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

Abstract

Almost all commercially grown apple cultivars in Turkey are exotic, with local varieties serving as important genetic resourcesfor breeding and marker development purposes. Among the latter is Amasya, which has a pleasing taste and flavor, but is unsuitablefor commercial use because of its small fruit size and alternate-bearing characteristics. Genetic maps of apple cultivars are importantresources to facilitate marker-assisted selection. Because of its good eating quality, Amasya is a good genetic resource for markerdevelopment to enhance fruit quality, especially flavor. In this study, we constructed a simple sequence repeat (SSR) marker-basedgenetic 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 genomicSSR primer pairs, 400 markers were mapped, with parental and consensus maps constructed independently. A reference map wasalso constructed using 207 common SSR markers, thereby producing the most dense SSR-based reference map currently reported forapple. The reference genetic map was 1351 cM long, with a mean marker density of 6.5 cM. The consensus map obtained by mapping396 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 previouslyunmapped in apple. As a result, once additional markers have been incorporated into the maps to increase saturation, the evaluation ofphenotypic 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 aidintegration of various apple linkage maps.