Nitrogen deficiency drives fungal compositional shifts without functional changes in wheat rhizosphere

Nitrogen (N) deficiency reduces crop yield, which may be alleviated by the symbiotic interactions between crop and fungi. However, the symbiotic wheat-fungal interaction in response to N deficiency remains elusive. A glasshouse experiment was conducted to investigate the effects of N deficiency on the rhizosphere fungal communities of wheat (Triticum aestivum L.) cultivars Gladius (low N-use efficiency) and Mace (high N-use efficiency). Plants were grown till mid-anthesis stage in Dermosol soil receiving 0 (Low-N) or 90 kg N ha-1 (High-N). The rhizosphere fungal communities were characterised by quantitative PCR, ITS rRNA metabarcoding, and metagenomics. The abundance and diversity of the rhizosphere fungal community were unaffected by N deficiency in both Mace and Gladius cultivars (P > 0.05). However, fungal composition varied with N treatments in Mace (P 0.05). Differential abundance analysis showed distinct fungal responses between the cultivars. Functional predictions revealed a dominance of saprotrophic fungi and a decline in symbiotic fungi under N deficiency. Metagenomic analysis indicated fungal-related genes, primarily involved in amino acid metabolism (22.70%), were unaffected by N deficiency (P > 0.05). An intraspecific functional profile of the fungal community was also identified (P < 0.05). The study demonstrated an intraspecific response in the rhizosphere fungal community between Mace and Gladius and suggested higher functional redundancy in the rhizosphere fungal community to tolerate N deficiency. Leveraging the stability of the fungal community could enable the development of next-generation biofertiliser products for sustainable agriculture.