MAPPING AND MARKER-ASSISTED SELECTION FOR A GENE FOR EXTREME RESISTANCE TO POTATO-VIRUS-Y

The chromosomal location of the major gene Ry(adg) controlling extreme resistance to potato virus Y (PVY) in Solanum tuberosum subsp. andige na was identified by RFLP analysis of a diploid potato population. A t otal of 64 tomato and potato RFLP markers were screened with the bulke d segregant analysis (BSA) on segregants extremely resistant, hypersen sitive or susceptible to PVY. Four markers TG508, GP125, CD17 and CT16 8 at the proximal end of chromosome XI showed close linkage with extre mely resistant phenotypes. TG508 was identified as the closest marker linked with the Ry(adg) locus with the maximum map distance estimated as 2.0 cM. The 4 markers linked with the Ry(adg) locus were tested on independent tetraploid and diploid potato clones and were subsequently found useful for marker-assisted selection for plants containing Ry(a dg).