Regulation mechanism and breeding application of rice floret-opening-time

Rice (Oryza sativa L.) is a strictly autogamous crop. Floret-opening-time (FOT) is an important agronomic trait in rice, which is complicatedly regulated by internal factors (plant hormones, genetic factors, etc.) and external environmental factors (temperature, light, humidity, CO₂ concentration, etc.). Floret opening at an appropriate time is very critical for the success of rice reproduction. If the floret opens too early in the morning, rice is vulnerable to pathogen infection caused by low temperature and heavy dew. In contrast, if the floret opens too late, the seed setting of rice would be severely affected by high temperature in the afternoon. Moreover, synchronized FOT between the male and female parents is a key requirement for successful production of hybrid seeds. In this review, we summarize the research progresses on the regulation of FOT in rice, mainly focusing on the aspects including the structural basis, physiological basis, genetic basis and molecular mechanism of controlling rice floret opening. We also present some important topics for future in-depth studies of FOT. Finally, we discuss the value of modulating FOT trait for improving rice production and indica-japonica inter-subspecies hybrid rice breeding.