Sodium chloride–ABA interaction in two common bean (Phaseolus vulgaris) cultivars differing in salinity tolerance

The involvement of exogenous abscisic acid (ABA) concentrations in common bean responses to saline stress was studied in two cultivars differing in NaCl tolerance. To examine this, salt-sensitive (cv. Coco) and salt-tolerant (cv. Africa) plants in symbiosis with Rhizobium tropici CIAT899 strain were grown under controlled conditions and treated with ABA previously to the saline treatment. Plants decreased the shoot and root growth, nitrogenase activity and ureides content of nodules and nitrogen percentage of shoot and increased root to shoot ratio and amino acids and proline content of shoot with individual treatments of ABA and NaCl. The ABA pre-treatment to salinized plants improved the growth parameters and normalized nodule weight of Coco and induced recuperation or a lower nitrogenase activity inhibition in both cultivars. Since the salt-tolerant cultivar Africa was the main Na accumulator in shoot of salinized plants grown in absence of ABA, our results support the hypothesis that sodium exclusion in shoot is a strategy of common bean to limit Na toxicity under our experimental conditions. Besides, the ABA treatment in these plants seems to limit sodium translocation to shoot resulting in the maintenance of high K/Na ratio. Finally, results found here support roles of ABA and proline in the alleviation of salt stress and osmotic adjustment of common bean plants respectively.