Low-methane rice

#The present invention generally relates to low-methane rice and in particular to rice plant material capable of reducing methane emissions from rice paddies.

#Rice is a main staple food in the world and over half of the human population eats rice as a staple food. Yearly production of rice is around 700 million tons. Rice agriculture is the largest anthropogenic source of atmospheric methane. The scenario is exacerbated by the expanding rice cultivation to meet the escalating demand for food in the coming decades. In fact, atmospheric methane has made a 20% contribution to global warming since preindustrial times.

#Therefore, there is an urgent need to establish sustainable technologies that allow for intensification of rice production while reducing methane fluxes from paddy fields. Strategies for developing high-yielding rice as a mean to curb methane emissions were proposed in 2002. However, as of yet no such “high-yield-low-methane” rice has been reported.

#The embodiments, together with further objects and advantages thereof, may best be understood by making reference to the following description taken together with the accompanying drawings, in which:

#FIG. 1. Schematic representation of rice growth conditions. Temporal sampling is at Week 4, Week 6, Week 8, Week 13 and Ripening and spatial sampling at different temporal time is indicated as Horizontal Positions 1-3 (H. Position 1-3) and Vertical Position 1-3 (V. Position 1-3).

#FIG. 2. Phenotyping of rice roots at Week 4, 6 and 7. Photographs of rice roots (FIG. 2A) and root length (FIG. 2B). *P<0.05 is shown for significant differences between SUSIBA2 rice and Nipponbare. Bars=2 cm.

#The present invention generally relates to low-methane rice and in particular to rice plant material capable of reducing methane emissions from rice paddies.

#The present invention is based on the discovery that the interaction between rice plants and methanogens is based on organic acids and in particular fumarate and other organic acids of the Krebs cycle, such as malate, secreted from the roots of the rice plants. The secreted organic acids, such as fumarate and/or malate, is in turn used as substrate by the methanogens for methanogen propagation. Hence, by reducing secretion of, in particular, fumarate from the roots of the rice plants, the amount of methanogens present in the soil in connection with the rice roots is significantly reduced as is the methane emission from the methanogens. As a consequence, a reduction in fumarate secretion from the rice roots is an effective means of achieving a low-methane rice that leads to a reduction in methane emissions from rice paddies.

#Hence, an aspect of the invention relates to a method of producing a low-methane rice plant. The method comprises modifying a rice plant material for reduced organic acid secretion from roots of the rice plant material or from roots of a rice plant obtained from the rice plant material. In this embodiment, an amount of organic acids secreted from the roots of the rice plant material or of the rice plant is equal to or less than 90% of an amount of the organic acids secreted from roots of a corresponding wild-type rice plant lacking the modification. The reduced organic acid secretion from the roots of the rice plant material or of the rice plant induces a reduction in methane emission from methanogens present in connection with the roots of the rice plant material or of the rice plant.