Application of thermo- and chemotherapy in vitro for elimination of some viruses infecting fruit trees and small fruits

Abstract: In vitro culture is known currently as a technique used to eliminate viruses from plants. In this study thermotherapy and chemotherapy in vitro were applied to eliminate ACLSV and PNRSV from myrobalan, PNRSV from ‘Empress’ plum, PDV from ‘Early Rivers’ sweet cherry, ACLSV from apple ‘Jonagold’ and pear ‘Pierre Corneille’, and RVCV from ‘Norna’ raspberry. Shoots were placed in a growth chamber where the temperature was raised gradually to 36°C and kept at this level for 4 weeks for thermotherapy. Chemotherapy was conducted using 10-100mg/l Virazole® (ribavirin) applied into the proliferation medium. Combining both methods was also used. ELISA assays for ACLSV, PNRSV and PDV were conducted one year after therapy. The rooted raspberry plants were planted in a greenhouse and observed for possible RVCV symptoms. Thermotherapy in vitro was highly effective for PNRSV and ACLSV elimination but it was not efficient for obtaining PDV-free sweet cherry and RVCV-free raspberry. Efficiency of chemo-therapy varied depending on concentration of Virazole®, virus and species of infected plant. Virazole® at concentration 25-100mg l-1 was effective in eliminating ACLSV from myrobalan and PNRSV from plum but was not successful in eliminating PNRSV from myrobalan and PDV from sweet cherry shoots. Combining thermotherapy and chemotherapy contributed to elimination of all studied viruses from most treated shoots.