Rosen S. Sokolov, Bistra Y. Atanassova and Elena T. Iakimova
In this study, the effects of compounds providing Fe in chelated (NaFeEDTA and Fe(III)AC) and non-chelated (FeSO4·7H2O) forms as components of culture media, on in vitro shoot multiplication and rooting of Magnolia soulangeana ‘Alexandrina’, Magnolia grandiflora and Prunus cerasifera ‘Nigra’ were comparatively evaluated. Each of the tested chemicals was used as a single Fe source in the basal salt medium. In the stages of shoot multiplication and rooting plant response was scored by biometrical indices (number of shoots, leaves and roots, shoot and root length, percent of rooted plants and root hairs). The occurrence of physiological disorders was estimated by visual observations. In presence of FeSO4, symptoms of chlorosis, hyperhy-dricity, early senescence and specific morphology of roots, suggesting Fe deficiency, were observed. These deteriorations were entirely prevented at the application of Fe chelates of which, in this experimental systems, Fe(III)AC was tested for the first time. The addition of Fe(III)AC positively affected the plant quality to extent comparable to that of NaFeEDTA. The obtained data suggest that both applied Fe chelates are more appropriate than non-chelated Fe form and can be alternatively used in the optimization of nutrient media for micropropagation of Magnolia and Prunus cerasifera genotypes.
Rossen S. Sokolov, Bistra Y. Atanassova and Elena T. Iakimova
The objective of this study was to assess the regeneration response of in vitro cultured Magnolia × soulangeana ‘Alexandrina’ and Magnolia liliiflora ‘Nigra’ to nutrient medium composition. In the primary culture (initiated from dormant axillary buds) combinations of Murashige and Skoog (MS) basal salts with 6-benzylaminopurine and α-naphthaleneacetic acid were tested. The primary explants of cv. ‘Alexandrina’ expressed higher regeneration rate than cv. ‘Nigra’. For both species, the regen eration was most strongly potentiated at addition of 0.25 mg dm−3 of the cytokinin alone. The auxin exerted undesir–able effects. Several basal salts media were applied in proliferation stage and their physiological effects were evaluated in reference to traditionally used MS. At culturing on Chée & Pool C2d Vitis Medium (VM) that is for the first time introduced to magnolia and on MS, M. liliiflora formed more but less elongated shoots than M. soulangeana. However, on VM, substantial increase (25-30%) of the number of axillary shoots and leaves, shoot length and fresh and dry weights over MS was established for both species. This suggested VM as promising composition of nutrients in multiplication stage. Microshoots obtained on MS, VM, Rugini Olive Medium and DKW Juglans Medium were successfully rooted in vitro and subsequently established ex vitro. The findings expand the information on magnolia response to culture conditions and contribute to elaboration of innovative elements of protocols for establishing tissue cultures with high regeneration capacity.
Andrei I. Kaninski, Ivanka Ivanova, Sergey Bistrichanov, Nadejda Zapryanova, Bistra Atanassova and Elena T. Iakimova
Native populations of endemic, rare and threatened Limonium species (L. meyeri, L. bulgaricum, L. latifolium, L. vulgare, L. asterotrichum and L. gmelinii) in Bulgaria were monitored and found seriously declined. To preserve these wild genotypes, an approach involving in vitro propagation of explants isolated from immature inflorescence stems was applied at the Institute of Ornamental Plants, Sofia. The rooted plantlets produced were acclimated and grown outdoors under an optimized cultivation regime, which resulted in the establishment of an ex situ plantation. Plant performance ex situ (determined by leaf rosette diameter, plant height and the number of flower stems) was substantially improved and the variation in the biometric indices was found remarkably lower than in natural environment. The developmental stages of ex situ plants appeared with a delay in relation to their onset in the native environment, but occurred synchronously within each species. Analysis of germination of seeds harvested from ex situ and in situ grown plants showed species-specific behaviour, but in general, seed vitality remained relatively low in laboratory conditions, in the soil and in vitro. In order to assess the potential for protecting the native Limonium species from uncontrolled harvesting, the possibility for the production of cut flowers in ex situ conditions was studied. High yield of cut flowers from ex situ plants in comparison with the potential yield from the wild plants and extended vase life in comparison with commercially produced Limonium sinuatum were obtained. The results demonstrated that the applied micropropagation and agrotechnique for protected cultivation are reliable tools for ex situ conservation of the endangered Limonium genotypes in the Bulgarian flora. In addition to its advantage as a rescue measure, the developed system was shown to be suitable for obtaining cut flowers of competitive market quality.