MICROPROPAGATION OF BETULA PENDULA ROTH CULTIVARS BY ADVENTITIOUS SHOOT INDUCTION FROM LEAF CALLUS

Fifty-year-old specimens of Betula pendula ‘Dalecarlica’, ‘Fastigiata’, ‘Purpurea’, ‘Youngii’, and var. typica were used as donor plants. For callus induction, leaves obtained from in vitro were used as initial explants. The effects of the cultivar types and different media (MS, WPM and S) supplemented with zeatin (2, 5, and 10 mg L^-1) or BA (0.5, 0.8, and 1.0 mg L^-1) on adventitious bud formation from callus segments were studied. The best regeneration potential was observed in ‘Youngii’ and the purest in ‘dalecarlica’. The best results were obtained on medium S containing 5 and 10 mg L^-1 zeatin. The effect of IBA (0.3 and 0.5 mg L^-1), NAA (0.3 and 0.5 mg L^-1) and their combinations on the rooting of adventitious shoots was investigated. The highest percentage of rooting (100%) and the best root system was achieved on half-strength MS medium in combination with 0.3 mg L^-1 IBA and 0.3 mg L^-1 NAA. The high air humidity and the type of substrate were important factors for successful acclimatization. Maximum survival of plants (from 98.3  1.7% up to 100.0  0.0%) was obtained by opening the test tubes in the cultivation room for a period of 6 days, ensuring high air humidity for 14 days, and utilizing peat. The genotypes of the donor and in vitro propagated plants were analyzed by seven isozyme systems (GOT, IDH, LAP, MDH, PGI, PGM, and 6- PGD). Changes of the isozyme fractions of in vitro- propagated plants in comparison with the donor plants were not found.