Pre‐flowering N storage and post‐flowering N remobilization in HD2086s/R209 rice hybrid are linked to stronger yield stability and improved nitrogen use efficiency

Abstract Cultivating rice ( Oryza sativa L.) hybrids enhances nitrogen (N) use efficiency and reduce N waste, but the physiological mechanisms underlying the superior N utilization of hybrids derived from male restorer and female sterile lines remain elusive. A 2‐year study evaluated seed yield, multiple N efficiency related traits, N accumulation, and N remobilization of hybrid HD2086s/R209 and its parents under five N rates. Principal component analysis revealed genetic divergence in N utilization patterns with annual environmental variations modifying genotypic responses to N levels. As N rates increased from N0 to N360, rice N utilization shifted from post‐flowering N remobilization dominance to pre‐flowering N storage coupled with post‐flowering sustained N uptake dominance. Benefiting from genetic complementarity, the hybrid outperformed its parents with stronger yield stability, higher maximum yield, and better adaptability. Its higher seed yield was associated with superior N utilization efficiency, primarily attributed to an improved N harvest index (NHI), while no genotypic difference was observed in seed N concentration. This superiority was further supported by (1) higher stem N accumulation at tillering and heading, (2) greater post‐flowering N remobilization associated with higher NHI, and (3) more effective tillers and higher dry matter accumulation. In contrast, parents relied on post‐flowering N remobilization under low N but showed poor coordination between N storage and remobilization under high N. This study characterizes the patterns of N utilization and allocation in hybrids, providing critical theoretical support for N‐efficient rice breeding.