Morphogen development of in vitro cultivated Shrub roses
The article presents the study's results of the morphogen development features of the Shrub roses explants during in vitro reproduction — five cultivars from the collection fund of the National Dendrological Park "Sofiyivka" of the National Academy of Sciences of Ukraine: 'Gärtnerfreude' (W. Kordes' Söhne, 1991), 'Lavender Dream' (G. P. Ilsink, 1984), 'Pomponella' (W. Kordes' Söhne, 2005), 'Red Cascade' (R. S. Moore, 1976), 'Sommerabend' (W. Kordes' Söhne, 1995). The listed cultivars belong to those Shrub roses that form a dense cover of shoots, leaves, and flowers and are applicable for decorating plots that are of little avail for growing other ornamental plants. Shrub roses of most varieties introduced into the National Dendrological Park "Sofiyivka" National Academy of Science of Ukraine have shown sufficient adaptive ability in the natural and climatic conditions of the introduction area. Studies of gas resistance have shown that roses of this class adapt well to the conditions of the high content of traffic fumes and dust while maintaining high decorative qualities, which gave reason to recommend them for wide use in landscaping settlements of the Right-Bank Forest-Steppe Zone of Ukraine. However, the experience of introducing Shrub roses into gardening has shown that to create landscape expositions, it is often necessary to have a large amount of planting material of a specific cultivar, and to solve the problem requires the use of new, promising propagation methods. One of them is the in vitro plant propagation method, developed based on biotechnology to preserve plants genetically identical to the original maternal form, which contributes to the production of morphologically aligned, genetically homogeneous planting material. Therefore, the study of the reproduction features of the garden class Shrub roses, cultivated in vitro, defined the dependence of the explants morphogen development on changes in the concentrations of cytokinins and auxins included in the nutrient media are relevant and have both scientific and practical interest. The authors revealed that the studied cultivars were successfully introduced into the culture in vitro, are capable of direct morphogenesis when using exogenous phytohormones 6-BAP, β-IBA, β-IAA, 1-NAA; however, they had unequal indicators in the morphogenetic reactions display the degree. It was found that the phytohormonal regulation of morphogen processes in explants was determined by the presence of specific ratios of both auxins and cytokinins in the nutrient medium. Using segments of shoots with axillary and apical buds, the authors obtained morphogen structures that were formed directly on explants by the direct morphogenesis type. Of the tested inducers of morphogenesis, the most effective for the Shrub roses was MS 6-BAP – 2.0 mg/l and β-IBA – 0.01 mg/l to the nutrient medium. Within 28–34 days after passage on nutrient media modified with the addition of phytohormones, active formation of morphogen structures was observed, which gave rise to shoots, the number of which averaged from 2.92 to 12.04 pcs. per explant. 'Red Cascade' and 'Sommerabend' cvs differed in the maximum indices of adventive shoot formation, which, in six passages, reached a multiplication rate of 12.2±0.33 and 7.24±0.35, respectively. ‘Gärtnerfreude’, ‘Lavender Dream’, ‘Pomponella’ cvs. under the influence of various concentrations of phytohormones had slightly lower indices of morphogen potential with the multiplication rate in the range of 3.66±0.15 to 6.33±0.11. Thus, the differentiation of meristemic tissues of the studied Shrub rose cultivars with the subsequent induction of morphogenesis depends on the concentration of both cytokinins and auxins in nutrient media and determines the successful reproduction of these plants in vitro. A short reproduction cycle allows for a short time to obtain the required amount of planting material while maintaining the necessary economically valuable traits.