In vitro regeneration and propagation of Hydrangea macrophylla thunb. 'Nachtigall'

The aim of the first set of experiments was to optimize adventitious shoot regeneration in Hydrangea macrophylla 'Nachtigall'. For this purpose leaf explants were cultured on Murashige and Skoog (MS) and B5-Gamborg (B5) media either with full or half-strength macro- and micronutrients, respectively. After eight weeks the highest regeneration rate and the highest number of regenerated shoots were observed on half-strength B5 medium. Consequently this medium was used in the subsequent experiment in which different cytokinins were compared. BAP, TDZ and meta-Topolin (m-Top) each in two concentrations were used. No shoot regeneration was observed on media supplemented with m-Top and only poor regeneration obtained on TDZ containing media. Using BAP resulted in regeneration rates between 29.4 and 80% and 2 to 3.1 shoots per regenerating explant. Another experiment was devoted to axillary shoot propagation. For this purpose, culture on solid medium, in temporary immersion system (TIS) and in permanent immersion system (PIS) was compared. The highest shoot production was obtained in PIS but the plant quality was very low due to hyperhydricity and yellowing. Plants in TIS showed a slightly lower propagation rate but were of excellent quality.