Modulation of salt stress effects on the growth, physio-chemical attributes and yields of Phaseolus vulgaris L. plants by the combined application of salicylic acid and Moringa oleifera leaf extract

• Combined SA + MLE mitigated the adverse effects of salt stress on bean plants.
• Growth traits of bean plants maximized by combined SA + MLE under salt stress.
• Essential nutrients in plants re-balanced by combined SA + MLE under salt stress.
• Water relations in bean plants improved by combined SA + MLE under salt stress.
• Antioxidants (proline and AsA) in bean plants improved by combined SA + MLE under salt stress.

Two field experiments were aimed to study the effects of salicylic acid (SA; 1 mM) and Moringa oleifera leaf extract (MLE; 1 extract: 30 tap water), used singly or in combination on the growth, physio-chemical attributes and yields of common bean (Phaseolus vulgaris L.) plants grown on a saline soil (EC = 6.23 – 6.28 dS m−1). The SA or MLE application, used as seed soaking or foliar spray, improved growth characteristics (i.e., shoot length, number and area of leaves per plant, and plant dry weight) and physio-chemical attributes (i.e., RWC% and MSI%, concentrations of total chlorophylls, total carotenoids, total soluble sugars, free proline and ascorbic acid, contents of N, P, K and Ca, and ratios of K/Na and Ca/Na) in bean plants. In addition, green pod and dry seed yields were improved when compared with the controls (tap water seed soaking or foliar spray). Combined treatments of SA and MLE (i.e., seed soaking in SA +  foliar spray with SA, seed soaking in SA + foliar spray with MLE, seed soaking in MLE + foliar spray with SA, and seed soaking in MLE + foliar spray with MLE) significantly increased all abovementioned parameters compared to the control (seed soaking in tap water + foliar spray with tap water). In contrast, there were significant reductions in leaf EL% and Na% under these combined treatments. The combined seed soaking in SA + foliar spray with MLE treatment was found to be highly effective at improving the growth and yields of bean plants by alleviating the inhibitory effects of soil salinity stress.