Abstract
Day-length is one of the major environmental factors used by plants to determine optimal time to flower. We study the variation of photoperiodic flowering pathway among the various rice cultivars. To investigate natural variation in rice (Oryza sativa L.), we employed the world rice core collection that was generated by NIAS gene bank. The core collection contains the maximum possible genetic diversity of rice with minimum of cultivars. In rice, previous reports showed that Hd3a is considered as a floral activator gene. We therefore investigate the expression level of Hd3a and days to flowering among the core collection. The results showed that strong correlation was observed between levels of Hd3a expression and flowering time. In addition, we investigate night-break effect on Hd3a expression among the core collection. We found that almost all cultivars possess the NB sensitivity. This result suggests that NB effect is a universal phenomenon among rice.
