Article

Nitrogen-fixing sinorhizobia with Medicago laciniata constitute a novel biovar (bv. medicaginis) of S. meliloti.

Laboratoire des Symbioses Tropicales et Méditerranéennes Cirad Ensa.M Ird UmII, TA10/J, Campus International de Baillarguet, 34 398 Montpellier Cedex 5, France.
Systematic and Applied Microbiology (impact factor: 3.37). 12/2006; 29(7):526-38. DOI:10.1016/j.syapm.2005.12.008 pp.526-38
Source: PubMed

ABSTRACT Sixty-eight new rhizobial isolates were obtained from root-nodules of Medicago laciniata and from Mediterranean soils in Tunisia and France. All of them were identified as Sinorhizobium meliloti on the basis of PCR-RFLP analyses of 16S rDNA and the intergenic spacer sequence between 16S and 23S rDNAs. DNA/DNA hybridization, phenotypic characterization and 16S rRNA gene sequencing led to the conclusion that they belong the same taxon. All new isolates shared the ability to nodulate and fix nitrogen with M. laciniata except 11 of them not capable of fixing nitrogen with this plant and originating from French soils containing no efficiently adapted symbionts with M. laciniata. The nitrogen-fixing rhizobia on M. laciniata differed markedly from the other S. meliloti or Sinorhizobium medicae isolates and references in their symbiotic traits such as nifDK RFLP diversity, nodA sequences and nitrogen effectiveness with tree other different annual Medicago species (M. truncatula, M. polymorpha and M. sauvagei). Two infrasubspecific (biovar) divisions are therefore proposed within S. meliloti: bv. medicaginis for Sinorhizobium efficient on M. laciniata and bv. meliloti for the classically known S. meliloti group represented by the strains ATCC9930(T) and RCR 2011 efficient on M. sativa.

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Keywords

16S rRNA gene sequencing
 
23S rDNAs
 
adapted symbionts
 
classically known S. meliloti group
 
different annual Medicago species
 
DNA/DNA hybridization
 
intergenic spacer sequence
 
M. laciniata
 
M. polymorpha
 
M. sativa
 
M. sauvagei
 
M. truncatula
 
Medicago laciniata
 
Mediterranean soils
 
new rhizobial
 
nodA sequences
 
phenotypic characterization
 
Sinorhizobium efficient
 
Sinorhizobium medicae
 
Sinorhizobium meliloti
 

Maria Del Carmen Villegas