Development of indirect somatic embryogenesis and plant regeneration system with immature embryos of the cultivated traditional Chinese medicinal herb Polygonatum cyrtonema

The dried rhizome of Polygonatum cyrtonema represents a highly valued traditional Chinese medicine. With a growing demand, the imperative arises for the establishment of an efficient tissue culture system for large-scale propagation. Here, we successfully developed a tissue culture system capable of yielding P. cyrtonema seedlings through somatic embryogenesis using immature embryos as explants within a 120-day timeframe. An optimum callus induction rate was achieved through a combination of 1.0 mg/L 6-BA and 0.5 mg/L 2,4-D in MS medium, resulting in the formation of numerous highly active callus. Subsequent transfer of primary callus to a medium containing 1.0 mg/L 6-BA and 1.0 mg/L 2,4-D in MS medium for 30 days yielded induction rates of 97.78%, 89.62%, 73.33%, and 66.67% for globular, heart, torpedo, and cotyledonary embryos, respectively. The highest rate of somatic embryo normal germination (73.33%) was observed in the MS+6-BA 2.0 mg/L+NAA 1.0 mg/L medium. Subsequent transfer of germinated somatic embryos to MS+IAA 0.5 mg/L+IBA 1.0 mg/L medium for 20 days resulted in robust tissue culture seedlings, with a survival rate of 93.33% when transplanted into a seedling substrate consisting of soil: perlite (3:1, v/v). This study not only marks the inaugural instance of somatic embryogenesis in Polygonatum species but also paves a foundation for the advent of breeding traditional Chinese medicinal herb P. cyrtonema via recent advanced biotechnological strategies.