In vitro micropropagation of Astragalus physocalyx (Fabaceae) and reintroduction of plants in its Locus Classicus on Mladezhki Hill in Plovdiv

Stoyan Stoyanov, Marina Stanilova, Elina Yankova-Tsvetkova, Yulian Marinov, Boryanka Traykova

Abstract: Astragalus physocalyx Fisch. is a tertiary relict, critically endangered worldwide according to the IUCN criteria, included in the Bern convention and protected by the Biodiversity Act of Bulgaria. It was discovered in 1834, on Mladezhki Hill in Plovdiv, but this locality was destroyed during the development of a stone quarry. Later, another population was discovered in Bulgaria with only 20 individuals and one each in North Macedonia, Greece and Turkiye. The objectives of this study were to develop a protocol for rapid in vitro propagation of A. physocalyx and to reintroduce the species into its natural habitats. Almost two-thirds of all collected calyxes were empty and in vitro seed germination was most successful after mechanical disruption of the hard seed coat, or after repeated seed treatment with boiling and ice water. Plants were multiplied by direct organogenesis on MS medium supplemented with 1.0 mg/L BAP + 0.2 mg/L NAA or with 0.3 mg/L GA3 resulting in 16.0 and 48.4 new explants per in vitro tuft, respectively, for a period of 2 months. In vitro rooted plants were easily adapted to soil mixture but needed several years in the greenhouse to reach size suitable for transfer into the wild. In April, 2018, thirty-six plants were planted outdoors: 18 in the only Bulgarian population near Kulata village and 18 on Mladezhki Hill in Plovdiv; the latter survived, branched, and in 2021, the largest bloomed. The “Locus Classicus” of the species can be considered restored as all plants are currently in good condition.

Keywords: endangered species; in vitro plant multiplication; Leguminosae; restoration of plant population; seed germination; tertiary relict

Citation: Stoyanov, S., Stanilova, M., Yankova-Tsvetkova, E., Marinov, Y. & Traykova, B. (2024). In vitro micropropagation of Astragalus physocalyx (Fabaceae) and reintroduction of plants in its “Locus Classicus” on Mladezhki Hill in Plovdiv. Bulg. J. Agric. Sci., 30 (Supplement 1), 31–37

Date published: 2024-12-13