Micropropagation of Ostrya virginiana (Mill.) K. Koch

Ostrya virginiana (Mill.) K.Koch (American Hophornbeam) is a member of Betulaceae and is primarily found in the eastern United States. It grows in USDA hardiness zones 3–9. American Hophornbeam is an underutilized ornamental landscape tree, which resulted from commercial clonal propagation limitations and its slower growth. American Hophornbeam has desirable ornamental features including exfoliating bark and unique fruit clusters that resemble fruit of hops. Currently, American Hophornbeam is seed propagated, with no clonal propagation reported within the species. Lacking clonal propagation has limited superior selections from being made and utilized with this species. The objective of this study was to develop a micropropagation protocol by evaluating nutrient salt formulations and plant growth regulator concentrations for establishment, shoot proliferation, and root initiation in vitro. Factorial combinations of thidiazuron (TDZ) concentrations (0, 0.05, or 0.10 μM) in conjunction with 6-benzylaminopurine (BA) concentrations (0, 2, 4 μM) and indole-3-butyric acid (IBA) concentrations (0, 0.5, 0.10 μM) were compared to determine which plant growth regulator combination(s) would stimulate the proliferation of the most viable axillary shoots. In combination, five nutrient salt formulations (MS, DKW, LP, or WPM) ranging from high to low salt formulations were studied to determine a suitable nutrient salt formulation for axillary shoot proliferation. Nodal explants that were 2 cm in length were used to initiate cultures and were maintained on the various medium treatments plus 3.0% sucrose and 0.7% agar at a pH of 5.8. Explants were incubated approximately 30 cm beneath cool-white fluorescent lamps that provide a photon flux of approximately 40 μmol·m^-2·s^-1 for a 16-h photoperiod at 25±3 °C. Initial results indicate that high nutrient salt formulations, combined with high cytokinins performed better at axillary shoot initiation. Poor shoot elongation was observed and further research needs to be performed to address this issue.