Screening and optimization of indole-3-acetic acid production by bacterial strain isolated from rice rhizosphere and its effects on plant growth

Abstract

The present study deals with the isolation of plant growth-promoting bacterial strains from rhizospheric soil collected from a rice field of Purba Bardhaman District, West Bengal, India. Among the isolated five strains, A5 was the best-performing strain as it had, plant growth promoting traits like, production of indole‑3‑acetic acid (IAA), siderophore, hydrogen cyanide and exopolysaccharides, ammonia, phosphate solubilization, nitrogen fixation etc. Strain A5, identified as Bacillus xiamensis by phenotypic characters and 16S rDNA sequence-based homology, was able to produce a copious amount of IAA, particularly in the case of 42‑h culture with 1.5% L‑tryptophan as a precursor. Media optimization with different carbon and nitrogen sources was conducted for maximum production of IAA. Strain A5 used fructose and casamino acid most efficiently as carbon and nitrogen sources, respectively. Growth parameters were increased in A5‑treated seedlings of mung bean compared to control seedlings. Considering the observed traits, strain A5 can definitely be considered as a novel plant growth-promoting bacterial strain that may serve very well as a biofertilizer in agricultural fields.