Breaking the soil barrier: Somatic embryogenesis and polyploidization enable high-yield saponin in Panax notoginseng (Burk.) F.H.Chen

Panax notoginseng (Burk.) F.H.Chen is a highly valuable medicinal plant. The saponins abundant in its roots and rhizomes are effective in medicine, health products, and skincare. However, its planting faces severe continuous-cropping obstacles, high soil-borne disease susceptibility, and product contamination by agro-residues and heavy metals. Moreover, its recalcitrant seeds require field-based germplasm conservation. All these are soil-related and/or land-consuming problems. In this study, we explored a soil-independent cultivation method for P. notoginseng. Seeds were employed as explants to induce embryogenic callus, which subsequently differentiated into somatic embryos and plantlets. We tested the approach of generating cotyledon embryos in a mechanically stirred bioreactor and screened methods to induce plantlets to produce roots and rhizomes. By treating the embryogenic callus with colchicine, we induced and selected homozygous tetraploid embryos and plantlets. We also investigated the conditions for mass-producing tetraploid roots and rhizomes in an submerged intermittent bioreactor. Further analysis revealed that mature cultures and tetraploid cultures had higher saponin content. Our results provide a robust scientific foundation for developing new soil-independent cultivation technologies and preserving P. notoginseng germplasm.