Micropropagation of Epilobium canum garretti (Firechalice) by Axillary Shoot Culture

Abstract

Epilobium canum subsp. garrettii (firechalice) is an herbaceous wildflower with landscape potential, but its seeds are difficult to germinate because of dormancy requirements. The objective of this study was to develop a complete micropropagation procedure for a selected accession of firechalice. Single-node stem explants from the plant were examined for their ability to establish on Murashige and Skoog (MS) medium or Woody Plant Medium (WPM). Shoot explants on MS medium supplemented with 4.4 μm benzyladenine (BA) produced more than double the number of axillary shoots compared to explants on WPM (12.6 vs. 4.9 shoots, P = 0.0001). Benzyladenine, kinetin (kin), 6-(γ,γ-dimethlyallylamino)purine (2iP), thidiazuron (TDZ), and meta-topolin (mT) at concentrations of 0, 1.1, 2.2, 4.4, or 8.8 μm were evaluated for shoot proliferation efficacy. Stem explants treated with 8.8 μm of BA or mT produced the most shoots, 11 or 15, respectively. Benzyladenine, 2iP, and kin failed to affect shoot height even at the highest concentrations used, but 4.4 or 8.8 μm TDZ reduced shoot height to less than half of the heights of control shoots (3.1 vs. 1.2 cm, P = 0.0001). Firechalice shoots formed three to four roots easily without auxin added to the medium, but four to six roots formed per shoot when using up to 9 μm of indole-3-butyric acid (IBA). In contrast, 9 μm naphthaleneacetic acid (NAA) prevented root formation. When using 0–9 μm IBA for rooting, 82.5% of the rooted shoots survived transplanting. Based on these results, optimum micropropagation of firechalice may be achieved with shoots established on MS medium plus 4.4 µm BA, a concentration of 4.4 or 8.8 μm BA or mT used for shoot proliferation, and use of up to 6 µm IBA during root induction should result in >80% shoot survival after transplanting.