Micropropagation of Sorbus torminalis (L.) Crantz: Hormonal Effects during Multiplication and Rooting Phases

In this study successful propagation of mature trees of Sorbus torminalis (L) Crantz was obtained by in vitro methods. The efficiency of shoot regeneration was tested in MS medium and in the multiplication phase. A complete bifactorial design between 6-benzylaminopurine (BAP) and indol-3-butyric acid (IBA) with five concentrations each, was applied. The type of hormone, concentration and their interaction significantly influenced multiplication parameters. The presence of BAP is crucial for shoot proliferation and development. The best multiplication rate, between 6.3 and 6.9, was recorded with 1 or 2 mg/L BAP with the lowest IBA concentrations. Elongation of shoots was also significantly affected by the range of hormone concentration, with a positive relation between elongation and IBA concentration in every BAP level. The length of the longest shoot, between 20.8 and 22.4 mm, was recorded in a medium containing 1 or 0.5 mg/L BAP, respectively, with 1 mg/L IBA. Different IBA concentrations in different induction times were tested for the rooting phase. The best results were obtained with the in vitro regenerated shoots immersed in MS agar medium, supplemented with 50 mg/L IBA, for 72 hours, followed by direct peat:perlit soil moisture transfer, with 77% of rooting and almost 100% of acclimatization success. The plantlets transplanted to soil showed normal growth the following spring and did not show any morphological variation.