Radish, Raphanus sativus(2n = 18), belonging to the brassicaceae family, is herbaceous plant with 1-2 years life cycle. It is cultivated worldwide for producing leafy and root vegetables. Although an economically important crop, the genetics of yield and quality traits, disease resistance are not well-studies. The major purpose of this project is development of molecular breeding technology in radish. In this project, quantitative trait loci (QTL) for Fusarium wilt resistance of radish were analyzed. To identify QTL, genetic linkage map of radish was constructed using F2 mapping population derived from a cross between two inbred lines, “DB01” (resistant) and “DB05” (susceptible). A total 319 markers have been mapped into nine linkage groups, covering 639.3cM with an average distance of 2cM between loci. QTL mapping detected 2 loci conferring Fusarium wilt resistance. Two QTLs were located on LG3 and LG7, respectively. The QTL of LG3, flanked by EAGGMCT6 and WALK500 marker, exhibited a LOD value ranging from 2.3 to 8.7, and the R2 (Phenotypic variations) ranging from 28 to 48% in four tests. This QTL was named qYR1. The QTL of LG7, flanked by EACCMCAC-202 and DCJ14-390 marker, exhibited a LOD value ranging from 6.2 to 10.6, and the R2 ranging from 42 to 55% in four tests. This QTL was named qYR2. The results of the QTL analysis may be useful in marker-assisted selection (MAS) of Fusarium wilt resistant radish cultivars.

Cytoplasmic male sterility caused by DCGMS (Dongbu cytoplasmic and genic male-sterility) cytoplasm and its nuclear restorer-of-fertility locus (Rfd1) with a linked molecular marker (A137) have been reported in radish (Raphanus sativus L.). To construct a linkage map of the Rfd1 locus, linked amplified fragment length polymorphism (AFLP) markers were screened using bulked segregant analysis. A 220-bp linked AFLP fragment sequence from radish showed homology with an Arabidopsis coding sequence. Using this Arabidopsis gene sequence, a simple PCR marker (A220) was developed. The A137 and A220 markers flanked the Rfd1 locus. Two homologous Arabidopsis genes with both marker sequences were positioned on Arabidopsis chromosome 3 with an interval of 2.4 Mb. To integrate the Rfd1 locus into a previously reported expressed sequence tag (EST)-simple sequence repeat (SSR) linkage map, the radish EST sequences located in three syntenic blocks within the 2.4-Mb interval were used to develop single nucleotide polymorphism (SNP) markers for tagging each block. The SNP marker in linkage group 2 co-segregated with male fertility in an F2 population. Using radish ESTs positioned in linkage group 2, five intron length polymorphism (ILP) markers and one cleaved amplified polymorphic sequence (CAPS) marker were developed and used to construct a linkage map of the Rfd1 locus. Two closely-linked markers delimited the Rfd1 locus within a 985-kb interval of Arabidopsis chromosome 3. Synteny between the radish and Arabidopsis genomes in the 985-kbp interval were used to develop three ILP and three CAPS markers. Two ILP markers further delimited the Rfd1 locus to a 220-kb interval of Arabidopsis chromosome 3.