Physiological Mechanisms of Plant Growth-Promoting Rhizobacteria in Enhancing Abiotic Stress Tolerance of Vegetable Crops: A Review

Global climate change is increasing the impacts of abiotic stresses on plants. Vegetables are rich in vitamins, minerals, dietary fiber, and a variety of phytochemicals, and thus, are of great significance to human health. The growth of vegetable crops is regulated by a variety of abiotic stress factors, which not only affect their normal growth and metabolism but also lead to reduced yield and quality. Plant growth-promoting rhizobacteria (PGPR) can modulate the morphological or physiological characteristics of plants via nitrogen fixation, phosphorus dissolution, potassium dissolution, production of siderophores, secretion of secondary metabolites and hormones, and induction of plant stress resistance gene expression. This consequently increases the nutrient utilization rate in plants, improving their yield, quality, and stress resistance. In this review, the literature focused on how rhizosphere growth-promoting bacteria can improve the resistance of vegetable crops to drought, extreme temperature, heavy metals, and salt stresses is reviewed, and relevant application prospects and research directions provide a reference for further research on stress resistance and strategies to increase the yield of vegetable crops.