GENETIC-LINKAGE MAPPING IN PEACH USING MORPHOLOGICAL, RFLP AND RAPD MARKERS

We have constructed a genetic linkage map of peach [Prunus persica (L. ) Batsch] consisting of RFLP, RAPD and morphological markers, based on 71 F-2 individuals derived from the self-fertilization of four F-1 in dividuals of a cross between 'New Jersey Pillar' and KV 77119. This pr ogeny, designated as the West Virginia (WV) family, segregates for gen es controlling canopy shape, fruit flesh color, and flower petal color , size and number. The segregation of 65 markers, comprising 46 RFLP l oci, 12 RAPD loci and seven morphological loci, was analyzed. Low-copy genomic and cDNA probes were used in the RFLP analysis. The current g enetic map for the WV family contains 47 markers assigned to eight lin kage groups covering 332 centi-Morgans (cM) of the peach nuclear genom e. The average distance between two adjacent markers is 8 cM. Linkage was detected between Pillar (Pi) and double flowers (DI). RFLP markers linked to Pi and flesh color (gamma) loci were also found. Eighteen m arkers remain unassigned. The individuals analyzed for linkage were no t a random sample of all F-2 trees, as an excess of pillar trees were chosen for analysis. Because of this, Pi and eight 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. Genomic clones that detect RFLPs in the WV family also detect significant levels of polymorphism among the 34 peach cultivars examined. Unique fingerprint patterns were created for all the cultivars using only six clones det ecting nine RFLP fragments. This suggests that RFLP markers from the W V family have a high probability of being polymorphic in crosses gener ated with other peach cultivars, making them ideal for anchor loci. Th is possibility was examined by testing RFLP markers developed with the WV family in three other unrelated peach families. In each of these t hree peach families respectively 43%, 54% and 36% of RFLP loci detecte d in the WV family were also polymorphic. This finding supports the po ssibility that these RFLP markers may serve as anchor loci in many oth er peach crosses.