Efficacy of Antiviral Agents and Thermotherapy in Eliminating Viruses from In Vitro Plantlets Derived from Apical Meristems of Fire Blight Resistant Apple Rootstocks G11 and G30

Apple, the highest cultivated fruit crop in Korea, has been threatened by fire blight, a destructive disease caused by Erwinia amylovora (Burrill) since its first report in May 2015. To combat this, researchers have turned to Cornell- Geneva (Geneva® series) apple rootstocks, known for their resistance to diseases, pests, and Korea’s cold weather. We aimed to produce virus-free plants using the fire blight resistant dwarfing apple rootstocks G11 and G30 in this study. We employed virus elimination methods such as apical meristem culture (size: 0.1∼0.3 ㎜), thermotherapy (37°C for 0, 10, 20 and 30 days) and antiviral treatment (ribavirin: 0, 20, 30, 40 ㎎/L). Since apple virus diseases such as Apple chlorotic leaf spot virus (ACLSV, Trichovirus), Apple stem pitting virus (ASPV, Foveavirus), Apple stem grooving virus (ASGV, Capillovirus), Apple mosaic virus (ApMV, Ilarvirus), and apple scar skin viroid (ASSVd) have been reported, they were used in the detection. As a result, after meristem culture, the virus-free rate for G11 and G30 was 30.3% and 20%, respectively. Additionally, shoot meristem cultures of G11 and G30 treated with 20.0 ㎎/L ribavirin showed increased virus elimination rates. Ribavirin treatment (20.0 ㎎/L) resulted in a 30.3% virus-free rate for G11 and 51.0% for G30. Thermotherapy (37℃) led to an 89.6% survival and 61.0% virus-free rate in G11 and 30.3% survival and 100% virus-free rate in G30. Combined thermotherapy (37°C) and ribavirin treatment (20.0 ㎎/L) for 20 days enhanced virus elimination to 100% in G30. This indicates that combining apical meristem culture, thermotherapy, and antiviral methods can effectively eliminate apple viruses from fire blight resistant apple rootstocks.