Identification of Salt tolerance Sinorhizobium meliloti strains in Alfalfa and Annual medics

In order to identification and isolation of salt tolerance Sinorhizobium meliloti strains, several soil samples and root nodules were collected from some regions of Khorassan Province and also some strains from Soil & Water Research Institute and one standard strain were studied. After nodulation test, strains was inoculated to Yeast Extract Monitol Broth (YEMB) medium at 28ºC degree centigrade and then exposed to different concentration of NaCl (0, 150, 300, 450, 600, 750 mM). Growth turbidity (OD420nm) as an indicator for bacterial growth was measured after for 72 hr. A factorial experiment was arranged in a Completely Randomized Design (CRD) with three replications. Results showed that all strains grew well in control treatment and six strains showed growth turbidity (OD) >1.0. Growth turbidity of 44 strains had high significant differences under salt stress. Salt concentrations greater than 600 mM severely affected the bacteria growth. Only eight strains showed OD>0.1, considered as salt tolerance strains. Amoung which, strain M32 showed significant difference (P<0.05). None grew in a salin solution of 750 mM.