In Vitro Propagation of Sweet Rowanberry Cultivar Discolor as an Alternative Fruit Crop Resource

Developing reliable in vitro propagation methods for rowanberry genotypes is essential for their use in breeding and horticultural programs. While different rowanberry species and cultivars are primarily valued for their ornamental and forestry properties, poor seed germination and the low success rate of conventional vegetative techniques constrain their propagation. Micropropagation offers a practical approach to obtaining uniform, disease-free plant material for selection, hybridization, and the subsequent horticultural use of particular valuable genotypes. Shoot multiplication of a prospective sweet rowanberry cultivar ‘Discolor’ was studied on a Murashige and Skoog (MS) medium supplemented with 6-benzylaminopurine (BAP) at concentrations of 1, 2, and 4 mg L−1, thidiazuron (TDZ) at concentrations of 0.5 and 1 mg L−1, and 6-(γ,γ-dimethylallylamino)purine (2iP) at a concentration of 10 mg L−1. Root induction was evaluated on a half-strength MS medium (50% MS) supplemented with 1 mg L−1 of naphthaleneacetic acid (NAA), indole-3-butyric acid (IBA), or indole-3-acetic acid (IAA). TDZ at 1 mg L−1 yielded the highest multiplication coefficient. However, media with TDZ at a lower concentration (0.5 mg L−1) or BAP (2–4 mg L−1) provided the best balance between proliferation rate and shoot quality. These media promoted the growth of vigorous, well-elongated shoots with minimal callus formation. In contrast, the phytohormone 2iP did not elicit physiological response in the in vitro multiplication of explants. The best rooting results were obtained using a 50% MS medium supplemented with 1 mg L−1 IAA, which provided the highest rooting percentage and root quality. IBA produced slightly lower, though comparable, results, while NAA resulted in weak, sporadic root formation. The established protocol enables the efficient in vitro propagation of the studied cultivar. This system supports its application in breeding and fruit production programs, as well as in maintaining valuable genetic resources within the genus Sorbus.