Rose

Roses, Rosa, are native to diverse habitats within the Northern hemisphere and over 130 species are recognized. Only seven to ten species, however, are in the background of most modern rose cultivars, leaving vast untapped genetic resources. Cultivars are almost exclusively asexually propagated. Roses are cross-pollinating, woody shrubs, and progeny can segregate widely for traits due to heterozygosity. Most cultivars are tetraploid, while most species are diploid. Limited fertility, reproductive barriers, germination challenges, relatively few founding cultivars among elite germplasm, and the need for large progeny sizes often pose significant challenges to breeders. Increasing knowledge of the inheritance of traits and molecular genetics techniques are valuable tools aiding modern rose breeders. The need for new cultivars remains strong as divergence among rose market types increases, production systems become more specialized, and new markets develop. Breeding objectives with high priority include cut flower cultivars adapted to emerging production regions, blooming potted florist roses with long display life, and lower-maintenance landscape roses.