INCIDENCE AND MOLECULAR VARIABILITY OF APPLE STEM PITTING AND APPLE CHLOROTIC LEAF SPOT VIRUSES IN APPLE AND PEAR ORCHARDS IN GREECE

摘要

A survey was conducted in the major pome fruit growing districts of Greece to assess the incidence of Apple stem pitting virus (ASPV) and Apple chlorotic leaf spot virus (ACLSV) using RT-PCR assays amplifying part of the RNA-dependent RNA polymerase (RdRp) and the coat protein genes of the viruses, respectively. ASPV was predominant in apple (91.8%) and pear (51.3%) and was detected in almost all the cultivars and rootstocks tested. It was also found for the first time in the Japanese pear (Pyrus serotina). The incidence of ACLSV in apples was also high (65.7%) and mixed infections with both viruses were frequently encountered. In pear, ACLSV incidence was lower (20.7%). This is the first extensive survey conducted in Greece for monitoring ACLSV and ASPV using molecular assays. Nucleotide sequencing of different apple and pear ASPV and ACLSV isolates and comparative analysis with already published homologous genomic regions revealed a significant level of variation up to 29% and 22% for the RdRp and the CP genes, respectively. However, high identity rates were found among isolates of both viruses from different geographical origins. Our results show the high impact of the use of infected plant material in the dissemination of ASPV and ACLSV and illustrate the need to implement programs for the production of certified pome fruit propagating material in Greece, in order to prevent further spread of the viruses.