In vitro propagation of Betula uber (Ashe) Fernald

Dormant bud and actively growing shoot tip explants of B. uber were cultured on Murashige & Skoog (MS) and modified woody plant (WPM) basal salts supplemented with organic nutrients and benzylaminopurine (BAP). Shoot tip explants were morphogenically more responsive than dormant bud explants. The modified WPM proved to be better than MS medium for the establishment and proliferation of B. uber cultures. Shoot proliferation was greatest at 8.9 μM BAP. However, BAP at 4.4 μM produced the greatest number of shoots > 10 mm. Indolebutyric acid (IBA) was more effective than naphthaleneacetic acid (NAA) for rooting of microcuttings in vitro. Rooting was best with a low level of IBA (2.5 μM) in the culture medium. Ex vitro rooting of microcuttings using a conventional potting mix of sand-peat-perlite (1:2:1 v/v/v) was superior to all in vitro rooting treatments. Plantlets were acclimated successfully to greenhouse conditions. Genotype differences with regard to both rooting and shooting abilities were observed.