A novel genotype DATTO5 developed using the five genes exhibits the fastest heading date designed in rice

The optimization of heading date is a key aspect for maximizing grain productivity in cereal crops including rice. The combinations of genes for heading date, a quantitative trait, are a major driver in the wide adaptability of cultivated rice worldwide. Here, we identified a novel QTL, qDTH3 (quantitative trait locus for days-to-heading on chromosome 3), for early flowering time in the F(2) population derived from a cross between Hoshinoyume (HS) and Daichinohoshi (DH) among local rice populations with extremely early heading date. The DH allele at qDTH3, qDTH3(DH), headed 2.7 days earlier than the HS allele at qDTH3, qDTH3(HS). We sought to design a genotype for earlier heading date by pyramiding of five heading date genes. We designated this aggregate of the five genes as DATTO5. Plants with DATTO5 were selected from the F(2) population derived from a cross between DH and HShd5, which is a near-isogenic line carrying a loss-of-function of days to heading 8 in a genetic background of HS. Plants with DATTO5 exhibited earlier heading date but reduced fitness, including shorter culm and panicle length and fewer seeds compared with HS, as a representative local rice variety with extremely early heading date.