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Beukes CW, Boshoff FS, Phalane FL, Hassen AI, le Roux MM, Stȩpkowski T, Venter SN, Steenkamp ET. Both Alpha- and Beta-Rhizobia Occupy the Root Nodules of Vachellia karroo in South Africa. Front Microbiol 2019; 10:1195. [PMID: 31214140 PMCID: PMC6558075 DOI: 10.3389/fmicb.2019.01195] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2018] [Accepted: 05/13/2019] [Indexed: 12/13/2022] Open
Abstract
Vachellia karroo (formerly Acacia karroo) is a wide-spread legume species indigenous to southern Africa. Little is known regarding the identity or diversity of rhizobia that associate with this plant in its native range in South Africa. The aims of this study were therefore: (i) to gather a collection of rhizobia associated with V. karroo from a wide range of geographic locations and biomes; (ii) to identify the isolates and infer their evolutionary relationships with known rhizobia; (iii) to confirm their nodulation abilities by using them in inoculation assays to induce nodules under glasshouse conditions. To achieve these aims, soil samples were collected from 28 locations in seven biomes throughout South Africa, which were then used to grow V. karroo seedlings under nitrogen-free conditions. The resulting 88 bacterial isolates were identified to genus-level using 16S rRNA sequence analysis and to putative species-level using recA-based phylogenetic analyses. Our results showed that the rhizobial isolates represented members of several genera of Alphaproteobacteria (Bradyrhizobium, Ensifer, Mesorhizobium, and Rhizobium), as well as Paraburkholderia from the Betaproteobacteria. Our study therefore greatly increases the known number of Paraburkholderia isolates which can associate with this southern African mimosoid host. We also show for the first time that members of this genus can associate with legumes, not only in the Fynbos biome, but also in the Albany Thicket and Succulent Karoo biomes. Twenty-six putative species were delineated among the 88 isolates, many of which appeared to be new to Science with other likely being conspecific or closely related to E. alkalisoli, M. abyssinicae, M. shonense, and P. tropica. We encountered only a single isolate of Bradyrhizobium, which is in contrast to the dominant association of this genus with Australian Acacia. V. karroo also associates with diverse genera in the Grassland biome where it is quite invasive and involved in bush encroachment. Our findings therefore suggest that V. karroo is a promiscuous host capable of forming effective nodules with both alpha- and beta-rhizobia, which could be a driving force behind the ecological success of this tree species.
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Affiliation(s)
- Chrizelle W Beukes
- Department of Biochemistry, Genetics and Microbiology, Forestry and Agricultural Biotechnology Institute, University of Pretoria, Pretoria, South Africa
| | - Francois S Boshoff
- Department of Biochemistry, Genetics and Microbiology, Forestry and Agricultural Biotechnology Institute, University of Pretoria, Pretoria, South Africa
| | - Francina L Phalane
- Agricultural Research Council, Plant Health and Protection Institute, Pretoria, South Africa
| | - Ahmed I Hassen
- Agricultural Research Council, Plant Health and Protection Institute, Pretoria, South Africa
| | - Marianne M le Roux
- South African National Biodiversity Institute, Pretoria National Botanical Garden, Pretoria, South Africa.,Department of Botany and Plant Biotechnology, University of Johannesburg, Johannesburg, South Africa
| | - Tomasz Stȩpkowski
- Autonomous Department of Microbial Biology, Faculty of Agriculture and Biology, Warsaw University of Life Sciences - SGGW, Warsaw, Poland
| | - Stephanus N Venter
- Department of Biochemistry, Genetics and Microbiology, Forestry and Agricultural Biotechnology Institute, University of Pretoria, Pretoria, South Africa
| | - Emma T Steenkamp
- Department of Biochemistry, Genetics and Microbiology, Forestry and Agricultural Biotechnology Institute, University of Pretoria, Pretoria, South Africa
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Beukes CW, Stępkowski T, Venter SN, Cłapa T, Phalane FL, le Roux MM, Steenkamp ET. Crotalarieae and Genisteae of the South African Great Escarpment are nodulated by novel Bradyrhizobium species with unique and diverse symbiotic loci. Mol Phylogenet Evol 2016; 100:206-218. [DOI: 10.1016/j.ympev.2016.04.011] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Revised: 03/30/2016] [Accepted: 04/07/2016] [Indexed: 12/21/2022]
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