Japonica-type Indica-Japonica hybrid rice increases yield with reduced CH4 and N2O emissions

Rice paddy fields serve as an important source of stable food supply and a notable contributor to atmospheric methane (CH4) and nitrous oxide (N2O). Rice cultivar selection acts as a pivotal factor in regulating greenhouse gas (GHGs) of CH4 and N2O emissions from rice paddy fields. However, little is known about how different types of rice cultivars affect CH4 and N2O emissions. In the study, three types of rice cultivars, including Japonica-type Indica-Japonica hybrid rice (JHR: ZJY1578 and JHY5), Indica-type hybrid rice (IHR: ZZY8 and JFY2), and inbred rice (IR: J67 and XS121), were selected to evaluate differences in mitigating GHGs. Results showed that the total CH4 and N2O emissions of two Japonica-type Indica-Japonica hybrid rice cultivars were 49.81-60.01 kg/ha and 0.67-0.83 g/ha, respectively, which were lower than those of the other two rice cultivar types. The total equivalent of carbon dioxide emissions of CH4 and N2O (TCO2-eq) of two Japonica hybrid rice significantly reduced by 16.7-46.9%, compared with the other two types of rice cultivars (IHR and IR). CH4 contributed 85.5-89.9% to the GWP, while 65.6-80.4% in the field of planting inbred rice. The reduction in GHGs emissions is mainly attributed to yield, available carbon and nitrogen contents, root morphological characteristics, and functional genes. Consequently, GHGs emissions in paddy fields could be mitigated by selecting or breeding cultivars with high yield, lower root exudates, and greater root porosity.