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orchards, but also for direct afforestation of certain areas or for reforestation forest stands with elite genotypes, as well as for further improvement. A number of investigations into in vitro propagation of wild cherry have been carried out to date (Druart et al. 1981; Pevalek-Kozlina and Jelaska 1987; Cornu 1990; Hammerschlag and Scorza 1991; Gruselle et al. 1995; Ružić et al. 2003; Szczygieł and Wojda 2008) – primarily because of the high timber value of this species. In the nature, the existence of wild cherry types of up to 50 individuals is exceptionally rare and occurs only in several cases. The in situ conservation of such genotypes may be difficult if they are privately owned or if they are overmature, since the tree trunk progressively begins to decay after 80 years of age. The ex situ conservation in clonal seed orchards makes it possible to conserve either the unmodified genetic constitution or genetic constitution with minimal possibility of change through mutations, selections, drift or gene contamination of plant material. The introduction of new conservation methods of wild cherry genetic resources, such as in vitro vegetative propagation or cryopreservation, would increase the possibility of controlling genetic stability, especially if molecular characterization of each clone is carried out. Meristem reproduction of selected elite trees of wild cherry was set up by Ivanička and Pretova (1986) and Douglas (1999). In Croatia, primary research into microclonal propagation of wild cherry for the purpose of obtaining rapid in vitro micropropagation was conducted by Pevalek-Kozlina and Jelaska (1987). The experiment included several differently-aged genotypes. Variability of elite wild cherry trees in combination with in vitro mass production was studied by Hammatt and Grant (1997) and Ďurkovič (2006). An annual height increment of 1.8-2.0 m of these wild cherry seedlings was recorded. The in vitro culture of wild cherry with meristem or shoot explants is performed by organogenesis through three stages of the process. These include differentiation of the explants into the leaf rosettes, micropropagation and shoot elongation, as well as their rooting, similarly to other woody species, and finally their outplanting. In Croatia, a clonal seed orchard of wild cherry with 27 selected clones was established in Kutina (Kajba et al. 2006, 2012). The ramets of this orchard provided the starting, planting stock for the research done in this work. To introduce the selected material into the in vitro procedure and mass vegetative propagation, twigs with formed buds in the dormant stage were used, as well as those in the growth stage. Drawing on previous research into micropropagation of cultivated and wild cherry, the possibility of optimizing the routine of tissue culture methods for clone propagation (plus trees) of wild cherry at all the stages was attempted, starting from the initial culture, micropropagation, elongation, rooting and acclimatisation and in vivo hardening of the plants to the stage of commercial plants. MATERIALS AND METHODS MATERIJAL I METODE RADA The grown shoots collected from grafted plants during different seasons of the year (July 2007-June 2008) provided the initial material. Plant material consisted of axillary and terminal buds of a total of 24 clones of wild cherry from the clonal seed orchard in Kutina. The following clones were used in experiment: G1, KP5 (summer); ĐU2, K5, L1, R1 (autumn); ĐU1, G2, K1, K3, KC1, KC2, KP2, KP3, L4, N3, NB1, PŽ, R2 (winter); and K3, L5, L6, N1 (spring). Clone K3 was introduced in the experiment twice (winter; spring). Clone L3 was not successfully disinfected and was not introduced into the initial culture. Twigs that were used to isolate axillary buds were excised in different developmental stages of plant material during all the four seasons of the year. The material was disinfected as described in Table 1. Different methods have been used for |