MARKER ENRICHMENT AND HIGH-RESOLUTION MAP OF THE SEGMENT OF POTATO CHROMOSOME-VII HARBORING THE NEMATODE RESISTANCE GENE GRO1

The dominant allele GRo1 confers on potato resistance to the root cyst nematode Globodera rostochiensis. The Gro1 locus has been mapped to c hromosome VII on the genetic map of potato, using RFLP markers. This m akes possible the cloning of Gro1 based on its map position. As part o f this strategy we have constructed a high-resolution genetic map of t he chromosome segment surrounding Gro1, based on RFLP, RAPD and AFLP m arkers. RAPD and AFLP markers closely linked to Gro1 were selected by bulked segregant analysis and mapped relative to the Gro1 locus in a s egregating population of 1105 plants. Three RFLP and one RAPD marker w ere found to be inseparable from the Gro1 locus. Two AFLP markers were identified that flanked Gro1 at genetic distances of 0.6 cM and 0.8 c M, respectively. A genetic distance of 1 cM in the Gro1 region corresp onds to a physical distance of ca. 100 kb as estimated by long-range r estriction analysis. Marker-assisted selection for nematode resistance was accomplished in the course of constructing the high-resolution ma p. Plants carrying the resistance allele Gro1 could be distinguished f rom susceptible plants by marker assays based on the polymerase chain reaction (PCR).