Аннотация
This study provides a comprehensive phytosanitary assessment of Cotoneaster melanocarpus stock plants during micropropagation in vitro. The results revealed that a substantial proportion of visually healthy donor material harbors latent microbial contamination, which represents a critical constraint for the efficiency of biotechnological propagation. Specifically, latent microflora was detected in 28–32% of donor plants and became active at the early stages of in vitro culture. At the culture initiation stage, despite the application of standard surface sterilization procedures, explant contamination levels reached 30–35%, indicating a predominantly endogenous origin of infection and highlighting the difficulty of its complete elimination. Rooting of microshoots on half-strength MS medium supplemented with 0.5 mg/L indolebutyric acid (IBA) demonstrated high efficiency, with 82–88% of shoots forming roots and an average of 3–4 morphologically normal roots per shoot. The findings demonstrate a direct relationship between the phytosanitary status of stock plants and the success of micropropagation. Preliminary phytosanitary screening of donor material reduces contamination losses in vitro, improves culture establishment, and prevents pathogen transmission to clonal progeny. The results are of practical importance for the production of high-quality, phytosanitary-safe planting material suitable for ornamental applications, forestry, and ecological restoration programs.