Variability in natural populations of Sinorhizobium meliloti in Morocco Options Méditerranéennes, A no. 92, 2010 -The contributions of grasslands to the conservation of Mediterranean biodiversity Variability in natural populations of Sinorhizobium melilot

----------------------------------------------------------------------------------------------------------- To cite th is article / Pou r citer cet article Abstract. In Morocco, alfalfa (Medicago sativa L.) is being grown in harsh environments (such as mountains and oasis) and is frequently subjected to abiotic stresses such as salinity, drought and high temperature. Both alfalfa and its nitrogen fixing symbiotic bacteria Sinorhizobium meliloti are affected by these abiotic stresses. Improvements in biological nitrogen fixation could be achieved through selection of tolerant strains of S. meliloti to these abiotic stresses and inoculating them to the crop and also growing tolerant cultivars. This study examines phenotypic diversity for tolerance to drought, extremes of temperature and soil pH, soil salinity and heavy metals and genotypic diversity at Repetitive Extragenic Pallindromic DNA regions of 157 Sinorhizobium isolates, sampled from marginal soils of arid and semi-arid regions of Morocco. The results revealed high degree of phenotypic and genotypic diversity in Sinorhizobium populations. Further more, the isolates which showed tolerance to salinity stress also showed tolerance to water stress, indicating direct relationships between these two physiological pathways. High salt and water stress tolerant strains were isolated and tested for their ability to biological nitrogen fixation. Some of the isolated tolerant strains were also efficient nitrogen fixers, under water and salt stress conditions. The Analysis of Molecular Variance revealed that largest proportion of significant genetic variation was distributed within regions than among regions. Keywords. Sinorhizobium meliloti -Phenotypic diversity -Genotypic diversity -Abiotic stresses. La variabilité des populations naturelles de Sinorhizobium meliloti au Maroc Résumé. Au Maroc, les populations locales de luzerne (Medicago sativa L.) sont cultivées dans des montagnes et des oasis présahariennes. Dans ces environnements, la luzerne et son microsymbion

Genotypic characterization of indigenous Sinorhizobium meliloti and Rhizobium sullae by rep- PCR, RAPD and ARDRA analyses

The rhizobia, Sinorhizobium meliloti and Rhizobium sullae, which fix nitrogen in root nodules of alfalfa (Medicago sativa L.) and sulla (Hedysarum sp.) forage legumes, respectively, were isolated from rootnodules and soils from Morocco. We used three PCR-based techniques namely, rep-PCR, RAPD and ARDRA techniques for genotypic characterization of 10 isolates of S. meliloti and R. sullae, in order toidentify rapid and reliable techniques for applications in population genetic analysis of these species. The analysis revealed characteristic banding patterns for S. meliloti and R. sullae isolates by all the three techniques, even though the isolates are from a narrow geographic region in Morocco. Furthermore, the results showed that the rep-PCR with REP and ERIC primers was more efficient than RAPD and ARDRA technique for genotyping S. meliloti isolates; and rep-PCR with REP primers and the ARDRA technique with restriction enzyme HinfI, were more efficient than the other rep-PCR and RAPD-PCR techniques for genotyping R. sullae isolates