'Topaz' is a modern Czech apple cultivar well accepted by consumers and scab-resistant, providing reasons for the significant spreadof cv. 'Topaz' in European orchards, especially in the organic fruit production industry. Growing the apple trees on their own rootsprovides some advantages in comparison with grafted trees. Micropropagation is the method of choice for plantlet production for thispurpose as well as for the establishment of healthy mother stock trees as a source of scions. The efficiency of axillary shoot proliferationwas examined on four media differing in plant growth regulators and their concentrations, and from three explant types: intact ordecapitated and defoliated microshoots placed vertically and one-nodal segments placed horizontally. All media consisted of Quoirin and Lepoivre (QL) macroelements and Murashige and Skoog (MS) microelements. Furthermore, rooting efficiency on six different media/treatments was analyzed. Media with 1 mg/L 6-benzylaminopurine (BA) or BA (0.5 mg/L) + 1.5 mg/L kinetin (Kin) produced similarnumber of microshoots per inoculated one (2.5 and 2.4, respectively). Medium with 1 mg/L thidiazuron (TDZ) produced significantlyhigher number of shoots (3.6) but they were fasciated. Three different explant types also produced similar numbers of microshoots.High rooting efficiency (68.7%), a high number of roots per shoot (6.6) and the best quality of shoots were obtained in rooting mediumcontaining 2 mg/L of indole-3-butyric acid (IBA). An efficient method of shoot proliferation was established, and, since rooting was themost critical step, an efficient procedure for rooting apple cv. 'Topaz' was established.

We evaluated the response of eight economically important Croatian grapevine cultivars and studied the impact of their sanitary status on in vitro introduction, by comparing the response of healthy and virus-infected genotypes of one cultivar. Nodal explant survival on three media, M1 (half-strength MS), M2 (full-strength MS) or M3 (full-strength MS with 4.4 µM L−1 benzylaminopurine) was measured after 2 weeks and regrowth after 8 weeks. After 8 weeks, average shoot length and node number were significantly higher on M2 compared to M1 and M3. M3 induced significantly shorter average internode length, compared to M1 and M2. Survival of one healthy and of five cultivar Plavac mali genotypes infected with GFLV, GLRaV-1, GLRaV-3, GLRaV-3+GVA and GLRaV-1+GLRaV-3 was 97.5 and 82.8–87.5%, respectively. Regrowth of the healthy genotype reached 95.5%, but dropped to 5.5–31.4% in infected ones. The healthy genotype showed significantly higher shoot length (6.3 cm) and node number (7.3) compared to infected genotypes, with shoot length between 1.2–2.6 cm and node number between 1.2–3.0. By contrast, internode length was not significantly different between the healthy and the infected genotypes. The present work represents the first successful in vitro introduction for three of the eight native Croatian cultivars studied.

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