IMPACT OF ACTINOBACTERIA ON THE GROWTH AND ACCLIMATIZATION OF MICROPROPAGATED RUBUS FRUTICOSUS L. PLANTS TO EX VITRO CONDITIONS

Microcloning is an effective method of plant reproduction that is actively developing in Ukraine for the mass propagation of valuable food crops such as blackberries. However, the problem of losing a large number of microclones often arises during the ex vitro acclimatization stage. Inoculation of the rhizosphere with potentially useful microorganisms could have a positive impact on the survival rate and biometric characteristics of acclimatized seedlings. The aim of this study was to establish the impact of 23 actinobacteria isolates on blackberry microclones (Rubus fruticosus L.) during acclimatization to ex vitro conditions, and to determine the protective potential and plant growth-promoting effects of these bacteria. Methods. The antagonistic properties of the experimental microorganisms were determined using the agar block method. Bacteria were inoculated into the rhizosphere of blackberry microclones before planting in the soil. Results. The antagonistic activity of actinobacteria against phytopathogenic fungi P. expansum, P. variotii, A. niger, C. cladosporioides, F. oxysporum, A. alternata, R. cerealis, and A. tenuissima was established. The positive effect of bacteria on micropropagated blackberry plants during acclimatization to ex vitro conditions resulted in an increase in the survival rate of microclones in the soil by 34.8%, average height of experimental plants by 2.0 cm, node number by 3.4 nodes, and leaf area by 0.4 cm2. Conclusion. It was established that isolates of mycelial actinobacteria Lim4, Myt7ch, Conc32, Conc4 were promising inoculants for ex vitro acclimatization of micropropagated plants and could be recommended for the subsequent research in order to establish the interaction mechanisms between these microorganisms and plants.