Abstract
Malus niedzwetzkyana is a rare and valuable wild species characterised by a high anthocyanin content. This species is of considerable interest as a promising source of bioactive compounds. In this study, we investigated the effect of explant type on callus induction and its morphological characteristics. Stems and leaves from 40-day-old plants grown in vitro on Murashige-Skoog (MS) medium were used as explants. The results showed that stem explants demonstrated a higher ability to form callus compared to leaf explants - 100% and 86.7%, respectively. MS medium with various concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D) (2.5; 3.0; 3.5 mg/l) and 6-benzylaminopurine (BAP) (0.5; 1.0 mg/l) had a significant effect on diameter, fresh and dry weight, as well as dry matter (p < 0.001). The combination of MS medium with 2,4-D at a concentration of 3.5 mg/L and BAP at 0.5 mg/L proved optimal, as it resulted in the formation of a uniform, loose callus of a pinkish burgundy colour. Thus, our results provide a basis to produce suspension cultures and the biotechnological production of biologically active substances from Malus niedzwetzkyana.