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Pokluda R, Ragasová LN, Jurica M, Kalisz A, Komorowska M, Niemiec M, Caruso G, Gąstoł M, Sekara A. The shaping of onion seedlings performance through substrate formulation and co-inoculation with beneficial microorganism consortia. FRONTIERS IN PLANT SCIENCE 2023; 14:1222557. [PMID: 37521928 PMCID: PMC10382143 DOI: 10.3389/fpls.2023.1222557] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/14/2023] [Accepted: 06/26/2023] [Indexed: 08/01/2023]
Abstract
Introduction Smart management in crop cultivation is increasingly supported by application of arbuscular mycorrhizal fungi (AMF) and plant growth-promoting microorganisms (PGPM), which sustain soil fertility and plant performance. The aim of this study was the evaluation of the effects of consortia composed of (Claroideoglomus claroideum BEG96, Claroideoglomus etunicatum BEG92, Funneliformis geosporum BEG199, Funneliformis mosseae BEG 95, and Rhizophagus irregularis BEG140) and PGPM (Azospirillum brasilense - AZ, or Saccharothrix sp. - S) on onion cultivated in growing media with a composition corresponding to a degraded soil. Methods Three types of substrate formulations were used, with peat:sand ratios of 50:50, 70:30, 100:0 (v:v). The analysis of substrate parameters crucial for its fertility (pH, salinity, sorption complex capacity, and elements' content) and characteristics reflecting onion seedlings' performance (fresh weight, stress biomarkers, and elements' content) was performed. Results AMF colonized onion roots in all treatments, showing increasing potential to form intercellular structures in the substrates rich in organic matter. Additionally, co-inoculation with PGPM microorganisms accelerated arbuscular mycorrhiza establishment. Increased antioxidant activity and glutathione peroxidase (GPOX) activity of onion roots sampled from the formulations composed of peat and sand in the ratio of 100:0, inoculated with AMF+S, and positive correlation between GPOX, fresh weight and antioxidant activity of onion roots reflected the successful induction of plant acclimatization response. Total phenols content was the highest in roots and leaves of onion grown in substrates with 70:30 peat:sand ratio, and, in the case of roots, it was correlated with AMF colonization parameters but not with antioxidant activity. Discussion AMF and PGPM efficiency in supporting onion growth should be linked to the increased onion root system capacity in mineral salts absorption, resulting in more efficient aboveground biomass production. AMF and PGPM consortia were effective in releasing minerals to soluble fraction in substrates rich in organic matter, making elements available for uptake by onion root system, though this phenomenon depended on the PGPM species. Microorganism consortia enhanced onion seedlings' performance also in substrates with lower content of organic carbon through plant biofertilization and phytostimulation.
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Affiliation(s)
- Robert Pokluda
- Department of Vegetable Sciences and Floriculture, Faculty of Horticulture, Mendel University, Brno, Czechia
| | - Lucia Nedorost Ragasová
- Department of Vegetable Sciences and Floriculture, Faculty of Horticulture, Mendel University, Brno, Czechia
| | - Miloš Jurica
- Department of Vegetable Sciences and Floriculture, Faculty of Horticulture, Mendel University, Brno, Czechia
| | - Andrzej Kalisz
- Department of Horticulture, Faculty of Biotechnology and Horticulture, University of Agriculture, Krakow, Poland
| | - Monika Komorowska
- Department of Agricultural and Environmental Chemistry, Faculty of Agriculture and Economics, University of Agriculture, Krakow, Poland
| | - Marcin Niemiec
- Department of Agricultural and Environmental Chemistry, Faculty of Agriculture and Economics, University of Agriculture, Krakow, Poland
| | - Gianluca Caruso
- Department of Agricultural Sciences, University of Naples Federico II, Naples, Italy
| | - Maciej Gąstoł
- Department of Horticulture, Faculty of Biotechnology and Horticulture, University of Agriculture, Krakow, Poland
| | - Agnieszka Sekara
- Department of Horticulture, Faculty of Biotechnology and Horticulture, University of Agriculture, Krakow, Poland
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Nitrogen-Fixing Symbiotic Paraburkholderia Species: Current Knowledge and Future Perspectives. NITROGEN 2023. [DOI: 10.3390/nitrogen4010010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/11/2023] Open
Abstract
A century after the discovery of rhizobia, the first Beta-proteobacteria species (beta-rhizobia) were isolated from legume nodules in South Africa and South America. Since then, numerous species belonging to the Burkholderiaceae family have been isolated. The presence of a highly branching lineage of nodulation genes in beta-rhizobia suggests a long symbiotic history. In this review, we focus on the beta-rhizobial genus Paraburkholderia, which includes two main groups: the South American mimosoid-nodulating Paraburkholderia and the South African predominantly papilionoid-nodulating Paraburkholderia. Here, we discuss the latest knowledge on Paraburkholderia nitrogen-fixing symbionts in each step of the symbiosis, from their survival in the soil, through the first contact with the legumes until the formation of an efficient nitrogen-fixing symbiosis in root nodules. Special attention is given to the strain P. phymatum STM815T that exhibits extraordinary features, such as the ability to: (i) enter into symbiosis with more than 50 legume species, including the agriculturally important common bean, (ii) outcompete other rhizobial species for nodulation of several legumes, and (iii) endure stressful soil conditions (e.g., high salt concentration and low pH) and high temperatures.
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Provorov NA, Andronov EE, Kimeklis AK, Onishchuk OP, Igolkina AA, Karasev ES. Microevolution, speciation and macroevolution in rhizobia: Genomic mechanisms and selective patterns. FRONTIERS IN PLANT SCIENCE 2022; 13:1026943. [PMID: 36388581 PMCID: PMC9640933 DOI: 10.3389/fpls.2022.1026943] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Accepted: 10/06/2022] [Indexed: 06/16/2023]
Abstract
Nodule bacteria (rhizobia), N2-fixing symbionts of leguminous plants, represent an excellent model to study the fundamental issues of evolutionary biology, including the tradeoff between microevolution, speciation, and macroevolution, which remains poorly understood for free-living organisms. Taxonomically, rhizobia are extremely diverse: they are represented by nearly a dozen families of α-proteobacteria (Rhizobiales) and by some β-proteobacteria. Their genomes are composed of core parts, including house-keeping genes (hkg), and of accessory parts, including symbiotically specialized (sym) genes. In multipartite genomes of evolutionary advanced fast-growing species (Rhizobiaceae), sym genes are clustered on extra-chromosomal replicons (megaplasmids, chromids), facilitating gene transfer in plant-associated microbial communities. In this review, we demonstrate that in rhizobia, microevolution and speciation involve different genomic and ecological mechanisms: the first one is based on the diversification of sym genes occurring under the impacts of host-induced natural selection (including its disruptive, frequency-dependent and group forms); the second one-on the diversification of hkgs under the impacts of unknown factors. By contrast, macroevolution represents the polyphyletic origin of super-species taxa, which are dependent on the transfer of sym genes from rhizobia to various soil-borne bacteria. Since the expression of newly acquired sym genes on foreign genomic backgrounds is usually restricted, conversion of resulted recombinants into the novel rhizobia species involves post-transfer genetic changes. They are presumably supported by host-induced selective processes resulting in the sequential derepression of nod genes responsible for nodulation and of nif/fix genes responsible for symbiotic N2 fixation.
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Affiliation(s)
- Nikolay A. Provorov
- Laboratory of Microbiological Monitoring and Bioremediation of Soils, All-Russian Research Institute for Agricultural Microbiology, Pushkin, Russia
| | - Evgeny E. Andronov
- Laboratory of Microbiological Monitoring and Bioremediation of Soils, All-Russian Research Institute for Agricultural Microbiology, Pushkin, Russia
- Laboratory of Soil Biology and Biochemistry, V.V. Dokuchaev Soil Science Institute, Moscow, Russia
| | - Anastasiia K. Kimeklis
- Laboratory of Microbiological Monitoring and Bioremediation of Soils, All-Russian Research Institute for Agricultural Microbiology, Pushkin, Russia
- Department of Applied Ecology, St. Petersburg State University, Saint-Petersburg, Russia
| | - Olga P. Onishchuk
- Laboratory of Microbiological Monitoring and Bioremediation of Soils, All-Russian Research Institute for Agricultural Microbiology, Pushkin, Russia
| | - Anna A. Igolkina
- Gregor Mendel Institute, Austrian Academy of Sciences, Vienna BioCenter, Vienna, Austria
| | - Evgeny S. Karasev
- Laboratory of Microbiological Monitoring and Bioremediation of Soils, All-Russian Research Institute for Agricultural Microbiology, Pushkin, Russia
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Mendoza-Suárez M, Andersen SU, Poole PS, Sánchez-Cañizares C. Competition, Nodule Occupancy, and Persistence of Inoculant Strains: Key Factors in the Rhizobium-Legume Symbioses. FRONTIERS IN PLANT SCIENCE 2021; 12:690567. [PMID: 34489993 PMCID: PMC8416774 DOI: 10.3389/fpls.2021.690567] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2021] [Accepted: 07/19/2021] [Indexed: 05/06/2023]
Abstract
Biological nitrogen fixation by Rhizobium-legume symbioses represents an environmentally friendly and inexpensive alternative to the use of chemical nitrogen fertilizers in legume crops. Rhizobial inoculants, applied frequently as biofertilizers, play an important role in sustainable agriculture. However, inoculants often fail to compete for nodule occupancy against native rhizobia with inferior nitrogen-fixing abilities, resulting in low yields. Strains with excellent performance under controlled conditions are typically selected as inoculants, but the rates of nodule occupancy compared to native strains are rarely investigated. Lack of persistence in the field after agricultural cycles, usually due to the transfer of symbiotic genes from the inoculant strain to naturalized populations, also limits the suitability of commercial inoculants. When rhizobial inoculants are based on native strains with a high nitrogen fixation ability, they often have superior performance in the field due to their genetic adaptations to the local environment. Therefore, knowledge from laboratory studies assessing competition and understanding how diverse strains of rhizobia behave, together with assays done under field conditions, may allow us to exploit the effectiveness of native populations selected as elite strains and to breed specific host cultivar-rhizobial strain combinations. Here, we review current knowledge at the molecular level on competition for nodulation and the advances in molecular tools for assessing competitiveness. We then describe ongoing approaches for inoculant development based on native strains and emphasize future perspectives and applications using a multidisciplinary approach to ensure optimal performance of both symbiotic partners.
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Affiliation(s)
| | - Stig U. Andersen
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | - Philip S. Poole
- Department of Plant Sciences, University of Oxford, Oxford, United Kingdom
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Youseif SH, Abd El-Megeed FH, Mohamed AH, Ageez A, Veliz E, Martínez-Romero E. Diverse Rhizobium strains isolated from root nodules of Trifolium alexandrinum in Egypt and symbiovars. Syst Appl Microbiol 2020; 44:126156. [PMID: 33232849 DOI: 10.1016/j.syapm.2020.126156] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Revised: 11/01/2020] [Accepted: 11/02/2020] [Indexed: 12/18/2022]
Abstract
Berseem clover (T. alexandrinum) is the main forage legume crop used as animal feed in Egypt. Here, eighty rhizobial isolates were isolated from root nodules of berseem clover grown in different regions in Egypt and were grouped by RFLP-16S rRNA ribotyping. Representative isolates were characterized using phylogenetic analyses of the 16S rRNA, rpoB, glnA, pgi, and nodC genes. We also investigated the performance of these isolates using phenotypic tests and nitrogen fixation efficiency assays. The majority of strains (<90%) were closely related to Rhizobium aegyptiacum and Rhizobium aethiopicum and of the remaining strains, six belonged to the Rhizobium leguminosarum genospecies complex and only one strain was assigned to Agrobacterium fabacearum. Despite their heterogeneous chromosomal background, most of the strains shared nodC gene alleles corresponding to symbiovar trifolii. Some of the strains closely affiliated to R. aegyptiacum and R. aethiopicum had superior nodulation and nitrogen fixation capabilities in berseem clover, compared to the commercial inoculant (Okadein®) and N-added treatments. R. leguminosarum strain NGB-CR 17 that harbored a nodC allele typical of symbiovar viciae, was also able to form an effective symbiosis with clover. Two strains with nodC alleles of symbiovar trifolii, R. aegyptiacum strains NGB-CR 129 and 136, were capable of forming effective nodules in Phaseolus vulgaris in axenic greenhouse conditions. This adds the symbiovar trifolii which is well-established in the Egyptian soils to the list of symbiovars that form nodules in P. vulgaris.
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Affiliation(s)
- Sameh H Youseif
- Department of Microbial Genetic Resources, National Gene Bank, Agricultural Research Center (ARC), Giza 12619, Egypt.
| | - Fayrouz H Abd El-Megeed
- Department of Microbial Genetic Resources, National Gene Bank, Agricultural Research Center (ARC), Giza 12619, Egypt
| | - Akram H Mohamed
- Department of Microbial Genetic Resources, National Gene Bank, Agricultural Research Center (ARC), Giza 12619, Egypt
| | - Amr Ageez
- Agricultural Genetic Engineering Research Institute, Agricultural Research Center (ARC), Giza 12619, Egypt; Faculty of Biotechnology, MSA University, 6 October City, Egypt
| | - Esteban Veliz
- Department of Plant Biology, University of California, Davis, Life Sciences Addition, 1 Shields Ave., Davis, CA, 95616, USA
| | - Esperanza Martínez-Romero
- Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, UNAM Cuernavaca, Morelos, Mexico
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Pastor-Bueis R, Sánchez-Cañizares C, James EK, González-Andrés F. Formulation of a Highly Effective Inoculant for Common Bean Based on an Autochthonous Elite Strain of Rhizobium leguminosarum bv. phaseoli, and Genomic-Based Insights Into Its Agronomic Performance. Front Microbiol 2019; 10:2724. [PMID: 31920999 PMCID: PMC6927923 DOI: 10.3389/fmicb.2019.02724] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2019] [Accepted: 11/08/2019] [Indexed: 01/08/2023] Open
Abstract
Common bean is a poor symbiotic N-fixer, with a low response to inoculation owing to its promiscuous nodulation with competitive but inefficient resident rhizobia. Consequently, farmers prefer to fertilize them rather than rely on their capacity for Biological Nitrogen Fixation (BNF). However, when rhizobial inoculants are based on autochthonous strains, they often have superior BNF performance in the field due to their genetic adaptations to the local environment. Nevertheless, there is scant information at the genomic level explaining their superiority or on how their genomes may influence the inoculant performance. This information is especially important in technologically advanced agri-systems like Europe, where environmental concerns and increasingly stringent fertilizer regulations are encouraging a return to the use of rhizobial inoculants, but based upon strains that have been thoroughly characterized in terms of their symbiotic performance and their genetics. The aim of this study was to design an inoculant formulation based on a superior autochthonous strain, Rhizobium leguminosarum bv. phaseoli LCS0306, to assess its performance in the field, and to determine the genomic features contributing to the high effectiveness of its symbiosis with common bean. Plants inoculated with the autochthonous strain LCS0306 fixed significantly more nitrogen than those with the allochthonous strains R. phaseoli ATCC 14482T and R. etli CFN42T, and had grain yield similar to the nitrogen-fertilized controls. Inoculation with LCS0306 was particularly efficacious when formulated with a carrier based upon a mixture of perlite and biochar. Whole genome comparisons revealed no differences in the classical symbiotic genes of strain LCS0306 within the symbiovar phaseoli. However, its symbiotic superior performance might be due to its genomic versatility, as it harbors a large assortment of genes contributing to fitness and competitiveness. It is concluded that inoculation with elite rhizobia formulated with perlite-biochar carriers might constitute a step-change in the sustainable cultivation of common bean in Spanish soils.
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Affiliation(s)
- Raquel Pastor-Bueis
- Institute of Environment, Natural Resources and Biodiversity, Universidad de León, León, Spain
| | | | - Euan K James
- The James Hutton Institute, Dundee, United Kingdom
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Search for Ancestral Features in Genomes of Rhizobium leguminosarum bv. viciae Strains Isolated from the Relict Legume Vavilovia formosa. Genes (Basel) 2019; 10:genes10120990. [PMID: 31805640 PMCID: PMC6969944 DOI: 10.3390/genes10120990] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Revised: 11/22/2019] [Accepted: 11/27/2019] [Indexed: 11/17/2022] Open
Abstract
Vavilovia formosa is a relict leguminous plant growing in hard-to-reach habitats in the rocky highlands of the Caucasus and Middle East, and it is considered as the putative closest living relative of the last common ancestor (LCA) of the Fabeae tribe. Symbionts of Vavilovia belonging to Rhizobium leguminosarum bv. viciae compose a discrete group that differs from the other strains, especially in the nucleotide sequences of the symbiotically specialised (sym) genes. Comparison of the genomes of Vavilovia strains with the reference group composed of R. leguminosarum bv. viciae strains isolated from Pisum and Vicia demonstrated that the vavilovia strains have a set of genomic features, probably indicating the important stages of microevolution of the symbiotic system. Specifically, symbionts of Vavilovia (considered as an ancestral group) demonstrated a scattered arrangement of sym genes (>90 kb cluster on pSym), with the location of nodT gene outside of the other nod operons, the presence of nodX and fixW, and the absence of chromosomal fixNOPQ copies. In contrast, the reference (derived) group harboured sym genes as a compact cluster (<60 kb) on a single pSym, lacking nodX and fixW, with nodT between nodN and nodO, and possessing chromosomal fixNOPQ copies. The TOM strain, obtained from nodules of the primitive “Afghan” peas, occupied an intermediate position because it has the chromosomal fixNOPQ copy, while the other features, the most important of which is presence of nodX and fixW, were similar to the Vavilovia strains. We suggest that genome evolution from the ancestral to the derived R. leguminosarum bv. viciae groups follows the “gain-and-loss of sym genes” and the “compaction of sym cluster” strategies, which are common for the macro-evolutionary and micro-evolutionary processes. The revealed genomic features are in concordance with a relict status of the vavilovia strains, indicating that V. formosa coexists with ancestral microsymbionts, which are presumably close to the LCA of R. leguminosarum bv. viciae.
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Iturralde ET, Covelli JM, Alvarez F, Pérez-Giménez J, Arrese-Igor C, Lodeiro AR. Soybean-Nodulating Strains With Low Intrinsic Competitiveness for Nodulation, Good Symbiotic Performance, and Stress-Tolerance Isolated From Soybean-Cropped Soils in Argentina. Front Microbiol 2019; 10:1061. [PMID: 31139173 PMCID: PMC6527597 DOI: 10.3389/fmicb.2019.01061] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Accepted: 04/26/2019] [Indexed: 01/04/2023] Open
Abstract
Soybean is the most important oilseed in the world, cropped in 120–130 million hectares each year. The three most important soybean producers are Argentina, Brazil, and United States, where soybean crops are routinely inoculated with symbiotic N2-fixing Bradyrhizobium spp. This extended inoculation gave rise to soybean-nodulating allochthonous populations (SNAPs) that compete against new inoculant for nodulation, thus impairing yield responses. Competitiveness depends on intrinsic factors contributed by genotype, extrinsic ones determined by growth and environmental conditions, and strain persistence in the soil. To assess these factors in Argentinean SNAPs, we studied 58 isolates from five sites of the main soybean cropping area. BOX-A1R DNA fingerprint distributed these isolates in 10 clades that paralleled the pHs of their original soils. By contrast, reference Bradyrhizobium spp. strains, including those used as soybean-inoculants, were confined to a single clade. More detailed characterization of a subset of 11 SNAP-isolates revealed that five were Bradyrhizobium japonicum, two Bradyrhizobium elkanii, two Rhizobium radiobacter (formerly Agrobacterium tumefaciens), one Bradyrhizobium diazoefficiens, and one Paenibacillus glycanilyticus-which did not nodulate when inoculated alone, and therefore was excluded from further characterization. The remaining subset of 10 SNAP-isolates was used for deeper characterization. All SNAP-isolates were aluminum- and heat-tolerant, and most of them were glyphosate-tolerant. Meanwhile, inoculant strains tested were sensitive to aluminum and glyphosate. In addition, all SNAP-isolates were motile to different degrees. Only three SNAP-isolates were deficient for N2-fixation, and none was intrinsically more competitive than the inoculant strain. These results are in contrast to the general belief that rhizobia from soil populations evolved as intrinsically more competitive for nodulation and less N2-fixing effective than inoculants strains. Shoot:root ratios, both as dry biomass and as total N, were highly correlated with leaf ureide contents, and therefore may be easy indicators of N2-fixing performance, suggesting that highly effective N2-fixing and well-adapted strains may be readily selected from SNAPs. In addition, intrinsic competitiveness of the inoculants strains seems already optimized against SNAP strains, and therefore our efforts to improve nodules occupation by inoculated strains should focus on the optimization of extrinsic competitiveness factors, such as inoculant formulation and inoculation technology.
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Affiliation(s)
- Esteban T Iturralde
- Facultad de Ciencias Exactas, Instituto de Biotecnología y Biología Molecular (IBBM), UNLP y CCT La Plata-CONICET, La Plata, Argentina
| | - Julieta M Covelli
- Facultad de Ciencias Exactas, Instituto de Biotecnología y Biología Molecular (IBBM), UNLP y CCT La Plata-CONICET, La Plata, Argentina
| | - Florencia Alvarez
- Facultad de Ciencias Exactas, Instituto de Biotecnología y Biología Molecular (IBBM), UNLP y CCT La Plata-CONICET, La Plata, Argentina
| | - Julieta Pérez-Giménez
- Facultad de Ciencias Exactas, Instituto de Biotecnología y Biología Molecular (IBBM), UNLP y CCT La Plata-CONICET, La Plata, Argentina
| | - Cesar Arrese-Igor
- Institute for Multidisciplinary Research in Applied Biology (IMAB), Universidad Pública de Navarra, Pamplona, Spain
| | - Aníbal R Lodeiro
- Facultad de Ciencias Exactas, Instituto de Biotecnología y Biología Molecular (IBBM), UNLP y CCT La Plata-CONICET, La Plata, Argentina
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Irisarri P, Cardozo G, Tartaglia C, Reyno R, Gutiérrez P, Lattanzi FA, Rebuffo M, Monza J. Selection of Competitive and Efficient Rhizobia Strains for White Clover. Front Microbiol 2019; 10:768. [PMID: 31065250 PMCID: PMC6489563 DOI: 10.3389/fmicb.2019.00768] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Accepted: 03/26/2019] [Indexed: 11/16/2022] Open
Abstract
The practice of inoculating forage legumes with rhizobia strains is widespread. It is assumed that the inoculated strain determines the performance of the symbiosis and nitrogen fixation rates. However, native-naturalized strains can be competitive, and actual nodule occupancy is often scarcely investigated. In consequence, failures in establishment, and low productivity attributed to poor performance of the inoculant may merely reflect the absence of the inoculated strain in the nodules. This study lays out a strategy followed for selecting a Rhizobium leguminosarum sv. trifolii strain for white clover (Trifolium repens) with competitive nodule occupancy. First, the competitiveness of native-naturalized rhizobia strains selected for their efficiency to fix N2 in clover and tagged with gusA was evaluated in controlled conditions with different soils. Second, three of these experimental strains with superior nodule occupancy plus the currently recommended commercial inoculant, an introduced strain, were tested in the field in 2 years and at two sites. Plant establishment, herbage productivity, fixation of atmospheric N2 (15N natural abundance), and nodule occupancy (ERIC-PCR genomic fingerprinting) were measured. In both years and sites, nodule occupancy of the native-naturalized experimental strains was either higher or similar to that of the commercial inoculant in both primary and secondary roots. The difference was even greater in stolon roots nodules, where nodule occupancy of the native-naturalized experimental strains was at least five times greater. The amount of N fixed per unit plant mass was consistently higher with native-naturalized experimental strains, although the proportion of N derived from atmospheric fixation was similar for all strains. Plant establishment and herbage production, as well as clover contribution in oversown native grasslands, were either similar or higher in white clover inoculated with the native-naturalized experimental strains. These results support the use of our implemented strategy for developing a competitive inoculant from native-naturalized strains.
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Affiliation(s)
- Pilar Irisarri
- Laboratorio de Microbiología, Departamento de Biología Vegetal, Facultad de Agronomía, Universidad de la República, Montevideo, Uruguay
| | - Gerónimo Cardozo
- Instituto Nacional de Investigación Agropecuaria, INIA Treinta y Tres, Treinta y Tres, Uruguay
| | - Carolina Tartaglia
- Laboratorio de Bioquímica, Departamento de Biología Vegetal, Facultad de Agronomía, Universidad de la República, Montevideo, Uruguay
| | - Rafael Reyno
- Instituto Nacional de Investigación Agropecuaria, INIA Tacuarembó, Tacuarembó, Uruguay
| | - Pamela Gutiérrez
- Laboratorio de Bioquímica, Departamento de Biología Vegetal, Facultad de Agronomía, Universidad de la República, Montevideo, Uruguay
| | - Fernando A. Lattanzi
- Instituto Nacional de Investigación Agropecuaria, INIA La Estanzuela, Colonia, Uruguay
| | - Mónica Rebuffo
- Instituto Nacional de Investigación Agropecuaria, INIA La Estanzuela, Colonia, Uruguay
| | - Jorge Monza
- Laboratorio de Bioquímica, Departamento de Biología Vegetal, Facultad de Agronomía, Universidad de la República, Montevideo, Uruguay
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Checcucci A, DiCenzo GC, Bazzicalupo M, Mengoni A. Trade, Diplomacy, and Warfare: The Quest for Elite Rhizobia Inoculant Strains. Front Microbiol 2017; 8:2207. [PMID: 29170661 PMCID: PMC5684177 DOI: 10.3389/fmicb.2017.02207] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Accepted: 10/26/2017] [Indexed: 01/12/2023] Open
Abstract
Rhizobia form symbiotic nitrogen-fixing nodules on leguminous plants, which provides an important source of fixed nitrogen input into the soil ecosystem. The improvement of symbiotic nitrogen fixation is one of the main challenges facing agriculture research. Doing so will reduce the usage of chemical nitrogen fertilizer, contributing to the development of sustainable agriculture practices to deal with the increasing global human population. Sociomicrobiological studies of rhizobia have become a model for the study of the evolution of mutualistic interactions. The exploitation of the wide range of social interactions rhizobia establish among themselves, with the soil and root microbiota, and with the host plant, could constitute a great advantage in the development of a new generation of highly effective rhizobia inoculants. Here, we provide a brief overview of the current knowledge on three main aspects of rhizobia interaction: trade of fixed nitrogen with the plant; diplomacy in terms of communication and possible synergistic effects; and warfare, as antagonism and plant control over symbiosis. Then, we propose new areas of investigation and the selection of strains based on the combination of the genetic determinants for the relevant rhizobia symbiotic behavioral phenotypes.
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Affiliation(s)
- Alice Checcucci
- Department of Biology, University of Florence, Florence, Italy
| | | | | | - Alessio Mengoni
- Department of Biology, University of Florence, Florence, Italy
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