Submitted to: Journal of Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/1995
Publication Date: N/A
Interpretive Summary: Genome mapping of peaches, by revealing the genes contained in parent trees, will allow breeders to more rapidly develop new and improved peach varieties. The first step in genome mapping is to develop a basic map which marks some genes on each chromosome. To develop this initial gene map, we used a cross between two very different peach types, a dwarf and a columnar type, which also differed in flower and fruit characteristics. We analyzed the DNA extracted from the offspring of this cross and matched the differences in DNA to differences in tree growth habit, fruit and flower types. In this way, these traits were "marked" on a gene map and the genes assigned to particular chromosomes. With this skeletal map now developed, work is continuing to map many more peach genes.
Technical Abstract: We have constructed a genetic linkage map of peach consisting of RFLP, RAPD and morphological markers based on 71 F(2) individuals derived from the self-fertilization of four F(1) individuals originating from a cross between 'New Jersey Pillar' and KV 77119 designated the West Virginia (WV) family. This progeny set was chosen because parental genotypes exhibit variation in canopy shape, fruit flesh color, and flower petal color, size and number. The segregation of 65 markers comprised of 46 RFLP loci, 12 RAPD loci and 7 morphological loci was analyzed. Low copy genomic and cDNA probes were used in the RFLP analysis. The current genetic map for the WV family contains 47 markers assigned to eight linkage groups, which cover 430 centiMorgans (cM) of the peach nuclear genome. The average distance between two adjacent markers is 9 cM. Linkage was detected between Pillar (Pi) and double flowers (Dl). RFLP markers linked to Pi and flesh color (Y) loci were found. Eighteen markers remain unassigned. Because of this, Pi and 8 other markers that deviated significantly from the expected Mendelian ratios (e.g., 1:2:1 or 3:1) were not eliminated from the linkage analysis. RFLP markers developed with the WV family were tested in two other unrelated peach families. Forty-three percent and 56% of genomic clones detecting RFLPs in the WV family detected polymorphisms among 39 peach cultivars examined. Unique fingerprint patterns were created for all the cultivars using only six low-copy probes. This suggests that RFLP markers from the WV family have a high probability of being polymorphic in crosses generated with other peach cultivars, making them ideal for anchor loci.