Physiological factors influencing climate-smart agriculture: Daylength-mediated interaction between tillering and flowering in rice

Introduction: Control of rice tillering and flowering is crucial for reducing greenhouse gas emissions from paddy fields, a key goal of climate-smart agriculture. However, the interaction between tillering and flowering is still debated and poorly understood. Methods We subjected plants of the rice cultivars ‘Saenuri’ and ‘Odae,’ to short- and long-day conditions after removing their tillers, and observed growth and flowering responses. Results and Discussion Different daylength conditions yielded contrasting results. Plants in tiller-removal groups grown under short days flowered early compared with that of the controls, whereas the opposite was observed under long days. Further, the expression of the florigen gene, Hd3a , promoting flowering, increased in the tiller-removal group under short days compared with that of the control. Conversely, the expression of the OsMFT1 gene, delaying flowering and increasing the number of spikelets per panicle, was upregulated under long days, and the phenotypic results were consistent. The number of spikelets per panicle in ‘Saenuri’ and ‘Odae’ plants in the tiller-removal groups under long day conditions increased approximately 3.4 and 2.2 times, respectively, compared with that of the corresponding control groups. Conclusion These findings reveal the daylength-dependent variability in tillering and flowering interactions, offering a novel perspective on their relationship. The results provide a foundation for developing climate-smart rice management practices and breeding strategies to optimize growth timing and enhance productivity under variable photoperiod conditions.