Morphology and heredity of tepal spots in Asiatic and Oriental hybrid lilies (Lilium spp.)

Petal spots constitute an important trait for ornamental flowers, because they generate variation in flower colour and pigmentation patterning. However, only a few reports have described the morphologies and inheritances of petal spots. Two types of spots-raised spots and splatters-appear on the flower tepals of lily (Lilium spp.). Here, we microscopically analysed the morphologies of raised spots and splatters, and compared them with those of petal spots in other species. The raised spots of lily showed an increase in the numbers of parenchymal and epidermal cells, and accumulation of anthocyanin pigments in these cells. We did not observe this type of morphology in the petal spots of rhododendron or Tricyrtis macropoda, indicating that the morphology observed in the raised spots is unique to lily. In the splatters of lily, anthocyanin pigments accumulated only in epidermal cells, and the shape of pigmented cells did not differ from that of unpigmented cells. These features were also observed in spots of T. macropoda. We subsequently investigated the inheritance of raised spots and splatters in an F-1 segregating population. We revealed that F-1 plants with raised spots, splatters, raised spots and splatters, or no spots showed a 1:1:1:1 segregation ratio, indicating that the two types of spots are genetically independent. Such knowledge will facilitate efficient selection during breeding programs focused on the development of cultivars with (or without) spots.