Nodulation and N2 fixation by soybean inoculated with salt-tolerant rhizobia or salt-sensitive bradyrhizobia in saline soil

Nodulation of soybean by a salt-tolerant Rhizobium strain USDA 208 and a salt-sensitive Bradyrhizobium strain RCR 3407 (CB1809) was evaluated in saline soil in the glasshouse. No significant differences in shoot and root dry weight, nodule number and nodule weight between the salt-tolerant Rhizobium strain and the salt-sensitive Bradyrhizobium strain were found. Nodulation of soybean was reduced more than 50% by the equivalent of 34.2 mm NaCl in soil. The specific activity of nodules formed by both strains was also reduced by salinity. Nodulation was more sensitive than plant growth to salinity. The salt-sensitive strain was more effective than the salt-tolerant strain under non-saline conditions, but the salt-tolerant strain fixed more N2 than the salt-sensitive strain under saline conditions.