Innovations in hybrid rice seed production: Integrating agronomy, mechanization, and biotechnology.

Hybrid rice production makes use of heterosis to safeguard global food security. However, currently dominant three-line and two-line systems for seed production rely heavily on manual labor and are highly vulnerable to climate fluctuations. These limitations have become a significant bottleneck to the sustainability of rice production. To address this issue, we summarize recent advances and propose a novel "dual-track" analytical framework. The Proximal Track focuses on the integration of agronomy with machinery. It analyzes mechanized innovations in split- and mixed-planting models, evaluating mixed-sowing strategies based on targeted phenotypic sorting (e.g., for seed-coat color and grain thickness), selective herbicides, and gene editing (e.g., thermosensitive female sterility). The Distal Track explores molecular-driven breakthroughs. It characterizes the core advantages of third-generation seed production technology for unrestricted crossing and large-scale propagation of male-sterile lines, before analyzing the latest progress in "one-line" synthetic apomixis for permanent fixation of heterosis. Finally, we propose the creation of tailored parental chassis varieties suitable for mechanized cultivation and the introduction of AI-driven meteorological-crop models for the prediction of complex genotype-by-environment risks. Ultimately, this framework can guide a paradigm shift from "agronomic-mechanistic integration" to "reproductive pathway rewiring," laying a foundation for the strategic leap from three-line and two-line systems to a one-line method.