Hd1, Ghd7, and DTH8synergistically determine the rice heading date and yield-related agronomic traits

Heading date determines the seasonal and regional adaptation of rice (Oryza sativaL.) varieties and is mainly controlled by photoperiod sensitivity (PS). The core heading date genes Hd1, Ghd7, DTH8, and PRR37act synergistically in regulating the PS. In this study, we systematically analyzed the heading date, PS, and agronomic traits of eight homozygous lines with various combinations of Hd1, Ghd7, and DTH8alleles in the prr37background under long-day (LD) and short-day (SD) conditions, respectively. We found that Hd1alone promotes heading, regardless of the day length. However, under LDs, Hd1suppresses flowering, in coordination with functional Ghd7or with Ghd7and DTH8. These loci cooperate to negatively regulate the Ehd1-Hd3a/RFT1pathway and delay heading. Under SDs, Hd1competes with various heading suppressors to promote heading. Therefore, the dual function of Hd1is vital for PS. The lines carrying Hd1alone show reduced plant height with fewer primary and secondary branches in panicles. Lines carrying Ghd7and DTH8(with hd1) showed delayed heading and improved agronomic traits. Overall, our results revealed the regulation of rice PS flowering using the core heading date genes and their effects on agronomic traits, providing valuable information for the selection of rice varieties for adaptation to different light and temperature conditions.