What's past is past, mostly: Brassicaceae host plants mask the feedback from the previous year's soil history on bacterial communities, except when the Brassicaceae hosts experience drought

Previous soil history and the current plant hosts are two plant-soil feedbacks that operate at different time-scales to influence the structure soil bacterial communities. In this study, we used a MiSeq metabarcoding strategy to describe the impact of five Brassicaceae host plant species, and three different soil histories, on the structure of their bacterial root and rhizosphere communities at full flower. We found that the Brassicaceae host plants were consistently significant in structuring the bacterial communities. Four host plants (Sinapis alba, Brassica napus, B. juncea, B. carinata) formed nearly the same bacterial communities, regardless of soil history. Camelina sativa host plants structured phylogenetically distinct bacterial communities compared to the other hosts, particularly in their roots. Soil history established the previous year was only a significant factor for bacterial community structure when the feedback of the Brassicaceae host plants was weakened, potentially due to limited soil moisture during a dry year. Understanding how plant-soil feedbacks operate at different time-scales and are involved in how microbial communities are structured is a pre-requisite for employing microbiome technologies in improving agricultural systems.