Authors:J. Dobránszki, K. Magyar-Tábori, E. Jámbor-Benczúr and et al.
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.