In Vitro Propagation of Temperate Zone Woody Plants with Potential Ornamental Use

During the past 10 years, the micropropagation of a number of woody species native to Greece has been studied in our laboratory, as a first step for their introduction for commercial use as ornamentals. The species are Arbutus andrachne, Arbutus unedo, Dianthus fruticosus, Euphorbia characias, Globularia alypum, Lithodora zahnii, xMalosorbus florentina, Quercus euboica, Sideritis athoa and Thymelaea hirsuta. For the initiation of in vitro cultures shoot tips or nodal stem pieces from young shoots were used as explants, with the exception of xM. florentina where buds from woody shoots were used as well. In vitro cultures of A. andrachne, A. unedo, xM. florentina and Q. euboica were successfully established from explants excised from adult plants grown in the wild, while of D. fruticosus, E. characias, G. alypum, L. zahnii, S. athoa and Th. hirsuta were established using seedlings as mother plants. A seasonal influence of explant collection on establishment of cultures was found in A. andrachne, xM. florentina and Q. euboica. The two Arbutus species and Q. euboica were successfully cultured on solid WPM salts supplemented with 100 mg/L myo-inositol, 1 mg/L thiamine, 0.5 mg/L nicotinic acid and 0.5 mg/L pyridoxine; the rest of the species were cultured on solid MS (basal media). The medium was supplemented in most cases with a cytokinin combined in some cases with an auxin for shoot production. BA was the cytokinin used for most species, however in A. andrachne only zeatin or 2iP could induce elongation of the microshoots, while in A. unedo elongation was achieved with the addition of NAA aside with BA in the medium. The addition of NAA along with cytokinin was needed for shoot production in E. characias and D. fruticosus; in the latter 2iP resulted in higher shoot production than BA and in xM. florentina BA was combined with IBA. In G. alypum and Th. hirsuta shoot production occurred without the presence of plant growth regulators. Shoot proliferation was achieved using the culture initiation medium except in A. unedo that required higher auxin concentration, Th. hirsuta required the addition of BA and E. characias required reduced concentrations of BA and NAA than in the initial culture. IBA added into the basal medium induced rooting in most species, with the exception of E. characias and Th. hirsuta that did not root, and xM. florentina that rooted only with the addition of IAA along with IBA. Microplants of all species were successfully (70-100%) acclimatized and established ex vitro in peat-perlite, except Q. euboica that needed soil of its natural environment for successful acclimatization because of the presence of a mycorrhiza.