<i>In vitro</i> propagation of katsura tree (<i>Cercidiphyllum japonicum</i> Sieb. Et Zucc), an endangered plant in China

Abstract

Katsura tree (Cercidiphyllum japonicum Sieb. Et Zucc) is a long-lived, deciduous, wind-pollinated tree with dimorphic leaves. It is valued as an ornamental or a shade tree for landscape and a commercially valuable tree. Conventional propagation through seeds and cutting is not sufficient to satisfy the progressive demand. There is an exigent need to develop protocols for rapid propagation of katsura trees. This study reports an in vitro propogation of the tree. The work focused on assessing the effects of basal medium, plant growth regulators (PGRs) combination on shoot and root proliferation. Nodal sections of young shoots were used as explants. Shoot initiation, and shoot and root proliferation were carried out on basal medium and PGRs combination. The optimal response of shoot initiation was observed in woody plant medium (WPM) supplemented with 1.0 mg L⁻¹BA and 0.01 mg L⁻¹IBA (indole-3-butyric acid) and the percentage of shoot initiation was up to 91.66%. For proliferation of micropropagated shoots, three orthogonal designs were carried out. The result shows that the highest proliferation coefficient (4.83) was obtained in the medium containing 1.0 mg L⁻¹ BA and 0.05 mg L⁻¹ NAA. With the application of benzyladenine (BA) and naphthalene acetic acid (NAA), emerald green and vigorous shoots were observed. Shoots about 2.0 cm long with 4 to 6 leaves were excised and transferred to root propagation media. When the concentration of NAA was 0.5 mg L⁻¹, the rooting percentage, mean number and mean length of roots were the highest, reaching 75% and 3.1 and 2.1 cm respectively. This efficient plant regeneration system would be helpful for genetic improvement through future conservation and biotechnology research.

Keywords: Katsura tree (Cercidiphyllum japonicum Sieb. Et Zucc), shoot initiation, shoot propagation, root propagation