Comprehensive analysis of SUSIBA2 rice: The low-methane trait and associated changes in soil carbon and microbial...

Rice cultivation is the primary source of anthropogenic methane (CH₄), which dramatically impacts global climate change. A growing body of evidence shows that optimizing photosynthate distribution is important for increasing rice yields and mitigating CH₄ emissions. Therefore, the molecular rice breeding with a barley HvSUSIBA2 gene that confers elevated photosynthate flux to grains, is predicted to enhance rice yield and mitigate CH₄ emissions in paddies. Here, in a series of field experiments with differences in growing season and rice variety, we show that SUSIBA2 rice reduced CH₄ emissions from paddies. SUSIBA2 rice grown in the early rice season and late rice season showed similar mitigation effects, with reduction rates of 50.98% for early rice and 50.97% for late rice. The reduction rate of SUSIBA2 rice during the winter rice season was significantly lower (22.26%) than those of other rice seasons. The reduction rates also varied between rice varieties, and SUSIBA2 japonica rice showed a more significant CH₄ mitigation effect than SUSIBA2 indica rice. Further yield-scaled CH₄ emission analyses indicated that the SUSIBA2 effect did not mitigate CH₄ emissions at the expense of yield. Compared with the wild type, SUSIBA2 rice significantly reduced soil organic carbon properties and the abundance of CH₄-related microbes, and altered methanogenic and methanotrophic communities, indicating that SUSIBA2 rice released less carbon to the soil, which reduced CH₄ production. Furthermore, a comparison of microbial communities between SUSIBA2 japonica and indica rice revealed different responses of methanogenic and methanotrophic communities, which may partly explain their differences in growth performance and CH₄ mitigation effect. Thus, our results show that SUSIBA2 rice substantially reduces CH₄ emissions and that SUSIBA2 can potentially mitigate the CH₄ emissions of japonica and indica rice under distinct cultivation conditions.