Tytarenko N. Improvement of clonal micropropagation biotechnology of Rubus fruticosus L. and Paulownia tomentosa Steud. using microorganisms.

In the dissertation, results of the improvement of clonal micropropagation biotechnology of Paulownia tomentosa (Thunb.) Steud. and Rubus fruticosus L. var. Thornfree using microorganisms at the post-aseptic acclimatization stage are presented. For the studied plant species, improved technological schemes for obtaining planting material, from the stage of in vitro culture establishment to the stage of obtaining acclimatized seedlings in closed ground, were proposed. Clonal micropropagation is the aseptic cultivation of plants in vitro for rapid reproduction, which allows obtaining a large number of genetically homogeneous seedlings with specific characteristics. To increase the effectiveness of this method, it is necessary to consider the physiological features of certain plant species and improve standard approaches at various stages of propagation, including post-aseptic acclimatization of microclones as a stage with large potential losses of plant material. Blackberry (Rubus fruticosus L.) is a fruit and berry crop that is becoming increasingly widespread in Ukrainian horticulture. Thornless varieties are the most convenient for both care and harvest. Micropropagation allows for the continuous production of a large number of blackberry seedlings, even under conditions of small production capacities. Paulownia (Paulownia tomentosa (Thunb.) Steud.) is a tree crop that is actively grown in many countries as a source of renewable energy, and in recent years, it has been actively cultivated in Ukraine. Owing to their ease of care, rapid growth, and energy potential, there is a demand for large batches of standardized seedlings. Given the current high commercial demand for micropro-pagated planting materials of both blackberry and paulownia, they were selected as model plants for enhancing micropropagation using beneficial microorganisms. As a result, for the first time, the use of fungicides during the surface sterilization of explants was proposed for the studied plant species, which made it possible to maintain a lower level of contamination (16.7% for paulownia and 8.3% for blackberry) and a higher survival rate (58.3% for paulownia and 73.3% for black-berry) than the control. The optimal concentration of ascorbic acid in the medium at the in vitro culture establishment stage was established (50 mg/l - for paulownia and 100 mg/l - for blackberry), and it was determined that a semi-liquid agar medium with 0.4% agar had a better effect on the growth and development of plant explants in the primary stages of micropropagation than solid 0.8% agar medium. For the first time, the use of alternative gelling components at different stages of micropropagation of blackberry and paulownia was investigated, and it was established that corn starch (7%) could be recommended for use at all stages of clonal micropropagation of plants of both studied species, except for blackberry rooting. Guar gum (3%) could be used only at the rooting stage of paulownia microclones because when used at other stages, a lower survival rate, bud proliferation, and number of formed shoots and nodes in plants were observed. The phytohormonal composition of the medium at the propagation stage was optimized to obtain the largest number of formed shoots and nodes on the cuttings in one cycle of cultivation (for paulownia - 2.0 mg/l BAP + 0.5 mg/l IAA, for blackberry - 1.5 mg/ l BAP+0.5 mg/l NAA).