Genetic diversity and differentiation in roses: A gardenrose perspective

tFor the first time genetic diversity among modern garden rose cultivars has been evaluated using a setof 24 microsatellite markers covering most chromosomes. A total of 518 different alleles were obtainedin the set of 138 rose cultivars and this led to the conclusion that in terms of genetic diversity cut rosescan 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 groupsand 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 hardinesswas clearly visible. Roses of Harkness and Olesen shared a similar genepool. Comparison of the differen-tiation among linkage groups indicated that linkage group 5 is potentially a region containing importantQTLs for winter hardiness. Linkage group 6 contains the largest amount of genetic diversity, while linkagegroup 2 is the most differentiated among types of garden roses.