Resilience of root and soil bacteria to drought stress depends on host plant's colonization affinity towards arbuscular mycorrhiza fungi

Water deficit is one of the most important climate events that has strong effect on agricultural ecosystem functionality comprising soil microbial communities and their functions. Arbuscular mycorrhizal fungi (AMF) are widely known for their roles in combating drought, including facilitation of drought-tolerant bacteria. However, differences in cultivar/variety affinity for mycorrhization have never been considered as influencing factors. In the present study, we evaluated the influence of mycorrhizal affinity of two durum wheat (T. turgidum subsp. Durum (Desf.)) varieties, Iride and Ramirez (high and low, respectively) on root and soil bacteriomes under well watered and drought conditions. We used the 16S metagenomics approach (amplicon sequencing) to assess the bacterial communities of root and soil samples. The suppression effect of drought was evident across a wide range of bacterial taxa, including drought-tolerant taxa, especially in the non-inoculated plants. Nevertheless, the protective effect of AMF was also shown, especially in the Iride variety (high AMF colonization affinity) in both compartments (root and soil), as the relative abundance of drought-depleted taxa, such as Planctomycetes, Bacteroidetes and Verrucomicrobia, was either similar under well-watered and water deficit conditions or increased under water deficit conditions. Moreover, drought reduced the network complexity of root and soil bacteria, especially in Ramirez variety which has a lower AMF colonization affinity. Together, our results suggest that not only AMF colonization, but also host plant colonization affinity is one of the regulating factors in alleviating drought-induced changes in wheat plants by altering plant-fungal-bacterial interactions.