Physiological factors Influencing Climate-Smart Agriculture: Daylength-Mediated Interaction Between Tillering and Flowering in Rice

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 remains debated and poorly understood. 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. Different daylength conditions yielded contrasting results. Plants in tiller-removal groups grown under short days flowered early compared to controls, whereas the opposite was observed under long days. Further, the expression of the florigen gene, Hd3a, which promotes flowering, increased in the tiller-removal group under short days compared to the control. Conversely, the expression of the OsMFT1 gene, which delays flowering and increases 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 to the corresponding control groups. Our findings on tillering and flowering responses to daylength provide a new perspective for the interpretation of studies related to the interaction between tillering and flowering in rice.