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 breed ing is hampered by the fact that RFLP technology requires good laborat ory facilities, technical skills and high financial input. Marker tech nology based on the polymerase chain reaction (PCR) would facilitate t he application of marker-assisted selection. PCR assays have been deve loped that are diagnostic for RFLP alleles at two marker loci, CP56 an d CP113, which are closely linked in coupling to the nematode resistan ce alleles Gro1 on chromosome VII and H1 on chromosome V of potato. By comparing DNA sequences among different marker alleles, point mutatio ns were identified based on which allele-specific oligonucleotides wer e designed. Using allele-specific oligonucleotides as primers in PCR r eactions, single-marker alleles were amplified by which the inheritanc e of Gro1 and H1 could be followed in crosses of diploid potato genoty pes containing the genetically characterized Gro1 or H1 resistance all ele. When tested in 136 unrelated tetraploid potato varieties, the mar ker allele indicative of Gro1 was not correlated with the presence of nematode resistance. The marker allele indicative for the H1 resistanc e allele was correlated with nematode resistance. It was, however, fou nd in four varieties only of the 136 tested.