The effects of genotype, basal medium, plant growth regulator (PGR), dark treatment, and antibiotics on shoot regeneration of two Buddleia cultivars, B. davidii 'Potters Purple' and Buddleia 'Lochinch', were investigated. In vitro shoots were regenerated from leaf tissues in either Murashige and Skoog (MS) or woody plant medium (WPM) media supplemented with benzyladenine (BA). In general, more shoots were regenerated in WPM medium than in MS medium. Dark treatment for 3 to 5 weeks dramatically increased shoot regeneration. Addition of indole-3-butyric acid (IBA) or naphthalene acetic acid (NAA) significantly enhanced the regeneration rate and shoots of each explant. The maximum regeneration rate (100%) of B. davidii 'Potters Purple' was achieved when cultured in WPM containing 5 mM BA plus 5 mM IBA. The maximum regeneration rate (98.4%) of Buddleia 'Lochinch' was found in WPM supplemented with 20 mM BA plus 4 mM IBA. Carbenicillin at 250 to 500 mgÁL -1 and cefotaxime at 125 to 250 mgÁL -1 , individually or combined, promoted shoot regeneration. Interactions between genotype and medium or PGRs were found. In vitro shoots were easily rooted in halfstrength MS medium with or without NAA. Rooted plants were transferred to potting mix and grown in the greenhouse. This research will facilitate genetic improvement and fast propagation of Buddleia species using biotechnology.

Shoots were regenerated from in vitro leaf tissues of two genotypes of Viburnum dentatum, a popular shrub species for landscape use. Adventitious shoots were induced when leaf tissues were cultured on woody plant medium (WPM) supplemented with either benzyladenine (BA) or thidiazuron (TDZ). Effects of cytokinin concentration, indole-3-butyric acid (IBA), and dark treatment on shoot regeneration were investigated. Dark treatment for the first 4 weeks of leaf explants cultured in the regeneration medium significantly increased the frequency of regeneration. The highest frequency of shoot regeneration (70%) for 'Synnesvedt' was obtained when leaf tissues were cultured in the medium with 40 lM BA or 8 lM TDZ with 4 weeks dark treatment. The highest frequency of shoot regeneration (90%) for 'MN34' was found in the 4 lM TDZ medium with 4 weeks dark treatment. Addition of IBA significantly enhanced shoot regeneration. Ethyl methanesulfonate (EMS) treatment inhibited callus proliferation, particularly in the early stage of callus recovery; however, no significant difference in shoot regeneration among different treatments was observed, indicating that the inhibitory effect of EMS was minimal after calluses re-acquired their capacity to grow and regenerate in the regular medium. Regenerated shoots ([1.5 cm) were rooted in the half-strength MS medium containing 5-10 lM IBA or naphthalene acetic acid (NAA). Rooted plants were transferred to the potting medium and grown in the greenhouse.

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In vitro shoot cultures for two birch species, Asian white birch (Betula platyphylla) and paper birch (Betula papyrifera), were initiated from shoot tips of mature trees and maintained in MS (Murashige and Skoog) medium containing 3% sucrose and 5–10 μM (micromolar) benzyladenine (BA). The effect of such factors as genotype, basal medium, and plant growth regulator (PGR) on proliferation was investigated. Shoots were proliferated in both MS and woody plant medium (WPM) supplemented with different concentrations of thidiazuron (TDZ), BA, and kinetin (Kin). Two birch species responded differently to these factors. In general, more shoots were proliferated in WPM than in MS medium. The maximum proliferation rate of Asian white birch was achieved by being cultured in WPM containing 4–8 μM TDZ, while paper birch gave rise to the maximum proliferation rate in WPM supplemented with 20 μM BA. Interactions between genotype and medium or cytokinin were found. Shoots produced on media with TDZ had thick stems and small, dark green leaves. Microshoots can be rooted both in vitro and ex vitro with or without IBA treatment. Plants were regenerated from leaf tissues of Asian white birch. Adventitious shoots regenerated when in vitro leaves were cultured on WPM supplemented with 10–20 μM BA with 2-week dark treatment. The effect of genotype, PGR, and culture condition on in vitro regeneration of birch species is being tested.