Domestication and association analysis of Hd1 in Chinese mini-core collections of rice

Hd1 is one of the major photoperiod genes with high degree of polymorphisms and contributes to rice (Oryza sativa L.) flowering in different light conditions. Ninety-two rice landraces and 111 accessions of common wild rice (O. rufipogon Griff.) from the mini-core collections in China were selected and sequenced to analyze the domestication process and association of Hd1 with rice flowering. Association analysis revealed that three insertions and two deletions in the coding region of Hd1 are highly correlated with flowering time in the short-day condition. Phylogenetic analysis suggested that the polymorphisms of Hd1 in wild rice are related to the distributions. Haplotype analysis indicated that Hd1 in most O. sativa L. ssp. indica Kato and O. sativa L. ssp. japonica Kato landraces evolved from different O. rufipogon groups containing functional Hd1 and that most aus varieties were domesticated from O. rufipogon containing the long-insertions Hd1, suggesting multiple origins of Hd1. Moreover, O. rufipogon which contained the long-insertions Hd1 could only be found in Southern China, implying that Southern China might be one of the domestication centers of O. sativa. This study provides much significant information to aid further understanding of the domestication process of Hd1.