The Grp1 locus confers broad-spectrum resistance to the potato cyst nematode species Globodera pallida and G. rostochiensis and is located in the GP21-GP179 interval on the short arm of chromosome V of potato.
A high-resolution map has been developed using the diploid mapping population RHAM026, comprising 1536 genotypes. The map showed that G. pallida and G. rostochiensis resistance could not be separated and are located between marker SPUD838 and TG432. Sequence information from the same region in other potato genotypes reveal the presence of resistance gene homologues belonging to the NBS-LRR class.
To be able to identify the gene or genes underlying Grp1 resistance, a physical map needs to be constructed. To do this, we can make use of sequence information in other potato genotypes to develop markers closer to the Grp1 gene. The closest markers will be used to screen a BAC library of the resistant potato genotype.