A SCAR MARKER LINKED TO THE TOMV RESISTANCE GENE, TM2(2), IN TOMATO

A polymerase chain reaction (PCR)-based co-dominant marker was develop ed which is tightly linked to Tm2(2). This dominant locus confers resi stance to ToMV in tomato. Random-amplified-polymorphic DNA (RAPD) scre ening was carried out with DNA from ToMV-susceptible and resistant tom ato near-isogenic lines. A polymorphic band linked to ToMV resistance was observed. The polymorphic fragment was cloned and the DNA sequence s of both ends determined. Specific PCR primers were designed from the se sequences. PCR amplification with the specific primers resulted in an amplified band (SCAR) in both susceptible and resistant tomato line s. The amplified band from the susceptible lines could, however, be di scerned from that of the resistant ones after cleavage with the restri ction enzyme Hind III. In an F-2 population of 90, the polymorphic mar kers co-segregated with susceptibility or resistance, as determined by biological assays for ToMV resistance. The reported SCAR marker is li nked to ToMV resistance not only in cultivars derived from American li neage, but also from European lineage. This method enables the distinc tion of homozygous and heterozygous individual plants in segregating p opulations, and provides a convenient and rapid assay for both selecti on and quality control during breeding programs and hybrid seed produc tion, respectively.