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.