Source–sink relationships in short-duration and hybrid rice cultivars in tropical Asia

Shortening the period of rice cropping enables farmers to reduce irrigation water in tropical lowlands. However, grain yield short-duration is often restricted by poor filling, whose causes are yet unknown. This study evaluated source–sink balance, which closely associated with rice. We compared percentage filled grains and stem nonstructural carbohydrates a popular cultivar high-yielding hybrid over wide range spikelets m−2 differentiating N inputs planting densities on lowland farm International Rice Research Institute, Philippines, during four seasons. Grain ranged from 2.2 8.6 t ha−1, producing consistently higher (by 27% average). Compared cultivar, had less at heading per spikelet 24% average) lower wet season 13% average), when source capacity was lowest. Source were significantly grains, suggesting that these indicators ratio modulate filling Although sink similar to, or smaller than, its limited resulted poorer filling. suggest role should be emphasized breeding