Made available in DSpace on 2016-01-26T18:56:31Z (GMT). No. of bitstreams: 1 Rafael Rebes Zilliani.pdf: 603873 bytes, checksum: 841c569299d71ab210698b9255ac75ba (MD5) Previous issue date: 2015-03-02 / Several environmental factors can alter the physiological processes of sugarcane plants, however, water deficit is the main factor limiting the productivity of this crop. The use of plant growth regulators can mitigate the effects of the drought, because these substances improve the regulation of physiological processes in the plant. In this context, the aim of this study was to evaluate the effects of a plant growth regulators solution (auxin, cytokinin and gibberellin) on the initial development and photosynthesis of sugarcane under water deficit. It was adopted a completely randomized 2 x 3 factorial design, two water regimes - control (100% of field capacity) and water deficit (20% of field capacity), and three doses of the bioregulators solution (0, 0.5 and 1.0 L h-1). The experimental plot consisted of plastic pots containing 12.0 kg of soil with one plant per pot of RB867515 and SP81-3250 cultivars, with ten replicates. The treatments with bioregulators solution was carried out with the commercial solution of plant growth regulators Stimulate® on stalks at planting and at 64 days after planting (DAP) by foliar application. Water deficit was initiated at 55 DAP and during this period were held biometric and physiological evaluations in plants. At 110 DAP biomass evaluation was performed. The drought reduced the relative water content of the plants, and all physiological parameters, maximum CO2 assimilation (Amax), stomatal conductance (Gs), maximum speed of Rubisco carboxylation and PEPCase enzymes (Vcmax and Vpmax) and, reduced plant growth and biomass production. However, plants that were treated with Stimulate® showed lower reduction in all physiological parameters, biometric and a smaller reduction in biomass when compared to plants not receiving treatment with the bioregulator solution. The bioregulators mainly stimulated the growth of the root system, which promoted greater absorption of water by plants and, consequently, better physiological performance under drought. The Stimulate® attenuated the effects of drought on physiological processes, promoting smaller reduction in Amax, Vcmax and Vpmax and also lower photochemical damage. This condition was responsible for the largest growth (height and leaf area) increasing the total biomass of plants (root, leaf and stem). / Vários fatores ambientais podem alterar os processos fisiológicos das plantas de cana-de-açúcar, porém o déficit hídrico é o principal fator que limita a produtividade desta cultura. O uso de reguladores vegetais pode atenuar os efeitos causados pelo déficit hídrico, em vista de que essas substâncias podem auxiliar na regulação dos processos fisiológicos da planta. Nesse contexto, o objetivo deste estudo foi avaliar os efeitos de uma solução de biorreguladores (auxina, citocinina e giberelina) sobre o desenvolvimento inicial e fotossíntese de cana-de-açúcar sob déficit hídrico. Foi adotado o delineamento inteiramente casualizado no esquema fatorial 2x3, sendo dois regimes hídricos, controle (100% da capacidade de campo) e déficit hídrico (20% da capacidade de campo) e três doses da solução de biorreguladores (0, 0,5 e 1,0 L ha-1). A parcela experimental foi constituída de vasos plásticos contendo 12,0 kg de solo com uma planta por vaso das cultivares RB867515 e SP81-3250, para cada tratamento utilizou-se dez repetições. Realizou-se o tratamento das plantas com a solução comercial de biorreguladores Stimulate® nos toletes no momento do plantio e aos 64 dias após o plantio (DAP) via aplicação foliar. O déficit hídrico foi iniciado aos 55 DAP e durante este período foram realizadas avaliações biométricas e fisiológicas nas plantas. Aos 110 DAP realizou-se a avalição de biomassa. O déficit hídrico reduziu o conteúdo relativo de água das plantas, bem como todos os parâmetros fisiológicos, assimilação máxima de CO2 (Amax), condutância estomática (Gs), velocidade máxima de carboxilação das enzimas Rubisco e PEPcase (Vcmax e Vpmax) e ainda, reduziu o crescimento das plantas e a produção de biomassa. No entanto, as plantas que foram tratadas com Stimulate® tiveram menor redução em todos os parâmetros fisiológicos, biométricos e menor redução na produção de biomassa quando comparadas as plantas que não receberam o tratamento com a solução de biorreguladores. Os biorreguladores estimularam principalmente o crescimento do sistema radicular, que promoveu maior absorção de água pelas plantas e, consequentemente, melhor desempenho fisiológico sob déficit hídrico. O Stimulate® atenuou os efeitos do déficit hídrico nos processos fisiológicos, promovendo menor redução em Amax, Vcmax e Vpmax e também menor dano fotoquímico. Essa condição foi responsável pelo maior crescimento (altura e área foliar) aumentando a produção de biomassa total das plantas (raiz, folhas e colmo).

Made available in DSpace on 2016-07-18T17:51:13Z (GMT). No. of bitstreams: 1 Rafael Rebes Zilliani.pdf: 603873 bytes, checksum: 841c569299d71ab210698b9255ac75ba (MD5) Previous issue date: 2015-03-02 / Several environmental factors can alter the physiological processes of sugarcane plants, however, water deficit is the main factor limiting the productivity of this crop. The use of plant growth regulators can mitigate the effects of the drought, because these substances improve the regulation of physiological processes in the plant. In this context, the aim of this study was to evaluate the effects of a plant growth regulators solution (auxin, cytokinin and gibberellin) on the initial development and photosynthesis of sugarcane under water deficit. It was adopted a completely randomized 2 x 3 factorial design, two water regimes - control (100% of field capacity) and water deficit (20% of field capacity), and three doses of the bioregulators solution (0, 0.5 and 1.0 L h-1). The experimental plot consisted of plastic pots containing 12.0 kg of soil with one plant per pot of RB867515 and SP81-3250 cultivars, with ten replicates. The treatments with bioregulators solution was carried out with the commercial solution of plant growth regulators Stimulate® on stalks at planting and at 64 days after planting (DAP) by foliar application. Water deficit was initiated at 55 DAP and during this period were held biometric and physiological evaluations in plants. At 110 DAP biomass evaluation was performed. The drought reduced the relative water content of the plants, and all physiological parameters, maximum CO2 assimilation (Amax), stomatal conductance (Gs), maximum speed of Rubisco carboxylation and PEPCase enzymes (Vcmax and Vpmax) and, reduced plant growth and biomass production. However, plants that were treated with Stimulate® showed lower reduction in all physiological parameters, biometric and a smaller reduction in biomass when compared to plants not receiving treatment with the bioregulator solution. The bioregulators mainly stimulated the growth of the root system, which promoted greater absorption of water by plants and, consequently, better physiological performance under drought. The Stimulate® attenuated the effects of drought on physiological processes, promoting smaller reduction in Amax, Vcmax and Vpmax and also lower photochemical damage. This condition was responsible for the largest growth (height and leaf area) increasing the total biomass of plants (root, leaf and stem). / Vários fatores ambientais podem alterar os processos fisiológicos das plantas de cana-de-açúcar, porém o déficit hídrico é o principal fator que limita a produtividade desta cultura. O uso de reguladores vegetais pode atenuar os efeitos causados pelo déficit hídrico, em vista de que essas substâncias podem auxiliar na regulação dos processos fisiológicos da planta. Nesse contexto, o objetivo deste estudo foi avaliar os efeitos de uma solução de biorreguladores (auxina, citocinina e giberelina) sobre o desenvolvimento inicial e fotossíntese de cana-de-açúcar sob déficit hídrico. Foi adotado o delineamento inteiramente casualizado no esquema fatorial 2x3, sendo dois regimes hídricos, controle (100% da capacidade de campo) e déficit hídrico (20% da capacidade de campo) e três doses da solução de biorreguladores (0, 0,5 e 1,0 L ha-1). A parcela experimental foi constituída de vasos plásticos contendo 12,0 kg de solo com uma planta por vaso das cultivares RB867515 e SP81-3250, para cada tratamento utilizou-se dez repetições. Realizou-se o tratamento das plantas com a solução comercial de biorreguladores Stimulate® nos toletes no momento do plantio e aos 64 dias após o plantio (DAP) via aplicação foliar. O déficit hídrico foi iniciado aos 55 DAP e durante este período foram realizadas avaliações biométricas e fisiológicas nas plantas. Aos 110 DAP realizou-se a avalição de biomassa. O déficit hídrico reduziu o conteúdo relativo de água das plantas, bem como todos os parâmetros fisiológicos, assimilação máxima de CO2 (Amax), condutância estomática (Gs), velocidade máxima de carboxilação das enzimas Rubisco e PEPcase (Vcmax e Vpmax) e ainda, reduziu o crescimento das plantas e a produção de biomassa. No entanto, as plantas que foram tratadas com Stimulate® tiveram menor redução em todos os parâmetros fisiológicos, biométricos e menor redução na produção de biomassa quando comparadas as plantas que não receberam o tratamento com a solução de biorreguladores. Os biorreguladores estimularam principalmente o crescimento do sistema radicular, que promoveu maior absorção de água pelas plantas e, consequentemente, melhor desempenho fisiológico sob déficit hídrico. O Stimulate® atenuou os efeitos do déficit hídrico nos processos fisiológicos, promovendo menor redução em Amax, Vcmax e Vpmax e também menor dano fotoquímico. Essa condição foi responsável pelo maior crescimento (altura e área foliar) aumentando a produção de biomassa total das plantas (raiz, folhas e colmo).

Thesis (M.Sc. (Horticulture)) -- University of Limpopo, 2017 / Refer to document / National Research Foundation of South Africa, and Agricultural Research Council-Universities Collaboration Centreꞌ for scholarship and research

Salt stress is a severe environmental challenge in agriculture, limiting the quality and productivity of the crops around the globe. Plant growth promoting rhizobacteria (PGPR) is proposed as a friendly solution to overcome those challenges. The desert plant endophytic bacterium, Enterobacter sp. SA187 has shown plant growth promotion and salt stress tolerance beneficial effect on the model plant Arabidopsis thaliana in vitro as well as under the field conditions on different crops. SA187 has a distinguished morphology of yellow colonies (SA187Y) that could be due to carotenoid biosynthesis. However, the bacteria tend to lose the yellow color upon incubation with the plants and the colonies turn to white (SA187W). In comparison to SA187Y, SA187W shows 50% reduction on the beneficial impact on A. thaliana fresh and dry weight of root and shoot system. By counting the CFU/plant, we showed that SA187Y and SA187W both have similar colonization rate in both shoots and roots. Under non-salt conditions, optimal bacterial colonization was observed on day 8 after inocubation, however, under the salt stress condition, the optimal colonization was observed at day 4. Moreover, during the time period of the incubation of the SA187Y with the plants, there was a consistent noticeable loss of the yellow color of the colonies. This change in color is only observed eight days after transfer and the number of white colonies increases with the increase of the incubation time. In addition, SA187W was GFP-tagged by Tn7 transposon system and visualized by confocal laser scanning microscopy. The SA187W-GFP colonies have shown a similar colonization pattern as SA187Y-GFP, bacteria were colonizing the differentiation zone and cell elongation zone in the roots. Finally, the gene expression of the carotenoid biosynthesis pathways genes in SA187Y showed an overall higher gene expression compared to SA187W. In conclusion, the color loss seems to affect the beneficial impact of the bacteria on plants. However, the reduced beneficial impact is not due to the colonization efficiency of bacteria on the plant roots but could be due to a regulation of gene expression of carotenoid biosynthesis.

Bacterial volatile organic compounds (VOCs) are signal molecules that may have beneficial roles in the soil-plant-microbiome ecosystem. In this Ph.D. thesis, I aimed to assess and characterize the role of bacterial VOCs in plant tolerance to drought and in the biocontrol of fungal pathogens. I started by studying two root endophytic bacteria isolated from pepper plants cultivated under desert farming conditions. They showed an enhancement of pepper tolerance to drought stress and an amelioration of its physiological status. Moreover, they induced the expression of a vacuolar pyrophosphatase proton pump (V-PPase), implicated in the regulation of the vacuolar osmotic pressure, facilitating water uptake. Besides, the exposure of Arabidopsis thaliana plants, grown under salinity stress, to the volatile 2,3-butanediol, described for its plant growth promotion (PGP) potential, enhanced the plants tolerance to salinity, proving the potential involvement of this volatile in the osmotic stress resistance mechanism. Then, I studied VOCs released by three bacteria associated to healthy rice plants. Their released VOCs mixtures modified the color pattern of Magnaporthe oryzae, the agent of the rice blast disease, and protected rice from the pathogen infection. A significant reduction of melanin production, sporulation and appressoria formation was measured in presence of the bacterial VOCs, without major effects on mycelial proliferation. 1-butanol-3-methyl, one of the nine VOCs co-produced by the studied bacteria, proved its potential of reducing M. oryzae melanin in vitro. In vivo tests confirmed the infection inhibition effects mediated by the rice-bacterial VOCs, with a reduction of 94% of the disease incidence. Lastly, I compared the genomes of the five bacteria considered in the previous experimental studies. The PGP traits and the VOCs pathways identified from the genome analyses confirmed the effects observed with the in vitro and in vivo assays, revealing a complex mode of promotion and protection offered by the studied plant-associated bacteria. In conclusion, plant-associated bacterial VOCs can play potentially important roles in modulating plant drought tolerance and reducing fungal virulence. Such biological resources represent novel tools to counteract the deleterious effects of abiotic and biotic stresses and have the potential to be exploited for sustainable approaches in agriculture.

One of the major challenges for agricultural research in the 21st century is to increase crop productivity to meet the growing demand for food and feed. Biotic (e.g. plant pathogens) and abiotic stresses (e.g. soil salinity) have detrimental effects on agricultural productivity, with yield losses being as high as 60% for major crops such as barley, corn, potatoes, sorghum, soybean and wheat, especially in semi-arid regions such as Saudi Arabia. Plant growth promoting bacteria isolated from pioneer desert plants could serve as an eco-friendly, sustainable solution for improving plant growth, stress tolerance and health. In this dissertation, culture-independent amplicon sequencing of bacterial communities revealed how native desert plants influence their surrounding bacterial communities in a phylogeny-dependent manner. By culture-dependent isolation of the plant endosphere compartments and a number of bioassays, more than a hundred bacterial isolates with various biochemical properties, such as nutrient acquisition, hormone production and growth under stress conditions were obtained. From this collection, five phylogenetically diverse bacterial strains were able to promote the growth of the model plant Arabidopsis thaliana under salinity stress conditions in a common mechanism of inducing transcriptional changes of tissue-specific ion transporters and lowering Na+/K+ ratios in the shoots. By combining a number of in vitro bioassays, plant phenotyping and volatile-mediated inhibition assays with next-generation sequencing technology, gas chromatography–mass spectrometry and bioinformatics tools, a candidate strain was presented as a multi-stress tolerance promoting bacterium with potential use in agriculture. Since recent research showed the importance of microbial partners for enhancing the growth and health of plants, a review of the different factors influencing plant-associated microbial communities is presented and a framework for the successful application of microbial inoculants in agriculture is proposed. The presented work demonstrates a holistic approach for tackling agricultural challenges using microbial inoculants from desert plants by combining culturomics, phenomics, genomics and transcriptomics. Microbial inoculants are promising tools for studying abiotic stress tolerance mechanisms in plants, and they provide an eco-friendly solution for increasing crop yield in arid and semi-arid regions, especially in light of a dramatically growing human population and detrimental effects of global warming and climate change.

<p>The phenylpropanoid pathway gives rise to a wide variety of specialized metabolites, but the majority of carbon flux going through this pathway is directed towards the synthesis of the lignin monomers: <i>p</i>-coumaryl alcohol, coniferyl alcohol and sinapyl alcohol. Lignin is a major impediment in biomass saccharification, which negatively affects animal feed and biofuel production. In an effort to improve biomass for the latter purposes, researchers have altered the polymer through genetic manipulations and generated biomass with lower recalcitrance to saccharification; however, in many cases these efforts have resulted in plant dwarfism. To date, we do not have a full understanding of the extent of lignin modifications a plant is able to tolerate without affecting its growth. More importantly, the mechanism that links dwarfism and modifications in lignin content and composition remains unknown. To contribute to answering these questions, we designed a strategy to incorporate a novel monomer into the lignin of <i>Arabidopsis thaliana</i>. We used mutants in genes that code for enzymes and regulators of the phenylpropanoid pathway to redirect the pathway’s flux towards the synthesis of <i>p</i>-coumaraldehyde and prevent the incorporation of <i>p-</i>coumaryl alcohol. Despite being mutated for the genes typically considered to be required for monolignol biosynthesis, the plants we generated continue to incorporate <i>p-</i>coumaryl alcohol into their lignin. This result suggests that the pathway’s architecture has not been completely elucidated and that there are more enzymes involved in lignification than previously thought. Additionally, we explored the connection between perturbations in phenylpropanoid metabolism and plant growth, by using an inducible system to track the changes in gene expression and metabolism that occur when phenylpropanoid metabolism is restored in a lignin biosynthetic mutant. The use of an inducible system allowed us to not only determine the metabolic processes affected in this mutant, but the proximal sequence of events that lead to restored growth when a functional copy of the mutant gene is induced. Finally, we redirected the flux through the pathway to assess the effects of simultaneously modulating lignin content and composition. Through this project we discovered that redirecting phenylpropanoid flux towards the synthesis of sinapyl alcohol in lignin-deficient mutant backgrounds, results in plant dwarfism. The growth impairment of these mutants can be overcome by providing exogenous coniferyl alcohol, suggesting that dwarfism in these mutants is caused by deficiency in coniferyl alcohol and/or derivatives thereof and not lignin alone. Altogether these projects allowed us to define the cellular processes affected by perturbations in phenylpropanoid homeostasis and the role of other phenylpropanoids besides lignin in this process.</p>

Microorganisms will play a significant role in the agricultural revolution in the coming decades and help meet the growing population's needs. Hence, understanding the impact of beneficial bacteria on crop development is key to the future of developing microbial products. The ability of PGPB to increase crop yields has been recently investigated in agriculture, as PGPB can support and protect plants under different stresses. Since PGPB interactions occur naturally, finding a method to apply beneficial bacteria while maintaining their efficiency and quality is a topic of interest. PGPB have been used as microbial inoculants, biofertilizers, and also as seed coatings. Preservation of microorganisms through desiccation has been used as the preferred method for long-term storage of microbial culture. The use of dry powders is favored over liquid cultures due to their ease of transportation and better quality control. For microbial preservation, freeze-drying has been defined as the most convenient and satisfactory preservation method for long-term storage. Freeze-drying is generally preferred over other drying techniques as it gives a high-quality dehydrated product. However, to reach a high-quality product, many parameters need to be monitored, such as bacterial cell concentration, growth medium, lyophilization buffer, rehydration, and duration of freeze-drying. In this research, SA190 was freeze-dried with 10% sucrose mixed with 5% trehalose as lyophilization buffer. Pseudomonas argentinensis SA190 was isolated from the root nodules of the desert plant Indigofera argentae in Saudi Arabia, specifically Jizan. The SA190 freeze-dried product was examined by several tests to assess the product viability and quality, such as accelerated test and water stability test. For future work, the effect of freeze-dried SA190 on plant growth and crop yield will be investigated. Moreover, optimization of the freeze-drying process, formulation, and packaging for commercial will be considered. In addition, bacterial strains isolated in DARWIN21 project with promising effects on plant growth, will be subjected to freeze-drying process.

The principal objective of this project was to evaluate the short-term effects of CBW incorporation into soil in terms of soil fertility, plant growth and soil microbiology. Treatments consisted of a control, standard woodchip treatment (incorporation rate of 150m3/ha), woodchip + woodland litter incorporation treatment (woodland litter incorporation of 10-20g/m2), woodchip + fertiliser treatment (KNO3 applied at 50kgN/ha at start and a continuous fertiliser application treatment) and double woodchip treatment. Standard soil NO-3 tests were conducted to determine soil fertility. To assess plant growth and development, plant DW, S:R DW and plant K levels were measured Finally, microbiological analyses were carried out through serial dilutions and plate counts, with in-depth microscopy. Results indicated that there were obvious differences between treatments throughout the study period. In all measurements, woodchip treatments were found to have significantly lower values than the control. The exception to the rule was the WC + fertiliser treatment (continuous complete nutrient fertiliser application), which showed comparable results with the control. The addition of woodland litter did not seem to affect any of the soil fertility, plant growth or microbial measurements. The differences between the unfertilised woodchip treatments and the control were explained by a general nutrient deficiency resulting from a ‘dilution effect’ to soil nutrients by adding woodchips. This was further exacerbated by immobilisation of nutrients from the micro-organisms in the soil.

Kochia scoparia (L.) Schrad. has had limited use as a forage crop during the past fifteen. years in parts of the western United States, Canada, and Argentina. Erickson and Moxon (1947) reported kochia* to be a good emergency feed for sheep and cattle during dry years in South Dakota. Salguero (1946) said that this species could be utilized in Argentina as silage or pasturage if harvested before flowering. Bell, et al. (1952) in Saskatoon, Canada studied this species in a comparison with other introduced plants and reported that it seemed to have desirable nutrient characteristics for livestock roughage. Plummer (1949) reported beef cattle in Ephraim, Utah had eaten and gained normally on kochia hay.