|Rinehart, Timothy - Tim|
Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/25/2009
Publication Date: 10/1/2009
Citation: Kardos, J.H., Rodacker, C.D., Dirr, M.A., Rinehart, T.A. 2009. Production and verification of Hydrangea macrophylla x H. angustipetala hybrids. HortScience. 44(6):1534-1537.
Interpretive Summary: Hydrangea angustipetala is a source of genetic diversity for traits such as powdery mildew resistance, early flowering, and narrow, evergreen foliage for incorporation into new cultivars with H. macrophylla. Hydrangea macrophylla, native to southern China and Japan, characteristically possesses 10 to 20 cm long, 6 to 14 cm wide, coarsely toothed, matte green to lustrous dark green leaves, stout stems, and lacecap or mophead inflorescences 8 to 25 cm in diameter on 1 to 2 m high and wide plants. Flower color in H. macrophylla ranges from white to pink to purple to blue. Variation exists within this species for growth habit, size of foliage, degree of foliage retention in winter, cold hardiness, inflorescence size, and fragrance (personal observation). Hybridization between this species and H. macrophylla could result in hybrids with narrow, semi-evergreen to evergreen, lustrous foliage, improved powdery mildew resistance, early flowering, and fragrant flowers.
Technical Abstract: The genetic diversity among H. macrophylla (Thunberg) Seringe taxa is limited due to the restricted native distribution and multiple breeding programs that utilized the same taxa and targeted similar breeding goals. This study assessed the compatibility of interspecific crosses between Hydrangea macrophylla and H. angustipetala Hayata as a source of genetic diversity. Two lacecap cultivars of H. macrophylla, ‘Lady in Red’ and Midnight Duchess™ (‘HYMMADII’), were compatible with one genotype of H. angustipetala . Hybridity of progeny was confirmed by simple sequence repeat (SSR) markers and morphological comparisons. The morphology of the hybrids was intermediate to the parents. Some hybrids had red or purple pigmented stems, which are characteristic of ‘Lady in Red’ or Midnight Duchess™, respectively. All hybrids had white lacecap inflorescences. Some of the hybrid inflorescences were fragrant. Winter leaf retention of the hybrids ranged from fully deciduous to semi-evergreen. Male fertility of progeny was evaluated by fluorescein diacetateFDA staining of pollen. ‘Lady in Red’, Midnight Duchess™, and H. angustipetala had 62%, 58%, and 79% stainable pollen, respectively, while the ‘Lady in Red’ × H. angustipetala and Midnight Duchess™ × H. angustipetala hybrids had means of 48% and 47% stainable pollen, respectively. Selected progeny were used to develop F2 and BC1 populations. The interspecific hybrids produced in this study were attractive, fertile plants that are being used in further breeding to develop new cultivars.