A Rhizobacterial Consortium Improves Crop Productivity, Stress Tolerance, and Soil Health

Abstract

Plant growth-promoting rhizobacteria (PGPR) offer an environmentally benign route to sustaining crop productivity while curtailing dependence on synthetic agrochemicals. This study isolated, characterised and functionally screened rhizobacteria recovered from four contrasting agricultural soils, and evaluated elite strains and a defined consortium across a graded series of controlled, stress, biocontrol and field experiments conducted over two cropping seasons. Forty-eight morphologically distinct isolates were obtained, of which twelve were shortlisted and assigned to six genera by 16S rRNA gene sequencing, with Bacillus and Pseudomonas predominating. In vitro screening identified three elite strains — Bacillus velezensis PGPR-4 and PGPR-8 and Pseudomonas putida PGPR-9 — that combined strong phosphate solubilisation, indole-3-acetic acid (IAA) production, siderophore synthesis and broad-spectrum antifungal activity; a fourth strain, Azospirillum brasilense PGPR-3, contributed vigorous nitrogen fixation. A compatible consortium of the four strains consistently outperformed the individual strains, raising germination, root and shoot length, biomass, chlorophyll content and nutrient uptake under controlled conditions, and mitigating drought and salinity stress through improved water relations, ionic balance and antioxidant defence. The consortium suppressed three soil-borne fungal pathogens with a biocontrol efficacy of approximately 65 %. Under field conditions the consortium alone approached the yield of the full recommended fertiliser dose, while the consortium combined with 75 % of the recommended dose exceeded it (5.0 t ha^⁻¹), demonstrating a substantial fertiliser-substitution effect. Inoculation also enhanced soil microbial biomass, enzyme activities and nutrient status while preserving microbial diversity.