In vitro propagation of Petasites hybridus (Asteraceae) from leaf and petiole explants and from inflorescence buds.

In vitro shoot regeneration from sterile leaf and petiole explants and from in-situ-collected inflorescence buds of Petasites hybridus was achieved by a simple two-step protocol. Murashige and Skoog (MS) nutrient medium was supplemented with 17.6 µM benzyladenine (BA)+0.54 µM naphthaleneacetic acid (NAA) to induce shoots. After 5 weeks of culture, 40% of the petiole and 27% of the leaf explants produced shoots compared to 76% of the inflorescence buds. Single shoots were excised and subcultured on MS medium supplemented with various cytokinins (N6-(Δ2-isopentenyl)adenine, BA, kinetin and thidiazuron). A concentration of 8.8 µM kinetin+0.54 µM NAA performed best in terms of shoot multiplication rate, average shoot length and spontaneous root induction.