In vitro responses of American chestnut to plant growth regulators in culture medium

This project investigated the role of plant growth regulators (auxins and cytokinins) at different concentrations in woody plant medium (WPM) for enhancing in vitro shoot proliferation, callus production and root initiation of the American chestnut (Castanea dentata). Micropropagated shoots there were initiated and maintained in WPM containing 0.1 mg BA/L was used as explant materials. Auxins that were tested in this research were indolebutyric acid (IBA), naphthaleneacetic acid (NAA), 2,4-dichlorophenoxyacetic acid (2,4-D), and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) and cytokinins were kinetin, N-(2-chloro-4-pyridyl)-N'-phenylurea (CPPU), thidiazuron (TDZ), and zeatin. The cytokinins, CPPU and TDZ at low concentrations were most effective for shoot initiation in comparison with other cytokinins tested, and resulted in a much higher percentage of explants producing shoots. Among the auxins tested, 2,4-D and 2,4,5-T were most effective for callus production. Root initiation was noticed from 2,4-D, 2,4,5-T and NAA treatments. Also, IBA at 0.5 mg/L significantly stimulated shoot initiation. It is our belief that this was a result of the interaction between exogenous auxin (IBA or 2,4-D) in the culture medium and "endogenous" cytokinin (BA) since the explant materials were from stock cultures that were initiated and maintained in WPM containing a low concentration of BA. These results also suggested that appropriate combination of an auxin and a cytokinin could enhance chestnut micropropagation.