Response of root endosphere bacterial communities of typical rice cultivars to nitrogen fertilizer reduction at the jointing stage.

Root endosphere bacterial communities play an essential role in regulating plant growth and resisting nutrient stress. However, there is still a lack of knowledge on the response of root endosphere bacterial communities of rice (Oryza sativa L.) to reduced nitrogen (N). We investigated endosphere bacterial communities and quantified the abundance of functional genes involved in N conversion and ethylene synthesis in the roots of hybrid rice and japonica rice at the jointing stage under the traditional high-yielding N fertilization (THYN) and reduced N fertilization (RN). Results showed different selection preferences of root endosphere bacterial communities of two rice cultivars under THYN treatment. Specifically, δ-proteobacteria and Firmicutes were enriched in the root endosphere of hybrid rice, while γ-proteobacteria and α-proteobacteria were enriched in the root endosphere of japonica rice. Root endosphere bacterial communities of two rice cultivars showed different tolerance to RN, but showed commonalities in the selection of bacteria taxon, such as the massive enrichment of Burkholderia-Caballeronia-Paraburkholderia in the root endosphere. Additionally, the relative abundances of nifH, amoA-archaea, nirS, nirK, and acdS genes in japonica rice roots were higher than those in roots of hybrid rice under THYN treatment. RN significantly increased the relative abundance of acdS gene in roots of hybrid rice, alleviating the decline in above-ground dry matter weight. Our study revealed potential microbiological strategies for rice to cope with insufficient N supply.