Plants grown in distinct soils typically harbor distinct microbial communities, but the degree of the soil microbiome influence on plant microbiome assembly remains largely undetermined. We also know that the microbes associated with seeds can contribute to the plant microbiome, but the magnitude of this contribution is likely variable. We quantified the influence of soil and seed microbiomes on the bacterial community composition of seedlings by independently inoculating seeds from a single cultivar of wheat (Triticum aestivum) with 219 unique soil slurries while holding other environmental factors constant, determining the composition of the seed, soil, and seedling bacterial communities via cultivation-independent methods. Soil bacterial communities exert a strong, but variable, influence on seedling bacterial community structure, with the extent of the soil bacterial contribution dependent on the soil in question. By testing a wide range of soils, we were able to show that the specific composition of the seedling microbiome is predictable from knowing which bacterial taxa are found in soil. Although the most ubiquitous taxa associated with the seedlings were seed derived, the contributions of the seed microbiome to the seedling microbiome were variable and dependent on soil bacterial community composition. Together this work improves our predictive understanding of how the plant microbiome assembles and how the seedling microbiome could be directly or indirectly manipulated to improve plant health.

生长在不同土壤中的植物通常具有不同的微生物群落，但土壤微生物组对植物微生物组组装的影响程度在很大程度上仍未确定。我们也知道与种子相关的微生物可以对植物微生物组做出贡献，但这种贡献的大小可能是可变的。我们通过独立接种单一小麦品种 ( Triticum aestivum ) 的种子，量化了土壤和种子微生物组对幼苗细菌群落组成的影响。) 使用 219 种独特的土壤泥浆，同时保持其他环境因素不变，通过独立于培养的方法确定种子、土壤和幼苗细菌群落的组成。土壤细菌群落对幼苗细菌群落结构产生强烈但可变的影响，土壤细菌贡献的程度取决于所讨论的土壤。通过测试广泛的土壤，我们能够证明，通过了解土壤中发现的细菌类群，可以预测幼苗微生物组的特定组成。尽管与幼苗相关的最普遍的分类群是种子衍生的，但种子微生物组对幼苗微生物组的贡献是可变的，并且取决于土壤细菌群落组成。