Maize root phenotypes affect rhizosphere microbial diversity and correlate with individual taxa under drought

Drought threatens food security globally. Adaptive root architectural and anatomical phenotypes and specific microbial taxa can improve maize (Zea mays L.) water uptake and tolerance to drought. However, synergisms between root phenotypes and microbiomes remain underexplored. We aimed to investigate the influence of maize genotypes with varying root architectures and anatomies on the rhizosphere microbiome under drought. We characterized grain yield, root architecture and anatomy, and rhizosphere prokaryotic and fungal communities of 22 maize inbred lines (IBM, B73 x Mo17) grown in four replicates in the field under drought and control conditions. We observed a genotype-dependent drought effect on root phenotypes and rhizosphere microbiomes. Microbial ß-diversity and cortical aerenchyma differentiated according to yield performance. Root cross section, living cortex, and stele areas, cortex to cross section ratio and number of metaxylem vessels affected grain yield under drought. Under control conditions, number of metaxylem vessels and cell files affected both prokaryotic and fungal ß-diversities, while parenchyma wall width (CPW) affected prokaryotic ß-diversity and correlated with grain yield. We found 97 and 166 significant correlations between relative abundances of microbial taxa and root architectural and anatomical phenotypes, respectively. Moreover, a greater number of correlations was found under control conditions. We identified drought-dependent associations between root phenotypes and microbiomes at community and taxon level. This study highlights the importance of investigating further the role of root phenotypes in predicting microbial assemblies and the implication for plant performance under drought.