Genetic diversity and differentiation in roses: A garden rose perspective

- We evaluated genetic diversity among 138 rose cultivars using 24 SSR markers.
- Cut roses can be considered as a subgroup of the garden roses.
- Genetic differentiation among garden rose types (Fst = 0.022) was similar in magnitude to the differentiation among breeders.
- Comparison of the differentiation among linkage groups indicated that linkage group 5 is carrying several QTLs important for winter hardiness.

For the first time genetic diversity among modern garden rose cultivars has been evaluated using a set of 24 microsatellite markers covering most chromosomes. A total of 518 different alleles were obtained in the set of 138 rose cultivars and this led to the conclusion that in terms of genetic diversity cut roses can be considered as a subgroup of the garden roses.Genetic differentiation among types of garden roses (Fst = 0.022) was four times that among cut roses, and similar in magnitude to the differentiation among breeders, due to the fact that horticultural groups and breeders overlap largely in classification. Winter hardy Svejda's cultivars (Canadian Explorer roses) showed the least similarities to European roses, and introgression from wild species for winter hardiness was clearly visible. Roses of Harkness and Olesen shared a similar genepool. Comparison of the differentiation among linkage groups indicated that linkage group 5 is potentially a region containing important QTLs for winter hardiness. Linkage group 6 contains the largest amount of genetic diversity, while linkage group 2 is the most differentiated among types of garden roses.