Optimizing Planting Density to Improve Source-Sink Relationship and Yield of Hybrid Wheat Under Late-Sowing Conditions

Overview

A two-year field experiment evaluated how planting density modulates source-sink relationships and yield of hybrid versus conventional winter wheat under late-sowing. Jingmai 17 (hybrid) and Jimai 22 (conventional) were grown at 150, 300, and 450 plants·m−2 to determine density-dependent effects on photosynthetic persistence, leaf senescence, assimilate translocation, and yield components. The principal outcome was that an intermediate density (300 plants·m−2) optimized source-sink coordination and produced the largest yield gains for both cultivars, with a pronounced advantage for the hybrid genotype.

Methods and approach

A randomized field trial conducted over two growing seasons compared three planting densities (150, 300, 450 plants·m−2) using a hybrid variety (Jingmai 17) and a conventional variety (Jimai 22). Measurements included grain yield, grain number per spike, thousand-grain weight, temporal photosynthetic capacity during grain filling, indices of leaf senescence, and metrics of assimilate translocation to grain. Statistical comparisons across densities and cultivars quantified relative changes in yield and physiological parameters to infer source-sink coordination efficiency.

Results

The intermediate density (300 plants·m−2) produced the largest yield increases for Jingmai 17 (2.4–9.7%) and Jimai 22 (1.4–10.6%) relative to other densities. This density maintained photosynthetic capacity during mid-to-late grain filling, delayed leaf senescence, and enhanced assimilate remobilization to grains. Improvements in both grain number per spike and thousand-grain weight were observed, indicating simultaneous enhancement of source strength and sink capacity. Across treatments, Jingmai 17 yielded 8.2–10.1% more than Jimai 22; the hybrid exhibited a more persistent source function, a larger and more stable sink, and higher source-sink coordination efficiency.

Implications

Under late-sowing regimes, adopting an intermediate planting density (300 plants·m−2) can optimize source-sink interactions and maximize yield potential of high-yielding hybrid wheat, achieving both higher and more stable yields than conventional varieties. Breeding and management strategies should prioritize genotypes with persistent post-anthesis photosynthesis and robust sink stability to exploit density-mediated gains. These findings inform cultivar selection and density recommendations for late-sown systems and guide targeted agronomic and genetic interventions to enhance source-sink coordination.