Micropropagation of Four Species of Hellebore (Helleborus) and Their Commercialization

Being one of the earliest spring flowering perennial plants in nature, Helleborus is attracting increasing interest and market in North America and Europe in recent years. There are more than 20 species in the genus Helleborus, among which H. × ballardiae and H. niger dominate the market nowadays, with H. × hybridus cultivars in great demand and with the highest market values. The slow natural propagation limits the commercialization of an elite breeding line. Although tissue culture techniques are widely applied to propagate many horticultural plants, Helleborus is still considered as one of the most recalcitrant plants, especially the species H. × hybridus.

In collaboration with Pine Knot Farms (http://www.pineknotfarms.com/), we have established an efficient tissue culture system for 4 species of Helleborus, H. × hybridus, H. × ballardiae, H. × nigercors, and H. niger. In the high value H. × hybridus, we have collected 132 elite breeding lines, with 82 growing in vitro. The tissue culture response rate is 62.1% (82/132). Calli and shoot regeneration were induced on young leaf segments, meristems and flower buds. Somatic embryogenesis was observed during subcultures and developed into plants. By modifying the medium composition and culture conditions, we have more than 20 genotypes of H. × hybridus in tissue culture, including various flower colors, double petal layers, and special color combinations. The H. × ballardiae, H. × nigercors and H. niger are commercially micro-propagated by Dan River Plants, LLC, using our tissue culture systems. Five genotypes of H. × hybridus are currently micro-propagated for commercialization, with additional genotypes planned for large-scale production annually.