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

Abstract

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 F₂ 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 F₂ 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.