What do we know about the seed microbiome?

The seed microbiome supports plant health and increases resilience under adverse environmental conditions. Seeds are also an important vector for transgenerational transfer of the plant microbiota. Even though research over the last decade has provided valuable insights into the functional roles of seed-associated microbes, these important members of the plant microbiome remain underexplored. This review systematically highlights recently discovered key functions of the seed microbiota. It covers taxonomic composition and diversity across plant species, transmission mechanisms, functional roles in germination and seedling establishment, growth promotion, and stress resistance. The review also addresses methodological challenges and highlights critical open questions regarding assembly, spatial compartmentalization, and translation into applications. Further research into seed microbiomes has the potential to not only increase the sustainability in plant production but also to increase food security in a changing climate. Reaching such outcomes will be facilitated by mechanistic studies that will disclose the remaining secrets of plant-microbe interplay at the very first developmental stage of most plants that nowadays inhabit Earth. Video Abstract.