Oilseed rape (Brassica napus L.) responses to potassium deficiency stress: accelerated differentiation of microbial communities within specific compartment niches

Abstract

Background

Understanding the factors influencing microbial community composition in the soil–plant continuum is vital for regulating plant health. Fertilization, particularly potassium (K) fertilization, in this regard remains underexplored.

Methods

The 16S rRNA gene sequencing was used to investigate the microbial communities in oilseed rape compartments (leaves, roots, rhizosphere, bulk soil) under applied varying levels of K fertilization (–K, without K, and + K, with recommended K).

Results

K application significantly enhanced bacterial α-diversity in the rhizosphere, root endosphere, and phyllosphere, with plant-associated compartments (root endosphere and phyllosphere) showing more pronounced diversity and community composition shifts than soil compartments (bulk soil and rhizosphere). K deficiency led to an increase in the number of compartments endemic ASVs and complexity of compartments microbial ecological network. Firmicutes and Proteobacteria were the dominant phyla across all compartments, though their relative abundances exhibited compartment-specific responses. Proteobacteria increased in the phyllosphere and rhizosphere but decreased in the root endosphere under + K treatment, while Firmicutes showed the opposite trend. Additionally, K application reduced bacterial translocation, particularly of Proteobacteria, from the rhizosphere to the root endosphere.

Conclusion

Optimal K fertilization modulates the distribution and transfer of the microbial assemblages within the soil–plant niches, potentially serving as a conduit for K nutrition to maintain plant health.