Direct adventitious shoot regeneration, in vitro flowering, fruiting, secondary metabolite content and antioxidant activity of Scrophularia takesimensis Nakai

Abstract

Effects of plant growth regulators, light quality and sucrose on direct adventitious shoot regeneration, in vitro flowering and fruiting of Scrophularia takesimensis were investigated. The highest mean number of shoots per leaf (23.4), petiole (17.2) and stem (20.3) explants was obtained on Murashige and Skoog (MS) medium fortified with 2.0 mg l−1 BA and 1.0 mg l−1 IAA under white fluorescent light (WFL). Red light emitting diodes (LED) gave better shoot growth followed by WFL and blue LED. However, red LED treatment decreased the number of roots and induced callus at the base of shoot. The highest number of roots per shoot (9.2) and a maximum root length (8.9 cm) were obtained when the cultures were maintained under WFL. Somaclonal variation was observed when the shoot buds were cultured on the modified MS medium containing 1.0 mg l−1 IBA. The variant had variegated leaves in comparison with those of normal plantlets. The greatest frequency of flower induction (96.8 %) was obtained when the shoots were cultured on the modified MS medium containing 6.0 % (w/v) sucrose for 45 days under blue LED. The in vitro developed flowers self-fertilized and formed fruits. The culture media and environment had a positive effect on the content of phenolic compounds. Harpagoside content was high in seeds and low in shoots developed in MS medium containing BA. Among the light sources, shoots maintained under blue LED found to be best for harpagoside production (4.9 mg g−1) followed by WFL (3.3 mg g−1) and red LED (2.7 mg g−1). In vitro regenerated shoots had higher capacity to detoxify DPPH free radicals than field-grown plant samples.