RAD-seq-Based High-Density Linkage Map Construction and QTL Mapping of Biomass-Related Traits in Sorghum Using a Japanese Landrace Takakibi NOG.

: Sorghum (Sorghum bicolor (L.) Moench) grown locally by Japanese farmers is generically termed Takakibi, although its genetic diversity compared with geographically distant varieties or even within Takakibi lines remains unclear. To explore the genomic diversity and genetic traits controlling biomass and other physiological traits in Takakibi, we focused on a landrace, NOG in this study. Admixture analysis of 460 sorghum accessions revealed that NOG belonged to the subgroup that represented Asian sorghums, and it was only distantly related to American/African accession including BTx623. In an attempt to dissect major traits related to biomass, we generated a recombinant inbred line (RIL) from a cross between BTx623 and NOG, and we constructed a high-density linkage map, based on 3,710 single nucleotide polymorphisms obtained by restriction-site associated DNA sequencing (RAD-seq) of 213 RIL individuals. Consequently, 13 fine QTLs were detected on chromosomes 2, 3, 6, 7, 8, and 9, which included five QTLs for days to heading, three for plant height and total shoot fresh weight; and two for Brix. Furthermore, we identified two dominant loci for plant height as being identical to the previously reported dw1 and dw3. Together, these results corroborate the diversified genome of Japanese Takakibi, and the RIL population and high-density linkage map generated in this study will be useful for dissecting other important traits in sorghum.