Elimination of Hop Stunt Viroid (HSVd) from Infected Peach and Pear Plants Using Cold Therapy and Chemotherapy

Hop stunt viroid (HSVd) was detected in several pear and peach trees collected during summer season by RT-PCR and molecular hybridization assays. Hop stunt viroid disease was very severe in summer; however, the multiplication of viroid decreases drastically in winter. In this study, the shoots cut from Prunus persicae cv. Florida prince and Pierre corneille cv. Balady infected plants treated by cold therapy, thermotherapy and/or chemotherapy was used successfully to eliminate Hop stunt viroid. Results demonstrated that application of 10 to 20 mg/L Virazole® followed by cold therapy for 30 days at 4°C in vitro gave a survival rate of 63 and 75% for pear and peach respectively. The presence of viroid in recovered plants was evaluated by tissue print hybridization technique. In vitro cold therapy combined with chemotherapy using shoot tip culture eliminates HSVd from infected peach and pear trees and reduces the risk of introducing this pathogen to Egypt