Plant Genome I Conference
Town & Country Conference Center, San Diego, CA, November, 1992.
PG-I: 78pg1
A PROCEDURE FOR OBTAINING ADDITIONAL REPULSION PHASE LINKAGE
INFORMATION IN F2 BREEDING POPULATIONS
Jose Chaparro 1, Dennis Werner 1, Dave O'Malley 2, and
Ronald Sederoff 2, Departments of Horticulture 1 and Forestry
2, North Carolina State University, Raleigh, NC 27695.
The use of F2 populations for the mapping of dominant
markers has been avoided due to the limited linkage information
obtained from repulsion phase markers. The testcross has been
used extensively because it provides more linkage information
than an F2 when equal numbers of progeny are used. However, the
generation of testcross populations requires more work than the
generation of F2 populations in self-pollinating species. As
part of a mapping project in peach we have developed a procedure
for determining the position of genes or markers of interest
within repulsion phase linkage groups generated in F2
populations. A genomic map is generated using a sample of 96
progeny from a large segregating F2 population (n > 400). With
dominant markers, only markers linked in coupling will be
assigned to the same linkage group. Therefore, the genomic map
consists of homolog specific linkage groups. The corresponding
homologous linkage groups (coupling/repulsion) are identified by
observing the segregation of repulsion phase markers in a sample
of 96 progeny homozygous recessive for the marker of interest.
Repulsion phase markers within 20 cM of the marker of interest
will deviate from a 3:1 segregation ratio. Individuals
homozygous recessive for both the trait of interest and repulsion
phase markers are genotyped for coupling phase markers to
generate a graphical genotype. The graphical genotype
information is used to determine the orientation of the linkage
groups and the region within the repulsion phase linkage group
where the locus of interest is located.
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