evaluation of potentially useful bacterial strains from rice and maize that were genetically diverse and persistently abundant in the rhizosphere and can be further utilized for integrated pest management of rice. Moreover, as these strains are . also capable of improving plant health and enhancing grain yield, they could be further utilized either individually or in consortia for integrated nutrient management of rice and maize.

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Stavropoulou, Archontia. « Untersuchungen über die Wirkung von Stoffwechselprodukten, insbesondere Auxinen, des wachstumsfördernden Rhizobakteriums (PGPR) Bacillus subtilis auf die pflanzliche Salztoleranz ». Doctoral thesis, Humboldt-Universität zu Berlin, Landwirtschaftlich-Gärtnerische Fakultät, 2005. http://dx.doi.org/10.18452/15301.

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Zur Aufklärung des Wirkungsmechanismus der toleranzerhöhenden Wirkung gegenüber Salinität des Pflanzenwurzeln besiedelnden PGPR Bacillus subtilis wurden bakterielle Stoffwechselprodukte der Stämme FZB24 und FZB41 bei der Testpflanze Tomate unter dem Einfluss von hohem Salzstress getestet. Das Kulturfiltrat mit der Gesamtheit der von B. subtilis produzierten Stoffwechselprodukte zeigte im axenischen Test zur Ermittlung des Wachstums nach 7-tägiger Behandlung der Sämlinge und nachfolgender Kultivierung unter Salzstress eine gewisse toleranzerhöhende Wirkung bei 0,1 %-Konzentration. Zur Produktaufschlüsselung wurde das Kulturfiltrat über Adsorberharz und HPLC fraktioniert. Diese Fraktionen, sowie die aus dem Kulturfiltrat nach 19 h Fermentation wurden ebenfalls bei Sämlingen axenisch getestet. Fraktionen mit verschiedenen Proteinen und Peptiden, die von B. subtilis produziert werden, zeigten teilweise eine konzentrationsabhängige Wirkung hinsichtlich der Wachstumsstimulierung und zugleich Toleranzerhöhung gegenüber Salzstress, weshalb nachfolgend ein Peptidextrakt aus B. subtilis einer Testung im axenischen System unterzogen wurde. Der Peptidextrakt zeigte gleichfalls eine erkennbare konzentrationsabhängige Wirkung. Mit gleichem Testsystem wurden Auxin-Präkursoren und Auxin selbst, die als Stoffwechselprodukte von B. subtilis nachgewiesen sind, sowohl als Wurzelbehandlung, wie auch als Blattbehandlung bei Sämlingen geprüft. Zusätzlich wurde die Wirkung der Auxine auf den Wassergehalt der Sämlinge unter Salzstress, sowie die Adventivwurzelbildung von Hypokotylsegmenten aus etiolierten Sämlingen in An- und Abwesenheit von Salinität getestet. Darüber hinaus wurde die Aufnahme und der Transport von Auxinen, ebenfalls bei Sprosssegmenten aus etiolierten Sämlingen in An- und Abwesenheit von Salinität geprüft. Schließlich wurde die Wirkung der Auxine auf das Wachstum und den Wassergehalt in einer Hydrokultur im Gewächshaus unter Salzstress ermittelt. Die Ergebnisse zeigen, dass namentlich Auxin-Präkursoren und z. T. Auxin als Stoffwechselprodukte von B. subtilis eine Erhöhung der Salzstresstoleranz bei der Testpflanze herbeiführen können, wenngleich die Wirkung auf die Salztoleranz sehr differenziert und unterschiedlich stark ausgeprägt war. Der vorhandene Effekt vor allem der Auxin-Präkursoren wird als offenbar bedeutendster Mechanismus für die wachstumsstimulierende und zugleich toleranzerhöhende Wirkung gegenüber Salinität des Rhizobakteriums bei Wurzelbesiedlung und Interaktion mit dem pflanzlichen Stoffwechsel diskutiert.
To find out the mode of tolerance increasing action against salinity of the plant root colonizing PGPR Bacillus subtilis, bacterial metabolites of the strains FZB24 and FZB41 were studied in the test plant tomato under the influence of high salinity. Because the culture filtrate with the whole range of produced metabolites by B. subtilis showed to a certain extent a tolerance increasing action at dilution of 0,1 % in axenic plant growth tests after 7 days treatment of seedlings and subsequent cultivation under salt stress, it has been fractionated with adsorber resin and HPLC. These fractions, as well as fractions from the culture filtrate after 19 h fermentation were tested also by seedlings in axenic culture. Fractions with different proteins and peptides, which were produced by B. subtilis, showed partly activities also depending of concentration with regard to the growth stimulation and at the same time tolerance increase against salt stress. Following also a peptide extract from B. subtilis was examined in the axenic plant test system, showing similarly a visible action depending of concentration. In the same test system there were tested further auxin precursors and auxin itself, which are known metabolites of B. subtilis, on seedlings both by root treatment and leaf treatment. Additionally was studied the action of auxins on the water content of the seedlings under salt stress, as well as on the adventitious root formation of hypokotyl segments from etiolated seedlings, in presence and absence of salinity. Finally it was studied the uptake and transport of auxins in segments of stems from etiolated seedlings in presence and absence of salinity. Lastly it was tested the action of auxins on plant growth and water content in a hydroponic cultivation under greenhouse conditions and salt stress. The results show that particularly auxin precursors and partly auxin as metabolites of B. subtilis can induce an increase in the salt stress tolerance of the test plant, although the action on the salt tolerance was differentiated and variable in its extent. The existing effect firstly of the auxin precursors is discussed as obviously main mechanism for the plant growth stimulating and at the same time tolerance increasing action of the rhizobacterium against salinity by root colonization and interaction with the plant metabolism.

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47

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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Suarez, Franco Christian [Verfasser]. « Isolation of rhizobacteria from salt tolerant plant species and evaluation of their plant growth-promotion / Christian Suarez Franco ». Gießen : Universitätsbibliothek, 2015. http://d-nb.info/1080476024/34.

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Pretorius, Theresa. « Efficacy of rhizobacteria for growth promotion and biocontrol of Fusarium oxysporum and Rhizoctonia solani on wheat in South Africa ». Diss., University of Pretoria, 2012. http://hdl.handle.net/2263/31229.

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Plant growth promoting rhizobacteria (PGPR) are found in the rhizosphere and directly contribute to nutrient availability and plant growth. Due to the global move away form reliance on chemical fertilisers and crop protection products, plant growth promoting rhizobacteria (PGPR) and their application for improving crop production is receiving much attention. In the current work the selected PGPR isolates from the University of Pretoria PGPR Culture Collection were evaluated on wheat seedlings for their ability to promote seedling growth and control of selected root diseases. The ability of the PGPR to control root and crown rot of wheat caused by Fusarium oxysporum, F. graminearum and Rhizoctonia solani was evaluated in greenhouse pot trials. In addition the seedling tray assay was also evaluated as a means to screen PGPR for biocontrol. Under the test conditions, the seedling tray assay was unsuccessful as a method to screen the PGPR for biocontrol of wheat root pathogens. In the greenhouse pot trials several isolates were able to improve the growth of wheat seedlings cultivated in pathogen inoculated soil. For growth promotion the bacterial isolates were assessed in greenhouse trials. Following initial selection trials further analyses were conducted with selected isolates to determine what effect the PGPR inoculum dose and fertiliser application has on growth promotion efficacy. The isolates T06, T07, T11, T13, T19, T21, T23 and T24 were most effective in promoting the growth of wheat seedlings in the greenhouse. The dose response and fertiliser trials indicated that these factors do affect isolate activity. To facilitate understanding of the isolates and their activities, the isolates that performed well in the greenhouse were identified through 16S rRNA sequence data and selected modes of action determined. The isolates were predominantly Bacilli, from the genera Bacillus, Lysinibacillus and Paenibacillus. In vitro assessments revealed that the isolates have a wide spectrum of activity, including phosphate solubilisation, indole acetic acid production, growth in nitrogen free media, inhibition of pathogens in dual culture, chitinase production and siderophore production. A selection protocol was developed to assist with the selection of the best isolates. Based on ratings given for the greenhouse and in vitro assay the top performing isolate were selected. Spider diagrams were then constructed to visually represent each isolate’s performance. The following best performing isolates were selected as a) T10 (Bacillus cereus) for control of R. solani, b) T28 (Bacillus cereus) for control of F. oxysporum, c) T31 (Bacillus cereus) for control of F. graminearum, d) T13 (Bacillus sp. / Bacillus pumilus) for growth promotion of wheat and e) T29 (Paenibacillus alvei) as the most versatile isolate.
Dissertation (MSc)--University of Pretoria, 2012.
Microbiology and Plant Pathology
MSc
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Rudolph, Nicole. « Efficacy of selected rhizobacterial isolates for biocontrol of Rhizoctonia solani and growth promotion of maize in South Africa ». Diss., University of Pretoria, 2014. http://hdl.handle.net/2263/79181.

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Plant growth promoting rhizobacteria (PGPR) are bacteria that colonize the volume of soil surrounding plant roots (known as the rhizosphere) which, when in association with a suitable host plant, promote plant growth. The growing demand for sustainable crop production strategies has placed increasing emphasis on PGPR and their potential use in agriculture. The current study therefore focused on the beneficial effects of PGPR isolates (selected from the PGPR culture collection at the University of Pretoria) on maize (Zea mays L.) and the ability of these isolates to control Rhizoctonia solani Kühn. The seed quality and vigour of two maize cultivars (PAN 6236B and PAN 6Q-308B) was determined using the standard germination, moisture and various vigour tests. PAN 6Q-308B was found to have lower vigour and was selected for use in the remainder of the tests performed in the study. In a modified seed germination bioassay the percentage germination, seedling mass, shoot and root length of PAN 6Q-308B was increased by selected PGPR isolates. The vigour index (VI) of PAN 6Q-308B was also increased by five isolates (S6, S7, T19, T29 and A32) which were then selected for evaluation in the greenhouse. In the greenhouse pot trial isolates T19, S7 and T29 gave the most promising results in terms of increasing the dry mass of maize seedlings. These isolates were evaluated in a formulation efficacy trial where they were applied individually and in combination as a soil drench, seed treatment and liquid suspension or powder formulation applied to a pelletised compost carrier. The four most effective treatments at increasing the dry root mass of maize included a soil drench application of either isolate T29 or T19, a soil drench application of the consortium of isolates T19, T29 and S7, and a powder formulation of isolate T29 applied onto the compost pellet carrier. Isolates A08, A07 and T19 were the most effective at reducing the disease symptoms of R. solani Kühn and increasing dry root matter above that of the R. solani inoculated control in a seedling tray trial. Pot trials were conducted to assess the efficacy of isolates A08, A07 and T19 for control of R. solani, when applied as a seed treatment or soil drench. All three isolates failed to control the pathogen when applied as a seed treatment but a soil drench of isolate T19 was found to be very effective. A six month shelf-life study was conducted to determine the survival of the PGPR isolates T19, S7 and T29 applied to a novel carrier comprising pelletised composted chicken manure. The isolates were individually applied to the pellets in a liquid or powder form. The latter was found to be the most suitable for supporting the survival of the PGPR isolates up to six months at 25˚C. The study revealed that the viability of the isolates decreased more rapidly at a temperature of 35˚C as opposed to 25˚C, and that the cell numbers of isolate T19 remained the most stable throughout the six months incubation period in comparison with the other isolates.
Dissertation (MSc)--University of Pretoria, 2014.
Microbilogy and Plant pathology
MSc
Unrestricted

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