Identification of QTLs Controlling Radish Root Shape Using Multiple Populations

Root shape is an important characteristic that affects the commodity of radish (Raphanus sativus L.), which can be measured using the ratio of root length (RL) to root diameter (RD). Although it is known that root shape is controlled by quantitative trait loci (QTLs), reliable QTLs for radish root shape are still lacking. In the present study, we used three F2 populations (1902, 1908 and 1909) derived from the crossing of five radish cultivars with highly divergent root shapes to perform QTL-seq. A total of 1282 individuals of the three F2 populations were measured to determine the root length and maximum diameter. High-depth resequencing of six extreme pools and five parents was performed, and QTL-seq was used to detect the QTLs controlling the radish root shape. We identified seven QTLs for root shape distributing on five radish chromosomes (R1, R2, R4, R5 and R7), among which rs7.1 and rs7.2 had an overlap of 1.02 Mb (13.79–14.81 Mb). In addition, two QTLs, rs4.1 and rs4.2, were adjacent to each other on chromosome R4. In conclusion, this study provides an important foundation for the fine mapping and functional analysis of the QTLs controlling the root shape and breeding for root shape in radish.