The single-seed microbiota reveals rare taxa-associated community robustness

Genetic and environmental cues affecting seed microbial communities have been investigated to assess the ecological characteristics of seed microbial communities. However, little is known concerning seed-to-seed microbial variations and ecological drivers at the single-seed level. We report rare taxa-associated heterogeneity and robustness of seed bacterial and fungal communities in individual seeds using 63 pooled and 70 single-seed samples from a single field-grown rice plant. Ordination analyses showed that seed-to-seed variation patterns could be clustered according to the originating panicle branch. Bacterial-fungal associations and in silico extinction experiments demonstrated that rare taxa contribute to the connectivity and robustness of the associations. Null modeling-based statistical analysis revealed that the distribution of rare taxa is mainly governed by dispersal limitation, whereas the distribution of prevalent taxa is mainly governed by homogeneous selection and ecological drift. Our findings provide an ecological framework for understanding the heterogeneity of seed microbial communities in a single plant; they will facilitate the development and application of seed microbiota or single microbe-based engineering strategies.