04 Plant growth-promoting rhizobacteria and their applications in agronomy.

Laurent LEGENDRE
Université de Lyon
In parallel to fungal symbioses, plant roots develop interactions with reciprocal benefices with a wide array of soil bacterial genera that are grouped under the name ‘plant growth-promoting rhizobacteria’(PGPR). These interactions may take place within the root, at its surface or in the rhizosphere, the area of soil that is influenced by the root. PGPR improve plant mineral nutrition, alter the root system architecture and provide direct and indirect protection against a panel of plant pests and abiotic stresses. Their presence in some soils can, in some instances, lead to enhanced tolerance to certain diseases or to the expression of the specific phenotype of some plant varieties. Numerous commercial products include them as active ingredients and are sold as biofertilizers or biocontrol agents to sustain crop yields in a context of changing climate and lesser use of chemical fertilizers and pesticides. True agronomic benefices are nevertheless often disappointing when single microbial isolates are used. Current research efforts are therefore aiming to construct synthetic bacterial communities (SynCom) to better take into account the complexity of the interactions among bacteria and the multitude of their phytobeneficial properties. Artifical selection methods are also used to render the host-SynCom interaction permanent and heritable.