Inoculation with the native Rhizobium gallicum 8a3 improves osmotic stress tolerance in common bean drought-sensitive cultivar

Abstract Symbiotic nitrogen fixation potential in common bean is considered to be low in comparison with other grain legumes. However, it may be possible to improve the nitrogen fixation potential of common bean using efficient rhizobia. In order to improve osmotic stress tolerance of a drought-sensitive common bean cultivar (COCOT) consumed in Tunisia, plants were inoculated either by the reference strain Rhizobium tropici CIAT 899 or by inoculation with rhizobia isolated from native soils Rhizobium gallicum 8a3. Fifteen days after sowing, osmotic stress was applied by means of 25 mM mannitol (low stress level) or by 75 mM mannitol (high stress level). Fifteen days after treatment plants were harvested and different physiological and biochemical parameters were analysed. Results showed no significant differences between the studied symbioses under control conditions. However after exposure to osmotic stress our results showed better tolerance of COCOT to osmotic stress when inoculated with the native R. ...