Mitigation of drought stress in Zea mays L. through plant growth-promoting rhizobacteria assisted by foliar sorghum water extract

Abstract

Climate change is introducing several challenges to agriculture’s sustainability. The drought stress is hampering cereal crop productivity. There is an increasing interest in exploring how well physiological flexibility in plants can buffer drought stress. Our study investigated how plant growth-promoting bacteria (PGPB) and SORGAAB, which is a water-based extract of Sorghum bicolor L. (10 g/100 ml), affect the physiological, biochemical, and vegetative profiles of Zea mays L. under drought conditions (50% field water capacity). Among all treatments, the application of drought + PGPB + SORGAAB spray at the three-leaf phase (V3) showed significant improvement in growth. We found that the drought + PGPB + SORGAAB treatment increased the amount of amylase (58%), chlorophyll-a and b (67 and 83%, respectively), catalase (58%), superoxide dismutase (45%), peroxidase (52%), and crude protein (69%), compared to the drought treatment alone. However, H₂O₂ levels went down by 57%. Our results also showed a 90.5% and 95% increase in macro- and micronutrient concentrations, respectively, under PGPB + SORGAB treatment. The combined application of PGPB + SORGAAB at the V3 phase was more effective in enhancing the vegetative biomass by yielding 2.41 and 5.67 g/pot of the shoot and root dry weights, thereby impacting the root-to-shoot ratios, and enabling maize plants to improve growth under drought conditions.