Raspberry bushy dwarf virus in Slovenia - geographic distribution, genetic diversity and population structure

Abstract

Raspberry bushy dwarf virus (RBDV) is a long-known virus naturally infecting Rubus and grapevine. It is also one of the economically most important viruses of raspberries, but there are only a limited number of sequences covering a substantial part of the genome available in the databases. The aim of this study was: i) to study the geographic distribution of RBDV in Slovenia, and ii) to sequence RNA2 of several red raspberry and grapevine RBDV isolates and study their phylogeny and population structure. Geographic distribution studies were performed over a period of 13 years in three wine-growing regions of Slovenia (Primorska, Podravje and Posavje). The highest incidence of RBDV was found in Podravje (58.8%) and the lowest in Primorska (5.1%). Big differences were observed between Vipavska dolina (10.2%) and three other wine-growing districts of Primorska region (0.4–1.2%). Almost complete RNA2 sequences were obtained for four red raspberry isolates and seven grapevine isolates. Additionally, only coat protein sequences were obtained for three red raspberry isolates. Phylogenetic and population diversity analyses were performed on all available RBDV sequences. Phylogenetic analysis has shown clear differences in sequences from Rubus and grapevine that form two highly supported clades. In RNA2 analysis additional two sub-clades were found in grapevine clade. Two major subclades were identified also in the Rubus clade with further differentiation within these subclades. Purifying or stabilizing selection was found to be acting on both, CP and MP genes while few codons were found to be under positive selection.