Appraisal of plant growth promoting rhizobacteria in enhancing drought tolerance across major cereal and legume crops: Meta-analysis

This meta-analysis quantifies the impact of plant growth promoting rhizobacteria (PGPR) on the growth and nutrient status of maize ( Zea mays L.), wheat ( Triticum aestivum L.), soybean ( Glycine max L. Merr.), and chickpea ( Cicer arietinum L.) under drought stress, while identifying key moderators of these microbial effects. Drought treatments in the studies ranged from mild ≈70–80% field capacity (FC)/water holding capacity (WHC) to moderate (≈40–69% FC/WHC or 50% ETc) and severe (<40% FC/WHC or prolonged water withholding). Across studies, PGPR inoculation significantly improved shoot dry weight (SDW), root dry weight (RDW), and yield by 38%, 52%, and 38%, respectively, while simultaneously increasing nitrogen, phosphorus, and potassium concentrations by 24%, 44%, and 28%. Crop type significantly moderated responses, as legumes generally exhibited stronger benefits than cereals, with SDW increasing by 79% and 30%, respectively. Drought severity strongly influenced PGPR effectiveness, with the largest improvements occurring under moderate drought, with RDW increasing by 61% and yield by 56%. Moderator analysis revealed that the variability in PGPR effectiveness was driven by experimental conditions (field vs. controlled), soil texture, and soil pH. Inoculation strategy also played a critical role with multi-strain consortia outperforming single-strain inoculants, increasing SDW by 70% compared to 28%. Furthermore, consortia combining taxonomically distinct phyla (Firmicutes and Proteobacteria) were more effective than those comprising closely related taxa. These findings provide valuable insight into agronomic and environmental moderators influencing PGPR effectiveness and support the targeted deployment of phylogenetically diverse microbial consortia to enhance drought resilience in major cropping systems. • PGPR significantly improved crop root dry weight (38%) and yield (52%) under drought. • Legumes showed a stronger response to PGPR than cereals under drought. • PGPR effectiveness was greater under moderate drought compared to mild and severe. • PGPR consortia combining taxonomically distinct phyla outperformed single strain. • PGPR effectiveness was driven by experimental conditions, soil texture and soil pH.