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  • Author or Editor: R.E. Ballard x
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Abstract

Black, purple, and tan discolorations have been found within red-pigmented areas of the peach fruit skin. Scanning electron and light micrographs show damage caused by defuzzing and roller drying, which could facilitate entry of causal agents associated with peach skin discoloration. Comparisons of reflectance and transmittance spectra (380-700 nm) of discolored (purple) and nondiscolored (red) peaches show the mean reflectance value for discolored peaches is 100% darker than nondiscolored peaches. However, transmittance spectra of acidified extracts of discolored and nondiscolored peach skins are similar throughout these wavelengths. Extracted pigment color was altered by pH changes and metallic ion concentration. At low pH, discoloration may be caused by ion complexing with anthocyanin pigment. At high pH, discoloration may result from alkaline hydrolysis of the pigment molecule.

Open Access

We have developed a highly saturated genetic linkage map in peach (diploid, 2n = 16) using two separate crosses. The first population consists of 48 randomly selected F2 individuals which were generated by selfing an F1 from the cross of `New Jersey Pillar' x KV 77119. This progeny set exhibits segregation for gross morphological traits including: canopy shape, fruit flesh color, and flower petal color, size, and number. The second population contains 48 F2 progeny derived from the cross of `Suncrest' x `Bailey'. These progeny segregate for quality traits such as fruit diameter, weight, flesh color, cling vs. free stone, soluble solids, pH of juice extract, and fruit developmental period. Nine linkage groups were identified in the first cross, which cover 590 cM of the genome. In the second cross, eight linkage groups were found that contain several significant chromosomal intervals contributing to fruit quality characteristics by QTL analysis. Anchor loci present in both maps were used to join the linkage groups to create a single combined map of the peach genome. Physical mapping is currently underway to assign the each linkage group to the appropriate chromosome.

Free access

Microsatellite or simple sequence repeat (SSR) markers were developed from Rosa wichurana Crépin to combine two previously constructed tetraploid rose (Rosa hybrida L.) genetic maps. To isolate SSR-containing sequences from rose a small-insert genomic library was constructed from diploid Rosa wichurana and screened with several SSR probes. Specific primers were designed for 43 unique SSR regions, of which 30 primer pairs gave rise to clear PCR products. Seventeen SSR primer pairs (57%) produced polymorphism in the tetraploid rose 90-69 mapping family. These markers were incorporated into existing maps of the parents 86-7 and 82-1134, which were constructed primarily with AFLP markers. The current map of the male parent, amphidiploid 86-7, consists of 286 markers assigned to 14 linkage groups and covering 770 cm. The map of the female tetraploid parent, 82-1134, consists of 256 markers assigned to 20 linkage groups and covering 920 cm. Nineteen rose SSR loci were mapped on the 86-7 map and 11 on the 82-1134 map. Several homeologous linkage groups within maps were identified based on SSR markers. In addition, some of the SSR markers provided anchoring points between the two parental maps. SSR markers were also useful for joining small linkage groups. Based on shared SSR markers, consensus orders for four rose linkage groups between parental maps were generated. Microsatellite markers developed in this study will provide valuable tools for many aspects of rose research including future consolidation of diploid and tetraploid rose genetic linkage maps, genetic, phylogenetic and population analyses, cultivar identification, and marker-assisted selection.

Free access

We have constructed a genetic linkage map of peach consisting of RFLP, RAPD, and morphological markers, based on 78 F2 individuals derived from the self-fertilization of four F1 individuals originating from a cross between `New Jersey Pillar' and KV 77119. 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 81 markers comprised of RFLP, RAPD and 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 57 markers assigned to 9 linkage groups, which cover 520 cM of the peach nuclear genome. The average distance between two adjacent markers was 9 cM. Linkage was detected between Pillar (Pi) and double flowers (Dl). RFLP markers loosely linked to Pi, flesh color (Y), and white flower (W) loci were found. Twenty-four markers remain unassigned.

Free access