New molecular markers associated with theSw-5gene conferring resistance toTomato spotted wilt virusin tomato

SummaryTomato spotted wilt virus (TSWV) is an important Tospovirus causing significant crop losses in tomato throughout the World. Resistance to TSWV is conferred by the Sw-5 gene. Screening for TSWV resistance under field conditions, and the development of resistant tomato genotypes based on phenotype is not only time-consuming, but also inconclusive because of variable inoculum pressure in the field. The development of molecular markers for marker-assisted selection (MAS) would help to avoid this problem and facilitate the screening of a large number of independent breeding lines. However, for MAS to be successful, the molecular markers must be reliable, easy to use, and highly reproducible. We evaluated four potential PCR-based markers, developed based on Sw-5 locus-specific sequences. All four PCR-based markers were used successfully to identify resistant and susceptible tomato genotypes, consistent with the phenotypic data. Three (NCSw-003, NCSw-007, and NCSw-011) of the four molecular markers were co-dominant, whereas one (NCSw-012) was dominant. Two of the four molecular markers (NCSw-003 and NCSw-012) were sequence-characterised amplified region (SCAR) markers. The other two (NCSw-007 and NCSw-011) were cleaved amplified polymorphic sequence (CAPS) markers. All four markers were 19 kbp from CT 220, a previously reported molecular marker. All four DNA markers were novel and may be useful to tomato breeders wishing to screen for TSWV resistance in segregating populations.