Modulating red: Far-red ratios accelerates speed breeding efficiency by coordinating photosynthesis and flowering in winter wheat (Triticum aestivum L.) under controlled environments.

The ratio of red to far-red light (R/FR) is well known to regulate plant photosynthesis and flowering. However, the molecular and physiological mechanisms underlying these coordinated responses in winter wheat remain largely unclear. In a controlled-environment growth chamber, we investigated flowering behavior, photosynthetic performance, genome-wide transcriptional responses, and breeding efficiency in winter wheat under four R/FR light treatments: 10:1, 2:1, 1:1, and 1:2. Compared with an R/FR ratio of 10:1, an R/FR ratio of 2:1 significantly enhanced breeding efficiency, enabling up to 4.7 generations annually, via enhancing photosynthetic capacity, accelerating floral transition and progeny seed early maturation, albeit causing a decrease in production. Transcriptomic profiling further demonstrated that low R/FR ratios extensively remodel the expression of core genes associated with gibberellin (GA) biosynthesis, photosynthesis, and the flowering regulatory pathway. Far-red light supplementation upregulated key gibberellin biosynthesis genes (e.g., TaGA20ox1, TaGA20ox2-like), increasing the accumulation of biologically active gibberellins (GA3 and GA4). This subsequently upregulated flowering promoters (e.g., TaFT and TaFT-like) and downregulated flowering inhibitors (e.g., CO-L9 and CO-L10), thereby accelerating flowering. Taken together, these findings provide a mechanistic framework showing that far-red light accelerates reproductive development in winter wheat by enhancing GA-mediated signaling pathways, while maintaining higher photosynthetic performance. This regulatory effect highlights the potential of R/FR manipulation to shorten generation cycles and improve breeding efficiency in controlled-environment agriculture systems for winter wheat.