Improved detection, mealybug transmission and prevalence of grapevine Roditis leaf discoloration-associated virus in Greek vineyards

Grapevine Roditis leaf discoloration-associated virus (GRLDaV) is a member of the species Badnavirus decoloratiovitis in the genus Badnavirus that was recently identified in grapevine using high throughput sequencing. In this study, a large-scale survey was conducted to monitor the prevalence of the virus in major viticultural areas of Greece. A total of 970 samples were collected from vines and molecularly analysed using PCR assays targeting two regions of the virus genome. GRLDaV was detected in 8 geographic areas of Greece, showing high frequency in southern and central Greece and an overall prevalence of 17.1%. GRLDaV was identified mainly in autochthonous grapevine varieties, and it showed higher frequency in the self-rooted ones, especially in the geographic region of the Cyclades islands. In transmission tests conducted using Planococcus ficus (Signoret) and 48 h acquisition access period (AAP) and inoculation access period (IAP), the virus was transmitted with an efficiency of 14.3% (3/21 grapevines). Finally, electron microscopy revealed the bacilliform morphology of GRLDaV virions, thus further confirming its episomal infection.