Effect of rice panicle size on paddy field CH4 emissions

Developing large rice (Oryza sativa L.) panicles has been widely regarded as an effective approach to increasing rice yield. However, it is unclear whether panicle size affects CH4 emissions from rice fields, especially during the reproductive stage. Here, we conducted two experiments (rice variety and mutant) to examine the effects of rice panicle size on CH4 emissions. The variety experiment under field conditions at two sites showed that rice yield was significantly and positively correlated with the spikelet number. Mean CH4 emissions during the reproductive stage were significantly and negatively correlated with spikelet number. The rice mutant experiment under pot and field conditions using a wild-type rice variety (WT) and its mutant (Mutant) demonstrated that CH4 emissions were significantly lower in the former with large panicles than in the later with small panicles, during the reproductive and grain filling stages (P < 0.01), whereas the rice yields showed an opposite. Root exudates and soil dissolved organic C concentration were significantly lower under the WT than under the Mutant. Soil CH4 production potential and mcrA gene copy number of the soil under Mutant were significantly higher than those of the soil under WT. There was no significant difference in soil CH4 oxidation potential and pmoA gene copy number between soils of these two rice varieties. Our results suggest that developing large panicles would benefit rice production for high yield with low CH4 emission.