Molecular mapping of the PSS1 locus. A, Identification of SSLP markers linked to PSS1. Similar amplification patterns of SSLP markers CIW20 and CIW22 in susceptible bulks (S1, S2, S3 and S4) and Col-0 suggested that PSS1 is putatively linked to the two markers. Amplification patterns of a distantly mapped SSLP marker, LUGSSLP08 in the bulked DNA samples are shown as the control. B, Co-segregation of PSS1 with six molecular markers of the south arm of chromosome 3. Twenty-two susceptible F2:3 families except one, F2:3 family 93, showed same amplification patterns as in Col-0 for these markers. F2:3 family 93 showed recombination between PSS1 and SBP_20.71. C, Molecular map of the PSS1 region. Five SBP markers were developed for the PSS1 region that was mapped to the southern arm of chromosome 3.