Effect of Transplanting Plant Numbers per Hill on Heterosis in Hybrid Rice

Abstract— Hybrid rice is the primary cereal crop in Southern China, playing a crucial role in national food security. With a yield advantage of 15–20% over inbred varieties, agronomic practices. Planting density including inter-plant spacing and the number of transplanted plants per hill has a fundamental effect on rice production. However, the impact of transplanting plant numbers per hill on the expression of hybrid vigor remains unclear. This study evaluates the effects of different transplanting densities under sparse planting conditions on key physiological and yield-related traits in hybrid rice, its paternal lines, and inbred varieties. Results indicate that transplanting plant numbers per hill significantly influence heterosis, affecting key traits such as better-parent heterosis (BPH), plant height (PH), spikelets per panicle (SPP), seed setting rate (SSR), harvest index (HI), and overall yield. The optimal transplanting density for maximizing yield was 1–2 plants per hill for hybrid rice and 3–4 plants per hill for inbred varieties. These findings provide a theoretical foundation for breeding, high-yield cultivation, and the mechanized adoption of hybrid rice.