Exploring the potential of P solubilizing rhizobacteria for enhanced yield and quality in turmeric (Curcuma longa L.)

Abstract

The study focused on isolation and characterization of a bevy of phosphorus solubilizing bacteria (PSB) and exploring the effects of the most promising PSB on yield and quality of turmeric. For this purpose, several bacterial strains isolated from the rhizosphere of turmeric grown across India were assessed for their capacity to solubilize tri-calcium phosphate (TCP) and di-calcium phosphate (DCP) under in vitro condition and in liquid medium. The soluble P turnover by the promising PSB was then investigated in soil per se and their effects were further validated in turmeric under both green house and field conditions for two successive years. The results revealed that Bacillus safensis (NCBI-MT192800), B. marisflavi (NCBI-MT 192801), B. cereus (NCBI- MT192803) and Pseudomonas aeruginosa (NCBI-MZ 540872) released significantly greater levels of labile P in the liquid medium due to their capacity to produce appreciable amounts of organic acids (gluconic, α ketogluconic, succinic, oxalic and tartaric). Green house studies on turmeric indicated that soil available P was significantly higher in the treatments involving PSB suggesting enhanced P solubilization and the treatment with B. safensis + 75 % P as rock phosphate (RP) increased rhizome yield by 129.0 % compared to the treatment with 100 % P applied as RP. The positive effects of PSB were also reflected in field experiments, wherein the treatments with combined application of B. safensis with 50 % or 75 % or 100 % P significantly increased soil available P by 143.0 – 246.0 %, rhizome yield by 29.0 – 120.0 %, P uptake by 51.0 – 223.0 % and curcumin content by 30.0 – 32.5 % compared to control (100 % P as RP). The use of B. safensis ensured 25.0 % reduction in exogenous inorganic P application while simultaneously enhancing turmeric yield and quality in P deficient soil.