Symbiotic characteristics of Rhizobium meliloti: and appraisal of the systematic treatment of nodulation and nitrogen fixation interactions between hosts and Rhizobia of diverse origins

Brockwell, J; Hely, FW

doi:10.1071/ar9660885

Cited by 77 publications

(43 citation statements)

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“…While most Medicago species nodulated and formed nitrogen-fixing symbioses when they were grown in Australian soils with naturalized rhizobial populations, Ballard and Charman (3) observed that there was a lower incidence of nodulation with M. laciniata. They attributed this observation to the specific rhizobial requirement of M. laciniata that had been reported previously by Brockwell and Hely (7). For nodulation of M. laciniata, Brockwell and Hely (7) suggested that its rhizobia have distinct nodule formation behavior that distinguishes them from other Medicago-nodulating rhizobia.…”

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confidence: 75%

Chromosomal and Symbiotic Relationships of Rhizobia Nodulating Medicago truncatula and M. laciniata

Berkum

Badri

Elia

et al. 2007

Appl Environ Microbiol

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Multilocus sequence typing (MLST) is a sequence-based method used to characterize bacterial genomes. This method was used to examine the genetic structure of Medicago-nodulating rhizobia at the Amra site, which is located in an arid region of Tunisia. Here the annual medics Medicago laciniata and M. truncatula are part of the natural flora. The goal of this study was to identify whether distinct chromosomal groups of rhizobia nodulate M. laciniata because of its restricted requirement for specific rhizobia. The MLST analysis involved determination of sequence variation in 10 chromosomal loci of 74 isolates each of M. laciniata and M. truncatula. M. truncatula was used as a control trap host, because unlike M. laciniata, it has relatively unrestricted rhizobial requirements. Allelic diversity among the plasmid nodC alleles in the isolates was also determined. The 148 isolates were placed into 26 chromosomal sequence types (STs), only 3 of which had been identified previously. The rhizobia of M. laciniata were shown to be part of the general Medicago-nodulating population in the soil because 99.95% of the isolates had chromosomal genotypes similar to those recovered from M. truncatula. However, the isolates recovered from M. laciniata were less diverse than those recovered from M. truncatula, and they also harbored an unusual nodC allele. This could perhaps be best explained by horizontal transfer of the different nodC alleles among members of the Medicago-nodulating rhizobial population at the field site. Evidence indicating a history of lateral transfer of rhizobial symbiotic genes across distinct chromosomal backgrounds is provided.Traditionally, legumes have been important in a practice referred to as low-input sustainable agriculture. The recognition of their agricultural importance led to the demonstration that legumes bearing nodules inhabited by bacteria assimilated dinitrogen in a process termed biological nitrogen fixation. The bacteria, commonly referred to as rhizobia, harbor the genetic information necessary for establishing the nitrogen fixation process when they reside symbiotically inside the nodules. Plants of the genus Medicago are legumes that benefit from such a symbiosis with rhizobia that are currently divided into two species, Sinorhizobium meliloti (11) and S. medicae (25).The plant genus Medicago L., as currently defined, consists of about 85 species (28), including Medicago sativa (alfalfa), the world's most important cultivated forage crop. Heyn (16) reported that this genus is native to Western Asia and the Mediterranean countries, although many annual species have invaded wide areas in both the Old and New Worlds.Among the 85 species, M. laciniata has symbiotic properties that are unusual. While most Medicago species nodulated and formed nitrogen-fixing symbioses when they were grown in Australian soils with naturalized rhizobial populations, Ballard and Charman (3) observed that there was a lower incidence of nodulation with M. laciniata. They attributed this observation to the spec...

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confidence: 75%

Chromosomal and Symbiotic Relationships of Rhizobia Nodulating Medicago truncatula and M. laciniata

Berkum

Badri

Elia

et al. 2007

Appl Environ Microbiol

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“…These results were compiled from the results of the current study (see Table S3) and also from the results from three previous studies (4,7,9). In general, members of the T. suavissima strain clade (CST Table 4).…”

Section: Resultsmentioning

confidence: 99%

“…The strain possessing this genotype was USDA6670 (syn., CC2013), a strain symbiotically effective with the native Australian legume Trigonella suavissima Lindl. (4). In subsequent studies, four other T. suavissima symbionts were also described as having multilocus genotypes similar to that of USDA6670 (5,6).…”

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confidence: 99%

“…In that report, the similarity of T. suavissima to other legume species of southern Europe was noted. Unlike its widely cultivated relative Medicago sativa L. (alfalfa or lucerne), which is native to western Asia and which can be nodulated by at least two Ensifer species, T. suavissima is more specific in its requirements for nitrogenfixing microsymbionts (4,9). Trigonella suavissima is also the only member of the tribe Trifolieae that is endemic to Australia (7).…”

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confidence: 99%

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Biogeography of a Novel Ensifer meliloti Clade Associated with the Australian Legume Trigonella suavissima

Eardly

Elia

Brockwell

et al. 2017

Appl Environ Microbiol

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Here, we describe a novel clade within Ensifer meliloti and consider how geographic and ecological isolation contributed to the limited distribution of this group. Members of the genus Ensifer are best known for their ability to form nitrogenfixing symbioses with forage legumes of three related genera, Medicago L., Melilotus Mill., and Trigonella L., which are members of the tribe Trifolieae. These legumes have a natural distribution extending from the Mediterranean Basin through western Asia, where there is an unsurpassed number of species belonging to these genera. Trigonella suavissima L. is unusual in that it is the only species in the tribe Trifolieae that is native to Australia. We compared the genetic diversity and taxonomic placement of rhizobia nodulating T. suavissima with those of members of an Ensifer reference collection. Our goal was to determine if the T. suavissima rhizobial strains, like their plant host, are naturally limited to the Australian continent. We used multilocus sequence analysis to estimate the genetic relatedness of 56 T. suavissima symbionts to 28 Ensifer reference strains. Sequence data were partitioned according to the replicons in which the loci are located. The results were used to construct replicon-specific phylogenetic trees. In both the chromosomal and chromid trees, the Australian strains formed a distinct clade within E. meliloti. The strains also shared few alleles with Ensifer reference strains from other continents. Carbon source utilization assays revealed that the strains are also unusual in their ability to utilize 2-oxoglutarate as a sole carbon source. A strategy was outlined for locating similar strains elsewhere.IMPORTANCE In this study, we employed a biogeographical approach to investigate the origins of a symbiotic relationship between an Australian legume and its nitrogen-fixing rhizobia. The question of the ancestral origins of these symbionts is based on the observation that the legume host is not closely related to other native Australian legumes. Previous research has shown that the legume host Trigonella suavissima is instead closely related to legumes native to the Mediterranean Basin and western Asia, suggesting that it may have been introduced in Australia from those regions. This led to the question of whether its rhizobia may have been introduced as well. In this study, we were unable to find persuasive evidence supporting this hypothesis. Instead, our results suggest either that the T. suavissima rhizobia are native to Australia or that our methods for locating their close relatives elsewhere are inadequate. A strategy to investigate the latter alternative is proposed.KEYWORDS Ensifer, rhizobium, Sinorhizobium meliloti, Trigonella, biogeography, clade, symbiotic nitrogen fixation

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“…However, suitable herbaceous legumes are needed as pasture components in lower rainfall regions and for those parts of the country likely to become hotter and dryer in the future. The symbiotic root nodule bacteria for introduced legume species are widespread within these parts of the country (Brockwell and Hely 1966;Khu 1969). The domestication of some of the native herbaceous legumes may fill this need.…”

Section: Forage Legumesmentioning

confidence: 99%

Use of functional traits to identify Australian forage grasses, legumes and shrubs for domestication and use in pastoral areas under a changing climate

Mitchell¹,

Norman

Whalley

2015

Crop Pasture Sci.

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Abstract. Considerable uncertainty exists about future climatic predictions but there is little doubt among experts that the future will be warmer. Climate change and the associated elevation in atmospheric CO 2 level and temperatures will provide novel challenges and potential opportunities for cultivated plant species. Plant breeding and domestication can contribute to improvements in both yield and quality of native grasses, legumes and forage shrubs. This review explores the use of functional traits to identify native Australian grasses, legumes and forage shrubs suitable for domestication, to meet the challenges and opportunities under a changing climate in pastoral areas in Australia. The potential of these species in terms of life history, regenerative traits, forage quality and quantity, drought tolerance and invasiveness is examined. The paper focuses on three Australian pastoral regions (high-rainfall temperate south, tropical and subtropical grasslands, low-rainfall semi-arid shrublands), in terms of future climate predictions and potential of selected native species to meet these requirements. Selection for adaptation to new climatic environments is challenging but many native species already possess the traits required to cope with the environment under future climate scenarios.

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Symbiotic characteristics of Rhizobium meliloti: and appraisal of the systematic treatment of nodulation and nitrogen fixation interactions between hosts and Rhizobia of diverse origins

Cited by 77 publications

References 0 publications

Chromosomal and Symbiotic Relationships of Rhizobia Nodulating Medicago truncatula and M. laciniata

Chromosomal and Symbiotic Relationships of Rhizobia Nodulating Medicago truncatula and M. laciniata

Biogeography of a Novel Ensifer meliloti Clade Associated with the Australian Legume Trigonella suavissima

Use of functional traits to identify Australian forage grasses, legumes and shrubs for domestication and use in pastoral areas under a changing climate

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