Micropropagation of mature elm trees in vitro

The micropropagation of wych elm (Ulmus glabra), smooth elm (U. minor), and European white elm (U. laevis) via organogenesis was established with the aim to provide material for forestry breeding. The induction of shoots and their multiplication were reached on Murashige and Skoog (MS) medium. The dormant winter buds were cultured in semi-liquid MS medium with 0.2 mg.l-1 of benzylaminopurine (BAP), 0.1 mg.l-1 β-indolebutyric acid (IBA), and glutamine (10 mg.l-1) under white fluorescent light (30 μmol.m-2.s-1) with a 16 hour photoperiod, 24 °C for 4-6 weeks. The multiplication of growing shoots was observed on MS medium, of the same composition of BAP and IBA, but with increased levels of 200 mg.l-1 glutamine and 200 mg.l-1 caseine-hydrolysate under the same culture conditions. Shoots about 4 cm in length of each elm species were used for rooting on one-third MS medium with 1 mg.l-1 α-naphthalene acetic acid (NAA). The average percentage of rooting reached 87%. During acclimatization, only 2% mortality of plantlets was recorded. Minimal percentage of plantlet mortality (up to 4%) was recorded after their transfer onto outdoor beds.