A PROCEDURE FOR OBTAINING ADDITIONAL REPULSION PHASE LINKAGE INFORMATION IN F2 FAMILIES

Abstract

F2 families provide less linkage information than testcross families for markers in repulsion phase orientation. However, generation of testcross families is often more difficult than the generation of F2 families in self-pollinating species. A procedure was developed for determining map position for markers within repulsion phase linkage groups generated in F2 families of peach. A genomic map consisting of homolog specific linkage groups of RAPD markers was generated in an F2 family obtained from NC 174RL × `Pillar'. Numerous markers were identified that mapped to either allele of the Gr (red leaf) locus. The relative position of markers in these homolog specific groups was determined by characterizing the segregation distortion of the repulsion phase RAPD markers in a sample of 96 progeny homozygous recessive grgr. Repulsion phase markers within 20cM of gr deviated from a 3:1 segregation ratio. Individuals homozygous recessive for both gr and repulsion phase markers were then genotyped for coupling phase RAPD markers to facilitate generation of a graphical genotype. This graphical genotype information was used to determine orientation of the homolog specific linkage groups and to determine map order within the repulsion phase linkage group.