Identification of a cytokinin treatment for in vitro propagation of two sweet cherry cultivars in preparation of a sanitation protocol

Sweet cherry (Prunus avium L.), member of the subgenus Cerasus, is a globally important vegetatively propagated fruit crop. Unfortunately, trees grown in fields and nurseries are threatened by the Prune dwarf virus (PDV). This virus causes malformations and a decrease in growth vigour and yield. A solution to get rid of the PDV virus in the Czech prospective sweet cherry cultivars 'Tamara' and 'Kasandra' is a part of the global sanitation programme. Tissue culture techniques are an important tool for quick multiplication of requested cultivars and offer the opportunity to improve the health status of micropropagated plants by combining in vitro culture with chemo or thermotherapy. The goal of this study was to identify factors affecting the ability of Czech sweet cherry cultivars to produce shoots under in vitro culture conditions. Six proliferation MS media containing 1, 2 and 4 mg L^-1 BAP (6-benzylaminopurine), 0.5 and 1 mg L^-1 TDZ (thidiazuron) or 10 mg L^-1 2iP (6-(g,g-dimethylallylamino) purine) were tested. Values of multiplication rate varied between 1.2 and 4.5. From the tested cytokinins, BAP at a concentration of 4 mg L^-1 was found to be more effective than TDZ and 2iP for shoot multiplication. In conclusion, our experiments confirmed that in vitro propagation of selected sweet cherry cultivars can be achieved. The described procedure enabled us to multiply and maintain in vitro plants throughout the year of the two sweet cultivars for further experiments with in vitro chemotherapy.