Comparison of rhizobia that nodulate Medicago laciniata and Medicago truncatula present in a single Tunisian arid soil

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The rhizobia present in a single arid region Tunisian soil that nodulate Medicago laciniata and Medicago truncatula were compared. All isolates, 40 from each host, were Sinorhizobium meliloti based on 16S rRNA polymerase chain reaction restriction fragment length polymorphism (PCR–RFLP) patterns and subsequent confirmation by sequence analysis of the 16S rRNA genes in four representatives from each host species. There was no apparent relationship between Medicago host species of isolation and the nodulating rhizobial genome as determined by repetitive extragenic palandromic PCR. The isolates of M. laciniata were distinguished from those of M. truncatula present in the same soil by variation in PCR–RFLP of nifDK, indicating that this dissimilarity is originally genetic and not geographic. While forming effective symbioses with their own respective isolates, both M. laciniata and M. truncatula formed ineffective true nodules, nodule-like structures, or no nodules at all in cross-inoculation tests, as confirmed by the histological observations.

Les rhizobiums nodulant Medicago laciniata et M. truncatula piégés sur un sol appartenant à l'étage bioclimatique aride de la Tunisie ont été comparés. Tous les isolats analysés, 40 de chaque plante hôte, se son avérés à partir , de l'identification moléculaire par PCR–RFLP du gène de l'ARNr 16S, appartenir à l'espèce Sinorhizobium meliloti. Ce résultat est confirmé par le séquençage de ce même gène chez quatre issus de chaque plante. L'analyse des profils REP-PCR n'a pas montré de relations phylogénétiques entre le génome des rhizobiums et leurs espèces végetales d'origine. Les isolats de M. laciniata se distinguaient de ceux piéges de M. truncatula dans le même sol par une variation de la séquence intergénique nifDK indiquant que cette différence était d’origine génétique et non géographique. Les observations histologiques ont montré que même si elles établissent des symbioses efficientes avec leurs propres isolats respectifs, M. laciniata et M. truncatula ont formé des nodules vrais maisinefficients, des pseudo-nodules ou pas de nodules du tout suite à des inoculations croisées.

Document Type: Research Article

Publication date: February 1, 2007

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  • Published since 1954, this monthly journal contains new research in the field of microbiology including applied microbiology and biotechnology; microbial structure and function; fungi and other eucaryotic protists; infection and immunity; microbial ecology; physiology, metabolism and enzymology; and virology, genetics, and molecular biology. It also publishes review articles and notes on an occasional basis, contributed by recognized scientists worldwide.
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