QTL mapping for Fusarium wilt resistance based on the whole-genome resequencing and their association with functional genes in Raphanus sativus

Abstract Fusarium wilt is an important disease of radish, leading to severe decrease in yield and quality. In this study, we used 180 F2 populations derived from a cross between radish inbred lines ‘YR4’ and ‘YR18’ to construct linkage group for the detecting quantitative trait locus (QTLs) related to Fusarium oxysporum resistance. Four QTLs related to Fusarium oxysporum resistance were detected on two linkage groups. Of the two major loci for FW resistance, FoRsR7.1FOR59 was delimited to the 2.18-Mb physical interval on chromosome R07, with a high LOD value (5.17–12.84). Additionally, it explained 9.34%-27.97% of the phenotypic variation in three inoculation tests. The other major QTL, FoRsR9.3FOR59, was also detected in all inoculation tests, but it had a relatively low value (3.38–4.52) and explained 6.24%-8.82% of the phenotypic variation. On the basis of the re-sequencing data for the parental lines, we identified 5 R-related genes and 13 unknown genes with sequence variations at the gene and protein levels. A semi-quantitative RT-PCR analysis revealed Rs382940 (TIR-NBS type) and Rs382200 (RLK type) were expressed only in ‘YR4’ from 0 to 6 days after the inoculation. Moreover, Rs382950 (TIR-NBS-LRR type) was more highly expressed in ‘YR4’ from 3 and 6 days after the inoculation. Therefore, these three genes are likely important for the FW resistance of radish. We identified several markers based on the potential candidate genes. These gene set might be useful for breeding system to introduce the Fusarium wilt resistance loci from ‘YR4’ to improve increasing tolerance to Fusarium oxysporum.