Different patterns of genealogical relationships found in the two major QTLs causing reduction of seed shattering during rice domestication.

The three quantitative trait loci (qSH1, qSH3, and qSH4) causing reduction of seed shattering were investigated to examine their relative importance during rice domestication. The qSH1 and qSH4 loci showed a distinct effect on the reduction of shattering, compared with the qSH3 locus. Fine mapping and sequence analysis strongly suggested that the qSH1 and qSH4 loci are the same as the recently reported genes. A non-shattering allele at qSH1 drastically changed the shattering phenotype to a non-shattering phenotype even in the presence of shattering alleles at the qSH3 and qSH4 loci, showing that qSH1 is genetically epistatic to the other loci. The level of the reduction in sequence diversity was compared between the qSH1 and qSH4 regions. The sequence diversity was severely reduced in the qSH1 region of Oryza sativa subsp. japonica compared with that of O. sativa subsp. indica, despite that the level of diversity was similarly reduced at the qSH4 region in the 2 subspecies. Phylogenetic reconstruction based on the combined sequences of the flanking sites showed different patterns in the 2 subspecies. The 2 subspecies formed a single clade with respect to qSH4, whereas they were separated into different lineages with respect to qSH1, suggesting that these loci had different histories during rice domestication.