An efficient micropropagation protocol for Metasequoia glyptostroboides Hu et Cheng from shoot segments of 2-year-old trees

Metasequoia glyptostroboides Hu et Cheng (dawn redwood), a known relict living fossil, is listed as a Class I rare and endangered tree in China. An efficient in vitro propagation protocol was established in this study to overcome the shortage of germplasm that cannot be compensated by conventional reproduction and as a way to preserve this tree. This objective was achieved by testing the effect of plant growth regulators (PGRs) on shoot propagation and root formation. Axillary shoots, which could be induced on PGR-free woody plant medium (WPM), were efficiently propagated on WPM supplemented with 16.0 µM zeatin and 2.5 µM indole-3-butyric acid. Improved rooting was possible on WPM supplemented with 0.05 µM α-naphthaleneacetic acid. Rooting was possible both in vitro in vermiculite-based PGR-free liquid culture and ex vitro in plastic bags containing perlite: vermiculite (1:1, v/v). This effective in vitro micropropagation protocol for M. glyptostroboides serves as a way to conserve this tree and provides an opportunity for mass production to alleviate strain on natural populations.