Survey of Apple chlorotic leaf spot virus and Apple stem grooving virus occurrence in Korea and frequency of mixed infections in Apple

Due to the absence of knowledge of the distribution of Apple stem grooving virus (ASGV) and Apple chlorotic leaf spot virus (ACLSV) in apples in Korea, we carried out a survey for these viruses in Gyeongsang and Chungcheong provinces in 2014. A total of 65 samples were collected and tested by RT-PCR using ASGV and ACLSV specific primers. ASGV was detected in 22 samples, and ACLSV in three samples; two of the samples showed double infection of ASGV and ACLSV. Phylogenetic analysis suggests that Korean ASGV and ACLSV were introduced from other countries. Prevalence of ASGV and ACLSV indicates that virus prevention and control may be poorly managed in orchards. Since fruit trees remain in the orchard for many years and it is not possible to eliminate virus from infected trees, healthy scions and virus-resistant rootstocks must be used for virus control. Because it is difficult to visually distinguish ASGV-infected and ACLSV-infected apple trees from healthy trees, thorough surveys by molecular biology methods must be performed routinely.