MAPPING OF THE CYST-NEMATODE RESISTANCE LOCUS GPA2 IN POTATO USING A STRATEGY BASED ON COMIGRATING AFLP MARKERS

The nematode resistance locus Gpa2 was mapped on chromosome 12 of pota to using information on the genomic positions of 733 known AFLP marker s. The minimum number of AFLP primer combinations required to map Gpa2 was three. This demonstrates that a reference collection of potato AF LP markers may be a valuable tool-for mapping studies in potato. By us e of RFLP probes, Gpa2 was more precisely mapped at the distal end of chromosome 12. Gpa2 confers resistance to a distinct group of populati ons of the potato cyst nematode Globodera pallida and originates from the same potato accession as locus HI, conferring resistance to pathot ype Ro(1) of G. rostochiensis. This study shows that these two nematod e resistance loci are unlinked and that Gpa2 is linked to the Rx1 locu s conferring resistance to potato virus X. The efficiency of AFLPs for genetic mapping of a highly heterozygous crop like potato is discusse d and compared with the RFLP technique.