High-yield Rice Emits up to 70% Less Methane

Global methane emissions are expected to increase as global warming continues and the human population grows. Rice, one of the world's key staples, is responsible for 12 percent of global methane emissions. Now, an international team of scientists has identified chemical compounds released by rice roots that determine how much methane the plants emit.

In their paper published in Molecular Plant, the scientists report that this information enabled them to breed a new strain of rice that emits up to 70 percent less methane. The methane emission from rice paddies is produced by microbes that break down organic compounds released from rice plant roots. These compounds, known as "root exudates," feed soil microbes, which in turn aid plant growth by releasing nutrients that the plants can absorb. To identify which root exudate compounds are converted into methane, the researchers compared root exudates from two different rice varieties—SUSIBA2, a low-methane emitting GMO variety, and Nipponbare, a non-GMO cultivar with average methane emissions.

The scientists found that SUSIBA2 roots produced significantly less fumarate and noted a correlation between the amount of fumarate secreted and the abundance of methane-releasing archaea or "methanogens" in the surrounding soil. In rice plants with added fumarate in the soil, methane emissions increased. Further study showed that SUSIBA2 plants also release significantly more ethanol. Adding ethanol to the soil surrounding rice plants reduced methane emissions.

When the research team grew these low fumarate and high ethanol (LFHE) rice varieties at various field sites throughout China, the LFHE rice produced 70 percent less methane on average compared with the elite variety from which it was bred. The LFHE crops also have high yields at yields—8.96 tons/hectare on average, compared to the 2024 global average of 4.71 tons/hectare.

For more details, download the open-access paper in Molecular Plant.