Plant growth-promoting rhizobacteria improve drought tolerance of crops: a review

Drought stress significantly impairs crop growth and productivity, threatening global food security. Plant growth-promoting rhizobacteria (PGPR) enhance crop stress tolerance through various physiological and molecular mechanisms, including regulation of nitrogen fixation, phosphate solubilization, plant hormone production, antioxidant system, nutrient uptake, and transcript abundance. This study explored the physiological and molecular mechanisms of rhizosphere microorganisms promoting drought resistance in various crops. The dynamic composition of the crop rhizosphere community structure was summarized and revealed the primary mechanisms of PGPR-mediated enhancement in host crop stress resistance. Furthermore, a comparison of PGPR-mediated drought resistance mechanisms in various crops was performed to identify the commonalities and differences. Finally, the potential applications of rhizosphere microorganisms are discussed, which provides insights and theoretical support for future research on the plant growth-promoting mechanisms and practical application of PGPRs for the breeding of drought-tolerant crops towards our sustainable food future.