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Abstract Plant growth-promoting rhizobacteria (PGPR) enhance rice productivity by boosting nutrient uptake and hormone production and pathogen suppression. However, identifying efficient and multifunctional PGPR strains adapted to specific rice-growing environments remains challenging. This study aimed to isolate and assess efficient rice rhizosphere PGPR from the rice rhizosphere for their growth-promoting potential under controlled conditions. Eighteen bacterial isolates were initially screened for key PGPR traits, including phosphate (P) and zinc (Zn) solubilization, indole acetic acid (IAA) production, potash (K) mobilization, and antagonistic activity. Based on superior performance, two isolates were identified as Acinetobacter junii SK13 (AJNAU-SK13) and Providencia vermicola SK16 (PVNAU-SK16). Their efficacy was evaluated under greenhouse conditions using individual (T1: AJNAU-SK13, T2: PVNAU-SK16) and combined (T3: AJNAU-SK13 + PVNAU-SK16) inoculations. All treatments significantly improved root and shoot growth, biomass, chlorophyll content, enzyme activities (protease, and amylase), and total soluble sugars (TSS) at 10 and 20 days after treatment (DAT). Notably, T2 increased root growth (150%, 85.71%, respectively) and chlorophyll content, while T3 enhanced shoot elongation (80%, 91.67%, respectively) and TSS accumulation (97.31% at 20 DAT). PVNAU-SK16 also stimulated gibberellic acid (GA₃) levels, whereas the combined treatment (T3) improved IAA content. Overall, the isolates significantly improved rice growth through complementary mechanisms, with T2 and T3 showing the strongest effects. Their ability to enhance nutrient availability, phytohormone levels, and biochemical activities highlights their potential as bioinoculants for sustainable rice cultivation. Future work should focus validation, bioformulation development, and multi-omics approaches to elucidate PGPR rice interactions.
Raval et al. (Mon,) studied this question.