Plant defence inducers rapidly influence the diversity of bacterial communities in a potting mix

• Effects of plant defence inducers on potting mix bacterial diversity were assessed.
• Inducers salicylic acid, methyl jasmonate, ethylene and abscisic acid were tested.
• We used 16S rRNA gene amplicon pyrosequencing to investigate bacterial diversity.
• Limnobacter, Cellvibrio, Algoriphagus and Massilia were affected by plant inducers.

Plant hormones and their functional analogues are used in agriculture to combat plant diseases and pests. These chemicals are generally targeted at shoots, but soils inevitably receive a dose during application. In this study, we used 16S rRNA gene amplicon pyrosequencing to determine whether the diversity of bacterial communities in a potting mix (referred here as ‘model soil’) is influenced by exposure to salicylic acid (SA), methyl jasmonate (MeJA), ethylene (ET) and abscisic acid (ABA). The number of operational taxonomic units (OTUs; richness) and Simpson's Diversity Index values (evenness) associated with each sample was not influenced by the hormone treatments, but changes in community composition were observed. Relative to the control, all hormones more than doubled the abundance of a Limnobacter population, ABA led to a four-fold increase in a Cellvibrio population, ET led to a c. 70% decrease in an Algoriphagus population, and MeJA and ABA applications halved the abundance of a Massilia population. These changes may influence plant productivity.