Novel Bacterial Consortia (BC6) Formulations Enhance Tomato Growth, Fruit Quality, and Metabolite Profile: Comparative Performance Under Multi-Stage Application.

With the aim to harness synergistic potential of multiple beneficial microbes, we developed consortia (BC6) bioformulations that comprise six bacterial strains in multiple delivery forms (both powder and liquid). The bioefficacy of the consortia was assessed in terms of plant growth, fruit quality, productivity, stress response and metabolite profile in tomato fruits. The novel liquid bioformulation demonstrated superior shelf-life stability beyond 12 months. Bacillus sp. IIVRBT-12, a prominent member of consortia exhibited plant growth-promoting (PGP) traits including phosphate (13.84 mg P-released/100 mg tricalcium phosphate) and zinc (47.24 mg ZnCO3 L- 1) solubilization. Bacillus sp. IIVRBB-3 showed high indole acetic acid (IAA) production (59.14 µg ml- 1) and ACC deaminase (872.42 nmol α-ketobutyrate mg-1h- 1) activity. Three-stage concomitant application (seed priming, root dip, and soil treatment) significantly improved plant growth with BC6-L treated plants showing enhanced height (89.95 cm) and root development (36.95 cm) compared to BC6-P, although both performed significantly against the control plants. The treatments improved flowering time and increased flowers per cluster (5.25 in BC6-L compared to 3.5 in BC6-P treated plants). Treatments enhanced fruit yield from 3.1 kg in BC6-P to 3.72 in BC6-L per plant. The consortia also significantly improved activity of defense enzymes and enhanced biochemical parameters (carotenoids, flavonoids, and ascorbic acid) of fruit nutritional quality. LC-MS/MS based putative metabolomic characterization of metabolites uniquely identified scopoletin, deoxyribose-5-phosphate, 2'-deoxycytidine-5'-diphosphate (sodium salt), adenosine monophosphate, 2'-deoxyuridine-5'-monophosphate (disodium salt) and cytidine-5'-monophosphate monohydrate in BC6 liquid inoculated plants. These findings demonstrated potential of BC6 consortia as an effective plant growth promoter offering enhanced crop productivity, improved nutritional quality, and increased stress resilience.