Detection of Azospirillum brasilense by qPCR throughout a maize field trial

Although Azospirillum brasilense is used in many inoculant formulations, information of its prevalence under field conditions is still scarce. In this work, we inoculated A. brasilense AbV5/AbV6 (2 × 108 CFU ml−1) on maize seeds and then evaluated its colonization profile throughout seventy-five days after seeding (DAS) in a field assay. The abundance of total bacteria and A. brasilense on the seed, root and soil rhizosphere were determined by qPCR using 16S rRNA and species-specific primers, respectively. A. brasilense was detected in soil at a concentration of 105 CFU g−1 of soil only until radicle emergency. From the fifth day onwards, it was detected at the roots in a concentration of 103 to 105 CFU g−1 of fresh root. Our results provide a sensitive approach to monitor A. brasilense in a field trial and reveal new information on the ecology of maize and A. brasilense association. [Display omitted] •brasilense was tracked by qPCR throughout seventy-five days under field conditions.•Right after radicle emergence, A. brasilense was detected only at maize roots.•brasilense at 105 CFU g−1 of fresh root increased maize yield.•An accurate approach for tracking and quantifying A. brasilense in the field was developed.