Survey on the characteristics and ability to promote plant growth of indigenous bacteria isolated from root nodules of mung bean Vigna radiata (L.) R. Wilczek grown in Thanh Duc, Tay Ninh province, Vietnam

This study isolated bacteria from mung bean root nodules in Thanh Duc, Tay Ninh, and evaluated their growth-promoting effects on 2-month-old plants grown in Leonard jars under garden conditions. Nodule surfaces were disinfected, with sterility confirmed via TYGA medium plating of the final rinse. Ammonium, soluble phosphate, and IAA concentration were subsequently determined through colorimetric analysis. The most promising strains were identified using MALDI-TOF MS. Finally, an in vivo assay was conducted using Leonard jars containing half-strength modified Hoagland’s solution (with and without nitrogen) to measure the impact of single and dual inoculations on two-month-old mung bean plants. A total of 32 strains were isolated and all exhibited ability to fix nitrogen, solubilize phosphate, and synthesize IAA with an average concentration of 0.53 – 1.13 mg/L for NH₄⁺, 109.63 – 143.17 mg/L for P₂O₅ and 0.51 – 4.03 mg/L for IAA, respectively. The three most effective strains-SX1, SX22 and SX27 were identified as Paenibacillus barcinonensis, Bacillus pumilus and Mesobacillus jeotgali.  In vivo plant growth promoting results on mung bean plants showed that strain SX27, when inoculated individually, had the best impact on shoot biomass under growth conditions using half-strength modified Hoagland’s solution without nitrogen. Meanwhile, the simultaneous inoculation of two strains SX1 and SX27 produced the highest values of shoot height, shoot biomass and root biomass under growth conditions using half strength modified Hoagland’s solution.