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Development of an in ovolo embryo culture procedure for Hydrangea

Reed, S.M.
Journal of environmental horticulture 2000 v.18 no.1 pp. 34
Hydrangea, Hydrangea macrophylla, embryo culture, ovule culture, interspecific hybridization, culture media, sucrose, pollination, ovules, germination, mortality, leaves, bacteria, Hydrangea paniculata, Tennessee
Panicle hydrangea (Hydrangea paniculata) is a potential source of cold hardiness that is needed for improvement of bigleaf hydrangea (H. macrophylla). Seeds have been produced from H. macrophylla X H. paniculata crosses, but seedlings derived from the few seed that germinated died at a very young age. The objective of this study was to investigate the use of in ovolo embryo culture for producing this interspecific hybrid. Six media, which differed in basal media formulation and sucrose concentration, were tested using H. macrophylla intraspecific ovules collected 3 to 4 and 5 to 6 weeks after pollination. The highest percent germination for both time periods was obtained on Gamborg's B-5 medium supplemented with 2% sucrose; therefore, this medium was chosen for culture of H. macrophylla X H. paniculata ovules. Plants germinated from interspecific ovules cultured 3 to 6 weeks after pollination, but all died before forming two sets of true leaves. A slow-growing bacterial contamination that was present in many of the interspecific cultures necessitated the elimination of cultures initiated 7 to 8 weeks after pollination, and may have been at least partially responsible for the death of the putative hybrids. A broad-spectrum biocide/fungicide was found to be 100% effective in controlling this endogenous contaminant, thereby allowing older ovules to be cultured. Putative H. macrophylla X H. paniculata hybrids have been obtained from ovules cultured 9 to 10 weeks after pollination.