Atmospheric methane is the second most important greenhouse gas after carbon dioxide, and is responsible for about 20% of the global warming effect since pre-industrial times1,2. Rice paddies are the largest anthropogenic methane source and produce 7–17% of atmospheric methane2,3. Warm waterlogged soil and exuded nutrients from rice roots provide ideal conditions for methanogenesis in paddies with annual methane emissions of 25–100-million tonnes3,4. This scenario will be exacerbated by an expansion in rice cultivation needed to meet the escalating demand for food in the coming decades4. There is an urgent need to establish sustainable technologies for increasing rice production while reducing methane fluxes from rice paddies. However, ongoing efforts for methane mitigation in rice paddies are mainly based on farming practices and measures that are difficult to implement5. Despite proposed strategies to increase rice productivity and reduce methane emissions4,6, no high-starch low-methane-emission rice has been developed. Here we show that the addition of a single transcription factor gene, barley SUSIBA2 (refs 7, 8), conferred a shift of carbon flux to SUSIBA2 rice, favouring the allocation of photosynthates to aboveground biomass over allocation to roots. The altered allocation resulted in an increased biomass and starch content in the seeds and stems, and suppressed methanogenesis, possibly through a reduction in root exudates. Three-year field trials in China demonstrated that the cultivation of SUSIBA2 rice was associated with a significant reduction in methane emissions and a decrease in rhizospheric methanogen levels. SUSIBA2 rice offers a sustainable means of providing increased starch content for food production while reducing greenhouse gas emissions from rice cultivation. Approaches to increase rice productivity and reduce methane emissions as seen in SUSIBA2 rice may be particularly beneficial in a future climate with rising temperatures resulting in increased methane emissions from paddies9,10.
The sequence of construct containing HvSBEIIb p:HvSUSIBA2 has been deposited in GenBank under accession number KR935231.
Special thanks to S. Stymne. We would also like to thank B. Müller, X. Feng, M. Erikson, L. Sun, S. Isaksson, J. Ascue and S. Mayer for their help in determining concentrations of methane and methanogens, and B. Ingemarsson for discussions concerning the work layout. This work was funded by the following organisations and foundations: The Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning (Formas) for Project No 219-2014-1172; the joint Formas/Sida-funded programme (Project No 220-2009-2069) on sustainable development in developing countries; the SLU Lärosätesansökan Programme (TC4F) for Team 4 supported by Vinnova; the Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning (Formas) under the Strategic Research Area for the TCBB Programme; National Natural Science Foundation of China (projects no 30771298 and no 31370389); the SLU programme BarleyFunFood; the Carl Trygger Foundation for Project No CTS 11: 450; funding in part by the US Department of Energy Contract DE-AC05-76RL01830 with the Pacific Northwest National Laboratory.
Extended data figures
This file contains Supplementary Table 2.