Improvement of Stachys sieboldii (Miq.) growth by virus elimination of shoot apices cultivated on media free of plant growth regulators

Chinese artichoke (Stachys sieboldii [Miq.]) is a popular healthcare food owing to its high contents of stachyose. Viral infections have caused the severe degeneration of germplasm in this plant species. An efficient virus elimination and micropropagation system is required to produce Chinese artichoke plants that are free of viruses. A protocol for virus elimination in Chinese artichoke was established by comparing the potential for growth of the terminal buds using shoot apices as starting materials, in media with or without plant growth regulators (PGRs) and various concentrations of sucrose. Murashige and Skoog (MS) medium without any PGR performed better than that supplemented with PGRs as indicated by a higher rate of survival of shoot apices, higher plant height, more root numbers and adventitious buds, and increased biomass (P < 0.05). An experiment to further optimize the sucrose concentration demonstrated that MS medium with 5.0% sucrose (w/v) efficiently induced the growth of both roots and shoots, thus, achieving the efficient micropropagation of Chinese artichoke within 4 wk. Compared with the mother plants in which viruses had not been eliminated, the virus-free plants had significantly higher numbers of tubers, increased yield, and a higher content of stachyose (P < 0.05). Higher contents of endogenous hormones were detected in Chinese artichoke, which may explain the efficient micropropagation without the use of exogenous PGRs. This simple protocol enabled the production of virus-free Chinese artichoke to enhance the yield of tubers and high content of stachyose.