Molecular Characterization of Salt Tolerant Rhizobial Strains Induced by Gamma Rays Using RAPD Markers

Rhizobia are soil-borne bacteria that form nodules with legume roots and convert nitrogen into ammonia. Legume plants are often a major part of native or agricultural ecosystems, which increas nitrogen in low fertility soils, e.g. saline soils. The major target of this study was to characterize salt-tolerant rhizobial strains with high symbiotic efficiency. We choose ten strains of rhizobia that were previously mutagenized. Obtained results showed that 40 krad was the highest dose of gamma rays supported by tested strains. The irradiated clones at 50 krad were more tolerant to salt stress compared to control strains, which proved that gamma irradiation was effective in changing physiological and phenotypic characteristics via random mutations. The rhizobial strains treated with gamma rays were investigated using randomly amplified polymorphic DNA profiles to differentiate the DNA patterns among gamma treated rhizobia and parental strains. The RAPD profiles showed different, similar or even the same RAPD patterns for both types of rhizobial strains. The increase of N2 fixation parameters with some mutants was related to tolerance acquisition that protects effective symbiosis against damage induced by abiotic stresses. Inoculation with mutant isolates resulted in higher total nitrogen content than parental strains. According to the results of this study it can be recommended that inoculation of Vicia faba with effective Rhizobium strains can result in significant increase in yield due to higher nitrogen fixation ability. [Mohamed M. Hassan and Ragaa A. Eissa. Molecular Characterization of Salt Tolerant Rhizobial Strains Induced by Gamma Rays Using RAPD Markers. N Y Sci J 2013;6(4):36-41]. (ISSN: 1554-0200). http://www.sciencepub.net/newyork.