Seed associated microbiota and vertical transmission of bacterial communities from seed to nodule in Sophora davidii

Background and aims Seed associated microbial communities are an important part of the plant microbiota. However, for legumes, seed microbiota and their life cycle including colonization and vertical transmission to nodule remain largely unknown. Here we explored the sources of seed microbes and tested the hypothesis that the plant microbiota is partially inherited through vertical transmission. Methods Nodules, rhizosphere soil and seeds were collected from Sophora davidii grown in fields, and from inoculation test with fermentation broth of nodule endophytes. Additionally, structure of seed microbial communities and vertical transmission of seed microbes across one plant generations were assessed through amplicon sequencing of bacterial 16S rRNA gene. Results A total of 4074 endophytic OTUs were detected from S. davidii seeds, in which 233 shared with rhizosphere and nodules were defined as core microbiota of this plant, including various rhizobia. The core microbiota of S. davidii seeds was vertically transmitted to the nodules of upcoming generation of plants. Moreover, Firmicutes was the dominant phylum in S. davidii seeds. Notably, the dominant bacteria changed from Mesorhizobium in the field nodules to Sinorhizobium in the passage nodules in pot culture with inoculation. Conclusions Diverse microbial community habited in S. davidii seeds, including various rhizobia. The core microbiota could be transmitted from seeds to nodules, including the rhizobial endophytes, which made S. davidii plants potential to nodulated with distinct rhizobia in different environments, as revealed by the changed of dominant genus from Mesorhizobium to Sinorhizobium in an artificial condition. This study gives empirical evidence for the source, colonization and vertical transmission routes of S. davidii seed bacterial communities.