Construction of dense genetic linkage maps of apple cultivars Kaşel-41and Williams' Pride by simple sequence repeat markers


Abstract: Abstract: Almost all commercially grown apple cultivars in Turkey are exotic, with local varieties serving as important genetic resources for breeding and marker development purposes. Among the latter is Amasya, which has a pleasing taste and flavor, but is unsuitable for commercial use because of its small fruit size and alternate-bearing characteristics. Genetic maps of apple cultivars are important resources to facilitate marker-assisted selection. Because of its good eating quality, Amasya is a good genetic resource for marker development to enhance fruit quality, especially flavor. In this study, we constructed a simple sequence repeat (SSR) marker-based genetic map of the Amasya apple cultivar using 96 F1 progenies generated from a cross between Kaşel-41 (a selection from Amasya) and Williams' Pride cultivars. Of 187 bacterial artificial chromosome SSRs, 150 expressed sequence tag SSRs, and of 362 genomic SSR primer pairs, 400 markers were mapped, with parental and consensus maps constructed independently. A reference map was also constructed using 207 common SSR markers, thereby producing the most dense SSR-based reference map currently reported for apple. The reference genetic map was 1351 cM long, with a mean marker density of 6.5 cM. The consensus map obtained by mapping 396 markers had a length of 1476.4 cM and a 3.82-cM mean marker density. We also identified the positions of 57 SSR loci previously unmapped in apple. As a result, once additional markers have been incorporated into the maps to increase saturation, the evaluation of phenotypic traits in the mapping population should facilitate linkage between molecular markers and fruit quality traits. Additionally, the constructed apple reference genetic map, with 207 SSR markers, should also assist the construction of new genetic maps and aid integration of various apple linkage maps.

Keywords: Apple, Malus, simple sequence repeat, microsatellite, genetic mapping

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