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

Abstract

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.

Stress Tolerance and Symbiotic and Phylogenic Features of Root Nodule Bacteria Associated with Medicago Species in Different Bioclimatic Regions of Tunisia

“…Payakapong et al (25) isolated a highly salt tolerant Ensifer species (Ensifer sp.BL3), and Hung et al (14) described strains of Rhizobium, Bradyrhizobium and Agrobacterium that could grow in a medium containing 4.5% NaCl and also grew well at 45°C. The diversity of rhizobia nodulating Medicago species has been widely reported (3,4,10,38) including in Tunisia (1,16,(44)(45)(46). Three different species, Ensifer meliloti (17), Ensifer medicae (27) and Rhizobium mongolense (37), were reported as microbial symbionts of Medicago species.…”

Salt tolerance of a Sinorhizobium meliloti strain isolated from dry lands: growth capacity and protein profile changes

“…Sinorhizobium meliloti strain A5 was isolated from root nodules of M. truncatula grown in arid lands in the south of Tunisia (Badri et al 2007;Zribi et al 2004). The standard S. meliloti strain RCR2011 (Rothamsted Collection of Rhizobium, Harpenden, Hertfordshire, UK; Mary et al 1985) was included in this study to compare the behavior of the two strains under salt stress.…”

“…Mnasri et al (2007) showed that hyper salttolerant strains of rhizobia are more competitive and more effective in nitrogen fixation under drought stress than less tolerant strains. The strain A5 is very efficient with all studied M. truncatula lines (Badri et al 2007), which promises its usefulness to promote host plant growth under osmotic stress conditions. Miller-Williams et al (2006) reported that the salt-sensitive mutants of S. meliloti obtained were less competitive for nodule occupancy than the wild-type.…”

“…Sinorhizobia nodulating Medicago truncatula in Tunisian soils display a very high genetic diversity related to geographic distribution (Zribi et al 2004(Zribi et al , 2005. S. meliloti strain A5 isolated from root nodules of M. truncatula grown in non-saline Tunisian soil suffering from drought (Badri et al 2007;Zribi et al 2004) was shown to be efficient with all studied M. truncatula lines (Badri et al 2007), which promise its usefulness to promote host plant growth under severe conditions.…”

Phenotypic and genotypic characterization of root nodules rhizobia of Medicago littoralis Rhode and Melilotus indicus (L.) All. growing in the Oasis of Touggourt, Oued Righ Valley, in the Algerian Sahara

“…E. numidicus ORS 1407 and E. garamanticus ORS 1400, which were isolated from Tunisian soil (Merabet et al 2010). Rome et al (1996); Yan et al (2000); Zahran (2001); Zribi et al (2004); Badri et al (2007). It appears that the majority of wild legumes are nodulated by strains belonging to Ensifer and Rhizobium genus and few by Mesorhizobium and Bradyrhizobium (Thami-Alami et al 2010; Rejii et al 2014).…”