Relevant bibliographies by topics / Rhizosphere

Academic literature on the topic 'Rhizosphere'

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Published: 4 June 2021
Last updated: 31 July 2024

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Journal articles on the topic "Rhizosphere"

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Khan, Abdul Latif, Sajjad Asaf, Raeid M. M. Abed, Yen Ning Chai, Ahmed N. Al-Rawahi, Tapan Kumar Mohanta, Ahmed Al-Rawahi, Daniel P. Schachtman, and Ahmed Al-Harrasi. "Rhizosphere Microbiome of Arid Land Medicinal Plants and Extra Cellular Enzymes Contribute to Their Abundance." Microorganisms 8, no. 2 (February 5, 2020): 213. http://dx.doi.org/10.3390/microorganisms8020213.

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Revealing the unexplored rhizosphere microbiome of plants in arid environments can help in understanding their interactions between microbial communities and plants during harsh growth conditions. Here, we report the first investigation of rhizospheric fungal and bacterial communities of Adenium obesum, Aloe dhufarensis and Cleome austroarabica using next-generation sequencing approaches. A. obesum and A. dhufarensis grows in dry tropical and C. austroarabica in arid conditions of Arabian Peninsula. The results indicated the presence of 121 fungal and 3662 bacterial operational taxonomic units (OTUs) whilst microbial diversity was significantly high in the rhizosphere of A. obesum and A. dhufarensis and low in C. austroarabica. Among fungal phyla, Ascomycota and Basidiomycota were abundantly associated within rhizospheres of all three plants. However, Mucoromycota was only present in the rhizospheres of A. obesum and A. dhufarensis, suggesting a variation in fungal niche on the basis of host and soil types. In case of bacterial communities, Actinobacteria, Proteobacteria, Bacteroidetes, Planctomycetes, Acidobacteria, and Verrucomicrobia were predominant microbial phyla. These results demonstrated varying abundances of microbial structure across different hosts and locations in arid environments. Rhizosphere’s extracellular enzymes analysis revealed varying quantities, where, glucosidase, cellulase, esterase, and 1-aminocyclopropane-1-carboxylate deaminase were significantly higher in the rhizosphere of A. dhufarensis, while phosphatase and indole-acetic acid were highest in the rhizosphere of A. obesum. In conclusion, current findings usher for the first time the core microbial communities in the rhizospheric regions of three arid plants that vary greatly with location, host and soil conditions, and suggest the presence of extracellular enzymes could help in maintaining plant growth during the harsh environmental conditions.
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Ahmad, Maqshoof, Zafar Iqbal, Bushra, Azhar Hussain, Muhammad Abdullah, Abed Alataway, Ahmed Z. Dewidar, and Mohamed A. Mattar. "Seasonal Changes Modulate the Rhizosphere of Desert Plant Species." Agronomy 13, no. 1 (December 23, 2022): 57. http://dx.doi.org/10.3390/agronomy13010057.

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Arid and semi-arid ecosystems are categorized as having degraded soils due to the limited availability of water and nutrients. The perennial shrubs in these regions have developed different ecological and physiological adaptations to cope with harsh conditions. The plant species vary in the chemical profile of their root exudates, which can induce variability in the microbial community in the rhizosphere. The present research has been conducted (i) to investigate the variation in composition, diversity, and structure of rhizosphere’s bacterial community of desert plants; (ii) to identify plant-specific effects on the rhizosphere microbial community structure; and (iii) to determine the influence of soil moisture on the rhizosphere’s microbial community and soil biological properties under stressful conditions. Ten desert plant species from the Cholistan desert were selected as test specimens. Bacterial communities from the rhizosphere of 10 plants of each species were explored. Soil samples were collected during monsoon (June–August) and dry months (March–May). Microbial community structure analyses were carried out through 16S rRNA sequencing by targeting V3 and V4 regions. Among tested plant species, the rhizosphere of Leptadenia pyrotechnica (S6 vs. S16), Aerva javanica (Burm. f.) Juss. ex Schult (S9 vs. S19), and Vachellia jacquemontii (Benth.) (S10 vs. S20) had greater microbial diversity in both seasons. Higher levels of microbial communities were found during monsoon season. Furthermore, Gammaproteobacteria were abundant in the rhizospheres of all studied plants during the monsoon season. In contrast, the rhizosphere was abundant with unidentified_Actinobacteria during the dry season. The rhizospheric soil was further analyzed for biological properties. The maximum microbial biomass carbon (165 mg kg–1) and microbial biomass nitrogen (6.7 mg kg–1) were found in the rhizosphere of Vachellia jacquemontii (Benth.) Benth during monsoon season. However, a minimum of microbial biomass carbon (119 mg kg–1) and microbial biomass nitrogen (4.2 mg kg–1) were found in the rhizosphere of Cleome pallida Kotschy during dry seasons. The diversified microbial community structure and biological properties enable desert plants to cope with adverse climate conditions.
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Jamiołkowska, Agnieszka, Barbara Skwaryło-Bednarz, Elżbieta Patkowska, Halina Buczkowska, Anna Gałązka, Jarosław Grządziel, and Marek Kopacki. "Effect of Mycorrhizal Inoculation and Irrigation on Biological Properties of Sweet Pepper Rhizosphere in Organic Field Cultivation." Agronomy 10, no. 11 (October 31, 2020): 1693. http://dx.doi.org/10.3390/agronomy10111693.

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The aim of the study was to evaluate the influence of mycorrhizal fungi (MF) and irrigation on biological properties of sweet pepper rhizosphere in organic field cultivation. For this purpose, MF were applied to plants in the form of commercial mycorrhizal inoculum (Rhizophagus aggregatus, R. intraradices, Claroideoglomus etunicatum, Endogone mosseae, Funneliformis caledonium, and Gigaspora margarita) and irrigation according to the combinations: mycorrhized plants (PM), mycorrhized and irrigated plants (PMI), and irrigated plants (PI). Plants without MF and irrigation served as the absolute control (P). The study used classic and molecular techniques, assessing catalase activity, biodiversity of soil microorganisms (soil DNA analysis), and the Community-Level Physiological Profiles (CLPP) analysis using Biolog EcoPlates. The highest catalase activity was recorded in the control and mycorrhized soil sample. The highest total number of bacteria was noted in the rhizosphere of control plants (P) and irrigated plants, while the lowest number in the rhizosphere of mycorrhized and irrigated plants. Plant irrigation contributed to the increase in the total number of fungi in the rhizosphere. The rhizospheric soil of PM and PMI were characterized by the highest utilization of amines, amides, and amino acids, whereas the lowest level of utilization was detected in the P and PI rhizospheres. The highest biodiversity and metabolic activity were observed in the rhizospheres from the PMI and PM samples, whereas lower catabolic activity were recorded in the P and PI rhizospheres. The mycorrhization of crops improved the biological properties of the rhizosphere, especially under conditions of drought stress.
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Sun, Yan, Ziyue Huang, Siyu Chen, Da Yang, Xinru Lin, Wenjun Liu, and Shangdong Yang. "Higher-Quality Pumpkin Cultivars Need to Recruit More Abundant Soil Microbes in Rhizospheres." Microorganisms 10, no. 11 (November 9, 2022): 2219. http://dx.doi.org/10.3390/microorganisms10112219.

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Two different qualities of pumpkin, cultivars G1519 and G1511, were grown in the same environment under identical management. However, their qualities, such as the contents of total soluble solids, starch, protein, and vitamin C, were significantly different. Do rhizospheric microbes contribute to pumpkin quality? To answer this question, this study investigated the soil microbial compositions in the rhizospheres of different quality pumpkin cultivars to determine the differences in these soil microbial compositions and thus determine how soil microbes may affect pumpkin quality. Firstly, a randomized complete block design with two pumpkin cultivars and three replications was performed in this study. The soil microbial compositions and structures in the rhizospheres of the two pumpkin cultivars were analyzed using a high-throughput sequencing technique. In comparison with the low-quality pumpkin cultivar (G1519), higher microbial diversity and richness could be found in the rhizospheres of the high-quality pumpkin cultivar (G1511). The results showed that there were significant differences in the soil bacterial and fungal community compositions in the rhizospheres of the high- and low-quality pumpkin cultivars. Although the compositions and proportions of microorganisms were similar in the rhizospheres of the two pumpkin cultivars, the proportions of Basidiomycota and Micropsalliota in the G1519 rhizosphere were much higher than those in the G1511 rhizosphere. Furthermore, the fungal phylum and genus Rozellomycota and Unclassified_p__Rozellomycota were unique in the rhizosphere of the high-quality pumpkin cultivar (G1511). All the above results indicate that soil microbes were enriched differentially in the rhizospheres of the low- and high-quality pumpkin cultivars. In other words, more abundant soil microbes were recruited in the rhizosphere of the high-quality pumpkin cultivar as compared to that of the low-quality cultivar. Rozellomycota and Unclassified_p__Rozellomycota may be functional microorganisms relating to pumpkin quality.
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Shen, Qingqing, Junyu Yang, Daifa Su, Zhiying Li, Wei Xiao, Yongxia Wang, and Xiaolong Cui. "Comparative Analysis of Fungal Diversity in Rhizospheric Soil from Wild and Reintroduced Magnolia sinica Estimated via High-Throughput Sequencing." Plants 9, no. 5 (May 8, 2020): 600. http://dx.doi.org/10.3390/plants9050600.

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Magnolia sinica is a critically endangered species and considered a “plant species with extremely small populations” (PSESP). It is an endemic species in southeastern Yunnan Province, China, with reproductive barriers. Rhizosphere fungi play a crucial role in plant growth and health. However, the composition, diversity, and function of fungal communities in wild and reintroduced M. sinica rhizospheres remain unknown. In this study, Illumina sequencing of the internal transcribed spacer 2 (ITS2) region was used to analyze rhizospheric soil samples from wild and reintroduced M. sinica. Thirteen phyla, 45 classes, 105 orders, 232 families, and 433 genera of fungi were detected. Basidiomycota and Ascomycota were dominant across all samples. The fungal community composition was similar between the wild and reintroduced rhizospheres, but the fungal taxa relative abundances differed. The fungal community richness was higher in the reintroduced rhizosphere than in the wild rhizosphere, but the diversity showed the opposite pattern. Soil nutrients and leaf litter significantly affected the fungal community composition and functional diversity. Here, the composition, structure, diversity, and ecological functions of the fungal communities in the rhizospheres of wild and reintroduced M. sinica were elucidated for the first time, laying a foundation for future research and endangered species protection.
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Dong, J., W. H. Mao, G. P. Zhang, F. B. Wu, and Y. Cai. "Root excretion and plant tolerance to cadmium toxicity - a review." Plant, Soil and Environment 53, No. 5 (January 7, 2008): 193–200. http://dx.doi.org/10.17221/2205-pse.

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Significant quantities of Cd have been added to soils globally due to various anthropogenic activities, posing a serious threat to safe food production and human health. Rhizosphere, as an important interface of soil and plant, plays a significant role in the agro-environmental system. This article presents a review of relationship between root excretion and microorganisms and plant resistance to Cd toxicity and possible mechanisms. Root exudates markedly altered in species and quantity under Cd stress. Root exudates can affect Cd absorption by plants through changing the physical and chemical characteristics of rhizospheres. The influence of root exudates on Cd bioavailability and toxicity may include modifying the rhizosphere pH and Eh, chelating/complexing and depositing with Cd ions, and altering the community construction, the numbers and activities of rhizospheric microbes. In this paper, the methods to reduce the transfer of Cd in soil-plant system by adjusting rhizosphere environment are discussed, and some aspects are also proposed that should be emphasized in the future research work.
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Allaouia, Ahmed Said Allaoui, Sailine Raissa, Said Hassane Fahimat, Soudjay Asnat, An-icha Mohamed, Nemati Mohamed Abdou, Soifiata Said Ismail, et al. "Bacterial population of Rhizospheres and non-Rhizospheres of the mangrove species Rhizophora mucronata from 0 to 10 cm deep." International Journal of Advanced Engineering Research and Science 9, no. 8 (2022): 079–89. http://dx.doi.org/10.22161/ijaers.98.11.

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The interaction of plants and microorganisms in the rhizospheres and non-rhizospheres of plants is well studied and mastered in the terrestrial environment. In general, given the rhizosphere effect exclusively defining the effectiveness of root exudates to promote multiplication, development and microbial growth in the rhizosphere zones, studies unanimously tend to report that the microbial biomass is rather high in the rhizosphere than in the non-rhizosphere. However, the trend may change in the marine environment. This study was conducted in both the rhizosphere and non-rhizosphere of the mangrove species Rhizophora mucronata at different depths ranging from 0-10 cm, to assess the bacterial community in the rhizosphere and non-rhizosphere and to also address the profile of bacterial community changes. The result showed no difference regarding the bacterial abundance in the rhizosphere and in the non-rhizosphere. However, the abundance of bacteria at 0-5 cm depth was significantly higher in rhizosphere and non-rhizosphere. This could be attributed to the large amount of nutrients available in the surface layer. The unequal distribution of nutrients in the rhizosphere and non-rhizosphere of the mangrove species Rhizophora mucronata could be the consequences of mineralization, immobilization of nutrients in the soil and especially root exudation. The general results of this study can be summarized by showing that if the abundance of bacteria in the rhizosphere zones of terrestrial plants is often high, the trend may be different in aquatic plants, more particularly mangroves, which constitute a separate ecosystem.
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Thuy, Phan Thi, Wei-Ching Chung, and Li-Sen Young. "Host Genotype and Edaphic Factors Cumulatively Influence the Occurrence of Siderophore-producing Bacteria Associated with Rice (Oryza sativa L.)." Vietnam Journal of Agricultural Sciences 5, no. 1 (March 30, 2022): 1313–25. http://dx.doi.org/10.31817/vjas.2022.5.1.01.

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Seed-borne rice endophytes are capable of disseminating into host plant tissues as well as to their rhizosphere. Here, we investigated the occurrence of siderophore-producing bacteria (SPB) in the seed endospheres of two distinct rice (Oryza sativa L.) cultivars, TK8 (ssp. japonica) and TCN1 (ssp. indica), and their dissemination into the rhizospheres through culture-dependent methods. Their patterns of occurrence in the rhizospheres as well as in the root and shoot tissues of 30 day-old cultivars grown in three different kinds of soils were tested. The significance of SPB on Fe sequestration of TCN1 was studied using Enterobacter sp. LS-756. TK8 seeds were found to be not only abundant in endopsheric SPB (> 10-fold), but also exhibited enhanced SPB dissemination into the rhizosphere (1.3-fold) as compared to TCN1. The proportion of endophytic SPB was consistently higher in roots than in shoots, and it was found to decline with decreasing soil pH. A similar declining trend was further evident through the analysis of SPB composition in the rhizospheric and bulk soils. LS-756-inoculated TCN1 seedlings under low availability of Fe showed 32%, 178%, and 368% increases in Fe, chlorophyll, and chlorophyll b contents as compared to the uninoculated controls. Thus, the occurrence of seed-borne endophytic SPB and their dissemination into the rhizosphere vary significantly according to the rice genotype. Higher co-occurrence of SPB in the rhizosphere and internal root tissues of rice plants grown under Fe-limited conditions and the enhanced Fe uptake due to SPB inoculation substantiated their potential involvement in Fe sequestration.
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Applebaum, Itaii, Mareeswaran Jeyaraman, Chen Sherman, Tirza Doniger, and Yosef Steinberger. "Structure and Function of the Soil Rhizosphere Fungal Communities in Medicinal Plants—A Preliminary Study." Agriculture 12, no. 2 (January 21, 2022): 152. http://dx.doi.org/10.3390/agriculture12020152.

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Plants regulate their rhizosphere microbiome, which partly comprises the fungal community. We conducted a study in order to determine the effect that five medicinal plant species (Origanum syriacum, Salvia fruticosa, Teucrium capitatum, Myrtus communis and Pistacia lentiscus) have on the fungal community in their rhizosphere. We measured abiotic parameters and used sequencing to determine the structure of the rhizosphere fungal community, both taxonomically, as phyla and genera, and functionally, as trophic modes. Our data shows that the rhizosphere fungal communities were significantly different, both taxonomically and functionally. The rhizosphere of M. communis had a significant relative abundance of saprotrophs and a lower relative abundance of symbiotrophs than the control soil and the rhizosphere of T. capitatum. The relative abundance of the genus Aureobasidium was significantly higher in the rhizosphere of P. lentiscus than in the control and for all other rhizospheres, but that of S. fruiticosa. The relative abundance of genus Alternaria was lower in the rhizospheres of S. fruticosa and M. communis than in the control soil. Our results highlight the potential use of these plants in agroforestry, as a means to influence the soil fungi population.
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Toberman, Hannah, Chengrong Chen, and Zhihong Xu. "Rhizosphere effects on soil nutrient dynamics and microbial activity in an Australian tropical lowland rainforest." Soil Research 49, no. 7 (2011): 652. http://dx.doi.org/10.1071/sr11202.

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Via vast exchanges of energy, water, carbon, and nutrients, tropical forests are a major driving force in the regulation of Earth’s biogeochemical, hydrological, and climatic cycles. Given the critical role of rhizosphere processes in nutrient cycling, it is likely that rhizosphere processes in tropical rainforests form a major component of the biome’s interactions with global cycles. Little is known, however, about rhizospheric processes in rainforest soils. In order to investigate the influence of rhizosphere processes upon rainforest nutrient cycling, we compared the nutrient status and microbial activity of rhizospheric soil from Australian lowland tropical rainforest with that of the surrounding bulk soil. We found a marked difference in the biological and chemical nature of the rhizosphere and bulk soils. Total carbon, microbial biomass carbon, total nitrogen, soluble nitrogen, and a suite of trace element concentrations, alongside microbial respiration and the rate and diversity of carbon substrate use, were all significantly higher in the rhizosphere soil than the bulk soil. Rhizosphere soil δ15N was significantly lower than that of the bulk soil. Ratios of carbon, nitrogen, phosphorus, and sulfur differed significantly between the rhizosphere and bulk soil. These clear differences suggest that rhizosphere processes strongly influence nutrient cycling in lowland tropical rainforest, and are likely to play an important role in its interaction with global cycles. This role may be under-represented with composite sampling of rhizosphere and bulk soil. Further research is required regarding the mechanisms of rainforest rhizospheric processes and their relationship with ecosystem productivity, stability, and environmental change.
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Dissertations / Theses on the topic "Rhizosphere"

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Burton, C. C. "Phosphomonoesterase and phosphodiesterase activities in rhizosphere and non-rhizosphere soil." Thesis, University of Kent, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378637.

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Dartnall, A. M. "Cyanogenesis and the rhizosphere." Thesis, University of Kent, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383179.

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Bergfield, William Alan. "Rhizosphere bacteria and benomyl interactions /." free to MU campus, to others for purchase, 2001. http://wwwlib.umi.com/cr/mo/fullcit?p3036805.

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Levy, Avram. "Modelling rhizosphere interactions of Burkholderia species." University of Western Australia. School of Biomedical and Chemical Sciences, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0123.

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[Truncated abstract] Genus Burkholderia encompasses a diverse collection of bacteria that inhabit rhizospheres throughout the world. Species can provide beneficial returns for eukaryotes, such as nitrogen fixation and nodule formation in plants and biocontrol of cropping systems. Burkholderia members can also cause disease in various animals, fungi and plants. These seemingly conflicting characteristics point to the capacity of Burkholderia spp. to interact with diverse eukaryotes. Within terrestrial ecosystems, Burkholderia spp. must negotiate favourable outcomes with both the primary producers and the primary decomposers, namely plants and fungi. It is these ongoing negotiations which govern many rhizosphere processes and lead to niche differentiation for Burkholderia spp. This research set out to design an in vitro model for investigating Burkholderiaeukaryote interactions. Surface and cellular interactions between Burkholderia spp. and both plants and fungi were then investigated. Specifically, mechanisms of adherence and invasion of plant and fungal cells were studied. The Burkholderia spp. B. vietnamiensis and B. pseudomallei were applied to mycorrhizal fungus spores as well as to several plant species. Bacterial inoculation had varying effects on germination of plant and fungal dormant forms. B. vietnamiensis-inoculation consistently increased Gigaspora decipiens spore germination, while B. pseudomallei produced no significant change. The effect of B. vietnamiensis on Acacia colei seed germination was density dependant, resulting in either increases or decreases in seed germination rates. ... Detection of B. pseudomallei in surface waters and soils was improved by the use of a rapid on-site molecular method. The related species B. thailandensis and B. ubonensis were also cultured from northern Western Australia. Mycorrhizal spores were isolated from soils of melioidosis-endemic regions. Burkholderia spp., including B. pseudomallei and B. vietnamiensis were detected in extracts of these mycorrhizal spores. Therefore, associations of Burkholderia spp. with mycorrhizal spores extend beyond the in vitro setting. These studies have increased our understanding of several specific interactions between Burkholderia spp. and eukaryotes of the rhizosphere. Common themes in adherence and invasion have emerged. Burkholderia spp. are able to closely associate with eukaryotes and to gain access to protected niches. Such access helps to explain the persistence of these bacteria in the environment during periods of desiccation and nutrient limitation.
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Yeates, G. "Microbial population dynamics of the rhizosphere." Thesis, University of Oxford, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334939.

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Macey, Michael. "Characterisation of methylotrophs in the rhizosphere." Thesis, University of East Anglia, 2017. https://ueaeprints.uea.ac.uk/66855/.

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Methanol is the second most abundant volatile organic compound in the atmosphere, with the majority of this methanol being produced as a waste metabolic by-product of the growth and decay of plants. There is a large disparity between the amount of methanol estimated as being produced and that which enters the atmosphere. This disparity is believed to be due to the utilisation of methanol by plant associated methylotrophs. The diversity and activity of methylotrophs associated with the root and rhizosphere of pea and wheat plants was assessed through a range of cultivation independent and dependent approaches. Enrichments performed with a range of environmental samples supplemented with methanol resulted in the isolation of several strains of methylotrophic bacteria, including two novel species of methylotroph belonging to the family Methylophilaceae, whose genomes were sequenced and their physiological capabilities assessed. The diversity and abundance of methanol dehydrogenase encoding genes in bulk soil and the pea and wheat rhizosphere was assessed through 454 sequencing and qPCR respectively. Sequencing showed high levels of diversity of methylotrophic bacteria within the bulk soil and also showed a shift in this diversity between the bulk soil and the plant associated soils, in spite of no shift in the abundance of these genes occurring. Active methylotrophs present in the bulk and plant associated soils were identified by DNA stable isotope probing using 13C labelled methanol. Next generation sequencing of the 16S rRNA genes and construction of metagenomes from the 13C labelled DNA revealed members of the Methylophilaceae as highly abundant in all of the soils. A greater diversity of the Methylophilaceae and the genus Methylobacterium were identified as active in the plant associated soils relative to the bulk soil. A 13CO2 stable isotope probing experiment identified methylotrophs as utilising plant exudates in the pea and wheat root and rhizosphere communities. Several methylotrophic genera were identified as exudate utilising, in addition to heterotrophic genera and Actinomycetes. The specific 13C labelled genera were shown to vary between both the wheat and pea plants and between the rhizosphere and root communities.
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Deery, Sarah Jane. "Monitoring rhizosphere microbial communities of tomato." Thesis, University of Nottingham, 2012. http://eprints.nottingham.ac.uk/12759/.

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Tomato is an economically important crop that can be devastated by many root infecting pathogens. The development of alternative and sustainable crop cultivation techniques and disease control methods is a must for the tomato industry, due to more strict government regulations and concerns over the sustainability of conventional chemical-intensive agriculture (Dixon and Margerison, 2009). In this thesis, the molecular fingerprinting method Terminal-Restriction Fragment Length Polymorphism (T-RFLP) and next generation sequencing method (pyrosequencing) were used, targeting ITS1, ITS2 and 23S ribosomal DNA to characterize and examine microbial community assemblages in the rhizosphere of tomato. These molecular techniques were employed alongside traditional cultivation, microscopy and plant health assessment techniques to determine the effects of growth media, plant age and disease control methods on rhizosphere microbial populations and tomato root health. Plant age and media were found to significantly affect microbial community assemblages; conversely, microbial populations were not altered by soil amendments or rootstock disease control measures used. These findings suggest that the factors influencing rhizosphere community structure can be ranked by importance. Furthermore, if the most influential factors are kept consistent then rhizosphere microbial structures are robust and difficult to perturb with changes in a factor contributing less control over microbial community composition. No direct link between crop health assessments and rhizosphere microbial community diversity or presence of root pathogens could be established. Furthermore, high abundance of potential pathogens and poor crop health assessments during the growing season did not always result in poor health or disease symptoms at the end of cropping assessment in our trials. These results imply that many factors control the rhizosphere competence and ecological role of different species, ultimately affecting the outcome of disease. As no known methods are capable of efficiently assessing the fate of total microorganisms in the rhizosphere over time and space, this study could be considered as part the ‘descriptive phase’ in this field (Kent and Triplett, 2002). Pyrosequencing increased the resolution and confidence of rDNA analysis compared to T-RFLP, identifying organism within samples to a genus and often species level. Advances in next generation sequencing and analytical tools and pipelines associated with this analysis are likely to develop as these methods become common practice. With this in mind, next generation sequencing represents the future approach for resolving complex microbial communities in environmental samples.
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Curnow, Philip Kenneth. "Influence of root exudates on rhizosphere pseudomonads." Thesis, Imperial College London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286230.

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Sheta, Omar T. "Phytoremediation and rhizosphere manipulation using different amendments." Thesis, University of Glasgow, 2006. http://theses.gla.ac.uk/2147/.

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In two pot experiments using two different crop ryegrass (Lolium perenne) and two flax (Linum usitatissimum) varieties Viola and Elise, ryegrass decreased in the pool of heavy metals compared with bare soil using EDTA as extractant. NH4+ decreased the soil pH, increased EDTA-extractable Zn and increased the Zn uptake. Lime addition increased the pH and depressed Zn uptake. The pool of extractable EDTA was not changed by growing both of the flax varieties. Lime increased EDTA-extractable Cu and Pb significantly, but decreased the Zn, and pH increased in this order NH4+NH4++lime>NH4+>NO3-. Ammonium decreased the pH more than other treatments. In agar using Bromocresol purple indicator NH4+ increased the pH in the rhizosphere of different plants. With two different initial pH treatments (7 and 3.2) the NH4_ decreased the pH in the rhizosphere at high initial pH 7 and maintained the low pH at initial pH 3.2 to 4 against the buffer capacity. At different initial pH 4, 5, 6, 7 and 8 the ammonium decreased the high pH and maintained the low pH, but NO3- had no effect on the pH. Ammonium increased the toxicity of Zn due to pH decreases. There was no effect of both nitrogen sources NH4+ or NO3- on rhizosphere pH when applied as a foliar application. These indicated that the NH4+ can decrease the pH in the rhizosphere of plants and could play an important role in manipulation of the rhizosphere bioavailability of heavy metals. Toxicity of the three metals is Cu>Pb>Zn in this order and the crops tolerance is following this order pea>flax>barley. An agar-Hoagland nutrient solution contaminated with two soils, sewage treated soil (SBS) and galena soil (G), was used with flax as a test crop. The ammonium treatment lowered the pH in both soils, but with galena treated greater than SBS soil, this is attributed to the buffering capacity of the SBS soil. Averaged over all the concentrations the NF4+ treatments resulted in higher Zn shoot content that NO3- treatment, while in Cu shoot content nitrate was more than ammonium. The transfer factor of lead with ammonium treatment was greater than nitrate treatments at the 0.1 and 0.25% galena and the transfer factor of the Zn and Pb more than Cu in all treatments. At high initial pH 8 and high concentration of Zn and Cu barley grew well and this is attributed to immobilisation of Zn and Cu compared with low pH 5 and 6.5 where the barley plant did not survive. Ammonium lowered the high pH 8 and caused lower biomass production of barley than nitrate.
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Giles, Madeline E. "Where does denitrification occur in the rhizosphere?" Thesis, University of Aberdeen, 2012. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=192249.

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Denitrification is the sequential reduction of NO3- to N2, through a number of intermediary steps, one of which is N2O, a potent green house gas. N2O has a global warming potential over 300 times greater than that of CO2 over a 100 a year period (IPCC, 2007). Soils are a significant source of N2O through the microbially mediated process of denitrification. The rhizosphere is a potentially important source of N2O as rhizodeposited carbon from plant roots can support a larger and more active microbial biomass. Despite this little is known about the effects of low molecular weight carbon (LMWC) on the production of N2O or N2 or how the production of these gases can vary with the small scale variation in carbon quantity found in the rhizosphere. Studies using a soil microcosm revealed that not all LMWC compounds were able to stimulate the production of N2O. Of the three compounds studied the addition of glucose or glutamine to soil resulted in a greater production of N2O than occurred in the control, while the addition of citric acid did not. An experimental system was developed that would allow the creation of a carbon gradient over 6 cm and along which N2O and N2 could be quantified. This allowed an insight into the potential for small scale variation in denitrification. Similar spatial variation in N2O and N2 concentrations were found in both glucose and glutamine treated soil, while no spatial variation in these gasses was found in citric acid treated soil. Peak N2 concentrations occurred closer to the carbon source than peak N2O concentrations, potentially as a result of the higher C : N ratio. This was associated with a shift in the bacterial community, and in glucose treated soil with an increase in the proportion of bacteria containing nosZ or nirK. Despite this spatial patterns in N2O production remained similar even in experiments where the community did not change. The bacterial community did however exert an influence by affecting the magnitude of N2O and N2 produced. The results from this thesis suggest that denitrification has the potential to vary in the rhizosphere as a result of changes in carbon concentrations, carbon compounds and the associated changes in the microbial community.
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Books on the topic "Rhizosphere"

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Singh, Udai B., Pramod K. Sahu, Harsh V. Singh, Pawan K. Sharma, and Sushil K. Sharma, eds. Rhizosphere Microbes. Singapore: Springer Nature Singapore, 2022. http://dx.doi.org/10.1007/978-981-19-5872-4.

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Curl, Elroy A., and Bryan Truelove. The Rhizosphere. Berlin, Heidelberg: Springer Berlin Heidelberg, 1986. http://dx.doi.org/10.1007/978-3-642-70722-3.

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Sharma, Sushil Kumar, Udai B. Singh, Pramod Kumar Sahu, Harsh Vardhan Singh, and Pawan Kumar Sharma, eds. Rhizosphere Microbes. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-9154-9.

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Bryan, Truelove, ed. The rhizosphere. Berlin: Springer-Verlag, 1986.

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M, Lynch J., ed. The Rhizosphere. Chichester, West Sussex, England: J. Wiley, 1990.

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1931-, Box James E., and Hammond Luther C. 1921-, eds. Rhizosphere dynamics. Boulder, Colo: Published by Westview Press for the American Assn. for the Advancement of Science, 1990.

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Pudake, Ramesh Namdeo, Maya Kumari, Deepak Rameshwar Sapkal, and Anil Kumar Sharma, eds. Millet Rhizosphere. Singapore: Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-99-2166-9.

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Anderson, Todd A., and Joel R. Coats, eds. Bioremediation through Rhizosphere Technology. Washington, DC: American Chemical Society, 1994. http://dx.doi.org/10.1021/bk-1994-0563.

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1963-, Anderson Todd A., Coats Joel R, American Chemical Society. Division of Agrochemicals., American Chemical Society. Division of Environmental Chemistry., and American Chemical Society Meeting, eds. Bioremediation through rhizosphere technology. Washington, DC: American Chemical Society, 1994.

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Pudake, Ramesh Namdeo, Binod Bihari Sahu, Maya Kumari, and Anil K. Sharma, eds. Omics Science for Rhizosphere Biology. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-16-0889-6.

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Book chapters on the topic "Rhizosphere"

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Sharma, Pankaj, Mayur Mukut Murlidhar Sharma, Arvind Malik, Medhavi Vashisth, Dilbag Singh, Rakesh Kumar, Baljinder Singh, Anupam Patra, Sahil Mehta, and Vimal Pandey. "Rhizosphere, Rhizosphere Biology, and Rhizospheric Engineering." In Plant Growth-Promoting Microbes for Sustainable Biotic and Abiotic Stress Management, 577–624. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-66587-6_21.

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Lipiec, Jerzy, and Jan Gliński. "Rhizosphere." In Encyclopedia of Agrophysics, 705–9. Dordrecht: Springer Netherlands, 2011. http://dx.doi.org/10.1007/978-90-481-3585-1_135.

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Waoo, Ashwini A. "Rhizosphere." In Bioremediation and Phytoremediation, 173–99. New York: Apple Academic Press, 2023. http://dx.doi.org/10.1201/9781003409595-12.

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Meek, Burl D., Ward Chesworth, Otto Spaargaren, and Michael Herlihy. "Rhizosphere." In Encyclopedia of Soil Science, 608. Dordrecht: Springer Netherlands, 2008. http://dx.doi.org/10.1007/978-1-4020-3995-9_487.

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Curl, Elroy A., and Bryan Truelove. "Rhizosphere Populations." In Advanced Series in Agricultural Sciences, 93–139. Berlin, Heidelberg: Springer Berlin Heidelberg, 1986. http://dx.doi.org/10.1007/978-3-642-70722-3_4.

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López, Manuel Fernández, Hugo C. Ramirez-Saad, Francisco Martínez-Abarca, J. Félix Aguirre-Garrido, and Nicolas Toro. "Rhizosphere Metagenomics." In Encyclopedia of Metagenomics, 544–50. Boston, MA: Springer US, 2015. http://dx.doi.org/10.1007/978-1-4899-7475-4_611.

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D. Schrey, Silvia, Anton Hartmann, and Rüdiger Hampp. "Rhizosphere Interactions." In Ecological Biochemistry, 292–311. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2014. http://dx.doi.org/10.1002/9783527686063.ch15.

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Minz, Dror, and Maya Ofek. "Rhizosphere Microorganisms." In Beneficial Microorganisms in Multicellular Life Forms, 105–21. Berlin, Heidelberg: Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-21680-0_7.

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López, Manuel Fernández, Hugo C. Ramirez-Saad, Francisco Martínez-Abarca, J. Félix Aguirre-Garrido, and Nicolas Toro. "Rhizosphere Metagenomics." In Encyclopedia of Metagenomics, 1–8. New York, NY: Springer New York, 2012. http://dx.doi.org/10.1007/978-1-4614-6418-1_611-1.

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Ravikumar, V. "Rhizosphere Modelling." In Sprinkler and Drip Irrigation, 439–514. Singapore: Springer Nature Singapore, 2022. http://dx.doi.org/10.1007/978-981-19-2775-1_16.

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Conference papers on the topic "Rhizosphere"

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Glazunova, Darina, Polina Kuryntseva, Polina Galitskaya, and Svetlana Selivanovskaya. "ASSESSMENT OF THE DIVERSITY OF RHIZOSPHERIC CULTIVATED BACTERIA IN WHEAT PLANTS GROWN ON DIFFERENT SOIL TYPES." In 22nd SGEM International Multidisciplinary Scientific GeoConference 2022. STEF92 Technology, 2022. http://dx.doi.org/10.5593/sgem2022v/6.2/s25.11.

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Microbial communities associated with the plant rhizosphere play an important role in carbon sequestration, regulation of nutrient cycling, and the efficient functioning of the ecosystem as a whole. The diversity of microorganisms inhabiting the plant rhizosphere and their complex interactions with the host plant significantly affect the morphology, physiology, growth, development, and health of plants. At the same time, it is known that the soil microbiome diversity is affected by the type of soil, the type of cultivated crop, and the method of tillage. In this study, the abundance and diversity of cultivated bacteria of the rhizosphere microbiome of wheat was assessed. Rhizospheric soil samples were taken from 5 fields with different types of soils (Greyzem, Chernozem, Podzols, Podzoluvisols, Podzoluvisols). Cultivated bacteria from the rhizosphere soil were isolated on meat-peptone and soil agars, and their number was determined. It has been established that the cultivated bacterial rhizobiome was least diverse in wheat plants grown on medium podzolic soil. The MALDI-TOF method was used to identify isolated cultivated isolate species. The genera Achromobacter, Acinetobacter, Bacillus, Microbacterium, Paenibacillus, Pseudomonas, Stenotrophomonas predominated among the isolated bacteria.
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Handakumbura, Pubudu. "Eavesdropping on Rhizosphere Conversations." In ASPB PLANT BIOLOGY 2020. USA: ASPB, 2020. http://dx.doi.org/10.46678/pb.20.989684.

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Farkhudinov, R. G., A. S. Grigoriadi, and Yu M. Sotnikova. "The effect of oil pollution on the activity of physiological and biochemical processes in Triticum aestivum L. and the number of rhizospheric microbiota." In 2nd International Scientific Conference "Plants and Microbes: the Future of Biotechnology". PLAMIC2020 Organizing committee, 2020. http://dx.doi.org/10.28983/plamic2020.069.

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The article presents the results of a study of the effect of oil pollution on the biochemical and morphometric parameters of the plant Triticum aestivum L., as well as a change in the number of rhizospheric microorganisms capable of degradation of petroleum hydrocarbons. It was shown that under the influence of pollution in plants increased the activity of redox enzymes. A significant increase in hydrocarbon-oxidizing bacteria and fungi was recorded in the rhizosphere.
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Yin, Chuntao. "Disease-induced changes in the rhizosphere microbiome reduced root disease." In IS-MPMI Congress. IS-MPMI, 2023. http://dx.doi.org/10.1094/ismpmi-2023-5r.

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Rhizosphere microbiota, referred to as the second genome of plants, are crucial to plant health. Increasing evidence reveals that plants can change their rhizosphere microbiome and promote microbial activity to reduce plant disease. However, how plant and phytopathogens factor in combination to structure the rhizosphere microbiome and govern microbial selection for adaptation to disease stress remains incompletely understood. In this study, rhizosphere microbiota from successive wheat plantings under the pressure of the soilborne pathogen Rhizoctonia solani AG8 were characterized. Amplicon sequence analyses revealed that bacterial and fungal communities clustered by planting cycles. The addition of AG8 enhanced the separation of the rhizosphere microbiota. The alpha diversity of bacteria and fungi significantly decreased over planting cycles. Compared with rhizosphere bacterial communities, AG8 was a major driver structuring fungal communities. Pathogen-infected monocultures enriched a group of bacterial genera with potential antagonistic activities or abilities for plant growth promotion or nitrogen fixation. Further, eleven bacterial species exhibited antagonistic activities toward Rhizoctonia spp., and four of them displayed broad antagonism against multiple soilborne fungal pathogens. These findings support the potential to improve plant health through manipulating rhizosphere microbiota.
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Abdurashytova, E. R., T. N. Melnichuk, S. F. Abdurashytov, and A. Yu Egovtseva. "Change of the integral indicator of the biological condition of the Sorghum bicolor L. rhizosphere under the influence of farming systems and microbial preparations." In РАЦИОНАЛЬНОЕ ИСПОЛЬЗОВАНИЕ ПРИРОДНЫХ РЕСУРСОВ В АГРОЦЕНОЗАХ. Federal State Budget Scientific Institution “Research Institute of Agriculture of Crimea”, 2020. http://dx.doi.org/10.33952/2542-0720-15.05.2020.05.

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A criterion for assessing the activity of biochemical and microbiological processes in the rhizosphere is necessary to explain the direction of the reaction of organisms, communities or ecosystems in response to anthropogenic influences. The purpose of the research is to assess the influence of farming systems (traditional and no-till) and the complex of microbial preparations (СMP) together with arbuscular mycorrhizal fungi (AMF) on microbiological processes in the rhizosphere of S. bicolor using the integral indicator of the biological condition (IIBC). Using IIBС, the direction of biological processes in the sorghum’s rhizosphere was shown. It depended both on the cultivation technology and the use of microbial preparations. IIBС of rhizosphere increased by 9.1% when using CMP and AMF in no-till, which indicated an increase in the biological activity of sorghum plants.
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Ibragimova, S. A., and K. A. Malafeeva. "Symbiosis of soil and rhizosphere bacteria." In 2nd International Scientific Conference "Plants and Microbes: the Future of Biotechnology". PLAMIC2020 Organizing committee, 2020. http://dx.doi.org/10.28983/plamic2020.105.

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The presence of symbiosis between different taxonomic groups of soil and rhizosphere bacteria is shown. In the mixed population, a high titer of active cells and the preservation of antagonistic activity against the phytopathogen were noted.
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Egovtseva, A. Yu, and T. N. Melnichuk. "Orientation of microbiological processes in the Triticum aestivum L. rhizosphere under conditions of seed bacterization by a complex of microbial preparations." In CURRENT STATE, PROBLEMS AND PROSPECTS OF THE DEVELOPMENT OF AGRARIAN SCIENCE. Federal State Budget Scientific Institution "Research Institute of Agriculture of Crimea", 2020. http://dx.doi.org/10.33952/2542-0720-2020-5-9-10-108.

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The aim of our research was to study the effect of presowing bacterization by a complex of microbial preparations (CMP) in various farming systems on the biological activity of the Triticum aestivum L. rhizosphere of southern Chernozem in the Crimean steppe. The three-year study proved the possibility of intensification and normalization of the microbiological status of the winter wheat rhizosphere using resource-saving technologies. The most pronounced effect of the complex of microbial preparations on the microbiological processes of the winter wheat rhizosphere was revealed in adverse weather conditions.
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Yakubovskaya, A. I., I. A. Kameneva, M. V. Gritchin, Ya V. Pukhalsky, and A. V. Slavinskaya. "Biological activity of Oryza sativa L. rhizosphere after introduction of associative bacteria strains." In РАЦИОНАЛЬНОЕ ИСПОЛЬЗОВАНИЕ ПРИРОДНЫХ РЕСУРСОВ В АГРОЦЕНОЗАХ. Federal State Budget Scientific Institution “Research Institute of Agriculture of Crimea”, 2020. http://dx.doi.org/10.33952/2542-0720-15.05.2020.22.

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The article presents the results of studies of biological activity in the rhizosphere system associative bacteria − Oryza sativa L. The pre-sowing treatment of seeds with associative symbionts activates biological processes in the rhizosphere and contributes to the increased productivity of Oryza sativa L. The number of grains per spike rose by 28.2-59.0%, 1000-grain weight – by 6.2%-10.6% compared to control.
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Shuliko, N. N. "THE BIOLOGICAL ACTIVITY OF THE RHIZOSPHERE OF SPRING BARLEY UNDER THE APPLICATION OF FERTILIZERS IN THE CONDITIONS OF THE SOUTHERN FOREST STEPPE OF WESTERN SIBERIA." In 11-я Всероссийская конференция молодых учёных и специалистов «Актуальные вопросы биологии, селекции, технологии возделывания и переработки сельскохозяйственных культур». V.S. Pustovoit All-Russian Research Institute of Oil Crops, 2021. http://dx.doi.org/10.25230/conf11-2021-270-274.

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The biological activity of the rhizosphere soil increased upon the application of mineral fertilizers (N18P42) and their combination with straw (N18P42 + straw) by 58 and 70 %, in comparison to the control. Of the three studied factors, the application of mineral fertilizers had the highest positive effect on the number of microorganisms in the barley rhizosphere, both separately and in combination with the studied factors.
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Tukmacheva, E. V., and O. F. Khamova. "THE DEPENDENCE OF GRAIN YIELD OF WINTER WHEAT ON THE INTENSITY OF CELLULOSE DECOMPOSITION IN MEADOW-CHERNOZEM SOIL." In 11-я Всероссийская конференция молодых учёных и специалистов «Актуальные вопросы биологии, селекции, технологии возделывания и переработки сельскохозяйственных культур». V.S. Pustovoit All-Russian Research Institute of Oil Crops, 2021. http://dx.doi.org/10.25230/conf11-2021-246-249.

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We studied the cellulolytic activity of the winter wheat rhizosphere soil in a stationary field experiment with the application of mineral nitrogen-phosphorus fertilizers (N15P23 per hectare of crop rotation area), straw, and seed inoculation. We estimated the crop yield depending on the intensity of cellulose decomposition in the soil. We established that the intensity of cellulose decomposition in the rhizosphere of winter wheat was most affected by the application of mineral fertilizers, as well as the combination of the application of mineral fertilizers, straw, and seed inoculation with the biopreparation rhizoagrin before sowing.
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Reports on the topic "Rhizosphere"

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Crowley, David E., Dror Minz, and Yitzhak Hadar. Shaping Plant Beneficial Rhizosphere Communities. United States Department of Agriculture, July 2013. http://dx.doi.org/10.32747/2013.7594387.bard.

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PGPR bacteria include taxonomically diverse bacterial species that function for improving plant mineral nutrition, stress tolerance, and disease suppression. A number of PGPR are being developed and commercialized as soil and seed inoculants, but to date, their interactions with resident bacterial populations are still poorly understood, and-almost nothing is known about the effects of soil management practices on their population size and activities. To this end, the original objectives of this research project were: 1) To examine microbial community interactions with plant-growth-promoting rhizobacteria (PGPR) and their plant hosts. 2) To explore the factors that affect PGPR population size and activity on plant root surfaces. In our original proposal, we initially prqposed the use oflow-resolution methods mainly involving the use of PCR-DGGE and PLFA profiles of community structure. However, early in the project we recognized that the methods for studying soil microbial communities were undergoing an exponential leap forward to much more high resolution methods using high-throughput sequencing. The application of these methods for studies on rhizosphere ecology thus became a central theme in these research project. Other related research by the US team focused on identifying PGPR bacterial strains and examining their effective population si~es that are required to enhance plant growth and on developing a simulation model that examines the process of root colonization. As summarized in the following report, we characterized the rhizosphere microbiome of four host plant species to determine the impact of the host (host signature effect) on resident versus active communities. Results of our studies showed a distinct plant host specific signature among wheat, maize, tomato and cucumber, based on the following three parameters: (I) each plant promoted the activity of a unique suite of soil bacterial populations; (2) significant variations were observed in the number and the degree of dominance of active populations; and (3)the level of contribution of active (rRNA-based) populations to the resident (DNA-based) community profiles. In the rhizoplane of all four plants a significant reduction of diversity was observed, relative to the bulk soil. Moreover, an increase in DNA-RNA correspondence indicated higher representation of active bacterial populations in the residing rhizoplane community. This research demonstrates that the host plant determines the bacterial community composition in its immediate vicinity, especially with respect to the active populations. Based on the studies from the US team, we suggest that the effective population size PGPR should be maintained at approximately 105 cells per gram of rhizosphere soil in the zone of elongation to obtain plant growth promotion effects, but emphasize that it is critical to also consider differences in the activity based on DNA-RNA correspondence. The results ofthis research provide fundamental new insight into the composition ofthe bacterial communities associated with plant roots, and the factors that affect their abundance and activity on root surfaces. Virtually all PGPR are multifunctional and may be expected to have diverse levels of activity with respect to production of plant growth hormones (regulation of root growth and architecture), suppression of stress ethylene (increased tolerance to drought and salinity), production of siderophores and antibiotics (disease suppression), and solubilization of phosphorus. The application of transcriptome methods pioneered in our research will ultimately lead to better understanding of how management practices such as use of compost and soil inoculants can be used to improve plant yields, stress tolerance, and disease resistance. As we look to the future, the use of metagenomic techniques combined with quantitative methods including microarrays, and quantitative peR methods that target specific genes should allow us to better classify, monitor, and manage the plant rhizosphere to improve crop yields in agricultural ecosystems. In addition, expression of several genes in rhizospheres of both cucumber and whet roots were identified, including mostly housekeeping genes. Denitrification, chemotaxis and motility genes were preferentially expressed in wheat while in cucumber roots bacterial genes involved in catalase, a large set of polysaccharide degradation and assimilatory sulfate reduction genes were preferentially expressed.
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Crowley, David, Yitzhak Hadar, and Yona Chen. Rhizosphere Ecology of Plant-Beneficial Microorganisms. United States Department of Agriculture, February 2000. http://dx.doi.org/10.32747/2000.7695843.bard.

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Rhizoferrin, a siderophore produced by Rhizopus arrhizus, has been shown in previous studies to be an outstanding Fe carrier to plants. However, calculations based on stability constants and thermodynamic equilibrium lead to contradicting conclusions. In this study a kinetic approach was employed to elucidate this apparent contradiction and to determine the behavior of rhizoferrin under conditions representing soil and nutrient solutions. Stability of Fe3+ complexes in nutrient solution, rate of metal exchange with Ca, and rate of Fe extraction by the free ligand were monitored for rhizoferrin and other chelating agents by 55Fe labeling. Ferric complexes of rhizoferrin, desferri-ferrioxamine-B (DFOB), and ethylenediamine-di(o-hydroxyphenylacetic acid) (EDDHA) were found to be stable in nutrient solution at pH 7.5 for 31 days, while ferric complexes of ethylenediaminetetraacetic acid (EDTA) and mugineic acid (MA) lost 50% of the chelated Fe within 2 days. Fe-Ca exchange in Ca solutions at pH 8.7 revealed rhizoferrin to hold Fe at non-equilibrium state for 3-4 weeks at 3.3 mM Ca and for longer periods at lower Ca concentrations. EDTA lost the ferric ion at a faster rate under the same conditions. Fe extraction from freshly prepared Fe-hydroxide at pH 8.7 and with 3.2 mM Ca was slow and followed the order. DFOB > EDDHA > MA > rhizoferrin > EDTA. Based on these results we suggest that a kinetic rather than equilibrium approach should be the basis for predictions of Fe-chelates efficiency. We conclude that the non-equilibrium state of rhizoferrin is of crucial importance for its behavior as a Fe carrier to plants.
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Callister, Stephen, James Moran, Lee Ann McCue, and Ljiljana Pasa-Tolic. Microbial Ecology of the Plant Rhizosphere (PlantMicrobe). Office of Scientific and Technical Information (OSTI), December 2020. http://dx.doi.org/10.2172/1988067.

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Fan, Teresa W. M., David Crowley, and Richard M. Higashi. Plant Rhizosphere Effects on Metal Mobilization and Transport. Office of Scientific and Technical Information (OSTI), June 1999. http://dx.doi.org/10.2172/827408.

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Fan, Teresa W. M., Richard M. Higashi, and David E. Crowley. Plant Rhizosphere Effects on Metal Mobilization and Transport. Office of Scientific and Technical Information (OSTI), June 2000. http://dx.doi.org/10.2172/827410.

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Fan, Teresa W. M., Richard M. Higashi, and David E. Crowley. PLANT RHIZOSPHERE EFFECTS ON METAL MOBILIZATION AND TRANSPORT. Office of Scientific and Technical Information (OSTI), December 2000. http://dx.doi.org/10.2172/827412.

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Neumann, Rebecca. Methane Oxidation in the Rhizosphere of Wetland Plants. Final Report. Office of Scientific and Technical Information (OSTI), November 2019. http://dx.doi.org/10.2172/1573358.

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Minz, Dror, Stefan J. Green, Noa Sela, Yitzhak Hadar, Janet Jansson, and Steven Lindow. Soil and rhizosphere microbiome response to treated waste water irrigation. United States Department of Agriculture, January 2013. http://dx.doi.org/10.32747/2013.7598153.bard.

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Research objectives : Identify genetic potential and community structure of soil and rhizosphere microbial community structure as affected by treated wastewater (TWW) irrigation. This objective was achieved through the examination soil and rhizosphere microbial communities of plants irrigated with fresh water (FW) and TWW. Genomic DNA extracted from soil and rhizosphere samples (Minz laboratory) was processed for DNA-based shotgun metagenome sequencing (Green laboratory). High-throughput bioinformatics was performed to compare both taxonomic and functional gene (and pathway) differences between sample types (treatment and location). Identify metabolic pathways induced or repressed by TWW irrigation. To accomplish this objective, shotgun metatranscriptome (RNA-based) sequencing was performed. Expressed genes and pathways were compared to identify significantly differentially expressed features between rhizosphere communities of plants irrigated with FW and TWW. Identify microbial gene functions and pathways affected by TWW irrigation*. To accomplish this objective, we will perform a metaproteome comparison between rhizosphere communities of plants irrigated with FW and TWW and selected soil microbial activities. Integration and evaluation of microbial community function in relation to its structure and genetic potential, and to infer the in situ physiology and function of microbial communities in soil and rhizospere under FW and TWW irrigation regimes. This objective is ongoing due to the need for extensive bioinformatics analysis. As a result of the capabilities of the new PI, we have also been characterizing the transcriptome of the plant roots as affected by the TWW irrigation and comparing the function of the plants to that of the microbiome. *This original objective was not achieved in the course of this study due to technical issues, especially the need to replace the American PIs during the project. However, the fact we were able to analyze more than one plant system as a result of the abilities of the new American PI strengthened the power of the conclusions derived from studies for the 1ˢᵗ and 2ⁿᵈ objectives. Background: As the world population grows, more urban waste is discharged to the environment, and fresh water sources are being polluted. Developing and industrial countries are increasing the use of wastewater and treated wastewater (TWW) for agriculture practice, thus turning the waste product into a valuable resource. Wastewater supplies a year- round reliable source of nutrient-rich water. Despite continuing enhancements in TWW quality, TWW irrigation can still result in unexplained and undesirable effects on crops. In part, these undesirable effects may be attributed to, among other factors, to the effects of TWW on the plant microbiome. Previous studies, including our own, have presented the TWW effect on soil microbial activity and community composition. To the best of our knowledge, however, no comprehensive study yet has been conducted on the microbial population associated BARD Report - Project 4662 Page 2 of 16 BARD Report - Project 4662 Page 3 of 16 with plant roots irrigated with TWW – a critical information gap. In this work, we characterize the effect of TWW irrigation on root-associated microbial community structure and function by using the most innovative tools available in analyzing bacterial community- a combination of microbial marker gene amplicon sequencing, microbial shotunmetagenomics (DNA-based total community and gene content characterization), microbial metatranscriptomics (RNA-based total community and gene content characterization), and plant host transcriptome response. At the core of this research, a mesocosm experiment was conducted to study and characterize the effect of TWW irrigation on tomato and lettuce plants. A focus of this study was on the plant roots, their associated microbial communities, and on the functional activities of plant root-associated microbial communities. We have found that TWW irrigation changes both the soil and root microbial community composition, and that the shift in the plant root microbiome associated with different irrigation was as significant as the changes caused by the plant host or soil type. The change in microbial community structure was accompanied by changes in the microbial community-wide functional potential (i.e., gene content of the entire microbial community, as determined through shotgun metagenome sequencing). The relative abundance of many genes was significantly different in TWW irrigated root microbiome relative to FW-irrigated root microbial communities. For example, the relative abundance of genes encoding for transporters increased in TWW-irrigated roots increased relative to FW-irrigated roots. Similarly, the relative abundance of genes linked to potassium efflux, respiratory systems and nitrogen metabolism were elevated in TWW irrigated roots when compared to FW-irrigated roots. The increased relative abundance of denitrifying genes in TWW systems relative FW systems, suggests that TWW-irrigated roots are more anaerobic compare to FW irrigated root. These gene functional data are consistent with geochemical measurements made from these systems. Specifically, the TWW irrigated soils had higher pH, total organic compound (TOC), sodium, potassium and electric conductivity values in comparison to FW soils. Thus, the root microbiome genetic functional potential can be correlated with pH, TOC and EC values and these factors must take part in the shaping the root microbiome. The expressed functions, as found by the metatranscriptome analysis, revealed many genes that increase in TWW-irrigated plant root microbial population relative to those in the FW-irrigated plants. The most substantial (and significant) were sodium-proton antiporters and Na(+)-translocatingNADH-quinoneoxidoreductase (NQR). The latter protein uses the cell respiratory machinery to harness redox force and convert the energy for efflux of sodium. As the roots and their microbiomes are exposed to the same environmental conditions, it was previously hypothesized that understanding the soil and rhizospheremicrobiome response will shed light on natural processes in these niches. This study demonstrate how newly available tools can better define complex processes and their downstream consequences, such as irrigation with water from different qualities, and to identify primary cues sensed by the plant host irrigated with TWW. From an agricultural perspective, many common practices are complicated processes with many ‘moving parts’, and are hard to characterize and predict. Multiple edaphic and microbial factors are involved, and these can react to many environmental cues. These complex systems are in turn affected by plant growth and exudation, and associated features such as irrigation, fertilization and use of pesticides. However, the combination of shotgun metagenomics, microbial shotgun metatranscriptomics, plant transcriptomics, and physical measurement of soil characteristics provides a mechanism for integrating data from highly complex agricultural systems to eventually provide for plant physiological response prediction and monitoring. BARD Report
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9

Harman, Gary E., and Ilan Chet. Enhancing Crop Yield through Colonization of the Rhizosphere with Beneficial Microbes. United States Department of Agriculture, December 2001. http://dx.doi.org/10.32747/2001.7580684.bard.

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Abstract:
At the start of this project, fungi in the genus Trichoderma were known to be potent biocontrol agents, and their primary mechanism was considered to via direct effects upon the target fungi. Due in large part to the efforts of the two PIs, we now know that this view is far too limited; while Trichoderma spp. do indeed have direct effects on pathogenic fungi, they have very far reaching effects directly upon plants. Indeed, these fungi must be considered as opportunistic plant symbionts; they provide a number of benefits to plants and themselves are favored by large numbers of healthy roots. Research under this BARD grant has demonstrated that These fungi induce resistance mechanisms in plants. They increase root development and depth of rooting; Bradyrhizobium enhances this effect in soybean. They enhance uptake of plant nutrients. They have abilities to solubilize nutrients, such as oxidized metals and insoluble phosphorus compounds by a variety of different mechanisms and biochemicals. This is a marked expansion of our knowledge of the abilities of these organisms. This knowledge has direct implications for understanding of basic plant responses and abilities, and already is being used to improve plant productivity and reduce pollution of the environment.
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10

Kapulnik, Yoram, and Donald A. Phillips. Isoflavonoid Regulation of Root Bacteria. United States Department of Agriculture, January 1996. http://dx.doi.org/10.32747/1996.7570561.bard.

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Abstract:
The overall objective of this project was to develop a conceptual framework for enhancing root colonization by beneficial bacteria. To accomplish this aim we tested the hypothesis that production and excretion of the plant phytoalexin medicarpin can be used for creation of a special niche along the legume roots, where beneficial microorganism, such as rhizobium, will have a selective advantage. On the Israeli side it was shown that higher medicarpin levels are exuded following the application of Rhizobium meliloti to the rhizosphere but the specific biochemical pathway governing medicarpin production was not induced significantly enough to support a constant production and excretion of this molecule to the rhizosphere. Furthermore, pathogenic bacteria and chemical elicitors were found to induce higher levels of this phytoalexin and it became important to test its natural abundance in field grown plants. On the US side, the occurrence of flavonoids and nucleosides in agricultural soils has been evaluated and biologically significant quantities of these molecules were identified. A more virulent Agrobacterium tumefaciens strain was isolated from alfalfa (Medicago sativa L.) which forms tumors on a wide range of plant species. This isolate contains genes that increase competitive colonization abilities on roots by reducing the accumulation of alfalfa isoflavonoids in the bacterial cells. Following gene tagging efforts the US lab found that mutation in the bacterial efflux pump operons of this isolate reduced its competitive abilities. This results support our original hypothesis that detoxification activity of isoflavenoids molecules, based on bacterial gene(s), is an important selection mechanism in the rhizosphere. In addition, we focused on biotin as a regulatory element in the rhizosphere to support growth of some rhizosphere microorganisms and designed a bacterial gene construct carrying the biotin-binding protein, streptavidin. Expressing this gene in tobacco roots did not affect the biotin level but its expression in alfalfa was lethal. In conclusion, the collaborative combination of basic and applied approaches toward the understanding of rhizosphere activity yielded new knowledge related to the colonization of roots by beneficial microorganisms in the presence of biological active molecules exuded from the plant roots.
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