Therefore, differences in response towards salinity, pH and temperature are expected. It is known that salt stress significantly reduces nitrogen fixation and nodulation in legumes. Hashem et al. (1998) proposed that salt stress may decrease the efficiency of the Rhizobium legume symbiosis by reducing plant growth and photosynthesis, and hence nitrogen demand by decreasing survival and proliferation of rhizobia in the soil and rhizosphere or by inhibiting very early symbiotic events, such as colonization, thus directly interfering with root nodule formation