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Sarkar A, Fwanyanga FM, Horn LN, Welzel S, Diederichs M, Kerk LJ, Zimmermann M, Reinhold-Hurek B. Towards inoculant development for Bambara groundnut ( Vigna subterranean (L.) Verdc) pulse crop production in Namibia. FRONTIERS IN PLANT SCIENCE 2023; 14:1270356. [PMID: 37965028 PMCID: PMC10641001 DOI: 10.3389/fpls.2023.1270356] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/05/2023] [Accepted: 10/04/2023] [Indexed: 11/16/2023]
Abstract
Introduction The globally expanding population, together with climate change, poses a risk to the availability of food for humankind. Bambara groundnut (BGN) (Vigna subterranea (L.) Verdc) is a neglected, relatively drought-tolerant native legume of Sub-Saharan Africa that has the potential to become a successful food crop because of its nutritional quality and climate-smart features. Nitrogen fixation from root nodule symbiosis with climate-adapted rhizobial symbionts can contribute nitrogen and organic material in nutrient-poor soil and improve yields. However, high soil temperature and drought often reduce the abundance of native rhizobia in such soil. Therefore, the formulation of climate-smart biofertilizers has the potential to improve the farming of BGN at a low cost in a sustainable manner. Method The effect of seven Bradyrhizobium spp. strains native to Namibia, including B. vignae and B. subterraneum, were tested on three Namibian BGN varieties (red, brown, cream) in greenhouse pot experiments in Namibia, using soil from the target region of Kavango. Each variety was treated with a mixed inoculant consisting of seven preselected strains ("MK") as well as with one promising single inoculant strain. Results The results revealed that in all three varieties, the two inoculants (mixed or single) outperformed the non-inoculated cultivars in terms of shoot dry weight by up to 70%; the mixed inoculant treatment performed significantly better (p < 0.05) in all cases compared to the single inoculant used. To test whether the inoculant strains were established in root nodules, they were identified by sequence analysis. In many cases, the indigenous strains of Kavango soil outcompeted the inoculant strains of the mix for nodule occupancy, depending on the BGN variety. As a further preselection, each of the individual strains of the mix was used to inoculate the three varieties under sterile conditions in a phytotron. The agronomic trait and root nodulation response of the host plant inoculations strongly differed with the BGN variety. Even competitiveness in nodule occupancy without involving any indigenous strains from soil differed and depended strictly on the variety. Discussion Severe differences in symbiont-plant interactions appear to occur in BGN depending on the plant variety, demanding for coupling of breeding efforts with selecting efficient inoculant strains.
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Affiliation(s)
- Abhijit Sarkar
- CBIB Center for Biomolecular Interactions Bremen, Department of Microbe-Plant Interactions, Faculty of Biology and Chemistry, University of Bremen, Bremen, Germany
| | - Felicitas M. Fwanyanga
- Zero Emissions Research Initiative, Multi-disciplinary Research Services, University of Namibia, Windhoek, Namibia
| | - Lydia N. Horn
- Zero Emissions Research Initiative, Multi-disciplinary Research Services, University of Namibia, Windhoek, Namibia
| | - Sina Welzel
- CBIB Center for Biomolecular Interactions Bremen, Department of Microbe-Plant Interactions, Faculty of Biology and Chemistry, University of Bremen, Bremen, Germany
| | - Marco Diederichs
- CBIB Center for Biomolecular Interactions Bremen, Department of Microbe-Plant Interactions, Faculty of Biology and Chemistry, University of Bremen, Bremen, Germany
| | - Luca Jonas Kerk
- CBIB Center for Biomolecular Interactions Bremen, Department of Microbe-Plant Interactions, Faculty of Biology and Chemistry, University of Bremen, Bremen, Germany
| | - Meret Zimmermann
- CBIB Center for Biomolecular Interactions Bremen, Department of Microbe-Plant Interactions, Faculty of Biology and Chemistry, University of Bremen, Bremen, Germany
| | - Barbara Reinhold-Hurek
- CBIB Center for Biomolecular Interactions Bremen, Department of Microbe-Plant Interactions, Faculty of Biology and Chemistry, University of Bremen, Bremen, Germany
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Saad MM, Michalet S, Fossou R, Putnik-Delić M, Crèvecoeur M, Meyer J, de Malézieux C, Hopfgartner G, Maksimović I, Perret X. Loss of NifQ Leads to Accumulation of Porphyrins and Altered Metal-Homeostasis in Nitrogen-Fixing Symbioses. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2019; 32:208-216. [PMID: 30070615 DOI: 10.1094/mpmi-07-18-0188-r] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Symbiotic nitrogen fixation between legumes and rhizobia involves a coordinated expression of many plant and bacterial genes as well as finely tuned metabolic activities of micro- and macrosymbionts. In spite of such complex interactions, symbiotic proficiency remains a resilient process, with host plants apparently capable of compensating for some deficiencies in rhizobia. What controls nodule homeostasis is still poorly understood and probably varies between plant species. In this respect, the promiscuous Sinorhizobium (Ensifer) fredii strain NGR234 has become a model to assess the relative contribution of single gene products to many symbioses. Here, we describe how a deletion in nifQ of NGR234 (strain NGRΔnifQ) makes nodules of Vigna unguiculata, V. radiata, and Macroptilium atropurpureum but not of the mimisoid tree Leucaena leucocephala, purple-red. This peculiar dark-nodule phenotype did not necessarily correlate with a decreased proficiency of NGRΔnifQ but coincided with a 20-fold or more accumulation of coproporphyrin III and uroporphyrin III in V. unguiculata nodules. Porphyrin accumulation was not restricted to plant cells infected with bacteroids but also extended to the nodule cortex. Nodule metal-homeostasis was altered but not sufficiently to prevent assembly and functioning of nitrogenase. Although the role of NifQ in donating molybdenum during assembly of nitrogenase cofactor FeMo-co makes it essential in free-living diazotrophs, our results highlight the dispensability of NifQ in many legume species.
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Affiliation(s)
- Maged M Saad
- 1 University of Geneva, Sciences III, Department of Botany and Plant Biology, Microbiology Unit, 30 quai Ernest-Ansermet, CH-1211 Geneva 4, Switzerland
- 2 King Abdullah University of Science and Technology (KAUST), Biological and Environmental Sciences and Engineering Division (BESE), Thuwal 6900-2355, Kingdom of Saudi Arabia
| | - Sophie Michalet
- 3 University of Geneva, Mass Spectrometry Core Facility (MZ 2.0), Faculty of Sciences, Bd d'Yvoy 11, CH-1211 Geneva 4, Switzerland
| | - Romain Fossou
- 1 University of Geneva, Sciences III, Department of Botany and Plant Biology, Microbiology Unit, 30 quai Ernest-Ansermet, CH-1211 Geneva 4, Switzerland
| | | | - Michèle Crèvecoeur
- 1 University of Geneva, Sciences III, Department of Botany and Plant Biology, Microbiology Unit, 30 quai Ernest-Ansermet, CH-1211 Geneva 4, Switzerland
| | - Julien Meyer
- 3 University of Geneva, Mass Spectrometry Core Facility (MZ 2.0), Faculty of Sciences, Bd d'Yvoy 11, CH-1211 Geneva 4, Switzerland
| | - Chloé de Malézieux
- 1 University of Geneva, Sciences III, Department of Botany and Plant Biology, Microbiology Unit, 30 quai Ernest-Ansermet, CH-1211 Geneva 4, Switzerland
| | - Gérard Hopfgartner
- 5 University of Geneva, Department of Inorganic and Analytical Chemistry, Faculty of Sciences, 26 quai Ernest-Ansermet, CH-1211 Geneva 4, Switzerland
| | - Ivana Maksimović
- 4 University of Novi Sad, Faculty of Agriculture, Novi Sad, Serbia; and
| | - Xavier Perret
- 1 University of Geneva, Sciences III, Department of Botany and Plant Biology, Microbiology Unit, 30 quai Ernest-Ansermet, CH-1211 Geneva 4, Switzerland
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Ayanaba A, Haugland RA, Sadowsky MJ, Upchurch RG, Weiland KD, Zablotowicz RM. Rapid Colored-Nodule Assay for Assessing Root Exudate-Enhanced Competitiveness of Bradyrhizobium japonicum. Appl Environ Microbiol 2010; 52:847-51. [PMID: 16347177 PMCID: PMC239125 DOI: 10.1128/aem.52.4.847-851.1986] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The effects of root exudate (RE) treatment on nodule occupancy by Bradyrhizobium japonicum were investigated by a rapid colored-nodule assay, which is based on the observation that B. japonicum L-110 and its antibiotically marked derivatives form dark-red nodules on certain soybean (Glycine max) cultivars, whereas other strains form beige nodules. The efficacy of the assay was confirmed by direct immunofluorescence and by antibiotic platings of nodule bacteria. Both logarithmic- and stationary-phase cultures of the reference strain, L-110Nal, were used in paired-competition studies with RE-treated or untreated cells of seven challenge strains. On the basis of field and greenhouse competition studies, these strains were placed into three competitiveness groups: high (AN-11, AN-16aStrRif, and AN-6), intermediate (AN-3 and 122SR), and low (I-110ARS and AN-18). Seedlings of G. max cv. Centennial were inoculated with two ratios of challenge to reference strain, 1:1 and 1:9, and nodule occupancy was determined after the V4 to V5 stage of ontogeny. Two of the strains showed increased occupancy in response to RE treatment at the 1:1 inoculation ratio. Logarithmic- and stationary-phase cultures of AN-6 showed increased occupancy, from 22 to 38% (P < 0.10) and from 23 59 39% (P < 0.05), respectively. While the maximum increase for stationary-phase cultures of AN-16aStrRif was from 34 to 47% (P < 0.05), logarithmic-phase cultures failed to respond to RE treatment. The results of these studies indicate that RE treatment increases the nodule occupancy of some, but not all, B. japonicum strains and that the colored-nodule assay could be rapidly and reliably used to determine the competitive ability of B. japonicum.
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Affiliation(s)
- A Ayanaba
- Allied-Signal Inc., Crop Science Laboratory, Solvay, New York 13209
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Sindhu SS, Sharma HR, Dadarwal KR. Competition among Bradyrhizobium strains for nodulation of green gram (Vigna radiata): use of dark-nodule strain. Folia Microbiol (Praha) 2003; 48:83-9. [PMID: 12744082 DOI: 10.1007/bf02931281] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
The competitiveness of dual-strain inoculum of Bradyrhizobium strains S24 and GR4 was demonstrated for nodulation of green gram (Vigna radiata). Strain S24 formed pink nodules, GR4 produced visually distinguishable dark-brown nodules. When a mixture of these Bradyrhizobium strains was applied as inoculum, nodules of both pink and dark-brown types were formed on the same root. The strain GR4, which was less competitive than strain S24, was mutagenized with N-methyl-N'-nitro-N-nitrosoguanidine to obtain pigment-diverse mutants and six selected mutants were screened for symbiotic parameters. One mutant produced pink nodules and appreciably increased plant dry mass. The competitive ability of this mutant lacking brown pigment was compared with that of strain S24 by using antibiotic resistance markers; it showed increased nodulation competitiveness than its parent strain GR4. The dark-brown nodule-phenotype could be useful in evaluating nodulation competitiveness of "cowpea miscellany" bradyrhizobia in soil where dark-brown nodule-forming strains are not indigenous.
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Affiliation(s)
- S S Sindhu
- Department of Microbiology, CCS Haryana Agricultural University, Hisar 125 004, Haryana, India
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Singh I, Ahmad M. Competitive interaction between non-nodulating and nodulating strains for nodulation of cowpea (Vigna unguiculata). FEMS Microbiol Lett 1991. [DOI: 10.1111/j.1574-6968.1991.tb04739.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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McLaughlin W, Singh I, Ahmad M. Characterization of Tn5-induced symbiotically defective mutants of cowpea rhizobia. FEMS Microbiol Lett 1987. [DOI: 10.1111/j.1574-6968.1987.tb02222.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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Transfer of plasmids RP4 and R68.45 and chromosomal mobilization in cowpea rhizobia. Arch Microbiol 1986. [DOI: 10.1007/bf00409893] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Abstract
Biological nitrogen fixation (BNF) technology with special reference to Rhizobium-legume symbiosis is growing very rapidly with the hope of combatting world hunger by producing cheaper protein for animal and human consumption in the Third World. One can see rapid progress made in the biochemistry and molecular biology of symbiotic nitrogen fixation in general; however, less progress has been made on the ecological aspects despite the fact that an enormous amount of literature is available on inoculation problems and on agronomic aspects of symbiotic nitrogen fixation. So far most information on Rhizobium concerns fast-growing rhizobia and their host legume. Although it is essential that food production using BNF technology should be maximized in the Third World, the least work has been done on slow-growing rhizobia, which are generally found in tropical and sub-tropical soils. The majority of the developing countries are in tropical and sub-tropical regions. Except for R. japonicum, a microsymbiont partner of soybean (Glycine max), the majority of the slow-growing rhizobia belong to the cowpea group, and we refer to cowpea rhizobia as tropical rhizobia species. In this review we have tried to consolidate the recent progress made on ecology and genetics of tropical rhizobia. By using recombinant DNA technology techniques it is expected that super strains of rhizobia with desirable characteristics can be produced. One must evaluate the efficiency and effectiveness of these genetically manipulated laboratory strains under field conditions. In conclusion, if one aims at combatting hunger in the Third World using BNF technology, an intensive research programme on fundamental and applied aspects of tropical rhizobia species is suggested. This involves close cooperation between molecular biologists and microbial ecologists.
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Affiliation(s)
- M H Ahmad
- Department of Biochemistry, University of the West Indies, Mona, Kingston 7, Jamaica
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