ADAPTATION EFFICIENCY OF BLACKBERRY VARIETIES AT THE EX VITRO STAGE DEPENDING ON SUBSTRATE TYPES

The aim of the study is to determine the effectiveness of substrates at the adaptation stage of blackberry variety microplants when growing virus-free planting material using micropropagation technology. Objectives: to determine the effect of substrate types on the rooting activity of blackberry varieties (average number and length of roots), as well as on the development of plant height and the increase in vegetative mass. The object of the study was regenerated blackberry plants. The studies were conducted at the Scientific and Production Center for Fruit and Berry Crops Nursery in 2024–2025. Microplants were transplanted from laboratory aseptic conditions to various nutrient substrates in cassettes with 90 cells and a volume of 50 ml each. Adaptation of the microplants was carried out for 28 days. Upon completion of the adaptation, biometric and morphometric parameters of the plants were recorded. The experiment was two-factorial: factor A – 6 variants of peat-based nutrient media; factor B – blackberry varieties. The experiment was repeated four times. Three cassettes with 90 cells each were used as the experimental variant. According to the data obtained, the most active root formation in regenerated plants during the adaptation period was observed in the variant with the "peat + perlite + vermiculite + sunflower husk" substrate, where the average number of roots exceeded the control and other variants by 2.8–13.4. Moreover, the maximum length of formed roots, on average, across blackberry varieties, was observed with the "peat + diatomaceous earth + rice husk" substrate, which exceeded the results of the other variants by 2–26 mm. Accounting for the development of aboveground mass and total vegetative mass revealed that the greatest height of microplants and the greatest vegetative mass of microplants, on average, across blackberry varieties, were observed with the "peat + zeolite + vermiculite" substrate, the results of which significantly exceeded the results of the other experimental variants.