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Trivedi P, Mattupalli C, Eversole K, Leach JE. Enabling sustainable agriculture through understanding and enhancement of microbiomes. THE NEW PHYTOLOGIST 2021; 230:2129-2147. [PMID: 33657660 DOI: 10.1111/nph.17319] [Citation(s) in RCA: 80] [Impact Index Per Article: 26.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Accepted: 02/04/2021] [Indexed: 05/18/2023]
Abstract
Harnessing plant-associated microbiomes offers an invaluable strategy to help agricultural production become more sustainable while also meeting growing demands for food, feed and fiber. A plethora of interconnected interactions among the host, environment and microbes, occurring both above and below ground, drive recognition, recruitment and colonization of plant-associated microbes, resulting in activation of downstream host responses and functionality. Dissecting these complex interactions by integrating multiomic approaches, high-throughput culturing, and computational and synthetic biology advances is providing deeper understanding of the structure and function of native microbial communities. Such insights are paving the way towards development of microbial products as well as microbiomes engineered with synthetic microbial communities capable of delivering agronomic solutions. While there is a growing market for microbial-based solutions to improve crop productivity, challenges with commercialization of these products remain. The continued translation of plant-associated microbiome knowledge into real-world scenarios will require concerted transdisciplinary research, cross-training of a next generation of scientists, and targeted educational efforts to prime growers and the general public for successful adoption of these innovative technologies.
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Affiliation(s)
- Pankaj Trivedi
- Microbiome Network and Department of Agricultural Biology, Colorado State University, Ft Collins, CO, 80523-1177, USA
| | - Chakradhar Mattupalli
- Department of Plant Pathology, Washington State University, Mount Vernon NWREC, 16650 State Route 536, Mount Vernon, WA, 98273, USA
| | - Kellye Eversole
- Eversole Associates, 5207 Wyoming Road, Bethesda, MD, 20816, USA
- International Alliance for Phytobiomes Research, 2841 NE Marywood Ct, Lee's Summit, MO, 64086, USA
| | - Jan E Leach
- Microbiome Network and Department of Agricultural Biology, Colorado State University, Ft Collins, CO, 80523-1177, USA
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Puente ML, Maroniche GA, Panepucci M, Sabio Y García J, García JE, Criado MV, Molina R, Cassán F. Localization and survival of Azospirillum brasilense Az39 in soybean leaves. Lett Appl Microbiol 2021; 72:626-633. [PMID: 33354785 DOI: 10.1111/lam.13444] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Revised: 12/17/2020] [Accepted: 12/18/2020] [Indexed: 11/30/2022]
Abstract
In recent years, foliar inoculation has gained acceptance among the available methods to deliver plant beneficial micro-organisms to crops under field conditions. Colonization efficiency by such micro-organisms largely depends on their ability to survive when applied on the leaves. In this work, we evaluated the survival and localization of Azospirillum brasilense Az39 (Az39) in excised soybean leaves. Scanning electron microscopy and confocal laser scanning microscopy of a red fluorescent-transformed variant of Az39 were used to determine bacterial localization, while the most probable number and plate count methods were applied for bacterial quantification. Microscopic observations indicated a decrease in the number of Az39 cells on the leaf surface at 24 h after treatment, whereas midribs and cell-cell junctions of the inner leaf epidermis became highly populated zones. The presence of Az39 inside xylem vessels was corroborated at 6 h after bacterization. Az39 population did not significantly decrease throughout 24 h. We could visualize Az39 cells on the surface and in internal tissues of soybean leaves and recover them through culture methodologies. These results evidence the survival capacity of Az39 on and inside leaves and suggest a previously unnoticed endophytic potential for this well-known plant growth-promoting rhizobacteria strain.
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Affiliation(s)
- M L Puente
- Instituto de Microbiología y Zoología Agrícola, Instituto Nacional de Tecnología Agropecuaria (INTA-IMYZA), Castelar, Argentina
| | - G A Maroniche
- Facultad de Ciencias Agrarias, CONICET, Universidad Nacional de Mar del Plata, Balcarce, Argentina
| | - M Panepucci
- Facultad de Agronomía, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - J Sabio Y García
- Instituto de Biotecnología-IABIMO, INTA-CONICET, INTA Castelar, Buenos Aires, Argentina
| | - J E García
- Instituto de Microbiología y Zoología Agrícola, Instituto Nacional de Tecnología Agropecuaria (INTA-IMYZA), Castelar, Argentina
| | - M V Criado
- Facultad de Agronomía, Instituto de Investigaciones en Biociencias Agrícolas y Ambientales (INBA)-CONICET, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - R Molina
- Laboratorio de Fisiología Vegetal e Interacción Planta-Microorganismo, Instituto de Investigaciones Agrobiotecnológicas, INIAB-CONICET, Río Cuarto, Argentina
| | - F Cassán
- Laboratorio de Fisiología Vegetal e Interacción Planta-Microorganismo, Instituto de Investigaciones Agrobiotecnológicas, INIAB-CONICET, Río Cuarto, Argentina
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Rodrigues TF, Bender FR, Sanzovo AWS, Ferreira E, Nogueira MA, Hungria M. Impact of pesticides in properties of Bradyrhizobium spp. and in the symbiotic performance with soybean. World J Microbiol Biotechnol 2020; 36:172. [PMID: 33068168 DOI: 10.1007/s11274-020-02949-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Accepted: 10/10/2020] [Indexed: 12/26/2022]
Abstract
Soybean [Glycine max (L.) Merr.] has great economic and nutritional importance mainly due to its high protein content. All plant's N needs can be met by the symbiosis with elite Bradyrhizobium strains applied as inoculants to the seeds at sowing time; however, the increasing use of pesticides in seed treatments can impair the contribution of the biological nitrogen fixation. In this study, we report decreases in cell survival of two strains, B. japonicum SEMIA 5079 and B. elkanii SEMIA 587 in seeds inoculated and treated with StandakTop™, composed of the fungicides pyraclostrobin and thiophanate-methyl and the insecticide fipronil, the pesticides most used in soybean seed treatment in several countries. Cell death was enhanced with the time of exposure to the pesticides, and B. elkanii was less tolerant, with almost no detectable viable cells after 15 days. Change in colony morphology with smaller colonies was observed in the presence of the pesticides, being more drastic with the time of exposure, and attributed to an adaptive response towards survival in the presence of the abiotic stress. However, morphological changes were reversible after elimination of the stressing agent and symbiotic performance under controlled greenhouse conditions was similar between strains that had been or not exposed to the pesticides. In addition, no changes in DNA profiles (BOX-PCR) of both strains were observed after the contact with the pesticides. In two field experiments, impacting effects of the pesticides were observed mainly on the total N accumulated in grains of plants relying on both N2-fixation and N-fertilizer. Our data indicate that StandakTop® affects parameters never reported before, including colony morphology of Bradyrhizobium spp. and N metabolism and/or N remobilization to soybean grains.
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Affiliation(s)
- Thiago Fernandes Rodrigues
- Department of Biochemistry and Biotechnology, Universidade Estadual de Londrina, C.P. 10.011, Londrina, Paraná, 86.057-970, Brazil
- Embrapa Soja, Caixa Postal 231, Londrina, Paraná, CEP 86001-970, Brazil
| | - Flavia Raquel Bender
- Department of Biochemistry and Biotechnology, Universidade Estadual de Londrina, C.P. 10.011, Londrina, Paraná, 86.057-970, Brazil
- Embrapa Soja, Caixa Postal 231, Londrina, Paraná, CEP 86001-970, Brazil
| | - Alisson Wilson Santos Sanzovo
- Embrapa Soja, Caixa Postal 231, Londrina, Paraná, CEP 86001-970, Brazil
- Department of Agronomy, Universidade Estadual de Londrina, C.P. 6001, Londrina, Paraná, 86.057-970, Brazil
| | - Eduara Ferreira
- Embrapa Soja, Caixa Postal 231, Londrina, Paraná, CEP 86001-970, Brazil
| | - Marco Antonio Nogueira
- Embrapa Soja, Caixa Postal 231, Londrina, Paraná, CEP 86001-970, Brazil
- Department of Agronomy, Universidade Estadual de Londrina, C.P. 6001, Londrina, Paraná, 86.057-970, Brazil
| | - Mariangela Hungria
- Department of Biochemistry and Biotechnology, Universidade Estadual de Londrina, C.P. 10.011, Londrina, Paraná, 86.057-970, Brazil.
- Embrapa Soja, Caixa Postal 231, Londrina, Paraná, CEP 86001-970, Brazil.
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Method for Recovering and Counting Viable Cells from Maize Seeds Inoculated with Azospirillum brasilense. JOURNAL OF PURE AND APPLIED MICROBIOLOGY 2020. [DOI: 10.22207/jpam.14.1.21] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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Elhady A, Hallmann J, Heuer H. Symbiosis of soybean with nitrogen fixing bacteria affected by root lesion nematodes in a density-dependent manner. Sci Rep 2020; 10:1619. [PMID: 32005934 PMCID: PMC6994534 DOI: 10.1038/s41598-020-58546-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2018] [Accepted: 01/17/2020] [Indexed: 11/09/2022] Open
Abstract
Early maturing varieties of soybean have a high yield potential in Europe, where the main biotic threat to soybean cultivation are root lesion nematodes (Pratylenchus spp.). Nitrogen fixation in root nodules by highly efficient inoculants of Bradyrhizobium japonicum is an incentive to grow soybean in low-input rotation systems. We investigated density-dependent effects of Pratylenchus penetrans on nitrogen fixation by co-inoculated B. japonicum. Less than 130 inoculated nematodes affected the number and weight of nodules, the density of viable bacteroids in nodules, and nitrogen fixation measured as concentration of ureides in leaves. With more inoculated nematodes, the percentage that invaded the roots increased, and adverse effects on the symbiosis accelerated, leading to non-functional nodules at 4,000 and more nematodes. When P. penetrans invaded roots that had fully established nodules, growth of nodules, density of bacteroids, and nitrogen fixation were affected but not the number of nodules. In contrast, nodulation of already infested roots resulted in a high number of small nodules with decreased densities of bacteroids and nitrogen fixation. P. penetrans invaded and damaged the nodules locally, but they also significantly affected the nodule symbiosis by a plant-mediated mechanism, as shown in an experiment with split-root systems.
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Affiliation(s)
- Ahmed Elhady
- Department of Epidemiology and Pathogen Diagnostics, Julius Kühn-Institut, Federal Research Centre for Cultivated Plants, Braunschweig, Germany
- Department of Plant Protection, Faculty of Agriculture, Benha University, Benha, Egypt
| | - Johannes Hallmann
- Department of Epidemiology and Pathogen Diagnostics, Julius Kühn-Institut, Federal Research Centre for Cultivated Plants, Braunschweig, Germany
| | - Holger Heuer
- Department of Epidemiology and Pathogen Diagnostics, Julius Kühn-Institut, Federal Research Centre for Cultivated Plants, Braunschweig, Germany.
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de Souza GK, Sampaio J, Longoni L, Ferreira S, Alvarenga S, Beneduzi A. Soybean inoculants in Brazil: an overview of quality control. Braz J Microbiol 2019; 50:205-211. [PMID: 30637629 PMCID: PMC6863340 DOI: 10.1007/s42770-018-0028-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Accepted: 08/06/2018] [Indexed: 11/25/2022] Open
Abstract
The bacterial strains SEMIA 587 and 5019 (Bradyrhizobium elkanii), 5079 (Bradyrhizobium japonicum), and 5080 (Bradyrhizobium diazoefficiens) are recommended for soybean inoculants in Brazil. In several countries, the current regulations are insufficient to induce companies for improving the quality of their products, leading to low performance and subsequent abandonment of inoculant use. From 2010 to 2014, 1086 samples coming mainly from Argentina and the southern region of Brazil were analyzed for viable cells counting, strains identification, and purity analysis according to the SDA/MAPA no. 30/2010 Normative Instruction. Most products were imported and formulated in liquid carriers with 5.0 × 109 colony-forming units (CFU)/mL. The strains most frequently used were SEMIA 5079/5080. Only 2.21% of samples had contaminants. The guaranteed concentration of viable cells in inoculants mostly ranged from 4.1 × 109 to 5.0 × 109 CFU/mL or CFU/g. The most frequently found concentration was above 1.1 × 1010 CFU/mL or CFU/g, which was higher than the product guarantee. The inoculants used for soybean crop in Brazil have excellent quality, leading the country to the leadership in taking advantage of the biological nitrogen fixation benefits for a productive and sustainable agriculture.
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Affiliation(s)
| | - Jamilla Sampaio
- Departamento de Diagnóstico e Pesquisa Agropecuária (ex-FEPAGRO) da Secretaria da Agricultura, Pecuária e Irrigação (SEAPI) do Rio Grande do Sul, Rua Gonçalves Dias, 570, Porto Alegre, RS, CEP 90130-060, Brazil
| | - Letícia Longoni
- Departamento de Diagnóstico e Pesquisa Agropecuária (ex-FEPAGRO) da Secretaria da Agricultura, Pecuária e Irrigação (SEAPI) do Rio Grande do Sul, Rua Gonçalves Dias, 570, Porto Alegre, RS, CEP 90130-060, Brazil
| | - Silviane Ferreira
- Departamento de Diagnóstico e Pesquisa Agropecuária (ex-FEPAGRO) da Secretaria da Agricultura, Pecuária e Irrigação (SEAPI) do Rio Grande do Sul, Rua Gonçalves Dias, 570, Porto Alegre, RS, CEP 90130-060, Brazil
| | - Samuel Alvarenga
- Departamento de Diagnóstico e Pesquisa Agropecuária (ex-FEPAGRO) da Secretaria da Agricultura, Pecuária e Irrigação (SEAPI) do Rio Grande do Sul, Rua Gonçalves Dias, 570, Porto Alegre, RS, CEP 90130-060, Brazil
| | - Anelise Beneduzi
- Universidade La Salle, Av. Vítor Barreto, 2288, Canoas, RS, CEP 92010-000, Brazil.
- Departamento de Diagnóstico e Pesquisa Agropecuária (ex-FEPAGRO) da Secretaria da Agricultura, Pecuária e Irrigação (SEAPI) do Rio Grande do Sul, Rua Gonçalves Dias, 570, Porto Alegre, RS, CEP 90130-060, Brazil.
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Improvement of soybean grain nutritional quality under foliar inoculation with Azospirillum brasilense strain Az39. Symbiosis 2018. [DOI: 10.1007/s13199-018-0568-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Torres D, Benavidez I, Donadio F, Mongiardini E, Rosas S, Spaepen S, Vanderleyden J, Pěnčík A, Novák O, Strnad M, Frébortová J, Cassán F. New insights into auxin metabolism in Bradyrhizobium japonicum. Res Microbiol 2018; 169:313-323. [PMID: 29751062 DOI: 10.1016/j.resmic.2018.04.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2017] [Revised: 04/20/2018] [Accepted: 04/20/2018] [Indexed: 11/28/2022]
Abstract
Bacterial metabolism of phytohormones includes several processes such as biosynthesis, catabolism, conjugation, hydrolysis and homeostatic regulation. However, only biosynthesis and occasionally catabolism are studied in depth in microorganisms. In this work, we evaluated and reconsidered IAA metabolism in Bradyrhizobiumjaponicum E109, one of the most widely used strains for soybean inoculation around the world. The genomic analysis of the strain showed the presence of several genes responsible for IAA biosynthesis, mainly via indole-3-acetonitrile (IAN), indole-3-acetamide (IAM) and tryptamine (TAM) pathways. However; in vitro experiments showed that IAA is not accumulated in the culture medium in significant amounts. On the contrary, a strong degradation activity was observed after exogenous addition of 0.1 mM of IAA, IBA or NAA to the medium. B. japonicum E109 was not able to grow in culture medium containing IAA as a sole carbon source. In YEM medium, the bacteria degraded IAA and hydrolyzed amino acid auxin conjugates with alanine (IAAla), phenylalanine (IAPhe), and leucine (IAPhe), releasing IAA which was quickly degraded. Finally, the presence of exogenous IAA induced physiological changes in the bacteria such as increased biomass and exopolysaccharide production, as well as infection effectiveness and symbiotic behavior in soybean plants.
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Affiliation(s)
- Daniela Torres
- Laboratorio de Fisiología Vegetal y de la Interacción Planta-microorganismo, Departamento de Ciencias Naturales, FCEFQyN, Universidad Nacional de Río Cuarto, Ruta 36, Km 601, Córdoba, Argentina
| | - Iliana Benavidez
- Laboratorio de Fisiología Vegetal y de la Interacción Planta-microorganismo, Departamento de Ciencias Naturales, FCEFQyN, Universidad Nacional de Río Cuarto, Ruta 36, Km 601, Córdoba, Argentina
| | - Florencia Donadio
- Laboratorio de Fisiología Vegetal y de la Interacción Planta-microorganismo, Departamento de Ciencias Naturales, FCEFQyN, Universidad Nacional de Río Cuarto, Ruta 36, Km 601, Córdoba, Argentina
| | - Elias Mongiardini
- Laboratorio de Interacción Rizobios y Soja, Instituto de Biotecnología y Biología Molecular, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, Argentina
| | - Susana Rosas
- Laboratorio de Fisiología Vegetal y de la Interacción Planta-microorganismo, Departamento de Ciencias Naturales, FCEFQyN, Universidad Nacional de Río Cuarto, Ruta 36, Km 601, Córdoba, Argentina
| | - Stijn Spaepen
- Katholieke Universiteit Leuven, Leuven, Belgium; Max Planck Institute for Plant Breeding Research, Plant Microbe Interactions, Köln, Germany
| | | | - Aleš Pěnčík
- Laboratory of Growth Regulators, Centre of the Region Haná for Biotechnological and Agricultural Research, Institute of Experimental Botany of the Czech Academy of Sciences & Faculty of Science of Palacký University, Olomouc, Czech Republic
| | - Ondřej Novák
- Laboratory of Growth Regulators, Centre of the Region Haná for Biotechnological and Agricultural Research, Institute of Experimental Botany of the Czech Academy of Sciences & Faculty of Science of Palacký University, Olomouc, Czech Republic
| | - Miroslav Strnad
- Laboratory of Growth Regulators, Centre of the Region Haná for Biotechnological and Agricultural Research, Institute of Experimental Botany of the Czech Academy of Sciences & Faculty of Science of Palacký University, Olomouc, Czech Republic
| | - Jitka Frébortová
- Department of Chemical Biology and Genetics, Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science of Palacký University, Olomouc, Czech Republic
| | - Fabricio Cassán
- Laboratorio de Fisiología Vegetal y de la Interacción Planta-microorganismo, Departamento de Ciencias Naturales, FCEFQyN, Universidad Nacional de Río Cuarto, Ruta 36, Km 601, Córdoba, Argentina.
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Berninger T, González López Ó, Bejarano A, Preininger C, Sessitsch A. Maintenance and assessment of cell viability in formulation of non-sporulating bacterial inoculants. Microb Biotechnol 2018; 11:277-301. [PMID: 29205959 PMCID: PMC5812248 DOI: 10.1111/1751-7915.12880] [Citation(s) in RCA: 73] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2017] [Revised: 09/11/2017] [Accepted: 10/08/2017] [Indexed: 01/20/2023] Open
Abstract
The application of beneficial, plant-associated microorganisms is a sustainable approach to improving crop performance in agriculture. However, microbial inoculants are often susceptible to prolonged periods of storage and deleterious environmental factors, which negatively impact their viability and ultimately limit efficacy in the field. This particularly concerns non-sporulating bacteria. To overcome this challenge, the availability of protective formulations is crucial. Numerous parameters influence the viability of microbial cells, with drying procedures generally being among the most critical ones. Thus, technological advances to attenuate the desiccation stress imposed on living cells are key to successful formulation development. In this review, we discuss the core aspects important to consider when aiming at high cell viability of non-sporulating bacteria to be applied as microbial inoculants in agriculture. We elaborate the suitability of commonly applied drying methods (freeze-drying, vacuum-drying, spray-drying, fluidized bed-drying, air-drying) and potential measures to prevent cell damage from desiccation (externally applied protectants, stress pre-conditioning, triggering of exopolysaccharide secretion, 'helper' strains). Furthermore, we point out methods for assessing bacterial viability, such as colony counting, spectrophotometry, microcalorimetry, flow cytometry and viability qPCR. Choosing appropriate technologies for maintenance of cell viability and evaluation thereof will render formulation development more efficient. This in turn will aid in utilizing the vast potential of promising, plant beneficial bacteria as sustainable alternatives to standard agrochemicals.
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Affiliation(s)
- Teresa Berninger
- AIT Austrian Institute of Technology GmbHCenter for Health and BioresourcesBioresources UnitKonrad‐Lorenz‐Straße 243430TullnAustria
| | - Óscar González López
- AIT Austrian Institute of Technology GmbHCenter for Health and BioresourcesBioresources UnitKonrad‐Lorenz‐Straße 243430TullnAustria
| | - Ana Bejarano
- AIT Austrian Institute of Technology GmbHCenter for Health and BioresourcesBioresources UnitKonrad‐Lorenz‐Straße 243430TullnAustria
| | - Claudia Preininger
- AIT Austrian Institute of Technology GmbHCenter for Health and BioresourcesBioresources UnitKonrad‐Lorenz‐Straße 243430TullnAustria
| | - Angela Sessitsch
- AIT Austrian Institute of Technology GmbHCenter for Health and BioresourcesBioresources UnitKonrad‐Lorenz‐Straße 243430TullnAustria
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Lodeiro AR. [Queries related to the technology of soybean seed inoculation with Bradyrhizobium spp]. Rev Argent Microbiol 2015; 47:261-73. [PMID: 26364183 DOI: 10.1016/j.ram.2015.06.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2014] [Revised: 05/29/2015] [Accepted: 06/06/2015] [Indexed: 10/23/2022] Open
Abstract
With the aim of exploiting symbiotic nitrogen fixation, soybean crops are inoculated with selected strains of Bradyrhizobium japonicum, Bradyrhizobium diazoefficiens or Bradyrhizobium elkanii (collectively referred to as Bradyrhizobium spp.). The most common method of inoculation used is seed inoculation, whether performed immediately before sowing or using preinoculated seeds or pretreated seeds by the professional seed treatment. The methodology of inoculation should not only cover the seeds with living rhizobia, but must also optimize the chances of these rhizobia to infect the roots and nodulate. To this end, inoculated rhizobia must be in such an amount and condition that would allow them to overcome the competition exerted by the rhizobia of the allochthonous population of the soil, which are usually less effective for nitrogen fixation and thus dilute the effect of inoculation on yield. This optimization requires solving some queries related to the current knowledge of seed inoculation, which are addressed in this article. I conclude that the aspects that require further research are the adhesion and survival of rhizobia on seeds, the release of rhizobia once the seeds are deposited in the soil, and the movement of rhizobia from the vicinity of the seeds to the infection sites in the roots.
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Affiliation(s)
- Aníbal R Lodeiro
- Laboratorio de Interacciones entre Rizobios y Soja (LIRyS), IBBM-Facultad de Ciencias Exactas, UNLP y CCT-La Plata CONICET, La Plata, Buenos Aires, Argentina.
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11
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Vriezen JAC, de Bruijn FJ, Nüsslein KR. Desiccation induces viable but Non-Culturable cells in Sinorhizobium meliloti 1021. AMB Express 2012; 2:6. [PMID: 22260437 PMCID: PMC3293009 DOI: 10.1186/2191-0855-2-6] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2012] [Accepted: 01/20/2012] [Indexed: 11/30/2022] Open
Abstract
Sinorhizobium meliloti is a microorganism commercially used in the production of e.g. Medicago sativa seed inocula. Many inocula are powder-based and production includes a drying step. Although S. meliloti survives drying well, the quality of the inocula is reduced during this process. In this study we determined survival during desiccation of the commercial strains 102F84 and 102F85 as well as the model strain USDA1021. The survival of S. meliloti 1021 was estimated during nine weeks at 22% relative humidity. We found that after an initial rapid decline of colony forming units, the decline slowed to a steady 10-fold reduction in colony forming units every 22 days. In spite of the reduction in colony forming units, the fraction of the population identified as viable (42-54%) based on the Baclight live/dead stain did not change significantly over time. This change in the ability of viable cells to form colonies shows (i) an underestimation of the survival of rhizobial cells using plating methods, and that (ii) in a part of the population desiccation induces a Viable But Non Culturable (VBNC)-like state, which has not been reported before. Resuscitation attempts did not lead to a higher recovery of colony forming units indicating the VBNC state is stable under the conditions tested. This observation has important consequences for the use of rhizobia. Finding methods to resuscitate this fraction may increase the quality of powder-based seed inocula.
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12
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A simple method to evaluate the number of bradyrhizobia on soybean seeds and its implication on inoculant quality control. AMB Express 2011; 1:25. [PMID: 21906269 PMCID: PMC3222311 DOI: 10.1186/2191-0855-1-25] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2011] [Accepted: 09/01/2011] [Indexed: 11/16/2022] Open
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