Abstract
Shoot proliferation is a very important micropropagation phase, decisive for economic efficiency of this method for a given taxon. To obtain a high multiplication ratio and a good quality of microshoots a detailed propagation protocol must be developed for particular species or even cultivars. Rhododendron ‘Kazimierz Odnowiciel’ is a relatively new cultivar distinguished by large, beautiful flowers and high frost resistance so there is a need to develop an efficient method of its propagation to satisfy a growing demand for this plant. The aim of the experiment was to evaluate effects of cytokinins: meta-Topolin (mT), zeatin (ZEA), 6-benzyladenine (BA), thidiazuron (TDZ), 2-isopentenyladenine (2iP), or the combination of 2iP+ZEA on proliferation of shoots in R. ‘Kazimierz Odnowiciel’ cultured on Anderson’s medium (AN). Biochemical changes in plant material affected by cytokinins during this phase of micropropagation were determined and occurrence of genetical changes was followed using ISSR markers. TDZ, ZEA or the combination of ZEA+2iP resulted in 100% explant regeneration. On the medium with TDZ or ZEA over two new shoots per explant were produced but the highest proliferation was attained on the medium containing ZEA+2iP – over three shoots per explant. Microshoots developed in this treatment had also the highest contents of chlorophyll, carotenoids and soluble sugars as well as the highest catalase activity. Microshoots formed on the medium with zeatin showed the lowest polymorphism (below 4%) relative to a stock plant.
Highlights
Rhododendrons – next to roses – are considered as the most beautiful ornamental shrubs
The highest regeneration ratio i.e. a number of axillary shoots produced by an explant was obtained in presence of two cytokinins used jointly - 2iP plus ZEA - where over 3 shoots appeared
The 13 ISSR markers used produced a total of 16 polymorphic products (18.8% of all products)
Summary
Rhododendrons – next to roses – are considered as the most beautiful ornamental shrubs. It was Parkinson who first introduced them into gardens in 1629. Micropropagation is one of the main methods of vegetative propagation in numerous valuable ornamentals. It is used for a mass production of genetically identical, physiologically uniform and properly growing plantlets which can be produced in a short time irrespective of atmospheric conditions (Rathore et al 2005; Rout et al 2006; Hussain et al 2012). Though nowadays multiplication of herbaceous plants has become less problematic woody plants remain often a major challenge Their micropropagation is possible, for many taxa the propagation procedures are imperfect or unproven they do not allow to obtain the planned effects. Plant growth regulators added to a culture medium can help to overcome the problems, especially cytokinins
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