Plant-growth stimulating bacteria × environments/bio-formulations interactions on the growth-promoting activities of Serratia marcescens and Pseudomonas fluorescens on chili

Chile has been used as a spice because of its flavor and zest, which complement the minerals, vitamins, and other elements it contains when cooked. The objective of the current study was to determine how P. fluorescens and S. marcescens promote plant growth in Chili plants. The PGPR's phosphate solubilizing, IAA, NH3, HCN production, and antifungal activities were ascertained using in vitro experiments. During the study period 2020–2022, the experiment was conducted using a completely randomized block design, with three replications of the three treatments for each microorganism, as follows: 1) P. fluorescens: T0 (control, unsterile soil), T1 (P. fluorescens in rice husk), and T2 (P. fluorescens in sawdust); 2) S. marcescens: T0 (control, unsterile soil), T1 (S. marcescens in rice husk), and T2 (S. marcescens in sawdust) with no fertilizer. After seeding, the chili plant's parameters were measured at 15, 30, 45, 60, and 75 days and compared to the control using four traits: plant height, root length, shoot length, and the number of leaves per plant. The following bio-formulation, employing T0, enhanced plant height growth after seeding: In rice husk, Days 75 (B2 × D5 × T2) = 21.20 for S. marcescens > Days 75 (B1 × D5 × T2) = 20.83 for P. fluorescens > Days 60 (B1 × D4 × T2) = 19.17 for P. fluorescens Days 75 (B2 × D5 × T0) for S. marcescens in control, days 60 (B1 × D4 × T1 (16.43 cm) for P. fluorescens in sawdust, and days 75 (B1 × D5 × T0) for P. fluorescens in control. The root length (cm) for P. fluorescens in sawdust is 7.23 days (B1 × D5 × T2), which is more than P. marcescens in sawdust (days 60 B1 × D4 × T2), P. fluorescens in control (days 75 (B1 × D5 × T0) = 6.60 cm), and S. marcescens in control (days 75 (B2 × D5 × T0) = 6.60 cm), etc. Rice husk and sawdust were used to create the bio-formulations. The maximum plant growth was achieved at 75 days when S. marcescens was grown in a sawdust medium, including sawdust as a carbon source and carboxymethyl cellulose as a carrier source. When the different compositions of the bio-formulation were tested on chili plants, it was found that P. fluorescens and S. marcescens in sawdust bio-formulation were more effective.