|Rinehart, Timothy - Tim|
Submitted to: Journal of the American Society for Horticultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/4/2007
Publication Date: 1/15/2008
Citation: Reed, S.M., Jones, K., Rinehart, T.A. 2008. Production and characterization of intergeneric hybrids between Dichroa febrifuga and Hydrangea macrophylla. Journal of the American Society for Horticultural Science. 133:84-91. Interpretive Summary: Dichroa febrifuga is an Asian shrub that is closely related to Hydrangea macrophylla, or bigleaf hydrangea. The purpose of this study was to hybridize these two species for the purpose of developing new ornamentals possessing the best traits of both parents. Desirable traits from D. febrifuga include evergreen foliage, persistent blue berries, ability to produce blue flowers independent of aluminum availability, and large individual flowers. In comparison, H. macrophylla is more cold hardy and has larger inflorescences than D. febrifuga, and the showy imperfect flowers found in H. macrophylla and most other member of this genus are absent from D. febrifuga. Hybrids between the two species were produced and were intermediate in appearance between the parents. A few hybrids produced blue flowers even though no aluminum was present in the soil. Hybrids in which D. febrifuga was used as the maternal parent were fertile and produced offspring when intercrossed or backcrossed to parental species. This work documents the first step in an effort to combine desirable horticultural features from D. febrifuga and H. macrophylla.
Technical Abstract: The potential of producing an intergeneric hybrid between Dichroa febrifuga Lour. and Hydrangea macrophylla (Thunb.) Ser. was investigated. Reciprocal hybridizations were made between D. febrifuga selection (GUIZ 48) and diploid (‘Veitchii’) and triploid (‘Kardinal’ and ‘Taube’) cultivars of H. macrophylla. Rescue was employed for approximately one-third of the crosses that produced fruit, while the rest were allowed to mature on the plant and seed collected and germinated. Reciprocal hybrids, which were verified with simple sequence repeat markers, were produced from both rescue and seed germination and with both diploid and triploid H. macrophylla cultivars. Hybrids were intermediate in appearance between parents, but variability in leaf, inflorescence and flower size and flower color existed among the hybrids. A somatic chromosome number of 2n = 6x = 108 was tentatively proposed for D. febrifuga GUIZ 48. Chromosome counts and flow cytometric measurements of nuclear DNA content indicated that some of the hybrids may be aneuploids, but neither analysis was definitive. While hybrids with H. macrophylla as the pistillate parent did not form pollen-producing anthers, pollen staining ranged from 5 to 62% in D. febrifuga × H. macrophylla hybrids. F2 and BC1 progeny were obtained using D. febrifuga x ‘Veitchii’ hybrids. This work documents the first step in an effort to combine desirable horticultural features from D. febrifuga and H. macrophylla.