Characterization of the PTGMS line Huhan 82S: floral traits, sterility–fertility window, and seed-production parameters for two-line hybrid rice

As freshwater availability declines, water-saving and drought-resistant (WDR) rice will be pivotal for future food security. Here, we characterised ‘Huhan 82S’, a newly bred photoperiod- and thermo-sensitive genic male-sterile (PTGMS) line for two-line hybrid seed production. Multi-season field trials and controlled cold-water assays showed that Huhan 82S remained male-sterile for 61 days, with fertility restored only when temperature fell below ≈22.5 °C. The line combines a compact canopy, vigorous tillering (10.7 panicles per plant), high bilateral stigma exsertion (45.3%), and a synchronised 5 day flowering burst—traits that favour out-crossing. Across 43 test hybrids with elite restorers, Huhan 82S delivered + 8.6% mid-parent heterosis for grain yield while maintaining grain-quality attributes (e.g. chalkiness, amylose content). For hybrid seed production, an operational GA3 window of 8–12 g per 667 m2 maximised seed set and seed yield in on-farm conditions, whereas higher doses (≥ 16 g per 667 m2) offered no further gains. Collectively, these results position Huhan 82S as a robust female parent for WDR breeding and provide actionable agronomic parameters for large-scale two-line seed production.