Marschner Review

Plant and Soil

, Volume 382, Issue 1, pp 1-16

First online:

Rhizobacterial salicylate production provokes headaches!

  • Peter A. H. M. BakkerAffiliated withPlant-Microbe Interactions, Department of Biology, Utrecht University Email author 
  • , LongXian RanAffiliated withCollege of Forestry, Agricultural University of Hebei
  • , Jesús Mercado-BlancoAffiliated withDepartamento de Protección de Cultivos, Instituto de agricultura Sostenible (CSIC)



Salicylic acid (SA) is produced in significant amounts by certain plant growth promoting rhizosphere bacteria, and some of these rhizobacteria have the ability to induce systemic resistance against diseases in plants. Exogenous application of SA to plants has long been known to lead to protection against a range of plant pathogens through the elicitation of systemic acquired resistance. Thus, it is reasonable to assume that the SA producing plant beneficial rhizobacteria elicit induced resistance through the production of SA.

Scope and conclusions

However, we discuss here that bacterial secretion of SA in vitro appears to be an artifact and that the bacteria will normally incorporate SA into SA-containing metabolites, mainly SA-based siderophores, under environmental conditions. Therefore, we argue that rhizobacteria do not likely excrete free SA into the rhizosphere thereby not inducing resistance in plants through this metabolite. SA detected in the rhizosphere is most likely produced by the plant and we discuss the impact of this phenolic compound on microbial interactions.


Antibiotic resistance Induced systemic resistance Microbial interactions Pseudomonas spp. Rhizosphere Salicylate Siderophores