Endophytic Bacteria and SA Application Improve Growth, Biochemical Properties, and Nutrient Uptake in White Beans Under Drought Stress

Drought is one of the major abiotic stresses limiting crop yields around the world. Legumes, especially white bean (Phaseolus vulgaris L.), can also be considered a primary plant source for providing the required proteins. Therefore, proper and environmentally friendly management is of great importance to tackle this global problem. This experiment was performed as a split-factorial arrangement based on a complete block design with four replicates. It is composed of drought stress (DS) (stress and control) as the main plot and salicylic acid (SA) (0, 1, and 2 mM, which foliar applied on six-leaf stage) and phosphate biofertilizer (PB) (control, Bacillus subtilis and Pseudomonas putida) as sub-plots over 2 years (2018 and 2019). Growth parameters decreased under drought stress. Moreover, relative water content (RWC), photosynthetic pigments, osmotic compounds, enzymatic reactions, and nutrient uptake were significantly affected by the interaction between drought, endophytic bacteria (Bacillus subtilis, Pseudomonas putida), and SA. In addition, chlorophyll a, chlorophyll b, and total chlorophyll, as well as soluble protein, increased greatly under stress by co-application of PB and SA. In contrast, catalase, superoxide dismutase activity, zinc, and iron absorption were only affected by phosphate biofertilizer. Moreover, individual application of SA increased RWC, proline, nitrogen, crude protein, phosphorus, and manganese content. These results proved that simultaneous application of SA and PB improved drought stress tolerance of bean plants by increasing photosynthetic pigments and soluble protein accumulation. Overall, this study reinforces the notion that SA and PB combined may be less beneficial than their sole application to improve white bean drought tolerance.

Automated summary

Drought is a major abiotic stress that limits crop yields worldwide. This study investigated the effects of drought stress, endophytic bacteria, and salicylic acid on the growth and physiological parameters of white bean plants. The results showed that the combined application of SB bacteria and SA significantly enhanced drought tolerance in the plants.