Objectivels Investigation of the characteristics of rhizosphere microbial communities in inbred maize lines Xu178 and Zong3 with significant differences in low-nitrogen tolerance and their association mechanisms with nitrogen utilization.

Methods A pot experiment method was used for the research. Both the two maize inbred lines were subjected to high nitrogen (applying N 0.2 g/kg soil) and low nitrogen (no nitrogen added) treatments, respectively. After growing 38 days, the seedlings were harvested for analysis of aboveground biomass and nutrient content. The soil were sampled for determination of physiochemical properties, and high-throughput sequencing and qPCR techniques were employed to analyze the rhizosphere microbial community structure, the abundance of N-cycling functional genes, and the characteristics of microbial interaction networks.

Results Under high- and low-N treatments, the biomass of Zong3 consistently surpassed that of Xu178, however, the ratio of Xong3’s aboveground biomass under low N condition to that under high N condition was notably lower than Xu178, underscoring Xu178’s remarkable tolerance to low N condition. In terms of rhizosphere bacteria under HN conditions, Xu178 exhibited a higher Simpson index and a significantly greater relative abundance of Proteobacteria and Burkholderiaceae compared to Zong3. Conversely, Zong3 showed enrichment in Actinobacteria and Firmicutes. When subjected to low nitrogen, Xu178 displayed a higher abundance of Acidobacteria and Burkholderiaceae. Functional gene analysis revealed that the rhizosphere soil of Xu178 contained significantly higher abundances of nitrogen-fixing genes (nifH), ammonia-oxidizing archaeal amoA (AOA amoA), ammonia-oxidizing bacterial amoA (AOB amoA), and denitrification genes (nirS) than that of Zong3. Interestingly, within the roots, the abundance of nifH genes in Zong3 was 50.43% higher than in Xu178 under high nitrogen conditions and 40.60% higher under low nitrogen conditions. The rhizosphere fungal network of Xu178 had a significantly higher average weighted degree (1.447) compared to Zong3’s (0.694), indicating lower modularity and enhanced collaborative efficiency. Core species in Xu178’s network, such as Xanthomonadaceae, Nostocaceae, and Glomeraceae, demonstrated robust nitrogen fixation and ammonia-oxidizing capabilities. In contrast, Zong3’s network structure was more intricate, characterized by high functional redundancy. Its core species, including Diplococcaceae and Calosphaeriaceae, were involved in nitrogen metabolism but lacked efficient nitrogen fixation abilities.

Conclusions Different low-nitrogen-tolerant maize genotypes can shape specific rhizosphere microbial communities and the expression of nitrogen cycling functional genes, and adapt to low-nitrogen environments through differentiated microbial interaction networks. The rhizosphere of the low-nitrogen-tolerant material Xu178 can enrich dominant nitrogen-transforming microbial populations, increase the abundance of rhizosphere nitrogen cycling functional genes, and construct an efficient synergistic microbial network, whereas the low-nitrogen-sensitive material Zong3 relies more on root endophytic nitrogen-fixing genes to maintain nitrogen metabolism. The differentiation of rhizosphere microecological characteristics between the two provides a microbiological basis for the breeding of high-nitrogen-use-efficiency maize varieties.