Phenotypic and genetic diversity in Sinorhizobium meliloti and S. medicae from drought and salt affected regions of Morocco

<p>Abstract</p> <p>Background</p> <p><it>Sinorhizobium meliloti </it>and <it>S. medicae </it>are symbiotic nitrogen fixing bacteria in root nodules of forage legume alfalfa (<it>Medicago sativa </it>L.). In Morocco, alfalfa is usually grown in marginal soils of arid and semi-arid regions frequently affected by drought, extremes of temperature and soil pH, soil salinity and heavy metals, which affect biological nitrogen fixing ability of rhizobia and productivity of the host. This study examines phenotypic diversity for tolerance to the above stresses and genotypic diversity at Repetitive Extragenic Pallindromic DNA regions of <it>Sinorhizobium </it>nodulating alfalfa, sampled from marginal soils of arid and semi-arid regions of Morocco.</p> <p>Results</p> <p><it>Rsa</it>I digestion of PCR amplified 16S rDNA of the 157 sampled isolates, assigned 136 isolates as <it>S. meliloti </it>and the rest as <it>S. medicae</it>. Further phenotyping of these alfalfa rhizobia for tolerance to the environmental stresses revealed a large degree of variation: 55.41%, 82.16%, 57.96% and 3.18% of the total isolates were tolerant to NaCl (>513 mM), water stress (-1.5 MPa), high temperature (40°C) and low pH (3.5), respectively. Sixty-seven isolates of <it>S. meliloti </it>and thirteen isolates of <it>S. medicae</it> that were tolerant to salinity were also tolerant to water stress. Most of the isolates of the two species showed tolerance to heavy metals (Cd, Mn and Zn) and antibiotics (chloramphenicol, spectinomycin, streptomycin and tetracycline). The phenotypic clusters observed by the cluster analysis clearly showed adaptations of the <it>S. meliloti </it>and <it>S. medicae </it>strains to the multiple stresses. Genotyping with rep-PCR revealed higher genetic diversity within these phenotypic clusters and classified all the 157 isolates into 148 genotypes. No relationship between genotypic profiles and the phenotypes was observed. The Analysis of Molecular Variance revealed that largest proportion of significant (P < 0.01) genetic variation was distributed within regions (89%) than among regions (11%).</p> <p>Conclusion</p> <p>High degree of phenotypic and genotypic diversity is present in <it>S. meliloti </it>and <it>S. medicae </it>populations from marginal soils affected by salt and drought, in arid and semi-arid regions of Morocco. Some of the tolerant strains have a potential for exploitation in salt and drought affected areas for biological nitrogen fixation in alfalfa.</p

A new Li-ion battery charger with charge mode selection based on 0.18 um CMOS for phone applications

A new architecture of Li-Ion battery charger with charge mode selection is presented in this work. To ensure high efficiency, good accuracy and complete protection mode, we propose an architecture based on variable current source, temperature detector and power control. To avoid the risk of damage, the Li- Ion batteries charging process must change between three modes of current (trickle current (TC), constant current (CC), and constant voltage (CV)) in order to charge the battery with degrading current. However, the interest of this study is to develop a fast battery charger with high accuracy that is able to switch between charging modes without reducing its power efficiency, and to guarantee a complete protection mode. The proposed charger circuit is designed to control the charging process in three modes using the charging mode selection. The obtained results show that the Li-ion batteries can be successfully charged in a short time without reducing their efficiency. The proposed charger is implemented in 180 nm CMOS technology with a maximum charging current equal to 1 A and a maximum battery voltage equal to 4.22 V, (with input range 2.7-4.5 V). The chip area is 1.5 mm2 and the power efficiency is 90.09 %

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

Genotypic characterization of indigenous Sinorhizobium meliloti and Rhizobium sullae by repPCR, 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 root nodules 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 to identify 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

QTL for water stress resistance and water use efficiency in alfalfa

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