Characterization of flo4-6, a Novel cyOsPPDKB Allele Conferring Floury Endosperm Characteristics Suitable for Dry-Milled Rice Flour Production

Rice cultivars with floury endosperm provide a useful raw material for producing dry-milled rice flour, helping to enhance the processed rice food industry. To expand the genetic resources for breeding floury endosperm rice cultivars, we developed Samkwang(SA)-flo3 (SK-flo3), a floury endosperm mutant line derived from the chemical mutagenesis of Samkwang, an elite Korean japonica rice cultivar. Compared with Samkwang, SK-flo3 showed significantly lower grain hardness, which is suitable for producing dry-milled flour without the soaking and drying processes required in regular wet rice milling. The dry-milled flour of SK-flo3 exhibited excellent physicochemical properties with less damaged starch and finer flour particles relative to Samkwang. Genetic analyses revealed a G-to-A point mutation in exon 7 of cyOsPPDKB, substituting glycine with aspartic acid as a causative mutation for the floury endosperm of SK-flo3. We named this allele flo4-6 and developed a molecular marker to efficiently transfer it to commercial rice cultivars. Our results provide useful genetic resources and information for developing specialty rice cultivars for high-quality rice flour production with reduced milling costs.