Identification of quantitative trait loci controlling radish root shape using QTL-seq

Abstract Root shape is an important characteristic that affects the commodity of radish (Raphanus sativus L.). This trait can be measured using the ratio of root length (RL) to root diameter (RD). Although it is known that root shape is controlled by multiple quantitative trait loci (QTLs), reliable QTLs for regulating radish root shape are still lacking. In the present study, three F2 populations were constructed by crossing five radish cultivars with significant differences in root shape. A total of 1282 F2 individuals were measured to determine the root length and maximum diameter. Highdepth resequencing of six extreme pools and five parents was performed, and the bulk-segregant approach coupled with whole genome re-sequencing (QTL-seq) was used to detect QTLs. The results showed that radish root shape was positively correlated with root length. Seven QTLs distributed on five radish chromosomes (R1, R2, R4, R5, and R7) were identified for root shape, two of which (rs7.1 and rs7.2) had an overlap of 1.02 Mb (13.79-14.81 Mb). In addition, rs4.1 and rs4.2 were adjacent to each other on the R4 chromosome. The present study provides an important foundation for the fine mapping and functional analysis of root shape QTLs as well as cultivar breeding for root shape.