In vitro Conservation and Thidiazuron-Induced Micropropagation of Rhododendron yedoense var. poukhanense (H. Lév.) Nakai

An efficient system of regeneration of Rhododendron yedoense var. poukhanense (H. Lév.) Nakai from seedlings has been developed based on the use of thidiazuron (TDZ) to promote a meristem proliferation. In vitro germinated seedlings are used as explants. The overall seed germination rate of R. yedoense var. poukhanense is 77.5%. The effect of a direct seed cultivation on Anderson’s medium (AM) supplemented with 1.0 µM TDZ or a 4-h pulse treatment of seeds with TDZ (7.5, 15.0, 30.0 µM) followed by their cultivation on the TDZ-free AM on the morphogenic potential of seedlings is studied. Regenerants of R. yedoense var. poukhanense obtained after both types of treatment require an additional passage on hormone-free AM (AM0) for elongation and an increase in the number of shoots per explant. The highest average number of shoots per explant is obtained after elongation under conditions of a direct cultivation of seedlings on AM supplemented with 1.0 µm TDZ and after a pulse treatment with 30.0 µm TDZ (9.32 and 10.32, respectively). The maximum percentage of rooted plants (50%) is obtained in the case of a 4-h pulse treatment with indole-3-butyric acid followed by in vitro cultivation on AM0. The study is the first to demonstrate the effect of different types of a TDZ treatment on the proliferation and development of shoots. The technology made it possible to obtain rooted and acclimatized microshoots induced by a TDZ pulse treatment. As a result, R. yedoense var. poukhanense has been included in the in vitro collection for conservation and propagation for further practical use.