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 x 10(8) 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 10(5) CFU g(-1) of soil only until radicle emergency. From the fifth day onwards, it was detected at the roots in a concentration of 10(3) to 10(5) 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.

Automated summary

Although Azospirillum brasilense is commonly used in inoculant formulations, its prevalence in field conditions is still limited. In this study, A. brasilense was found in soil only at radicle emergency, and from the fifth day onwards, it was detected in roots at concentrations ranging from 10(3) to 10(5) CFU g(-1) of fresh root. This research provided a sensitive method for monitoring A. brasilense in field trials and offered new insights into the ecology of maize and A. brasilense interaction.