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  • Author or Editor: E. Jámbor-Benczúr x
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The effects of a new type of aromatic cytokinin, meta-topolin, on the morphology and histology of apple leaves and its post-effects on the subsequent shoot regeneration from in vitro leaves were studied in cv. Royal Gala. The media applied for pre-treatment differed from each other in their cytokinin composition: medium No. 1 contained no cytokinin, No. 2 was supplemented with 0.5 mg l-1 benzyladenine, while Nos. 3-6 contained meta-topolin, the new type of cytokinin, in four concentrations (0.5-1.0-1.5-2.0 mg l-1). After a 3-week pre-treatment on these media shoot regeneration was induced on two test regeneration media containing thidiazuron (0.2 mg l-1) or benzyladenine (5.0 mg l-1). Irrespective of the pre-treatments, high regeneration (97-100%) was observed on all the regeneration media. however, the conditioning of apple shoots for three weeks on medium supplemented with meta-topolin in a concentration range between 0.5 and 1.5 mg l-1 caused a significant decrease in the rate of vitrified shoots (down to 13.4%) and increased the number of regenerated shoots per leaf segment significantly (up to 15.1). There was a positive correlation between the histological status and regeneration capacity of in vitro leaves. According to these results, meta-topolin, as a new source of cytokinin, could increase the morphogenic potential of apple leaves.

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The in vitro shoot multiplication of apple cv. Jonagold was tested on media containing benzyladenine, benzyladenine riboside or meta-topolin in different concentrations (from 0.0 to 5.0 mg l-1). The optimal concentration for the best multiplication varied according to the type of cytokinin. The highest multiplication rate (on average 6.9 and 5.9 new shoots per explant) was achieved using 5.0 mg l-1 meta-topolin or 2.0 mg l-1 benzyladenine riboside. The longest shoots were formed on media containing benzyladenine riboside at a concentration of 0.5 mg l-1. The length of newly developed shoots was strongly suppressed by high concentrations of different cytokinins, but the suppression effect of a high concentration of meta-topolin on shoot length was less than that of benzyladenine or benzyladenine riboside. In this study meta-topolin and benzyladenine riboside proved to be effective cytokinins to induce adequate shoot proliferation, while benzyladenine was the least active cytokinin

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