Synthetic Community Inoculation on Seeds Revealed its Transient Colonization Capacity but Legacy Effects on Plant Microbiota Assembly

Seed microbiota have the potential to influence the overall plant microbiota assembly. However, to date, studies have mostly focused on early plant development stages. This study aimed to investigate the influence of seed microbiota on plant microbiota assembly throughout an entire life cycle. To achieve this, bacterial synthetic communities (SynComs) were reconstructed and inoculated on common bean seeds to eliminate the natural variability of seed microbiota and provide four different primary inocula for comparison. We then examined bacterial and fungal communities at different developmental stages (seedling, vegetative, flowering, pod-filling, and senescent stages) and in different plant compartments (rhizosphere, root, leaf, seed) of the common bean. SynComs inoculated on seeds significantly contributed to the seedling microbiota, with higher colonization success in the leaves compared to roots and rhizospheres. Strain identity and SynCom composition influenced the strain colonization capacity across the habitats. Also, bacterial SynCom colonization induced composition modification in the seedling root and leaf microbiota. After the seedling stage, SynComs members were not detected in plant compartments but promoted persistent changes in microbial community composition until the next generation of seeds. In conclusion, SynCom inoculated on seeds have a transient colonization that can influence the overall plant microbiota assembly through priority effects.