Optimization of IAA production by telluric bacteria isolated from northern Algeria

IAA production is among the most important mechanisms used by PGPB to improve plant growth, health, and productivity. Out of twenty-eight telluric bacterial isolates, the four producing high IAA amounts were identified by 16S rDNA gene sequencing as Bacillus subtilis (A7), Bacillus pumilus (E11), and Pseudomonas fluorescens (A5 and E9). IAA production conditions viz. incubation time, pH, temperature, tryptophan concentration, and carbon and nitrogen sources at different concentrations were optimized. These strains showed variations in the optimum of each parameter except incubation time which was 4 days for all strains. Fructose at 0.5% was the optimum carbon source for three of the tested strains. The four strains showed different preferences for the nitrogen source concerning IAA production.