DEVELOPMENT OF PCR ASSAYS DIAGNOSTIC FOR RFLP MARKER ALLELES CLOSELY LINKED TO ALLELES GRO1 AND H1, CONFERRING RESISTANCE TO THE ROOT CYST-NEMATODE GLOBODERA-ROSTOCHIENSIS IN POTATO

The use of RFLPs for marker-assisted selection schemes in potato breeding is hampered by the fact that RFLP technology requires good laboratory facilities, technical skills and high financial input. Marker technology based on the polymerase chain reaction (PCR) would facilitate the application of marker-assisted selection. PCR assays have been developed that are diagnostic for RFLP alleles at two marker loci, CP56 and CP113, which are closely linked in coupling to the nematode resistance alleles Gro1 on chromosome VII and H1 on chromosome V of potato. By comparing DNA sequences among different marker alleles, point mutations were identified based on which allele-specific oligonucleotides were designed. Using allele-specific oligonucleotides as primers in PCR reactions, single-marker alleles were amplified by which the inheritance of Gro1 and H1 could be followed in crosses of diploid potato genotypes containing the genetically characterized Gro1 or H1 resistance allele. When tested in 136 unrelated tetraploid potato varieties, the marker allele indicative of Gro1 was not correlated with the presence of nematode resistance. The marker allele indicative for the H1 resistance allele was correlated with nematode resistance. It was, however, found in four varieties only of the 136 tested.