Induction of callusogenesis from different types of explants of rare plant species of the genus Carlina L.

Aim. To investigate the characteristics of callus induction from different types of explants of Carlina L. species and to determine the optimal conditions for callus tissue formation. Methods. The objects of the study were Carlina onopordifolia Besser ex Szafer, Kulcz. et Pawł., Carlina cirsioides Klokov, and Carlina acaulis L. Root and leaf explants were cultured on Murashige and Skoog (MS) medium supplemented with different combinations of the auxins indole-3-acetic acid (IAA) and 2,4-dichlorophenoxyacetic acid (2,4-D), and the cytokinins kinetin (KIN) and 6-benzylaminopurine (BAP). The efficiency of callus induction was evaluated as the percentage of explants capable of callus formation. Results. Plants of all studied species were capable of forming callus tissue in vitro. The efficiency of callus induction depended on the explant type, the composition of the nutrient medium, and the concentrations and ratios of plant growth regulators. Leaf explants exhibited the highest callogenic activity, with callus induction frequencies ranging from 80% to 100% on most media, whereas root explants showed lower and more variable responses. The most effective media for callus induction were those supplemented with IAA at concentrations of 1.0–3.0 mg/L in combination with KIN (0.1–0.5 mg/L), where callus induction frequencies reached 90–100% regardless of explant type. The addition of 2,4-D at concentrations of 0.5–1.0 mg/L also ensured high callus induction rates, whereas increasing its concentration to 2.0–3.0 mg/L inhibited callus formation. Leaf explants cultured on dedifferentiation media retained their ability to form morphogenic structures. Conclusions. The optimal conditions for callus induction in Carlina species were determined. The obtained results may be applied to the conservation of rare Carlina species and to further studies of the biosynthetic activity of callus cultures, as well as to the development of biotechnological systems for the production of biologically active compounds.