In vitro assessment of PGPR consortia as bioinoculants for enhancement of upland rice seedling growth

Plant growth-promoting rhizobacteria (PGPR) are recognized for their ability to enhance root system development and improve nutrient uptake in crops, representing a sustainable alternative to synthetic fertilizers. The objective of this study was to evaluate the effectiveness of single PGPR strains and consortia on the root development of upland rice seedlings. A completely randomized design with 29 treatments (7 single inoculants, 21 consortia, and 1 uninoculated control), each with five replications, was established. The strains included M01 (Leclercia adecarboxylata), M02 (Priestia megaterium BRM69509), M03 (Pseudomonas sp. BRM69536), M04 (Pseudomonas sp. BRM69515), M05 (Enterobacter hormaechei BRM69541), M06 (Bacillus toyonensis BRM32110), and M07 (Serratia marcescens BRM65920). Seeds were pre-germinated and maintained in a germination chamber at 28 °C with a 12-h photoperiod. After 12 days, seedling roots were imaged and analyzed for length, surface area, diameter, and volume. The consortium of P. megaterium BRM69509 and B. toyonensis BRM32110 increased root length by 42.52% relative to the control and formed a distinct superior group according to the Scott–Knott test (P < 0.05). For root surface area, consortium M24 (B. toyonensis + Pseudomonas sp. BRM69515) showed the highest numerical value, although grouped with other top-performing treatments. Root diameter was significantly enhanced by multiple treatments, particularly those involving L. adecarboxylata and E. hormaechei, with L. adecarboxylata + P. megaterium are presenting the highest numerical values within the top statistical group. Similarly, root volume was maximized in treatments grouped in the highest cluster, with L. adecarboxylata + B. toyonensis BRM32110 showing the highest numerical value. In conclusion, specific PGPR consortia demonstrated superior performance compared to single inoculants, substantially improving root architecture and thereby enhancing nutrient and water uptake. These findings highlight the potential of PGPR consortia as effective bioinoculants for sustainable upland rice production.