Aim of the study:
The aim of the study was to assess the effect of substrate composition on the rooting, adaptation, and early development of highbush blueberry regenerants.

Material and methods:
The effect of peat-based substrates on the growth and early development of highbush blueberry (Vaccinium corymbosum L., cv. ‘Bluecrop’) regenerants was assessed under controlled ex vitro conditions. Nine variants based on high-moor and low-moor peat with perlite and sapropel were tested in triplicate. Plant growth, rooting, nutrient accumulation, and substrate properties were evaluated according to DSTU and ISO standards, and the results were analyzed using ANOVA.

Results and conclusions:
High-moor peat-based substrates provided more favorable conditions for the adaptation, growth, and rooting of highbush blueberry regenerants than substrates prepared from low-moor peat. In the high-moor peat treatments, plant survival ranged from 94.7 to 99.4%, whereas in the low-moor peat treatments it ranged from 78.4 to 88.4%. The best results for biomass accumulation and root system development were obtained with high-moor peat supplemented with 10% perlite. This treatment was characterized by the highest fresh biomass and the greatest root length. The addition of 10% sapropel increased regenerant survival and promoted greater accumulation of nitrogen, phosphorus, and potassium in plant tissues. The combined application of perlite and sapropel did not further improve the analyzed parameters compared with the separate use of these components. The results indicate that high-moor peat supplemented separately with perlite or sapropel may be considered a promising substrate for the cultivation of highbush blueberry regenerants under controlled ex vitro conditions.