Combined Foliar Application of GA3 and Boron Enriches Seed Boron, Biostimulates α-Amylase and Enhances Seedling Vigour in Novel Indian TGMS Based Pusa Jawahar Rice Hybrid 56

Hybrid rice offers a substantial yield advantage over conventional varieties, yet seed production in thermo-sensitive genic male sterility based hybrids is often limited by low seed set, poor grain filling, and suboptimal seed physiological quality. Improving the reproductive efficiency and metabolic performance of thermo-sensitive genic male sterility hybrids is therefore essential for reliable hybrid seed production. This study investigated the individual and combined effects of foliar-applied gibberellic acid (GA3; 100 and 200 ppm) and boron (0.5 and 1%) at the early heading stage (5–10%) on seed yield, metabolic activity, and seed quality traits in the TGMS hybrid PJRH56 (Pusa 1S × PRR158). Field experiments were conducted using a randomized block design with three replications. The combined treatment GA3 (200 ppm) + B (1%) (T8) produced the most significant improvements across reproductive and seed quality parameters. T8 enhanced spikelet fertility (59.80%; a 119% increase over control), seed yield per plot (479.93 g; 73% increase), and 1000-seed weight (22.42 g). Key seed quality indicators, including seedling vigor indices (SVI-I: 3538.53; SVI-II: 10.58), α-amylase activity (5.48 µmol maltose/min), and seed boron content (12.29 µg/g), were also significantly elevated. These improvements reflect the synergistic role of GA3 and boron in enhancing pollination efficiency, boron translocation, grain filling, and metabolic up-regulation during seed development. Enhanced α-amylase activity and reserve utilization further strengthened seedling establishment. Overall, foliar application of GA3 (200 ppm) with boron (1%) at early heading offers a practical and effective strategy to enhance seed physiological efficiency, quality, and vigor in TGMS hybrid rice, supporting more reliable hybrid seed production under changing climatic conditions.