Single and combined abiotic stressors affect maize rhizosphere bacterial microbiota

Rhizosphere microbiomes are influenced by abiotic stresses, but we know a little about their response to combinations of stresses. In this study we tested: (i) if drought and heat stress influence the maize rhizosphere microbial community; (ii) if the combination of drought and heat has a different outcome compared to a single stress; (iii) if rhizosphere microbiota clusters according to root class and root zone. We setup a microcosm system using maize as model plant. We exposed plants to drought, heat stress and their combination, and used 16S amplicon-sequencing to reconstruct bacterial communities of different root classes (crown and primary) and root zones (apical, sub-apical and basal). We found both drought and heat affect the structure of rhizosphere bacterial communities. The combination of these stressors also influenced the structure of rhizosphere microbial communities, but this effect did not differ compared to the single stresses. Interestingly, we found differences in microbial communities inhabiting the rhizosphere of crown and primary roots in the control treatment, but this difference disappeared once stresses were applied. Stress also lead to an increased abundance of beneficial organisms.