Finding optimal microorganisms to increase crop productivity and sustainability under drought – a structured reflection

ABSTRACT Considering the more frequent and longer drought events due to climate change, improving plant drought tolerance became a priority. The search for plant growth promoting rhizobacteria (PGPR) able to improve plant drought tolerance has been long addressed, but with inconsistent results. Here, we summarize the PGPR mechanisms that improve plant drought tolerance, identify the pitfalls in current PGPR isolation and selection routines, and discuss the key points to define new strategies to get optimal PGPR for plant drought tolerance. Drought and host genotype impact rhizo-communities, and host-mediated selection strategies may be used to obtain a drought-adapted rhizomicrobiome that can be a source for PGPR isolation. Alternatively, an integrated omics-level analysis can improve our knowledge on the mechanisms of rhizomicrobiome construction, and a targeted approach can be designed, which will be focused on key PGP traits. New strategies to build PGPR consortia for improvement of plant drought tolerance are also suggested.