Physiological and Symbiotic Characteristics of Rhizobia Isolated from Medicago Polymorpha L and Trigonella Stellate L Growing in semi-arid Regions of Libya

Physiological and symbiotic characteristics of 17 indigenous rhizobial isolates obtained from root nodules of wild legumes, ( Trigonella stellate L. and Medicago polymorpha L.) that growing in different locations of Libya (northeast and northwest) and their cross-nodulation with cultivated Medicago sativa were studied. The results showed that the isolates were effective in their symbiosis with cultivated Medicago sativa L. A numerical taxonomic analysis performed on 56 non-symbiotic characteristics showed that at similarity level of 87%, the isolates formed four distinguished groups and three isolates remained separate. The results showed high variability among the isolates in their tolerance to various temperatures, and the majority of rhizobia isolates were sensitive to high acidity and are not able to grow at pH of 4.5. The tested isolates demonstrated a wide diversity in their tolerance to salinity, from sensitive unable to grow at 1% (w/v) to resistant to high salinity on a medium containing 4% (w/v) of NaCl. All isolates forming the four groups, including reference strains, were sensitive to CuCl 2.2H 2O, but they grew in medium containing HgCl 2. The isolates forming the four groups varied in their resistance to salts. The rhizobial isolates revealed a great diversity in their ability to react with antibiotic from sensitive to resistant