Composition of soil microbial communities in the rhizosphere of cucumber cultivars with differing nitrogen acquisition efficiency

• Nitrogen supply changed cucumber rhizosphere microbial community composition.
• Cucumber cultivars with the same NAE shared a similar AOB community composition.
• Cucumber with high NAE had higher number of ammonifiers in the rhizosphere.
• Plant can control the composition and functionality of the rhizosphere microbiome.

Crop cultivars with high nitrogen acquisition efficiency (NAE) in agriculture can alleviate the problem of excessive use of nitrogen fertilizer. Soil microbial communities play an important role in nutrient cycling. However, the relationship between rhizosphere microbial communities and plant NAE is still not clear. In this experiment, cucumber cultivars with high NAE (Jinyou-2 and Jinyou-31) and low NAE (Jinlv-30 and Meihao) were grown in pots under limiting and not limiting N supply. The composition of rhizosphere microbial communities was analyzed with the most probable number, real-time PCR and PCR-denaturing gradient gel electrophoresis (DGGE). Generally, N supply rate increased the abundance of rhizosphere ammonia-oxidizing bacteria (AOB), and changed the composition of bacterial, fungal and AOB communities. The abundances of rhizosphere ammonifiers were higher in cucumber cultivars with high NAE than in cultivars with low NAE under limiting N supply. The composition of rhizosphere AOB community, rather than the bacterial and fungal communities, was more similar between cultivars with the same NAE than between cultivars with contrasting NAE. When subjected to the same N fertilization rate, no differences in rhizosphere microbial biomass N and C, abundances of bacteria, fungi and AOB were found between cultivars with low and high NAE. Overall, our results suggest that the abundance of rhizosphere ammonifiers and the composition of AOB community may be linked to the NAE of cucumber.