Mapping and marker-assisted selection for a gene for extreme resistance to potato virus Y

The chromosomal location of the major gene [Ry.sub.adg] controlling extreme resistance to potato virus Y (PVY) in Solanum tuberosum subsp. andigena was identified by RFLP analysis of a diploid potato population. A total of 64 tomato and potato RFLP markers were screened with the bulked segregant analysis (BSA) on segregants extremely resistant, hypersensitive or susceptible to PVY. Four markers TG508, GP125, CD17 and CT168 at the proximal end of chromosome XI showed close linkage with extremely resistant phenotypes. TG508 was identified as the closest marker linked with the [Ry.sub.adg] locus with the maximum map distance estimated as 2.0 cM. The 4 markers linked with the [Ry.sub.adg] locus were tested on independent tetraploid and diploid potato clones and were subsequently found useful for marker-assisted selection for plants containing [Ry.sub.adg].