Embryo culture, callus induction, and flavonoid profile of Strychnos pseudoquina A. St.-Hil., an important medicinal species from the Brazilian Cerrado biome

Key message Plant tissue culture techniques can be efficient for the micropropagation and flavonoids production in Strychnos pseudoquina A. St.-Hil. Despite being described by the nineteenth century naturalist Auguste de Saint-Hilaire as an important native Brazilian medicinal species, Strychnos pseudoquina A. St.-Hil. remains poorly characterized. To preserve biodiversity in the Cerrado hotspot and tackle the negative consequences of S. pseudoquina overharvesting, the possibility of in vitro propagation and callus induction of this species was investigated. Thus, this study has established a novel protocol for: (i) in vitro cultivation of S. pseudoquina using zygotic embryo culture; (ii) callogenesis; and (iii) in vitro plantlet development in three different culture media: Murashige and Skooog (MS), Woody Plant Medium (WPM), and "Juan, Antonio, Diva and Silvia" medium (JADS). This was complemented by a liquid chromatography coupled to mass spectrometry (LC-MS/MS) analysis for the identification of flavonoid profile of ex vitro extracts from S. pseudoquina bark and leaves, as well as extracts from leaves, stems, roots, and root-derived calli of in vitro grown plants to assess the production of secondary metabolites. Results support the feasibility of S. pseudoquina preservation via embryo culturing and subsequent plantlet recovery and development. The use of zygotic embryos reduces substantially the time to generate seedlings. Cultured zygotic embryos germination occurred within 7 days, overcoming S. pseudoquina seed dormancy that usually takes 65 days and, under optimal conditions enables the emergence of true leaves. Additionally, root-derived callus of S. pseudoquina could represent an alternative source for flavonoid production and in vitro conservation of the species.