Improved biocontrol performance of acid-tolerant Pseudomonas koreensis CLP-23 against Ralstonia solanacearum causing tobacco wilt

• CLP-23 exhibited strong antagonistic activity to Ralstonia solanacearum under acidic conditions. • CLP-23 facilitated plant growth under acidic stress environmental conditions. • CLP-23 enhanced soil enzyme activities and nutrient contents of acidic tobacco rhizosphere soil. • CLP-23 has potential for application in acidified tobacco field soil infected with R. solanacearum . Pseudomonas koreensis , a subgroup of the P. fluorescens complex, is a potential plant growth-promoting rhizobacterium. The aim of this study was to evaluate the biocontrol effects of Pseudomonas koreensis CLP-23 against R. solanacearum under acidic conditions, both in vitro and in vivo . P. koreensis CLP-23 had an antagonistic activity against R. solanacearum , with the strongest antagonism at pH 5.5. Additionally, P. koreensis CLP-23 enhanced the plant growth-promoting (PGP) characteristics, including protease production, indole-3-acetic acid synthesis, and phosphate solubilization, particularly at a pH of 5.5. In pot and field, P. koreensis CLP-23 improved biomass accumulation and enhanced bioccontrol efficacy to tobacco wilt in soils with pH 5.5, respectively. Morover, P. koreensis CLP-23 significantly enhanced phosphatase and urease activities as well as available phosphorus and potassium contents in the rhizosphere soil within 45 d post-inoculation. Our results indicated that an acid-tolerant P. koreensis CLP-23 plays an important role in the tobacco wilt prevention, the process of growth enhancement under acidic soil.