Submitted to: Symbiosis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/13/2025
Publication Date: N/A
Citation: N/A

Interpretive Summary: Plant variety (genotype) and plant-to-plant variation may affect the collection of bacteria and fungi on the seeds it produces (its microbiome). The microbes on the seeds may then influence the traits of the seedlings. This work used the model grass Brachypodium hybridum to examine these questions. The genotype of the grass had an effect on the fungi of the seeds but no effect on the bacterial community of the seeds relative to the variation between maternal plants. The microbiomes of the seeds did not affect most traits measured except for germination during cold stratification. There has been interest in using seed microbiomes to improve seedling performance. This work indicated that the microbiome of a genotype may be somewhat heritable but it has modest effects on the seedling.

Technical Abstract: Seed microbiomes represent the first colonization of the plant by microbes and influence community assembly of subsequent microbes. The role that parental genotype plays in structuring and sourcing the seed microbiome is crucial to understanding the seed microbiome and patterns in microbiome variation. Seed-borne microbes become part of the seedling microbiome and have the potential to influence seedling traits and whether variation in seedling traits can be explained by seed fungal and bacterial microbiome characteristics is important to improving our ability to predict seedling-microbiome trait responses a priori for application. Unfortunately, the relationship between seedling traits or germination response and seed microbiome characteristics have only been quantitatively linked in one study to our knowledge. So, here we grew individuals of a wild collection and an inbred line of the annual grass, Brachypodium hybridum in a greenhouse for seed production and used high throughput amplicon sequencing to characterize offspring seed microbiome. We also characterized the growth of sibling seedlings to those sequenced. We found that for only one of the eight traits evaluated, seed germination during cold stratification, the abundance of the most prevalent microbial families had a marginal positive influence on whether germination happened during cold stratification (R2 = 0.29, p = 0.07). These results critically show that seed microbiomes are strongly influenced by parental genotype and seed microbiomes may have diminishing influences on seed and seedling traits. Thus, more work is needed to realize the goal of microbiome-trait prediction.