(287) Factors Affecting In Vitro Proliferation and Regeneration of Birch Species

Abstract

In vitro shoot cultures for two birch species, Asian white birch (Betula platyphylla) and paper birch (Betula papyrifera), were initiated from shoot tips of mature trees and maintained in MS (Murashige and Skoog) medium containing 3% sucrose and 5–10 μM (micromolar) benzyladenine (BA). The effect of such factors as genotype, basal medium, and plant growth regulator (PGR) on proliferation was investigated. Shoots were proliferated in both MS and woody plant medium (WPM) supplemented with different concentrations of thidiazuron (TDZ), BA, and kinetin (Kin). Two birch species responded differently to these factors. In general, more shoots were proliferated in WPM than in MS medium. The maximum proliferation rate of Asian white birch was achieved by being cultured in WPM containing 4–8 μM TDZ, while paper birch gave rise to the maximum proliferation rate in WPM supplemented with 20 μM BA. Interactions between genotype and medium or cytokinin were found. Shoots produced on media with TDZ had thick stems and small, dark green leaves. Microshoots can be rooted both in vitro and ex vitro with or without IBA treatment. Plants were regenerated from leaf tissues of Asian white birch. Adventitious shoots regenerated when in vitro leaves were cultured on WPM supplemented with 10–20 μM BA with 2-week dark treatment. The effect of genotype, PGR, and culture condition on in vitro regeneration of birch species is being tested.