Salt tolerance of a common bean (Phaseolus vulgaris L.) cultivar as affected by rhizobia

In this work, we analyzed the effect of rhizobia on salt-tolerance in common bean (Phaseolus vulgaris L.). For this purpose, a salt-sensitive cultivar (cv. Coco blanc) was inoculated separately with three rhizobia strains (Ar2, B155, and KH28) under glasshouse conditions. Symbiotic parameters (nodule number and nodule mass), shoot nitrogen content, plant growth, root to shoot ratio (RSR) and efficiency in utilization of the rhizobial symbiosis (EURS) were recorded in plants grown in absence (control) and presence of salt (30 mM NaCl). Nodule number and mass were greatly reduced by NaCl in plants inoculated either with Ar2 or B155. In contrast, the two symbiotic parameters were less affected by salt in plants inoculated with KH28. Salt-stressed plants showed a decrease in shoot nitrogen content and growth; but, in plants inoculated with KH28, the decrease was significantly lower. Without salt, RSR was not different between the three symbiotic associations but it tended to increase with salt, being significantly higher with KH28. In addition, nodule efficiency of KH28 was the highest under saline conditions. We concluded that rhizobia strains with superior symbiotic efficiency under saline conditions may significantly improve salt-tolerance in common bean (P. vulgaris L.).