 The study investigates the transmission of bacteria from radish seeds to seedlings using individual strains and synthetic communities, syncoms, under in vitro conditions. Syncoms were composed of highly abundant, subdominant, or rare bacterial seed taxa. The study found that stenotrophomonas rhizophila became dominant on seedlings, but most strains had variable transmission success and some had detrimental effects on seedling phenotypes. The results confirmed that the plant core microbiome includes pathogenic taxa and syncom inoculation can manipulate seed and seedling microbiota diversity, making it a promising tool to better understand early stages of plant microbiota assembly. This article was authored by Simonin, Marie, Prevose, Anne, Marie, Coralie, and others.