Fusarium crown root rot (FCRR) is a severe fungal disease caused by Fusarium oxysporum f. sp. radicis-lycopersici (FORL) in tomato. Resistance to FORL is conferred by single dominant locus Frl on chromosome 9, but its precise genomic location is not clearly determined. In this study, detailed location of Frl was assessed by using a set of molecular markers physically anchored on Chr.9 and F2 and RIL population derived from FORL-resistant inbred AV107-4 (S.lycopersicum) x susceptible L3708 (S. pimpinellifolium). Bioassay of the two populations with a FORL strain isolated from Korea resulted in single dominant heritance of the resistance. Two SCAR and 11 CAPS markers encompassing 3.6Mb~72Mb of Chr.9 were developed from the Tomato-EXPEN 2000 map and SolCAP SNP-array analysis. These markers were genotyped on 345 F2 plants. A high level of cosegregation with the resistance were observed for 5 markers which were mapped at a large physical interval of 5.1Mb (T1212) to 46.4Mb (SSR237), indicating that genetic recombination was highly suppressed in this region. Cosegregation of these markers with Frl was confirmed by using 126 RILs. The results implied that, in contrast with the previously reported long arm, Frl is present on a pericentromeric region of short arm of Chr. 9, in which crossing-over is severely suppressed. The marker set was further tested on 12 FORL-resistance or susceptibility commercial cultivars. Unlike the biparental populations, frequent linkage break was observed for T1212 and D4 in commercial cultivars. T1212 and D4 showed 50% and 100% match with the phenotype, respectively. D4, a CAPS, was converted to a high resolution melting (HRM) marker and tested on 55 breeding lines from private seed companies (Fig.3). All breeding lines showed the HRM genotype for resistance allele, indicating that D4 can be useful for selecting FORL-resistance tomato plants.

• Bichsaem Kim(Department of Horticultural Bioscience, Pusan National University)
• Jihyun Hwang(Department of Horticultural Bioscience, Pusan National University)
• Joon Young Kim(Department of Plant Science, Gangneung-Wonju National University)
• Byung Sup Kim(Department of Plant Science, Gangneung-Wonju National University)
• Sung Ran Min(Plant Systems Engineering Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB))
• Huijung Jung(Department of Horticulture, Sunchon National University)
• Ill-Sup Nou(Department of Horticulture, Sunchon National University)
• Younghoon Park(Department of Horticultural Bioscience, Pusan National University)