In vitro propagation and re-introduction of Golden Paintbrush (Castilleja levisecta), a critically imperiled plant species

Golden paintbrush ( Castilleja levisecta Greenm.) is a hemi-parasitic herbaceous perennial native to the Pacific Northwest of North America and is considered critically imperilled with only 11 populations remaining in the wild. The main objective of this study was to develop ex-situ and in situ conservation through micropropagation and field plantings. In vitro cultures were initiated using nodal explants from two plants raised from seeds collected from a natural population. Shoots were then multiplied on MS basal medium with 2.0 µM BA, 3.0 µM Kinetin, 2.2 g/L phytagel and 3% sucrose. Explant position on source plants, culture vessel design and application of different plant growth regulator levels for 6-Benzylaminopurine (BA), Kinetin (Kn) and Thiadiazuron (TDZ) were tested in order to optimize micropropagation protocols. Clones from the plants showed differences in plant height and number of nodes in response to various BA and TDZ concentrations. In vitro shoots were successfully rooted under ex-v...