interactions. However, little is known about the effect of changes in the soil bacterial community in general and
especially the loss of rare soil microbes on these interactions. Here, the influence of rare soil microbe reduction
on induced systemic resistance (ISR) in a wild ecotype of Arabidopsis thaliana against the aphid Myzus persicae
• Methods To create a gradient of microbial abundances, soil was inoculated with a serial dilution of a microbial
community and responses of Arabidopsis plants that originated from the same site as the soil microbes were
tested. Plant biomass, transcription of genes involved in plant defences, and insect performance were measured.
In addition, the effects of the PGPR strain Pseudomonas fluorescens SS101 on plant and insect performance were
tested under the influence of the various soil dilution treatments.
• Key Results Plant biomass showed a hump-shaped relationship with soil microbial community dilution,
independent of aphid or Pseudomonas treatments. Both aphid infestation and inoculation with Pseudomonas
reduced plant biomass, and led to downregulation of PR1 (salicylic acid-responsive gene) and CYP79B3 (involved
in synthesis of glucosinolates). Aphid performance and gene transcription were unaffected by soil dilution.
• Conclusions Neither the loss of rare microbial species, as caused by soil dilution, nor Pseudomonas affect the
resistance of A. thaliana against M. persicae. However, both Pseudomonas survival and plant biomass respond to
rare species loss. Thus, loss of rare soil microbial species can have a significant impact on both above- and belowground
Data from: Soil microbial species loss affects plant biomass and survival of an introduced bacterial strain, but not inducible plant defences
Kurm, V. (Creator), van der Putten, W. H. (Creator), Pineda, A. M. (Creator) & Hol, W. H. G. (Creator), Dryad, 11 Jan 2018