Variation of the bacterial communities in the rhizosphere of three species of the genus Tagetes (Marigold) over time

In the present study, the molecular profiles of rhizospheric bacterial communities of Tagetes terniflora, T. remotiflora and T. coronopifolia were analyzed at different times using soil samples under greenhouse conditions. To this end, samples spanning were obtained at 3, 30, 60 and 90 days. Metagenomic DNA was extracted and the 16S rDNA genes were amplified by PCR-touchdown to reduces the formation of spurious by-products. The amplified fragments were run through Denaturing Gradient Gel Electrophoresis (DGGE) to obtain their molecular profiles. Shannon’s index showed a decline of bacterial diversity over time. Also, to visualize spatial proximities by species, a non-metric MDS ordination was conducted, generating a stress value of 0.179. A one way-ANOSIM showed significant differences between T. terniflora and T. coronopifolia (R = 0.78, p <0.05), and between T. remotiflora and T. coronopifolia (R = 0.791, p <0.05). Sequencing of some DGGE profiles bands showed that Pseudomonas was present at 3, 30 and 60 days in all species of Tagetes, while Chloroflexus and Delftia were present at 3 and 60 days in T. remotiflora and T. coronopifolia, respectively. The study demonstrated that the beneficial populations were positively selected and sample time and species affect the dynamic succession in the rhizobacteria communities.