Optimization of the culture medium for the in vitro micropropagation of Hydrangea L. plants
Uman National University, 1 Instytutska Str., UA20305 Uman, Ukraine
*Correspondence: abrovdi@ukr.net
Abstract:
Species of the genus Hydrangea L. are valuable ornamental plants widely used in landscaping, creating a demand for large quantities of genetically uniform planting material. Traditional vegetative propagation may be insufficiently effective for producing the required quantities of planting material, whereas in vitro micropropagation enables the rapid production of large numbers of regenerated plants under controlled conditions. However, the efficiency of hydrangea micropropagation depends considerably on genotype, the balance of plant growth regulators, the carbohydrate source, and mineral nutrition. Therefore, determining optimal conditions for their in vitro cultivation is of considerable importance. The aim of the study was to investigate and optimize the composition of the culture medium for the micropropagation of Hydrangea L. species to obtain high-quality, genetically uniform plant material for ornamental horticulture. The study was conducted in vitro during 2020‑2024 using 1.0–1.5 cm long shoots containing apical meristems of H. macrophylla ‘Nikko Blue’, H. paniculata ‘Grandiflora’ and H. arborescens ‘Annabelle’. The explants were cultured for shoot multiplication on a medium based on the Murashige and Skoog (MS) formulation, supplemented with plant growth regulators, iron, and carbohydrates at various concentrations. Statistical analysis of the results was performed using analysis of variance (ANOVA) and Fisher’s F-test to assess the statistical significance of the effects of the factors under study. Differences between the means were evaluated using the least significant difference (LSD₀₅) at a significance level of p < 0.05. The use of MS medium supplemented with 6-benzylaminopurine in combination with auxins and gibberellin suppresses apical dominance and stimulates the growth of axillary buds in Hydrangea explants. The highest efficiency of micropropagation was achieved through repeated subculturing and the cultivation of shoot clusters without division during the early stages, which contributed to an increase in the multiplication rate from 0.0 in the first passage to 5.75 in the fourth passage. The differences observed exceeded the LSD₀₅ value (0.31). The highest multiplication rate, with an average of 5.75 across the Hydrangea species and cultivars studied, was obtained on MS-35 medium, whereas the lowest rate, 1.14, was recorded on MS-42 medium. The highest multiplication rate for an individual genotype was obtained for H. arborescens on MS-35 medium, reaching 5.93. The highest number of shoots was obtained with the addition of 3.0 mg L-1 glucose and 3.0 mg L‑1 sucrose to the culture medium, reaching 6.3 and 6.1 shoots per explant, respectively. The maximum shoot length (7.8 cm) was recorded on MS-35 medium supplemented with 3.0 mg L-1 sucrose. The addition of FeSO₄ to MS-35 medium significantly increased the number and length of shoots mg L-1, with 8.36 shoots per explant and a shoot length of 4.62 cm, whereas the corresponding values in the control were 3.8 shoots per explant and 1.95 cm, respectively. The differences between the treatments exceeded the LSD₀₅ values, which were 0.31 for the number of shoots and 0.19 for shoot length (p < 0.05). Thus, optimisation of the culture medium composition can increase the efficiency of micropropagation of Hydrangea species and provides a basis for the standardised production of large quantities of plant material in vitro. The results can be used to develop technological protocols for the accelerated clonal propagation of the studied genotypes.
Key words:
carbohydrate sources, culture medium, explant, micropropagation, phytohormones