Molecular Assessment of Remontant (Reblooming) Hydrangea macrophylla Cultivars

Randomly amplified polymorphic DNA (RAPD) markers were used to distinguish five remontant and two cold-hardy Hy- drangea macrophylla (Thunb.) Ser. taxa. Eleven primers generated sufficient polymorphisms to separate these seven culti- vars into two groups. One group contained 'Penny Mac', 'Dooley' and 'Nikko Blue', while the remaining taxa, 'David Ramsay', 'Endless Summer', 'Decatur Blue' and 'Oak Hill' were clustered in the second group. All hydrangea cultivars examined are closely related; the most divergent cultivars exhibited 88% similarity based on RAPD markers. Index words: RAPD (randomly amplified polymorphic DNA) markers, Hydrangea, remontant. Species used in this study: Hydrangea macrophylla. Chemicals used in this study: Tris(hydroxymethyl)aminomethane (Tris), borate (boric acid), ethylenediaminetetraacetic acid (EDTA). Abstract Two experiments were conducted to develop a protocol for propagation of Castanopsis sclerophylla (Lindley & Paxton) Schottky by stem cuttings. In the first experiment completed in 2000, stem cuttings were taken on three dates representing three growth stages (softwood, semi-hardwood, or hardwood). Semi-hardwood and hardwood cuttings were treated with 0, 2500 (0.25%), 5000 (0.5%), 7500 (0.75%), or 10,000 (1.0%) ppm of the free acid of indolebutyric acid (IBA) dissolved in 50% isopropyl alcohol, whereas softwood cuttings were treated with the same concentrations of the potassium (K) salt of IBA (K- IBA) dissolved in distilled water. Cuttings were placed in a raised greenhouse bench and rooted under intermittent mist. Cuttings taken at the semi-hardwood and hardwood stages began to drop their leaves after approximately 2 weeks and the majority eventually died, with negligible rooting of surviving cuttings. The response of the softwood cuttings to K-IBA was quadratic with the greatest rooting (63%) at 7500 ppm K-IBA. Seventy softwood cuttings that rooted were potted for obser- vance of overwinter survival. Of these, 90% produced a flush of growth during the summer, with 80% overwinter survival. In the second experiment conducted in 2001, semi-hardwood cuttings were taken and treated with 0, 2500 (0.25%), 5000 (0.5%), 7500 (0.75%), or 10,000 (1.0%) ppm K-IBA and placed in a raised greenhouse bench with intermittent mist for rooting as in the first experiment. Results were similar to the semi-hardwood cuttings treated in the first experiment with the free acid of IBA, indicating semi-hardwood cuttings do not root and that the auxin and/or isopropyl alcohol were not toxic to the cuttings.