Soil antimony pollution and plant growth stage affect the biodiversity of auxin-producing bacteria isolated from the rhizosphere of Achillea ageratum L.

Abstract A total of 4512 rhizobacteria were isolated at three stages of plant growth from Achillea ageratum colonizing a polluted site with an antimony concentration gradient. For 222 of these isolates auxin production (aux(+)) was verified in vitro. The percentage of aux(+) isolates increased with soil antimony concentration, as well as with plant growth stage. An amplified rDNA restriction analysis clustered the aux(+) isolates into 51 clusters, one of which was numerically predominant and present throughout plant development and at all antimony concentrations. The aux(+) population was genetically very diverse, and this diversity was related to both antimony concentration and plant growth stage.