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Verification and establishment of Hydrangea macrophylla 'Kardinal' x H. paniculata 'Brussels Lace' interspecific hybrids

Reed, S.M., Riedel, G.L., Pooler, M.R.
Journal of environmental horticulture 2001 v.19 no.2 pp. 85
height, plant characteristics, Hydrangea, Hydrangea macrophylla, interspecific hybridization, plant breeding, flowers, ovule culture, rooting, mortality, genetic markers, internodes, length, leaf area, leaves, hybrids, cold tolerance, random amplified polymorphic DNA technique, backcrossing, Hydrangea paniculata, shape
An interspecific hydrangea breeding project with the goal of producing cold-hardy hydrangeas with brightly coloured flowers was initiated in 1997. The objective of the current study was to transfer Hydrangea macrophylla × H. paniculata plants obtained using ovule culture to in vivo conditions and to verify their hybrid nature. Putative hybrids, representing five H. macrophylla × H. paniculata cultivar combinations, were propagated and rooted in vitro ('Blaumeise' × 'Pink Diamond'; 'Kardinal' × 'Brussels Lace'; 'Kardinal' × 'Pink Diamond'; 'Kardinal' × 'Unique'; and 'Pia' × 'Tardiva'). 'Kardinal' × 'Brussels Lace' putative hybrids were the only plants that produced roots and survived transfer to the greenhouse. RAPD markers were used to verify hybridity in 13 of these plants, only 5 of which survived. Four of the 'Kardinal' × 'Brussels Lace' hybrids were greatly reduced in size and slow-growing, having an average height of only 6.4 cm (2.5 in) 8 months after being removed from in vitro conditions. Height, internode length, leaf length and leaf width were approximately six times greater in the remaining 'Kardinal' × 'Brussels Lace' hybrid than in the four small hybrids. All hybrids resembled H. paniculata in leaf shape and pubescence, and appeared to be less susceptible than H. macrophylla to powdery mildew. Intercrosses between hybrids and backcrosses to parental species will be made when the hybrids flower.