EVALUATION OF RHIZOBIUM-MELILOTI STRAINS ISOLATED FROM INDIGENOUS POPULATIONS IN NORTHERN GREECE

Eight different Rhizobium meliloti strains (designated as strains 3, 6, 8, 15, 17, 18, 19 and 22) were isolated from fields cultivated with alfalfa. The growth characteristics of the isolated strains under different NaCl concentrations were investigated. Strains 15 and 22 showed marked tolerance to high NaCl concentration. Symbiosis of one alfalfa variety (Medicago sativa cv. Ipati) inoculated with these strains showed marked differences in nitrogen fixing characteristics (nodule number, dry weight and total nitrogen content). Strains 8, 15 and 22 demonstrated the best performance with respect to all characteristics examined. The supply of low levels of nitrate to inoculated alfalfa planes affected all the nitrogen fixing characteristics. Nodule number per plant decreased and the ranking of the different strains with respect to nodule number was altered. Dry weight was significantly increased by the supply of the nitrate, even in the case of symbioses with the highly effective strains 8, 15 and 22. Total nitrogen content was increased by the supply of nitrate. This increase was higher in plants inoculated with the less effective strains.