THE REACTION OF RASPBERRY AND BLACKBERRY CULTIVARS TO DROUGHT STRESS SIMULATED IN VITRO BY POLYETHYLENE GLYCOL (PEG) 6000

The goal of this study was to evaluate whether Rubus genotypes could be selected in vitro for tolerance to drought stress. Drought conditions were simulated by introducing polyethylene glycol 6000 (PEG) into proliferation or growth regulator free media. The ability to produce axillary shoots, dry weight and proline content were used for evaluation of the stress reaction. All the cultivars reacted to PEG in the medium with a decrease in the axillary shoot number and an increase in proline content. The reaction differed in strength depending on the concentration of the stressor in the medium, the length of the stress period, and the genotype. To yield a practical value for breeding, the results obtained in vitro will be compared with results from in vivo experiments which are underway.