Influence of rhizobacterial volatile compounds on growth and root system architecture of Brachypodium distachyon (L.) Beauv.

Many rhizobacterial strains are classified as plant growth-promoting rhizobacteria (PGPR) and are potentially useful to enhance plant fitness and productivity. Among the mechanisms by which PGPR improve plant growth, the emission of volatile organic compounds (VOCs) and their biological impacts on plants remain little documented. The aim of this work is to evaluate the growth promotion ability of 19 bacterial strains on the model grass Brachypodium distachyon Bd21 (Bd21), with a focus on this peculiar mode of interaction. A collection of 19 strains was selected for their known growth promotion potential. The impact of the rhizobacteria on the model grass was studied using an in vitro cocultivation system allowing interactions through VOCs without physical contact between plants and bacteria. The results show that the VOCs of several strains promote total biomass production, modulate biomass partitioning and affect shoot and root architecture of Bd21. The effects of the PGPR strains emitting different volatile blends were investigated via principal component analysis coupled to clustering and univariate analysis to unravel their biological effects. On the basis of volatile emissions and of their effects on plant growth, two strains have been selected in order to evaluate such interactions using an ex vitro system. The set-up of this system is in progress.