Possibilities for application of in vitro techniques in propagation of species of the genus Tilia sp.

Valeria Ivanova, Lilyana Nacheva and Valentin Panchev

Abstract: The propagation of the three types of linden used in the landscaping in Bulgaria is carried out mainly by seeds and cuttings, but both methods have a number of disadvantages. Alternative possibilities in this regard are provided by in vitro propagation, but studies on the types of explants, methods of surface disinfection, media composition, conditions for adaptation from in vitro to ex vitro growth are very limited. Having in mind that lindens are one of the most preferred and most widely used deciduous species in European and world ornamental horticulture, the clarification of these issues becomes particularly relevant. The aim of the present study was to develop an effective protocol for in vitro micropropagation of linden. Apical buds and stem cuttings from the top of mature cuttings or actively growing annual shoots of adult trees, apical and nodal segments of actively growing seedlings were used as initial explants. Two surface disinfection methods were studied – with 5% solution of calcium hypochlorite [Ca(OCl)2] and 2% silver nitrate (AgNO3). In the studies, nutrient media for multiplication based on MS (Murashige & Skoog, 1962), DKW (Driver & Kuniyuki, 1984) and WPM (McCown woody plant medium, 1980) were used. The effect of cytokinins 6-benzylaminopurine (BAP), Kinetin (6-furfurylaminopurine), meta-topolin (mT, [6- (3-hydroxybenzylamino) purine]), 2-iP (6-γ-γ-dimethylalylamino) -purine) at an equimolar concentration of 5μM on the multiplication of large-leaved linden (Tilia platyphyllos Scop.) was studied. The best disinfection procedure was found by sequential application of Ca(OCl2) and AgNO3 to explants from actively growing shoots, with the best results obtained with Tilia cordata Mill. In the multiplication of Tilia platyphyllos Scop. the maximum number of lateral shoots (2.93) was reported on the medium with meta-topolin, followed by those with BAP (1.73). The highest rooting rate (84.61%) of large-leaved linden (Tilia platyphyllos Scop.) was achieved on MS medium with half strength macronutrient content enriched with 0.3 mg l-1 indolyl-3- butyric acid (IBA).

Keywords: auxins; in vitro culture; meta-topolin; Tilia cordata Mill.; Tilia platyphyllos Scop.; Tilia tomentosa Moench.

Date published: 2021-09-15