Full Length Research Paper

Influence of plant growth regulators on axillary shoot multiplication and iron source on growth of Scrophularia takesimensis Nakai - a rare endemic medicinal plant

Iyyakkannu Sivanesan¹, Seung Jae Hwang¹ and Byoung Ryong Jeong^1,2*

¹Department of Horticulture, Division of Applied Life Science (BK21 Program), Graduate School, Gyeongsang National University, Jinju, Korea 660-701.

²Institute of Agriculture and Life Science, Gyeongsang National University, Jinju, Korea 60701.

*Corresponding author: E-mail:brjeong@gnu.ac.kr. Tel.: +82-55-751-5489; Fax: +82-55-757-7542.

Abbreviations: 2iP, 6-(g, g-dimethlyallylamino) purine; BAP, 6-benzylaminopurine; IAA, indole-3-acetic acid; IBA, indole-3-butyric acid; MS, Murashige and Skoog medium; MMS, modified Murashige and Skoog medium; PGRs, plant growth regulators; TDZ, thidiazuron.

Accepted 28 November, 2008

An efficient protocol for the in vitro propagation of Scrophularia takesimensis, a rare endemic medicinal plant, is described. Shoot multiplication was induced by culturing nodal explants on MS medium containing 3% (w/v) sucrose, 0.8% (w/v) agar, and different concentrations and combinations of plant growth regulators. The greatest percentage of shoot induction was achieved when nodal explants were cultured on MS medium supplemented with 2.0 mg l^-1 BAP and 1.0 mg l^-1 IAA with an average of 16 shoots per explant. The microshoots were separated from the multiple shoots and sub-cultured onto MS medium with 3% (w/v) sucrose and 0.8% (w/v) agar for further growth, and rooting. The plantlets growth was slow and often showed chlorosis on leaves. This problem was overcome by transferring microshoots to MS medium modified by increasing FeSO₄ (55.6 mg·L^-1) and Na₂EDTA (74.52 mg·L^-1) salts concentration. The iron concentration had a significant effect on chlorophyll content of the leaves. Chlorophyll content was increased by increasing FeSO₄ and Na₂EDTA salts concentration. Maximum rooting was obtained on modified MS medium supplemented with 1.0 mg l^-1 IBA. The in vitro-grown plantlets were successfully established in the field with 96% of survival. This protocol could be utilized for conservation and clonal propagation of this economically important plant.

Key words: Chlorosis, conservation, endangered plants, in vitro propagation, nodal explants, Scrophularia takesimensis.