Alfalfa （Medicago sativa L.） is being grown in harsh environment in Iraq and is mostly subjected to abiotic stresses such as drought, salinity, pH and temperature. Both alfalfa and its nitrogen fixing symbiotic bact...Alfalfa （Medicago sativa L.） is being grown in harsh environment in Iraq and is mostly subjected to abiotic stresses such as drought, salinity, pH and temperature. Both alfalfa and its nitrogen fixing symbiotic bacteria Sinorhizobium meliloti are affected by these environmental stresses. Enhancing nitrogen fixation biologically could be achieved through selection of tolerant strains of S. meliloti to these environmental stresses and inoculating them to the crop, also growing tolerant cultivars. This study examines phenotypic diversity for tolerance to drought, salinity, temperature and pH. Sixty isolates sampled from different areas of Iraq. The results revealed high degree of phenotypic diversity in Sinorhizobium populations. Furthermore, the isolates which showed tolerance to drought stress also showed tolerance to salinity and high degree of temperature, indicating direct relationship between three physiological path ways. Also 58.3% of drought tolerant isolates were alkaline tolerant they tolerated up to pH 9, point to say almost all drought tolerant isolates in this study illustrated strong ＋ positive reaction to catalase enzyme. And 91.6% themes were negative for Gelatinase enzyme test. While only 50% of drought sensitive isolates were negative for drought sensitive isolates could grow at high temperature （42 ℃）.展开更多
文摘Alfalfa （Medicago sativa L.） is being grown in harsh environment in Iraq and is mostly subjected to abiotic stresses such as drought, salinity, pH and temperature. Both alfalfa and its nitrogen fixing symbiotic bacteria Sinorhizobium meliloti are affected by these environmental stresses. Enhancing nitrogen fixation biologically could be achieved through selection of tolerant strains of S. meliloti to these environmental stresses and inoculating them to the crop, also growing tolerant cultivars. This study examines phenotypic diversity for tolerance to drought, salinity, temperature and pH. Sixty isolates sampled from different areas of Iraq. The results revealed high degree of phenotypic diversity in Sinorhizobium populations. Furthermore, the isolates which showed tolerance to drought stress also showed tolerance to salinity and high degree of temperature, indicating direct relationship between three physiological path ways. Also 58.3% of drought tolerant isolates were alkaline tolerant they tolerated up to pH 9, point to say almost all drought tolerant isolates in this study illustrated strong ＋ positive reaction to catalase enzyme. And 91.6% themes were negative for Gelatinase enzyme test. While only 50% of drought sensitive isolates were negative for drought sensitive isolates could grow at high temperature （42 ℃）.
