ENVIRONMENTAL STRESS RESISTANCES OF ROOT-NODULE BACTERIA FROM MEDICAGO FALCATE L.

The symbiotic system of Legumes and root-nodule bacteria is a significant process for enriching barren and dry soils and supporting plant growth. The aim of this study was to isolate root-nodule bacteria from Medicago falcate and to select high activity strains with resistance to environmental stress. As a result, only MSZ-25 strain grew in the medium containing 0.8M NaCl, with pH4.8-9.8 and at temperatures of 4-45°С. All rhizobial isolates were tolerant to the concentrations of 0.01-0.1% Pb(NO3)2, 0.01% ZnSO4, CdCI2, CuCI2 and NiCI2. The strains were also resisted to penicillin 10μ/ml, erythromycin 10μ/ml, and chlorampenicol 10μ/ml but the growths of all isolates were inhibited by kanamycin 30μ/ml, novobiocin 30μ/ml and tetracycline 10μ/ml.